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The Central Nervous System 中樞神經系統

本章重點: •中樞神經系統的基本組成與功 能 •大腦分葉與功能區介紹 •間腦、腦幹、小腦位置與功能 •脊髓的基本構造與功能 •神經傳導路徑

授課老師 : 解剖學科 白滿惠 學校分機:3262

Email:pai0507@tmu.edu.tw


Central nervous system (CNS) 中樞神經系統

Brain Spinal cord


Spinal cord

脊鍓

- is located within the vertebral canal of the vertebral column - 5 Spinal cord segments : (cervical, thoracic, lumbar, sacral, and coccygeal segments) - Functions : 1. highway for upward and downward travel of sensory and motor information 2. spinal cord reflexes 3. integration nerve impulses


Spinal cord

L2

•Extend from the medulla oblongata to the superior border of the 2nd lumbar vertebrae (42~45cm long; 3/4 inch diameter) •Growth of cord stops at age 5 •2 enlargements : 1. Cervical enlargement (for upper limbs ;C4~T1) 2. Lumbar enlargement (for lower limbs;

T9~T12)


Structures Covering the Spinal Cord • (bony) Vertebral column • Epidural space filled with fat • Dura mater – dense irregular CT tube • Subdural space filled with interstitial fluid • Arachnoid : spider web of collagen fibers • Subarachnoid space : filled CSF • Pia mater – thin layer covers blood vessels – denticulate ligaments


External Anatomy of Spinal Cord •Conus medullaris (圓椎) –cone-shaped end of spinal cord •Filum terminale(終絲) –thread-like extension of pia mater –stabilizes spinal cord in canal •Caudae equinae (馬尾) –dorsal & ventral roots of lowest spinal nerves


Spinal tap or Lumbar Puncture脊髓穿刺 • Technique –long needle into subarachnoid space –safe from L3 to L5 • Purpose –sampling CSF for diagnosis –injection of antibiotics, anesthetics or chemotherapy –measurement of CSF pressure


Inner Structures of Spinal Cord

- H-shaped gray matter, central canal and outer white matter - gray matter : Ventral horn, Gray commissure and Dorsal horn - white matter : anterior, posterior and lateral faniculus ; Ascending and descending tracts


Ascending tracts


Descending tracts


The Brain

• A portion of CNS contained within the cranium 頭顱 • Largest organ in the body at almost 1300~1500g • 4 Principal Parts of the Brain 1. Cerebrum 大腦 (cerebral hemispheres) 2. Diencephalon 間腦 3. Cerebellum 小腦 4. Brain stem- medulla, pons and midbrain


Protective Coverings of the Brain epidural space

• Skin, periosteum, skull, epidural space, meninges & fluid (CSF) • Meninges 腦膜 : 1.dura mater硬腦膜 –2 layers of dense irregular CT subdural space (subdural hematoma) 2.arachnoid mater 蜘蛛膜 –arachnoid trabeculae subarachnoid space 3.pia mater 軟腦膜 –areolar CT (highly vascularized)


Crainal dural septa

•Dural septa (double layer) - provide stabilization and support

1. falx cerebri大腦鎌 (the largest) - projects into longitudinal fissure and separates left and right cerebral hemispheres. - crista galli; internal occipital crest 2. tentorium cerebelli 小腦天幕 - separates cerebrum from cerebellum - tentorial notch 3. falx cerebelli小腦鎌 - divides the left and right cerebellar hemishperes


Dura venous sinus

•Dura sinus - large blood-filled spaces are formed by fused periosteal and meningeal layers of dura mater - no valves - transport blood to the internal jugular vein

1. Superior sagittal sinus

- runs within the superior margin of the falx cerebri.

2. Inferior sagittal sinus

-runs within the inferior margin of the falx cerebri.

3. Transverse sinuses

- run within the posterior border of the tentorium cerebelli.

4. Occipital sinus

- runs in the posterior border vertical border of the falx cerebelli.


