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12. The simplest level of organization within an organism is found at the chemical level and is composed of atoms and molecules. At the cellular level of organization, molecules are organized into cells and subcellular components, forming the basic units of life. Groupings of similar cells performing similar functions are referred to as tissues, and groups of tissues may be found working in concert, forming organs at the organ level of organization. Related groups of organs working together in order to coordinate activities within the organism are called organ systems. 13. A hierarchical organization, metabolism, growth and development, responsiveness, regulation, and reproduction are characteristics common to all living organisms. All living things are arranged in a hierarchical manner with increasing levels of complexity from molecules to cells. They are capable of metabolism, growth and development, and responsiveness to stimuli. They are also able to regulate their internal environment in order to maintain homeostasis, ultimately surviving long enough to reproduce. 14. The human body consists of eleven organ systems. They are the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, urinary, digestive, and reproductive systems. 15. A body in anatomical position is standing upright with the feet flat on the floor. The upper limbs are at the side of the body with palms facing anteriorly. The head is level and the eyes are looking forward. The anatomic position is the point of common reference used by anatomists and physiologists for accuracy and clarity. It provides an initial point of reference, from which all anatomic parts are described. 16. The forearm is the antebrachial region, the wrist is the carpal region, the chest is the thoracic region, the armpit is the axillary region, the thigh is the femoral region, and the entire foot is the pes. 17. The cranial cavity and vertebral canal are located within the posterior aspect of the body. The cranial cavity houses the brain and the vertebral canal contains the spinal cord. 18. The serous membranes are found lining the compartments of the ventral cavity of the body. They consist of a parietal layer lining the inside of the body wall and a visceral layer covering internal organs. In between the two membranes is a potential space, the serous cavity, which contains serous fluid. 19. A homeostatic system consists of a receptor that detects an internal or external stimulus, a control system that integrates the input from the receptor, and an effector, such as a muscle or a gland, that causes changes in response to the stimulus. 20. Negative feedback systems involve responses that are in opposition to the stimulus, thereby maintaining the environment near the set point or normal level. Conversely, positive feedback systems entail a series of responses, each increasing in intensity until a climax event is reached, at which point the system will return to homeostasis.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: The pain is coming from a region below the umbilicus, hence it is in the lower portion of the abdomen and it is located on the right side. It is therefore in the right lower quadrant. 2. D Feedback: The right iliac region is located just medial to the pelvic bones. 3. B Feedback: X-rays are not absorbed by soft tissue such as the appendix. They are usually used to visualize dense structures. 4. B Feedback: Sweat glands release sweat at the surface of the skin.

5. B Feedback: Serotonin is a neurotransmitter responsible for regulating both pathways associated with depression in the brain and gastric motility in the stomach. Drugs such as SSRIs are used to treat depression in individuals with low levels of serotonin in the brain by inhibiting its reuptake by neurons. Because the SSRI drugs cannot specifically target the brain, they also have an effect within the digestive system, causing nausea and diarrhea.

Answers to “Can You Synthesize What You’ve Learned?” 1. Lynn has broken the bones within her forearm, the radius and ulna. She has an abrasion on her chin as well as bruising on her buttocks and thigh. 2. The epinephrine counteracted the effect of the bee sting, acting in opposition to the stimulus; it was therefore an example of negative feedback. 3. X-rays and CT scans are optimal for visualizing dense tissues, such as tumors. An MRI or ultrasound would be better suited for examining soft tissues.

Chapter 2 Answers to “What Did You Learn?” 1. The mass of an atom is determined by the combined number of protons and neutrons within its nucleus. The charge of an atom is determined by the number of positively charged protons and negatively charged electrons. 2. The nucleus of a chlorine atom consists of 17 protons and 18 neutrons. The electrons are arranged into three separate shells; the first shell closest to the nucleus contains two electrons, the second shell contains eight electrons, and the third outer shell contains seven electrons, for a total of 17 electrons.

17P 18N

3. Isotopes are atoms of the same element. They only differ in their number of neutrons, thus they differ in their atomic mass. A radioisotope is unstable because of extra neutrons. Stability can ultimately be reached through the loss of nuclear components in the form of high-energy radiation (e.g., alpha particles, beta particles). Thus, the radioisotope will decay as radiation is released. 4. The octet rule is the tendency for atoms to lose, gain, or share electrons to obtain a complete outer shell and thus become chemically stable. 5. Common cations (positively charged ions) of the human body include: sodium ions (Na +), potassium ions (K+), calcium ions (Ca2+), magnesium ions (Mg2+), and hydrogen ions (H+). Common anions (negatively charged ions) include: chloride ions (Cl–), bicarbonate ions (HCO3−), and phosphate ions (PO43–). 6. Sodium (atomic number 11), potassium (atomic number 19), calcium (atomic number 20), magnesium (atomic number 12), hydrogen (atomic number 1), and chlorine (atomic number 17) should be highlighted. 7. In order to satisfy the octet rule, atoms may either lose or gain electrons to become chemically stable (have a complete outer shell of electrons). However, a charge is developed because the number of positively charged protons is no longer equal to the number of negatively charged electrons. For example, atoms with only one electron in their outer shell may give up the electron, resulting in a positive cation, now with a full outer shell. Conversely, atoms with seven electrons in their outer shell may accept an electron from another atom, becoming a negative anion, but now with a full outer shell. 8. Ionic bonds are formed due to an attraction between ions with different charges. Therefore, an ionic bond cannot be formed between two cations, nor can it be formed between two anions. 9. The structural formula exhibits the type and number of atoms in a molecule, and their arrangement within the molecule. In comparison, the molecular formula provides information only for the type and number of atoms in a molecule (but not how the atoms are arranged within the molecule). 10. Isomers are molecules composed of the same type and number of elements, but are arranged differently (i.e., they have the same molecular formula, but a different structural formula). 11. A covalent bond is formed when atoms share electrons in their outer orbitals in order to satisfy the octet rule. 12. Nitrogen is more electronegative that hydrogen, thus it is designated with a partial negative charge, whereas hydrogen is less electronegative than nitrogen and is designated with a partial positive charge.