Ventricular system

腦室系統

•Cerebrospinal Fluid 大腦脊髓液 (CSF) -filled cavity •Lateral ventricles ,3rd ventricle ,Cerebral aqueduct, 4th ventricles and central canal Functions : 1. mechanical protection : floats brain & softens impact with bony walls 2.chemical protection : optimal ionic concentrations for action potentials 3. Circulation : nutrients and waste products to and from bloodstream


Cerebrospinal Fluid 大腦脊髓液 (CSF) •80-150 ml (3-5oz) •Clear liquid containing glucose, proteins, & ions •Choroids plexuses (networks of capillaries) form the CSF •Reabsorbed through arachnoid villi (grapelike clusters of arachnoid penetrate dural venous sinus)

Hydrocephalus水腦症

• 20 ml/hour reabsorption rate = same as production rate


Flow of Cerebrospinal Fluid


Cerebrum

大腦

(Cerebral Hemispheres)

•the largest part of the brain (about 83%) •grew so quickly formed folds (gyri腦回) and grooves (sulci or fissures腦溝) increase the area of cerebral cortex •Longitudinal fissure separates left & right cerebral hemispheres


5 Lobes and major Fissures 腦島

額葉

頂葉 顳葉

枕葉

•Deeper sulci or fissures divide cerebrum into lobes •Central sulcus 中央溝, Parieto-occipital sulcus, Lateral sulcus 外側溝 •5 lobes : Frontal lobe 額葉, Parietal lobe 頂葉, Occipital lobe 枕葉, Temporal lobe 顳葉, Insula 腦島(deep within the lateral sulcus) •Lobes are named for the skull bones overlying them


5 Cerebral lobes

額葉

頂葉

腦島 顳葉

枕葉 小腦


Cerebral lobes

Frontal lobe •Located deep to the frontal bone •forms anterior part of the cerebral hemisphere. •Involved with voluntary motor function, concentration, verbal communication, decision making, planning, and personality.

Parietal lobe

•Forms the superoposterior part of each hemisphere •underlies the parietal bone. •Terminates posteriorly at the parieto-occipital sulcus. •Involved with general sensory functions.


Cerebral lobes

Temporal lobe •Located inferior to the lateral sulcus underlying the temporal bone. •Involved with hearing and smell

Occipital lobe •Located in the posterior region of each hemisphere underlying the occipital bone. •Processes incoming visual information. •Stores visual memories.


Insula

• Located deep to the lateral sulcus. • Involved in memory and interpretation of taste.


Cerebral Hemispheres

- is composed of gray matter, white matter and gray matter nuclei within the white matter 1. Cerebral cortex 大腦皮質 (灰質,神經細胞體所在之處; 1800cm2) - The home of conscious mind (sensations, voluntary movements, communicate, remember, and understand) 2. Cerebral white matter 大腦白質 (神經纖維所在之處) 3. Deep gray matter of the cerebrum ( ex. basal ganglia基底核)


Cerebral cortex

(40% of the total mass of the brain)

- the superficial gray matter layer of the cerebrum - is only 2~4 mm thick - contain neuron cell bodies細胞本 體, dendrites樹突, and very short unmyelinated axons軸突 - Most have 6 layers (neocortex 新皮質) - The home of conscious mind (sensations, voluntary movements, communicate, remember, and understand)


Functional areas of cerebral cortex - Brodmann classification (德國 1909) : 52 areas - 1990 : PET and fMRI (functional neuroimaging techniques)

- is considered to be made up of 1. motor area (M)運動區 2. sensory area (S)感覺區 3. association area (As) 聯合區 - mediate higher mental functions

鼴鼠


Location of Major functional areas

Motor cortex (M) : part of the precentral gyrus Somatsensory cortex (S) : occupies postcentral gyrus Visual cortex (V) : the banks of calcarine sulcus Auditory cortex (Au) : the transverse temporal gyrus


Motor Areas of Cerebral Cortex 運動區

•most motor cortex are in the frontal lobe •Function : Voluntary motor initiation

額葉

1. Primary motor area (4) : precentral gyrus • is the thickest cortex in the brain • controls voluntary contractions of skeletal muscles on other side 2. Motor speech area (44; 45) : Broca’ s area • production of speech - control of tongue & airway • 97% of the population are localized in the left hemisphere (dominant hemisphere) http://www.youtube.com/watch?v=12dO78c6-q8 (Broca’s aphsia)


Sensory Areas of Cerebral Cortex - sensory impulses arrive mainly in the posterior part of each hemisphere

–Receive sensory information from the thalamus Primary somatosensory area (postcentral gyrus) : area 3,1,2 Primary visual area (17) : receive impulses that convey visual information 視覺區 Primary auditory area (41, 42) :interpret the pitch and rhythm 聽覺區 Primary gustatory area (43) : receive impulses for taste 味覺區