13. A covalent bond between atoms of the same element (with both atoms equally electronegative) will result in electrons being shared equally between the two atoms. Thus, the resulting bond is a nonpolar bond. A covalent bond formed between two different atoms (with one atom more electronegative than the other) will result in electrons being shared unequally between the two atoms. Thus, the resulting bond is a polar bond. The more electronegative atom will have a slightly negative charge and the less electronegative atom will have a slightly positive charge. Note: Because carbon and hydrogen atoms are nearly equal in terms of electronegativity, atoms of these two different elements essentially share electrons equally and form a nonpolar covalent bond between them. 14. Both molecular oxygen (O2) and carbon dioxide (CO2) are nonpolar molecules. (This is significant for understanding how these respiratory gases are transported in the blood, a topic that is covered in chapter 23.) 15. A hydrogen bond is a weak attraction between a partially positive hydrogen atom within a polar molecule and a partially negative atom within a polar molecule (usually oxygen, but sometimes nitrogen). 16. Hydrogen bonds are the intermolecular bonds that are significant in determining the properties of water. 17. Surfactant is required to decrease surface tension (the cohesive attraction between water molecules) in the alveoli of the lungs. Body temperature is regulated through sweating because of water’s high heat of vaporization. Sweating is less effective on a humid day because of the increased water in the environment that impedes additional water evaporating from the skin. 18. Nonelectrolyte molecules such as glucose dissolve but do not dissociate in water. Electrolytes such as sodium chloride (NaCl) both dissolve and disassociate into constituent ions in water, forming a solution capable of conducting electricity. 19. In an aqueous environment, amphipathic molecules such as phospholipids will orient themselves so that their hydrophobic domains face each other while the hydrophilic portions are exposed to water. This is the basis for the arrangement of phospholipids within a bilayer and a micelle. 20. Each water molecule can disassociate into one positively charged hydrogen ion and one negatively charged hydroxyl ion. It is considered neutral since it has an equal distribution of positive and negative charges. 21. An acid dissociates in water and releases hydrogen ions. 22. pH is a measure of the relative amounts of H+ in a solution. The relationship between [H+] and pH is inverse. As [H+] increases, pH decreases, whereas as [H+] decreases, pH increases. 23. A buffer helps prevent pH changes if either excess acid or base is added. It acts either to accept H + from excess acid or donate H+ to neutralize excess base. (Buffers act as H+ sponges, absorbing H+ if acid is added and releasing H+ if base is added.) 24. Blood would be characterized as a suspension because blood cells settle to the bottom of a tube when left standing. 25. Blood is also considered a colloid because it contains a mixture of proteins within the liquid portion of the blood, and it is a solution because it contains salts, glucose, and other dissolved nonprotein substances in the plasma. 26. The concentration of a solution may be expressed as (1) mass of solute per volume of solution [mass/volume], (2) grams of solute per 100 milliliters (mL) of solution [mass/volume percent], (3) moles of solute per liter of solution [molarity], and (4) moles of solute per kilogram of solvent [molality]. 27. The six common elements that form biological macromolecules include: carbon (C), hydrogen (H), and oxygen (O), and in some cases may also contain nitrogen (N), phosphorus (P), and sulfur (S). Hydrogen is the element that both (a) forms a common ion and (b) is a common element in biomolecules. 28. Carboxylic acids and phosphates are capable of acting as acids.

29. A polymer is composed of repeating monomer subunits. Proteins are composed of amino acid monomers, carbohydrates contain sugar monomers, and nucleic acids have nucleotide monomers. 30. Lipids are fatty, water-insoluble, hydrophobic molecules and do not typically dissolve in water. 31. Phospholipids are amphipathic molecules that form chemical barriers of cell membranes. They contain both a hydrophilic head group (that dissolves in water) and a pair of hydrophobic fatty acid tails (that do not dissolve in water), making them ideally suited for forming cellular membranes. 32. Glycogen is composed of repeating glucose monomers or subunits and is stored by animals within the liver and skeletal muscle cells. 33. Fructose, galactose, and glucose are monosaccharides. Sucrose, maltose, and lactose are disaccharides. Glycogen and starch are polysaccharides. 34. Nucleic acids store and transfer genetic information within cells. They ultimately determine the types of proteins synthesized within cells. 35. RNA molecules contain a ribose sugar in their nucleotides rather than the deoxyribose sugar that is within the nucleotides of DNA. The nucleotides of both RNA and DNA may contain the nitrogenous bases of adenine, guanine, and cytosine. The base uracil is present within nucleotides of RNA. In comparison, the base thymine is present in the nucleotides composing DNA. RNA is a single strand, whereas DNA is a double strand (double helix). 36. Amino acids are the monomers of a protein and they are covalently linked by peptide bonds. 37. A dipeptide consists of 2 amino acids, an oligopeptide contains 3 to 20 amino acids, a polypeptide contains 21 to 199 amino acids, and a protein consists of 200 or more amino acids. The term protein is generally used to refer to oligopeptide, polypeptide, and protein. 38. The R group of leucine is a nonpolar hydrocarbon, making it a nonpolar amino acid. 39. The tertiary structure refers to the three-dimensional shape exhibited by one completed polypeptide chain. The quaternary structure refers to the three-dimensional shape of two or more polypeptide chains that form the functional protein. 40. Denaturing a protein changes its conformation and affects its activity. Exposure of a protein to higher than normal concentration of hydrogen ions (a decrease in pH) results in the positively charged H + binding with negatively charged structures that were participating in electrostatic interactions that were holding the protein in its final shape. The loss of these electrostatic interactions between the amino acids that compose the protein results in its unfolding (or denaturation).

Answers to “Do You Know the Basics?” 1. C Feedback: Isotopes are atoms of the same element that have the same number of protons and electrons, but differ in the number of neutrons. 2. A Feedback: Lipids are hydrophobic molecules and are not soluble (do not dissolve) in water. 3. C Feedback: Water has a high specific heat, allowing it to absorb and release energy without changing temperature. In addition, the high heat of vaporization for water allows it to dissipate a large amount of energy during evaporative cooling of the skin.

4. D Feedback: A pH less than 7.0 is acidic and a pH greater than 7.0 is basic. 5. D Feedback: The formed elements of blood act as a suspension. Dissolved proteins in the plasma act as a colloid. The numerous dissolved solutes also make blood a solution. 6. A Feedback: Triglycerides are not considered polymers because they are not composed of repeating monomer subunits. 7. C Feedback: Glucose is stored in animal tissues as glycogen. 8. B Feedback: Although phosphates which contain phosphorus are common ions in the body, phosphorus itself is not a common ion. 9. B Feedback: A hydrogen bond is an intermolecular attraction between a slightly positive hydrogen atom within a polar molecule and a slightly negative atom (e.g., oxygen, nitrogen) in a polar molecule. 10. B Feedback: Denaturing a protein changes its conformation. Excessive denaturation can permanently affect protein structure and possibly its function as well. 11. Common cations of the human body include sodium ions (Na +), potassium ions (K+), calcium ions (Ca2+), magnesium ions (Mg2+), and hydrogen ions (H+). Common anions include chloride ions (Cl-), bicarbonate ions (HCO3-), and phosphate ions (PO43-). 12. Polar bonds have varying degrees of unequal electron sharing between two different atoms, except for C-H, an oxygen atom bonded to a hydrogen atom. Oxygen, the more electronegative of the atoms, will have a stronger pull on the electrons and will thus have a slightly more negative charge around it, while the hydrogen atom will be relatively more positive (or less negative). A polar molecule is a molecule that contains a prevalence of polar bonds between the atoms that compose it. For example, water is a polar molecule composed of two polar covalent bonds between the oxygen atom and each hydrogen atom. 13.

14. Polar molecules (e.g., glucose) will dissolve in water because hydrogen bonds are formed between the water and the polar molecules. The polar molecule does not dissociate, remaining intact as in this example of a glucose molecule. In comparison, ionic compounds both dissolve and dissociate. Ionic compounds such as sodium chloride (NaCl) will disassociate in water because the polar water molecules will disrupt the electrostatic interactions between sodium and chloride ions, thereby separating them. 15. An acid contributes hydrogen ions to a solution, making it more acidic (having a lower pH). A base binds hydrogen ions from a solution, making it more basic (having a higher pH). pH is the measure of hydrogen ions in a solution. A buffer is capable of either absorbing or releasing hydrogen ions, thereby helping to prevent pH changes when acids or bases are added. 16. The concentration of a solution may be expressed as either the ratio of the mass of solute compared to the volume of the solution (mass/volume), as the percent of mass of solute in 100 milliliters of solution (mass/volume %), as the number of moles of solute per liter of solution (molarity), or the number of moles of solute per kilogram of solvent (molality). 17. Proteins are composed of amino acids (repeating units); carbohydrates are composed of simple sugars (repeating units); nucleic acids are composed of nucleotides (repeating units); but lipids are not composed of repeating units. There are four primary types of lipids: triglycerides (composed of glycerol and fatty acids); phospholipids (composed of glycerol, two fatty acids, a phosphate, and various organic groups); steroids (cholesterol, steroid hormones, and bile salts—composed predominantly of hydrocarbons that differ in the side chains extending from the rings); and eicosanoids (prostaglandins, thromboxanes, and leukotrienes—composed of modified 20-carbon fatty acids synthesized from arachidonic acid). 18. Nucleotides (composed of a sugar, phosphate, and a nitrogenous) that compose DNA and RNA contain nitrogen that forms a nitrogenous waste called uric acid. Amino acids contain an amine functional group, —NH2, that is converted to a nitrogenous waste called urea. Both uric acid and urea must be effectively eliminated by the kidney for an individual to remain healthy. 19. In an aqueous environment, amphipathic molecules such as phospholipids will orient themselves so that their hydrophobic domains face each other while the hydrophilic domains are exposed to water. This is the basis behind the arrangement of phospholipids within a phospholipid bilayer of the plasma membrane of a cell. 20. A protein’s function is dependent upon the retention of its normal 3-dimensional shape. Denaturation is a change in the conformation of a protein that changes/affects its activity. Exposure of a protein to either an increase in temperature or a pH outside of its normal environment can denature the protein by disrupting electrostatic interactions such as ionic bonds within the molecule. An increase in temperature can weaken the intramolecular attractions between the amino acids in the primary structure of the protein strand, causing the protein to unfold or denature such that it can no longer function normally. Changes in H+ concentration that are associated with changes in pH interfere with the electrostatic interactions within the protein that hold it in its 3-dimensional shape. Exposure of a protein to higher than normal concentration of hydrogen ions (a decrease in pH) results in the positively charged H + binding with negatively charged structures that were participating in electrostatic interactions that were holding the protein in its final shape. Exposure of a protein to lower than normal concentration of hydrogen ions (an increase in pH) results in the positively charged H + that were participating in electrostatic interactions and holding the protein in its final shape being removed. The loss of these electrostatic interactions between the amino acids that compose the protein results in its unfolding (or denaturation).

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: Surface tension is high within the air sacs in the lungs of premature infants that are not producing sufficient surfactant. Surfactant is a detergent-like substance that prevents hydrostatic interactions between water molecules, thereby preventing the lungs from collapsing and the alveolar walls from sticking together. Premature babies often lack the ability to produce surfactant and are at risk for respiratory problems.

2. B Feedback: Electrolytes such as sodium ions, potassium ions, and chloride ions are capable of conducting electricity. Nonelectrolytic molecules such as glucose are not able to conduct electricity. 3. B Feedback: Radioisotopes emit high-energy radiation. 4. D Feedback: Calcium (Ca2+) ions are an important structural component of bone tissue. 5. C Feedback: Proteins consist of covalently bonded amino acids held together by peptide bonds. If insulin is administered orally, the peptide bonds are broken by enzymes of the digestive system (to form individual amino acids).

Answers to “Can You Synthesize What You’ve Learned?” 1. High-energy radiation can cause mutations within DNA. 2. The number of hydrogen ions in the blood increases, resulting in a lower pH (a condition called acidosis). The increasing number of hydrogen ions may interfere with the hydrostatic interactions holding proteins together, thus denaturing the proteins. 3. The drug would regulate the levels of the monosaccharide glucose within the blood.

Chapter 3 Answers to “What Did You Learn?” 1. Kinetic energy is the energy of motion. Movement of sodium ions along a concentration gradient or the movement of electrons from a higher to lower energy state are both examples of kinetic energy. 2. The movement of muscle is an example of mechanical energy, a form of kinetic energy that involves the movement of an object due to an applied force. 3. Even though energy can neither be created nor destroyed, it can be transformed or converted from one form to another. Such transformations are not completely efficient, always resulting in the release of some of the energy as heat, which is not available to do work. 4. Reactants are the substrates or substances that are present prior to a chemical reaction. The reactants are converted to products during the reaction. 5. Formation of a complex molecule from simpler chemical structures would be classified as: (a) a synthesis reaction, (b) an endergonic reaction, and (c) a form of anabolism. 6. ATP is formed from glucose oxidation and used as the energy currency for energy-requiring processes within the cell. 7. When equilibrium is disturbed in a reversible reaction, the system will adjust and the reaction is driven toward either the reactants or the products until equilibrium is reestablished. For example, an increase in substrates drives the chemical reaction to the right (making more product) until a new equilibrium is reached. 8. Initially, the effect of a fever (elevation in temperature) increases the kinetic energy of the molecules, providing enough energy to break chemical bonds. The consequence of high fever may result in the denaturing of proteins and potentially cause the death of the cell (and possibly the death of the individual). 9. Enzymes are catalysts that decrease the energy of activation required for a chemical reaction to proceed. 10. The active site is a region in the enzyme that is the temporary binding site for the substrate to the enzyme. 11. Enzymes are proteins that catalyze metabolic reaction by lowering the activation energy necessary for the reaction. The structure of the protein directly affects its affinity for its specific substrate. (1) Substrate enters the enzyme’s active site and temporarily binds to it, forming an enzyme-substrate complex. (2) Binding of substrate into the active site induces conformational changes in the enzyme; this response is referred to as the induced-fit model of enzyme function. (3) Chemical bonds in the substrate are stressed by changes in the enzyme shape. This lowers the Ea, (activation energy) so that bonds in the substrate(s) are more easily broken and new chemical bonds may be formed. (4) A new molecule (called [a] product[s]) is released from the enzyme. Inorganic cofactors are attached to enzymes and may be required for the normal function of some enzymes. 12. The name of an enzyme is usually based upon the name of the substrate or the product involved in the chemical reaction, or sometimes the name of the enzyme subclass. The suffix -ase is added to the final word of the name. 13. The rate of an enzyme-catalyzed reaction may be increased as the concentration of substrate is increased, until all of the enzyme molecules are saturated. Enzymes function most efficiently at their optimal temperature. Decreasing temperature from an enzyme’s optimum range will decrease its activity. Increasing temperature increases the rate of the reaction until enzymes denature. Changing pH in either direction (increase or decrease) from its optimal pH will readily denature the protein as the change in hydrogen ion concentration interferes with electrostatic interactions within the enzyme, denaturing it. 14. Inhibitors prevent an enzyme from converting substrate to product. Competitive inhibitors affect enzyme activity by competing with substrates at the active site of the enzyme. Noncompetitive inhibitors do not resemble the