Somatotopy

體位分層

* Highly discriminating or finely controlled parts of the body have disproportionately large representations


Association Areas of Cerebral Cortex

• Somatosensory area (5 & 7) : integrate & interpret • Visual association area (18 & 19) :recognize & evaluate • Auditory association area(22): words become speech • Premotor area (6) : learned skilled movements such as typing • Frontal eye field (8) : scanning eye movements


Functions of the Cerebral Cortex • Frontal lobe – Motor area – Speech centers • Parietal lobe – Sensory area – Estimation of distances, sizes, shapes • Temporal lobe – Auditory area – Olfactory area • Occipital lobe – Visual receiving area – Visual association area


Functions of the Cerebral Cortex


Cerebral White Matter 大腦白質

•underlying the cortex consist of axons organized into tract 1. Association fibers between gyri in the same hemisphere 2. Commissural fibers from one hemisphere to other 3. Projection fibersform descending & ascending tracts •Corpus callosum胼胝體 is band of white matter connecting left and right cerebral hemispheres


Cerebral White Matter


Deep Gray Matter of the Cerebrum

1.Basal ganglia 基底神經核- involved in motor control 2.Basal forebrain nuclei - associated with memory, learning 3.Claustrum殼核 - a nucleus of unknown function 4.Amygdala 杏仁體- located in cerebrum but is considered part of the limbic system


Basal ganglia

基底核

•Consists of Caudate nucleus and lentiform nucleus (putaman, golbus pallidus) •Input & output with cerebral cortex, thalamus & hypothalamus •Control large automatic movements of skeletal muscles (start, stop and regulate movement)

•degeneration of basal nuclei  Dyskinesia 運動困難 •Parkinson’ s disease(英國1817); Huntington’ s disease(美國1872) •http://www.nhs.uk/news/2009/10October/Pages/Gout-chemical-and-Parkinsons.aspx (Parkinson’ s disease) •http://www.nhs.uk/Conditions/Huntingtons-disease/Pages/Introduction.aspx (Huntington’ s diease)


Limbic System邊緣系統

• is a ring of structures on the inner border of the cerebrum and floor of the diencephalons • Encircles the upper part of the brain stem and the corpus callosum • Contents : Olfactory bulb, fornix, parahippocampal, cingulate gyri, hippocampus(memory), amygdala (fear), hypothalamus, anterior thalamic nuclei,,,,,


Functions of The limbic system - operates by influencing the endocrine system and the autonomic nervous system

1. 扣帶回(cingulate gyri) :調整心 跳、血壓,以及處理認知及注意力 的自律功能。 2. 穹隆(Fornix):把訊號由海馬體傳 至乳頭狀體(mammillary bodies)及 中隔內核(septal nuclei)。 3. 下視丘(Hypothalamus):經由激素 的產生及釋放,使自律神經系統變 得規律(Circadian rhythm) 。影響 及調整心跳、血壓、飢餓、口渴、 性刺激及睡眠 。 4. 丘腦(thalamus):大腦皮質的「中 轉站」。

• is also called Emotional brain : pain, pleasure, anger, affection


Cerebellum小腦 (11% of the brain mass)

•is posterior to the medulla and pons and inferior to the cerebrum •Transverse fissure between cerebellum & cerebrum •Consists of 2 cerebellar hemispheres (divided into 3 part : anterior 前葉and posterior lobes後葉, flocculonodular lobe小葉結狀葉)

and

vermis 蚓部(central area) •Function : Coordinate skilled movements and regulate posture and balance


Cerebellum Cerebellar cortex 分子層

蒲金氏細胞層 顆粒層

• Gray matter: Cerebellar cortex (folia) & deep cerebellar nuclei - is made up of 3 layers : molecular layer, purkinje cells layer, and granular layer • White matter : Arbor vitae 小腦活樹 - All fibers enter and leave the cerebellum are ipsilateral (Run to and 同側 from the same side of the body )


Cerebellar Peduncles小腦腳 Connect the midbrain to the cerebellum Connect the pons to the cerebellum

Connect the medulla oblongata to the cerebellum

• Superior, middle & inferior peduncles attach to brainstem – Superior : carries motor fibers that extend to motor control areas – middle : carries sensory fibers from cerebral cortex & basal ganglia – inferior : carries sensory information from spinal cord