substrate, but they inhibit an enzyme by binding to a site on the enzyme other than the active site (a site called the allosteric site). This modulates the shape of the enzyme altering the shape of its active site. 15. A metabolic pathway is formed by numerous enzymes. Each enzyme catalyzes one progressive change to its specific substrate molecule and then releases the product. Thus, the product of one enzyme becomes the substrate of the next enzyme. Negative feedback is a means to regulate the activity of metabolic pathways. The product from a metabolic pathway acts as an allosteric inhibitor to turn off an enzyme early in the pathway and regulate enzyme activity. 16. Phosphorylation (the adding of a phosphate group) and dephosphorylation (the removal of a phosphate group) are processes that regulate enzymes by turning on some enzymes and turning off other enzymes. 17. The overall chemical reaction for cellular respiration of glucose is: C6H12O2 + 6 O2 → 6 CO2 + 6 H2O. The oxidation of glucose, an exergonic reaction, results in a step-by-step enzymatic breakdown of glucose with the accompanying release of energy to synthesize ATP. If oxygen is available, glucose is completely broken down and carbon dioxide and water are formed. 18.The four stages of cellular respiration for glucose oxidation include: (1) glycolysis (which occurs within the cytosol of the cell), and the (2) intermediate stage, (3) citric acid cycle (or Krebs cycle), and (4) electron transport system. (Stages 2, 3, and 4 occur within the mitochondria). 19. Glycolysis is a process that occurs within the cytosol and does not require oxygen. The net reaction entails the breakdown of glucose (a 6-carbon molecule) into two pyruvate molecules (each a 3-carbon molecule). The reaction involves the initial input of two molecules of ATP and yields four molecules of ATP, for a net yield of two molecules of ATP. Two molecules of NAD+ are also reduced to form NADH (and H+) from energy released during the oxidation of glucose. 20. Pyruvate may either enter a mitochondrion (if sufficient oxygen is available) to be completely oxidized to carbon dioxide (with the energy released in its chemical bonds) or (if oxygen is lacking) be converted to lactate (a process described in detail in a later section). 21. The intermediate stage of cellular respiration is an aerobic process (requires oxygen) that occurs within mitochondria, which “links” the metabolic pathway of glycolysis (that occurs in the cytosol) with the metabolic pathway of the citric acid cycle. During this process CO2 is released from pyruvate (through decarboxylation) and two electrons and a hydrogen ion are transferred to NAD+ to form. (NOTE: this process would occur twice for each glucose molecule). 22. The citric acid cycle is an aerobic process that occurs within the matrix of mitochondria. It uses acetyl CoA as the initial substrate and forms two CO2 molecules and one CoA molecule as the products. The oxidation of acetyl CoA yields: one molecule of ATP, three molecules of NADH, and one molecule of FADH2. (NOTE: this process would occur twice for each glucose molecule). 23. Cellular respiration of one molecule of glucose yields: two molecules of ATP and two molecules of NADH during glycolysis; two molecules of NADH during the intermediate stage (per original glucose molecule); and two molecules of ATP, six molecules of NADH, and two molecules of FADH2 during the citric acid cycle (per original glucose molecule). 24. NADH and FADH2 serve as coenzymes to temporarily hold energy by binding electrons and hydrogen released during the breakdown of glucose during glycolysis, the intermediate stage, and the citric acid cycle. These coenzymes hold the electrons until the electrons are transferred to the electron transport chain, which allows the formation of ATP through oxidative phosphorylation. 25. The three primary steps of the electron transport system are the following: (1) Electrons are transferred from coenzymes to O2, (2) Proton gradient is established, and (3) Proton gradient is harnessed to form ATP.

26. Glycolysis yields a net of two molecules of ATP for every molecule of glucose. Under aerobic conditions the complete oxidation of one molecule of glucose yields a net of 30 molecules of ATP. 27. In conditions of insufficient oxygen, pyruvate is converted to lactate in the cytosol. This facilitates the regeneration of two molecules of NAD+, which can then be utilized to continue with the glycolysis of more glucose, yielding limited amounts of ATP (2 ATP per glucose). 28. Fatty acids are enzymatically changed two carbon units at a time to form acetyl CoA. This is called betaoxidation of fatty acids. Acetyl CoA is oxidized within mitochondria (through the intermediate stage and the citric acid cycle). Thus, because processes that occur within mitochondria require oxygen, fatty acids can only be oxidized is sufficient oxygen is available.

Answers to “Do You Know the Basics?” 1. A Feedback: Chemical energy is converted to mechanical energy. Energy from the hydrolysis of ATP (which releases chemical energy from the high energy bond between the second and third phosphate) is used to move a body part in response to an applied force exerted by the muscle contraction. 2. A Feedback: Oxidation-reduction reactions involve the exchange of electrons between the oxidizing and the reducing agent. 3. B Feedback: Increasing (or decreasing) pH interferes with electrostatic interactions within the enzyme, causing denaturation of the enzyme (and a subsequent decrease in enzyme activity). 4. C Feedback: Since ATP does not bind to the active site of phosphofructokinase, it is not a competitive inhibitor. It is an example of an allosteric/noncompetitive inhibitor. 5. D Feedback: Enzymes are very specific for their substrate and therefore each enzyme is capable of catalyzing only one specific reaction. 6. A Feedback: Glycolysis yields two molecules of pyruvate from one molecule of glucose. 7. D Feedback: NAD+ and FAD are coenzymes involved in oxidation-reduction reactions where they bind electrons and hydrogen that are released from both glucose and its (glucose's) breakdown products. 8. A Feedback: Glycolysis is able to continue when there is insufficient oxygen available because oxygen is not required (i.e., glycolysis is not aerobic). 9. C Feedback: One molecule of glucose may yield a net of 2 molecules of ATP if insufficient oxygen is available and a net of 30 molecules of ATP if sufficient oxygen is present. 10. D Feedback: Oxidative phosphorylation involves the transfer of electrons from NADH and FADH 2 to oxygen in the electron transport chain, the establishment of a proton gradient through the use of energy from electrons passed along the electron transport chain, and finally using the proton gradient to form ATP as H + moves down its

concentration gradient and is transported across the inner mitochondrial membrane by ATP synthetase to form bonds between ADP and Pi. 11. Chemical energy is energy stored in chemical bonds; it is a form of potential energy. Energy stored in glycogen or triglycerides represents chemical energy. The remaining forms of energy are classified as forms of kinetic energy. Electrical energy is the movement of charged particles such as electrons along a wire or the propagation of an impulse in a neuron (nerve cell). Mechanical energy involves the movement of an object due to an applied force; muscle contraction is an example of mechanical energy. Sound energy is movement of compressed molecules through a medium (e.g., air) that is initiated by a vibrating object; vibration of the vocal cords of the larynx is an example. Radiant energy is the movement of electromagnetic waves that travel in the universe and vary in wavelength and frequency; visible light that is perceived by the eye is an example of radiant energy. 12. Chemical reactions are classified as reactions that cause (1) changes in chemical structure, (2) changes in chemical energy, and (3) whether the reaction is irreversible or reversible. Oxidation-reduction reactions are exchange reactions during which electrons are transferred from one substance to another. 13. ATP cycling is the continuous formation of ATP (from ADP and Pi) during cellular respiration and then the splitting of ATP back into ADP and Pi for the energy-requiring cellular processes. 14. Enzymes are globular proteins that catalyze metabolic reactions (both decomposition and synthesis reactions) by lowering the activation energy necessary for the reaction. The substrate enters the active site of the enzyme, and the enzyme temporarily binds with the substrate to form an enzyme-substrate complex. Entry of the substrate into the active site induces the conformation (structure) of the enzyme to change slightly, resulting in an even closer fit between substrate and enzyme. This response is referred to as the induced-fit model of enzyme function. Stress on chemical bonds in the substrate molecule is caused by the change in enzyme shape. Consequently, this stress lowers Ea, and the bonds in the substrates are more easily broken, permitting new chemical bonds to be formed. The newly formed molecule, now called the product, is released from the enzyme. The enzyme is then free to repeat the process again and again with other substrates. 15. A metabolic pathway consists of a series of enzyme-catalyzed reactions. The product of one enzyme becomes the substrate of the next enzyme in the metabolic pathway. Often the final product of the pathway serves as an allosteric inhibitor of enzymes within the pathway, causing a conformation change in the protein. This rearrangement may affect the affinity for the substrate at the enzymes’ active sites, thereby providing for negative feedback within the pathway. 16. Glycolysis is a process that occurs within the cytosol of a cell and does not require oxygen. The net reaction entails the breakdown of glucose (a 6-carbon molecule) into two pyruvate molecules (each a 3-carbon molecule). The reaction involves the initial input of two molecules of ATP and yields four molecules of ATP, for a net yield of two molecules of ATP. Two molecules of NAD+ are also reduced to form NADH and H+ from electrons and protons released during the oxidation of glucose. 17. If sufficient oxygen is available, pyruvate enters a mitochondrion to complete its aerobic breakdown yielding carbon dioxide and water. If insufficient oxygen is present, pyruvate is converted to lactate in the cytosol. This facilitates the regeneration of two molecules of NAD+, which can then be utilized for continuing the steps of glycolysis to yield two molecules of ATP per glucose molecule. 18. Oxygen serves as the final electron acceptor of the electron transport chain during oxidative phosphorylation. Molecular oxygen (O2) in the mitochondrial matrix is split and each oxygen atom along with electrons from the electron transport chain combine with two hydrogen ions, yielding a molecule of water. 19. The carbon in carbon dioxide is liberated from glucose (or other fuel molecules such as fatty acids) during cellular respiration. 20. Healthy respiratory and cardiovascular systems provide metabolically active tissues with adequate oxygen to drive efficient aerobic respiration (which yields greater amounts of ATP than if there is insufficient oxygen). Tissues deprived of oxygen will not be able to burn fuels efficiently nor produce adequate amounts of ATP.

Answers to “Can You Synthesize What You’ve Learned?” 1. Blood osmotic pressure would be predicted to decrease in an individual who has cirrhosis of the liver and is not producing adequate levels of albumin. The lower amounts of albumin in the blood impairs the ability to "pull" fluid from the interstitial spaces back into the blood. Excess fluid remains in the interstitial space, causing edema. 2. Pneumonia results in lower levels of oxygen in the blood. Thus, the concentration gradient for oxygen between the blood and cells decreases. Consequently, there is less diffusion of oxygen out of the blood into tissues. 3. The removal of LDL particles from the blood into cells is accomplished by receptor-mediated endocytosis, the mechanism dependent upon the presence of receptor proteins. A mutation in the gene coding for the receptor(s) responsible for the endocytosis of LDL would result in less being endocytosed by his cells, and more remaining in his blood.

Chapter 5 Answers to “What Did You Learn?” 1.

Many epithelial tissues are exposed to damage and abrasion, and therefore need to be replaced frequently.

2. Epithelial cells line all of the membranes where substances may enter the body. They must therefore have the capacity to regulate what may pass through the membranes. 3.

Simple epithelium consists of a single layer of cells. Stratified epithelium consists of two or more layers.

Simple squamous epithelium lines the air sacs of the lungs.

Keratinized stratified squamous epithelium is the correct tissue.

Multicellular exocrine glands consist of a duct and either a tubular or an acinar secretory section.

7. The cells of a merocrine gland secrete their products by exocytosis. The cells of a holocrine gland will rupture completely in order to release their contents. 8. Resident cells are fixed in position within the connective tissue. Wandering cells are components of the immune system and move through the tissue, providing for repair and for protection from infection. 9. Glycosaminoglycans (GAG) are large extracellular carbohydrates that absorb water within the ground substance of a connective tissue, thereby regulating the viscosity of the solution. 10. The functions of connective tissue include physical protection, support, binding of structures, storage, transport and immune protection. 11. Mesenchyme is an embryonic tissue composed of stellate and spindle-shaped cells surrounded by a ground substance. It is the embryonic origin of all adult connective tissues. 12. Loose connective tissue consists predominantly of ground substance with few fibers. Dense connective tissues have very little ground substance, and consist largely of a dense arrangement of fibers. 13. Fibrocartilage has many parallel collagen fibers, and large chondrocytes in lacunae. It resists compression and acts as a shock absorber in some joints. Fibrocartilage may be found in intervertebral discs, the pubic symphysis, and the menisci of knee joints. 14. Blood is derived from mesenchyme like all other connective tissues. It contains a very fluid ground substance called plasma, numerous dissolved proteins, and formed cellular elements. 15. Cardiac and skeletal muscles are both striated and contain similar arrangements of intracellular contractile proteins. Whereas cardiac muscle consists of individual branching cells, skeletal muscle consists of large multinucleated cells. Cardiac muscle is voluntary; skeletal muscle is involuntary. 16. Neurons are specialized for transmitting nervous impulses. Glial cells do not transmit the nervous impulse; however, they serve numerous critical support functions in the nervous system. 17. The stomach is an organ that contains all four tissue types. It is lined with epithelium, it has numerous layers of smooth muscle, it is highly innervated, and it contains several types of connective tissue. 18.

The parietal layer lines the inside of the body wall. The deeper visceral layer lines organs.

19. The three primary germ layers – the ectoderm, endoderm, and mesoderm – form by the third week of embryonic development.

Answers to “Can You Synthesize What You’ve Learned?” 1. The student is looking at areolar connective tissue. Areolar connective tissue is found in the papillary layer of the dermis, as well as the subcutaneous layer of the skin. It also surrounds organs, nerve cells, some muscle cells, and blood vessels. 2. The articular cartilage at the ends of long bones consists of hyaline cartilage. Chondroitin sulfate is a component of the hyaline cartilage matrix. Therefore the supplement may help reduce the effects of arthritis in the joint, if that is indeed the cause of the pain.