Diencephalon間腦

•Forms the central core of forebrain and surround 3rd ventricle •is surrounded by the cerebral hemisphere •Extend from the brain stem to the cerebrum includes thalamus(superior), hypothalamus(inferior), epithalamus, and subthalamus


丘腦

Thalamus

(egg shaped; 80%) •1 inch long mass of gray mater in each half of brain and connected across the 3rd ventricle by interthalamic adhesion •form the superlateral walls of the 3rd ventricle •contain many thalamic nuclei - receives impulses from cerebellum or basal ganglia •principal relay station for sensory information on way to cortex


Thalamic nuclei


Hypothalamus 下丘腦

• is inferior to the thalamus • contain about a dozen nuclei of gray matter • Pituitary gland : the master endocrine gland • is the main visceral control center (control and integrate the ANS)


Hypothalamus


Functions of Hypothalamus • Controls and integrates activities of the ANS which regulates smooth, cardiac muscle and glands • Synthesizes regulatory hormones that control the anterior pituitary • Contains cell bodies of axons that end in posterior pituitary where they secrete hormones • Regulates rage, aggression, pain, pleasure & arousal • Feeding, thirst & satiety centers • Controls body temperature • Regulates daily patterns of sleep • Major regulator of homeostasis


Epithalamus 上丘腦

•Forms part of the roof of the 3rd ventricle Pineal gland松果腺 –endocrine gland the size of small pea –secretes melatonin 褪黑激素 during darkness –promotes sleepiness & sets biological clock


Subthalamus

丘腦下核

–small area just inferior to thalamus –work with basal ganglia, cerebrum & cerebellum to help control body movements


Brain stem腦幹 •between the spinal cord and the diencephalon •lie in the posterior cranial fossa of the skull •act as passageway for all the fiber tracts •Consist of midbrain, pons, and medulla oblongata


Midbrain 中腦 • One inch in length • Extends from pons to diencephalon • Cerebral aqueduct (大 腦導水管)connects 3rd ventricle above to 4th ventricle below


Cross section of Midbrain 1. Cerebral peduncles - clusters of motor & sensory fibers 2. Substantia nigra - helps controls subconscious muscle activity 3. Red nucleus - rich blood supply & iron-containing pigment - cortex & cerebellum coordinate muscular movements by sending information here from the cortex and cerebellum


Dorsal Surface of Midbrain

4. Superior cerebellar peduncles connect the midbrain to the cerebellum 5. Corpora quadrigemina = superior & inferior colliculi – coordinate eye movements with visual stimuli(superior) – coordinate head movements with auditory stimuli(inferior)


Pons

橋腦

• One inch long • White fiber tracts ascend and descend • Pneumotaxic & apneustic areas help control breathing • Middle cerebellar peduncles carry sensory info to the cerebellum • Cranial nerves 5 ~ 7


延髓

Medulla Oblongata • Continuation of spinal cord • Cardiovascular center – force & rate of heart beat – diameter of blood vessels

• Respiratory center – sets basic rhythm of breathing

• Information in & out of cerebellum • Reflex centers for coughing, sneezing, swallowing etc


Ventral Surface of Medulla Oblongata

錐體交叉

1. Pyramids –large motor tract –decussation of most fibers • left cortex controls right muscles 2. Olive –Inferior olivary nucleus –send sensory input to cerebellum –proprioceptive signals –gives precision to movements


Dorsal Surface of Medulla Oblongata

•Nucleus gracilis 薄核& nucleus cuneatus 楔狀核

–transmit sensory impulses from skin and proprioceptors –relay information to thalamus on opposite side of brain

•5 cranial nerves arise from medulla -- 8 ~ 12


Reticular Formation • Run through the central core of the brain stem • Consist loosely clustered nuclei within the white matter • Reticular activating system (網狀活化系統) –alerts cerebral cortex to sensory signals (sound of alarm, flash light, smoke or intruder) to awaken from

sleep –maintains consciousness & helps keep you awake with stimuli from ears, eyes, skin and muscles • Motor function is involvement with maintaining muscle tone


Central nervous system


參考書目 : 1. McKinley and O'Loughlin : Human Anatomy. (2nd ed.) 2. Memmler's Structure and function of human body. 9th ed. 3. Tortora GJ : Principles of Human Anatomy. 11th ed. New York: Harper Collins Co. 4. Marieb and Mallatt : Human Anatomy 5th ed. Benjamin /Cummings Co.


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