Chapter 6 Answers to “What Did You Learn?” 1. The thorn would first penetrate the stratum corneum, the most superficial layer of the epidermis. It would then puncture the stratum lucidum, the stratum granulosum, the stratum spinosum, and finally the stratum basale. 2. Keratinization occurs due to the production of keratin, a hardening agent, within keratinocytes. Within the stratum spinosum, the cells fill up with keratin, and the nucleus and organelles become polymerized within the protein, eventually killing the cell. The cells then rupture, releasing keratin at the stratum granulosum. The subsequent superficial layers of the stratum lucidum and corneum consist of ruptured keratinocytes embedded in keratin. This provides for a hardened waterproof barrier between the external environment and the dermis below. 3. Hemoglobin turns red when bound to oxygen. As blood vessels bring hemoglobin close to the surface within the dermis, the skin takes on a reddish hue. 4. Friction ridges increase friction on contact with the skin. It has been hypothesized that they may also provide for pliability at the surface of the skin. 5. The papillary layer, composed primarily of areolar connective tissue, is the most superficial layer of the dermis. The reticular layer lies deep to the papillary layer, makes up the majority of the thickness of the skin, and is predominantly dense irregular connective tissue. Dermal papillae, the folds within the papillary layer, contain numerous capillaries and tactile receptors. The reticular layer contains most of the structures associated with the dermis, such as the hair follicles, sebaceous and sweat glands, nerves, and blood vessels. 6. Tension lines correspond to the direction of collagen bundles within the dermis of the skin. They are relevant clinically as these represent the optimum direction for an incision through the skin. An incision perpendicular to the tension lines can be easily pulled apart and is more likely to result in scarring. 7.

The subcutaneous layer, deep to the skin, consists predominantly of areolar and adipose tissues.

8. Vitamin D3, also called cholecalciferol, is synthesized from a steroid precursor by the keratinocytes when they are exposed to ultraviolet radiation. 9. The skin is water resistant, but not entirely waterproof. Some water is always lost through the skin when you sweat. More water is typically lost through transpiration, a process in which fluids slowly penetrate through the epidermis and then evaporate into the surrounding air. 10. The skin can dissipate heat by vasodilating the blood vessels in the dermis. This allows for more warm blood to travel close to the body surface, and the heat from the blood to dissipate through the skin. In addition, sweating allows fluid to be released on the surface of the skin, and when that fluid evaporates, it cools the body. 11. The hyponychium is a thick layer of stratum corneum, deep to the free edge of the nail. The eponychium, or cuticle, is a small fold of skin that covers the proximal edge of the body of the nail. 12.

The three zones of hair are the hair bulb, the root, and the shaft.

13. Hair on the scalp protects from exposure to the sun. Hairs within the nostrils, ears, or eyelashes protect the respective openings from debris. The eyebrows help to keep sweat out of the eyes. On a cold day the hair on the scalp also acts as insulation, preventing the loss of body heat. 14. Merocrine sweat glands are distributed throughout the body, whereas apocrine glands are primarily associated with hair follicles in the axillary, genital, and anal regions. Sweat produced by merocrine glands contains over 99% water with salts and trace amounts of metabolic waste. Its primary function is thermoregulation by evaporative cooling. Sweat from apocrine glands, along with water and salts, also contains an abundance of proteins and lipids.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: Red bone marrow contains active hematopoietic cells, which are needed to treat leukemia. In adults, the red marrow is only located within the spongy bone of flat bones, such as the hip. 2. C Feedback: Collagen, a protein, is destroyed with excessive heat, leaving bone tissue dry and brittle. Hypoxyapatite crystals dissolve in acid, leaving behind flexible collagen fibers. 3. B Feedback: Yellow marrow found within the medullary cavity of long bones is rich in adipose tissue. 4. A Feedback: The fusion of the epiphyses to the diaphysis occurs in response to hormones produced at puberty, thus providing an indication as to the age of the skeleton. 5. C Feedback: Chondrocytes form attacks within the zone of proliferation. These then become enlarged within the zone of hypertrophy.

Answers to “Can You Synthesize What You’ve Learned?” 1. Removal of the parathyroid glands would prevent the person from responding to decreases in blood calcium and prevent the release of parathyroid hormone. Maintaining the parathyroid glands after the removal of the thyroid gland would significantly improve the person’s ability to regulate blood calcium levels. 2. Mechanical stress—such as that experienced during weight-bearing exercise—induces bone growth, consequently contributing to bone mass. When bones are immobilized to facilitate repair, they are not experiencing stress. Consequently, the amount of bone resorption exceeds the amount of interstitial and appositional growth, thereby weakening the bone. 3. Elise’s history indicates numerous factors that can contribute to decreased bone mass and subsequent difficulty in bone repair. Due to a lack of activity and physical interactions with other children her developing bones may have experienced less mechanical stress during a formative developmental period, severely affecting bone mass. Spending most of her time indoors, she may have a deficiency in vitamin D, because of her limited exposure to UV light. Consumption of soft drinks also decreases bone density, in concert with the other factors, leaving her susceptible to damage and prolonged repair.

Chapter 8 Answers to “What Did You Learn?” 1. The axial skeleton primarily serves to provide a framework for and protection of internal organs, as well as hemopoiesis. It consists of the skull, vertebral column, and thoracic cage. 2.

Foramina and fissures are both openings. A foramen is rounded whereas a fissure is elongated.

3. The cranium of the skull consists of the frontal, parietal, occipital, ethmoid, sphenoid, and temporal bones. The zygomatic, lacrimal, nasal, inferior nasal conchae, maxillae, vomer, mandible, and palatine bones comprise the face. 4. The frontal bones, maxillae, nasal bones, zygomatic bones, and mandible are the predominant bones visible from the anterior of the skull. 5. The sphenoid and temporal bones comprise the middle cranial fossa, which houses the temporal lobes of the brain and the pituitary gland. 6. The lambdoid suture is the articulation between the occipital and parietal bones. It is the last cranial suture to fuse, usually by age 40. 7.

The palatine, maxillae, and zygomatic bones form the floor of the orbit of the eye.

The maxillary, sphenoid, ethmoid, and frontal bones contain the paranasal sinuses.

The malleus, incus, and stapes are auditory ossicles located within the petrous portion of the temporal bone.

10. Generally, male skulls have a more predominant superciliary arch and a more sloping frontal bone than female skulls. The female skull will likely have a sharper supraorbital margin, a more triangular mental protuberance, a smoother, less prominent occipital protuberance, and a more obtuse mandibular angle. 11.

The posterior and anterior are the largest of the fontanelles, closing by 9 and 15 months of age, respectively.

12.

The five lumbar vertebrae comprise the “small” of the back.

13.

The cervical and lumbar curvatures of the spine are secondary curvatures that appear after birth.

14. Transverse foramina, which contain the vertebral artery and vein, are located in the transverse processes of cervical vertebrae. The vertebral foramen is located posterior to the body of a vertebra and contains the spinal cord and meninges. The intervertebral foramina are located in between the pedicles of consecutive vertebra and allow for passage of spinal nerve roots joining the spinal cord. 15. The atlas lacks a body and elongated superior articular facets for articulation with the occipital condyles of the skull. The axis has a superior projection called the dens which serves as a pivot point for the atlas. 16. The sternal angle is the articulation between the manubrium and the body of the sternum. It is located at the level of the articulation of the second rib with the sternum. 17. The head of the rib articulates with costal facets on the bodies of consecutive vertebrae. The tubercle of the rib articulates with the transverse costal facet of the inferior vertebra. 18. The lower limbs are well suited for supporting weight and propulsion when walking. In contrast, the upper limbs are suited for dexterous activities, such as grasping objects and handling tools. 19.

The sternal end of the clavicle is pyramidal in shape, whereas the acromial end is broader and flatter.

Answers to “Can You Synthesize What You’ve Learned?” 1. ATP is required to break the crossbridges between thick and thin filaments. However, within a few hours after the heart stops beating, ATP levels in skeletal muscle fibers have been completely exhausted. ATP is not being synthesized because cell respiration has terminated at the time of death, so no ATP is available and crossbridges cannot detach. All skeletal muscles lock into a contracted position and the body of the deceased individual becomes rigid. This physiologic state, is termed rigor mortis. It continues for about 15 to 24 hours. Rigor mortis then disappears because lysosomal enzymes are released within the muscle fibers, causing autolysis (self-destruction and breakdown) of the myofibrils. Additionally, the lack of ATP has another effect. The sarcoplasmic reticulum loses its ability to return Ca2+ from the sarcoplasm and move it back into the sarcoplasmic reticulum. As a result, the Ca 2+ already present in the sarcoplasm, as well as the Ca2+ that continues to leak out of the sarcoplasmic reticulum, supports a sustained contraction in the fibers. 2. Botulism is a potentially fatal muscular paralysis that is caused by a toxin produced by the bacterium, Clostridium botulinum. The toxin prevents the release of acetylcholine (ACh) at synaptic knobs and leads to muscular paralysis. Curare is a potent drug that acts by preventing release of acetylcholine and the subsequent stimulation of the skeletal muscle (at the neuromuscular junction). Thus, although both botulism and curare act differently (one prevents release of acetylcholine and the other prevents the transmission of neural impulses) they have the same ultimate effect and that is flaccid muscular paralysis from lack of stimulation. 3. Smooth muscle contracts in response to being stretched. Its response, however, is not continuous if the stretch is prolonged. Instead, the smooth muscle exhibits what is called the stress-relaxation response. This occurs when smooth muscle is “stressed” by being stretched. The smooth muscle responds by contracting, but after a given period of time, it then relaxes. For example, swallowed materials entering the stomach cause its wall to stretch, and the smooth muscle in the wall initially contracts. After a period of time it relaxes, allowing additional food to more easily enter the stomach. Thus, in the current example, one may ‘feel’ the need to urinate as the bladder fills with urine because the smooth muscle in its wall is stretched, that sensation subsides and passes because the ‘stretched’ smooth muscle will relax.

Chapter 11 Answers to “What Did You Learn?” 1. The proximal attachment is closer to the trunk of the body and typically is the less movable part of a muscle, whereas the distal attachment is further from the trunk of the body and typically is the more movable part of the muscle. 2.

Parallel muscles have a lot of endurance but are relatively weaker than pennate muscles.

3. The agonist is the prime mover for an action and generates the majority of the force. The synergist facilitates the movement produced by the agonist by either contributing tension or stabilizing the bones involved. 4. A description of the shape of a muscle may be incorporated into its name: A deltoid muscle is triangular in shape, orbicularis implies that the muscle has fibers arranged in a circle, a rhomboid muscle has the shape of a rhomboid, and the trapezius muscle is shaped like a trapezoid. The length of the muscle may also be incorporated into the nomenclature: The terms longus and longissimus refer to relatively long muscles and brevis refers to short muscles. 5. The gluteus maximus gets its name from (1) the gluteal region of the body (buttocks) = gluteus, and (2) the size of the muscle = maximus (largest). 6.

The levator anguli oris, zygomaticus major, zygomaticus minor, and risorius muscles all contribute to smiling.

The depressor anguli oris contracts to pull the corners of the mouth inferiorly when frowning.

The lateral rectus muscle abducts the eye.

9. The pterygoid muscles are responsible for protraction and side-to-side movement of the mandible. The medial pterygoid muscle may also elevate the mandible. 10. The extrinsic tongue muscles are used in various combinations to accomplish the precise, complex, and delicate tongue movements required for proper speech and manipulating food within the mouth. 11. The digastric, geniohyoid, mylohyoid, and stylohyoid muscles are suprahyoid muscles. All four are capable of elevating the hyoid bone. 12. The sternocleidomastoid and scalene muscles flex the neck. Extension at the neck may be accomplished by the splenius capitis, splenius cervicis, longissimus capitis, rectus capitis posterior major, or rectus capitis posterior minor muscles. 13. The erector spinae is the largest muscle mass in the back. The muscles of the erector spinae consist of three groups of muscles: iliocostalis (located laterally), longissimus (located intermedially), and spinalis (located medially). The muscles of the erector spinae are used to maintain posture and help us stand erect. 14. The external intercostal muscles elevate the ribs during inspiration. The internal intercostals depress the ribs, but only during a forced expiration; a normal exhalation takes no active muscular effort. 15. Contraction of the diaphragm moves the entire muscle inferiorly, which expands the thoracic cavity, thus decreasing pressure in the thoracic cavity and increasing pressure in abdominopelvic cavity. 16. All four abdominal muscles compress the abdominal wall. The rectus abdominis flexes the vertebral column. The external and internal obliques and the transverse abdominis muscles produce lateral flexion when contracted

3. C Feedback: Calcium ions enter the synaptic knob and binds synaptic vesicles containing neurotransmitter triggering events that result in the fusion with the neuron plasma membrane resulting in the release of neurotransmitter into the synaptic cleft. 4. C Feedback: The transmissive segment (synaptic knob) releases neurotransmitter into the synaptic cleft. Some neurotransmitters such as serotonin are normally removed from the synaptic cleft by reuptake (i.e., the neurotransmitter molecules are returned to the synaptic knob). 5. A Feedback: A reverberating circuit is associated with repetitive processing (such as repeating a phone number over and over).

Answers to “Can You Synthesize What You’ve Learned?” 1. As the immune system destroys neurolemmocytes in the peripheral nervous system, saltatory conduction is prevented, and conduction of action potential in the neurons of CNS is greatly diminished, possibly affecting vision and motor control. 2. Repair of damaged neurons is possible only if the amount of damage or the distance of the damage to the target is minimal. Regeneration requires formation of a regeneration tube from the remnants of the neurilemma and endoneurium of the original neuron. Growth of the new axon within the tube then occurs at approximately 2–5 mm per day—a rate much slower than blood vessel repair. 3. Depolarization of the axon requires the opening of voltage-gated Na+ channels. Neurotoxins that affect the opening of these channels would inhibit depolarization, and subsequently the action potential, along the axon.

Chapter 13 Answers to “What Did You Learn?” 1. The brain is composed of four major regions: the cerebrum, diencephalon, brainstem, and cerebellum. 2. A neural groove is formed as the cells on the periphery of the neural plate divide and produce neural crests. As the crests continue to expand, they merge, surrounding the neural groove, which now becomes the neural tube. 3. The five secondary brain vesicles are the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon. In the adult brain, the telencephalon forms the cerebrum; the diencephalon forms the thalamus, hypothalamus, subthalamus, and epithalamus; the mesencephalon forms the rostral end of the brainstem; the metencephalon forms the pons and cerebellum; and the myelencephalon forms the medulla oblongata. 4. Gray matter of the cerebrum is located within the outer cerebral cortex, as well as within deeper cerebral nuclei. Within the spinal cord, gray matter is limited to one large central portion, surrounded by columns of white matter. 5. Pia mater, subarachnoid space, arachnoid mater, subdural space, inner meningeal layer of dura mater, and outer periosteal layer of dura mater. Dural venous sinuses are located between the inner meningeal and outer periosteal layers of dura mater. 6. The falx cerebri is a large fold of dura mater located along the midsagittal plane within the longitudinal fissure, separating the left and right hemispheres of the brain. It is attached anteriorly to the crista galli and posteriorly to the internal occipital crest, stabilizing the brain within the cranium. 7. The fourth ventricle is located between the pons and cerebellum. It opens to the subarachnoid space via a single median aperture and paired lateral apertures. 8. The CSF provides the brain with buoyancy. Allowing the brain to float within a surrounding fluid distributes its weight within the cranium, protecting it from damage. CSF also provides a liquid cushion to protect delicate neural structures from sudden movements. Lastly, the CSF provides for environmental stability; it transports nutrients and chemical messengers to the brain, and removes waste products. 9. CSF is produced by the choroid plexus within the ventricles. It flows from the lateral ventricles and third ventricle into the cerebral aqueduct and then into the fourth ventricle. Additionally, a relatively small amount of CSF from the central canal of the spinal cord travels to the fourth ventricle as well. Most of the CSF in the fourth ventricle flows into the subarachnoid space by passing through openings in its membranous roof, either the paired lateral apertures or the single median aperture. CSF flows through the subarachnoid space surrounding the brain, spinal cord, and nerve fibers. As additional CSF is incorporated into the subarachnoid space, one-way flaps in the arachnoid villi open into the dural venous sinuses, allowing excess CSF to be released into the venous bloodstream. These flaps allow the CSF to be released into the blood without allowing any venous blood to enter the subarachnoid space. 10. The blood-brain barrier strictly regulates which substances can and cannot enter the interstitial fluid of the brain from capillaries. 11. The cerebrum is the location of conscious thought processes and the origin of all complex intellectual functions. 12.

The corpus callosum provides the main method of communication between the hemispheres of the brain.

13. The five lobes are the frontal lobe, parietal lobe, temporal lobe, occipital lobe, and insula. The frontal lobe is primarily concerned with voluntary motor functions, concentration, verbal communication, decision making, planning, and personality. The parietal lobe is concerned with sensory reception as well as understanding speech and formulating words. The temporal lobe is involved with hearing, interpreting speech and language, and smell.

2. The blood-brain barrier would prevent the supplemented dopamine from entering the nervous system. Nervous tissue is isolated from the general circulation by the blood-brain barrier, which strictly regulates which substances can enter the brain. The advantage of the blood-brain barrier is that it helps prevent exposure of neurons in the brain to drugs, waste products in the blood, and variations in levels of normal substances such as hormones. 3. Dustin is more likely to survive damage to the cerebrum than the medulla oblongata. The cerebral cortex manages memories as well as somatic sensory and motor processing, some of which, although important, are not deadly if damaged. The medulla oblongata, however, controls multiple autonomic functions necessary for maintaining homeostasis, which cannot be interrupted.

Chapter 14 Answers to “What Did You Learn?” 1. The spinal cord and its attached spinal nerves provide an essential structural and functional link between both the torso and limbs of the body and the brain. Sensory input is relayed from the torso and limbs to the brain and motor output is relayed from the brain to the torso and limbs. The spinal cord and spinal nerves are responsible for spinal reflexes, which involve nervous system responses that have the spinal cord as the integration center.

2. A typical adult spinal cord is approximately ¾ of an inch in diameter and ranges between 16 to 18 inches (42 to 45 centimeters) in length. It is continuous with the medulla oblongata of the brain superiorly and extends through the vertebral column to the inferior border of the L1 vertebra.

3. There are 31 pairs of spinal nerves, which are identified as 8 cervical nerves (called C1-C8), 12 thoracic nerves (T1-T12), 5 lumbar nerves (L1-L5), 5 sacral nerves (S1-S5), and 1 coccygeal nerve (Co1). 4. The cauda equina is formed as spinal nerve roots inferior to the conus medullaris grow at the same rate of the vertebral column (which is greater than that of the spinal cord). Thus, these spinal nerve roots extend inferiorly from the spinal cord prior to exiting the vertebral column. The spinal nerve roots that compose the cauda equina include L2-L5, S1-S5, and CO1. 5. The epidural space lies between the dura mater and the inner walls of the vertebrae (that surround the vertebral foramen). The subdural space is a potential space between the arachnoid mater and dura mater. The subarachnoid space lies between the pia mater and arachnoid mater, and it contains the cerebrospinal fluid (CSF). 6. The order for sensory input to the spinal cord is: sensory receptor, spinal nerve, posterior root, a posterior horn. 7. The structures for relaying motor output from the spinal cord to skeletal muscles is: anterior horn, anterior root, spinal nerve, and effector (skeletal muscle).

8. The three types of funiculi are anterior, lateral, and posterior and are composed of white matter. The anterior and lateral funiculi contain both ascending (sensory) and descending (motor) tracts. The posterior funiculi contain ascending (sensory) tracts only. 9. The characteristics common to most nervous system pathways are that most pathways: (1) have paired tracts, (2) are composed of two or more neurons, (3) have common location for cell bodies and location of axons, and (4) exhibit crossing-over (decussation) of tracts from one side of the body to the other side (contralateral pathways), with limited number of tracts remaining on the same side of the body (ipsilateral pathways). 10. Sensory pathways use a series of two or three neurons to transmit nerve signals from the body to the brain. (1) The first neuron is the primary neuron. Its cell body resides in the posterior root ganglia of spinal nerves. It transmits nerve signals from the receptor to the secondary neuron. (2) The second neuron is an interneuron within the spinal cord that extends to and transmits nerve signals from the primary neuron to either the tertiary neuron or to the cerebellum. (3) The third neuron is an interneuron within the cerebrum (specifically the primary somatosensory cortex of the parietal lobe). Pathways that lead to the cerebellum do not have a tertiary neuron. 11. The posterior funiculus-medial lemniscal pathway conducts sensory stimuli concerned with proprioceptive (posture and balance) information about limb position and discriminative touch, precise pressure, and vibration sensations.