STRUKTUR & FUNGSI SISTEM SARAF PUSAT

RASHIDDY WONG ABDULLAHPSUK UNIT PP BPL KKM

Copyright 2010, John Wiley & Sons, Inc.

SISTEM SARAF Kawalan tubuh dan jaringan komunikasi adalah

berpusat di sistem saraf.Tiga fungsi utama sistem saraf adalah untuk deria (sensori), integrasi dan motor.

Deria (sensori) bertugas untuk mengesan perubahan di dalam tubuh dan persekitaran luar.

Integrasi pula bertindak untuk mentafsir perubahan. motor memberi respon kepada tafsiran di dalam

bentuk kontraksi otot atau rembesan kelenjar.

Copyright 2010, John Wiley & Sons, Inc.

Struktur dan Fungsi Sistem Saraf

sistem saraf dibahagi kepada dua bhg. Utama. sistem saraf pusat Sistem saraf periferi

Organisasi sistem saraf sangat kompleks Mempunyai 2 jenis sel

- sel neuron dan neuroglia

Neuron terbahagi kepada tiga bahagian: - badan sel- dendrit - akson. # Badan sel - mengandungi nukleus dan neukloleus yang dikelilingi oleh sitoplasma.- berfungsi melakukan proses sintesis bahan-bahan yang diperlukan oleh sel saraf.

Dendrit

# terbina daripada sitoplasma badan sel yang memanjang dan kelihatan bercabang-cabang. - Dendrit bertugas untuk menghantar impuls ke badan sel.

Copyright 2010, John Wiley & Sons, Inc.

Akson satu cuaran yang panjang, nipis&mengkhusus.

Akson bertindak sebagai pembawa impuls dari badan sel keneuron atau tisu lain.

Akson mempunyai panjang yang berbeza mengikut tempatia berada.

Terdapat akson yang diseliputi oleh mielin. Sarung mielin berfungsi untuk meningkatkan

kelajuan perjalanan impuls

Copyright 2010, John Wiley & Sons, Inc.

Spinal Meninges and Spaces

Copyright 2010, John Wiley & Sons, Inc.

Sejenis bahan kimia yang dikenali sebagai neurotransmiter terhasil di hujung saraf apabila neuron menerima rangsangan fizikal atau kimia.

Reseptor akanmenerima neurotransmiter yang menyebabkan berlaku perubahan elektrik dan

mencetuskan potensial aksi.

Sistem Saraf Pusat Pusat kawalan seluruh sistem. Terdiri daripada otak dan korda spina. Sistem saraf pusat menerima semua kederiaan

tubuh melalui reseptor. ditafsir untuk menentukan tindakan yang

perlu diambil. Rangsangan otot untuk berkontraksi kelenjar untuk merembes .

Organisasi Sistem Saraf Organisasi sistem saraf terbahagi kepada

tiga iaitu otak, korda spina dan saraf.

Otak Otak organ yang paling penting di dalam

tubuh manusia. Otak dianggarkan mempunyai berat kira-kira

1.5kg bagi orang dewasa. Otak terletak di dalam rongga kranium dan

merupakan sebahagian sistem saraf pusat. Tisu saraf otak adalah lembut, berwarna

kelabu dan putih .

OTAK

Otak terbahagi kepada empat bahagian utama iaitu batang otak (medula oblongata)

pons dan otak tengah), Diensefalon (talamus dan hipotalamus), serebrum dan serebelum.

(i) Batang Otak Dipanggil sebagai batang otak kerana

bentuknya seperti batang. Batang otak terletak di bahagian bawah

kranium.

Medula Oblongata Berhubung dengan korda spina. Mempunyai panjang kira-kira 3cm dan

dipisahkan dari pons oleh alur horizontal. Terbina daripada jirim putih Pada bahagian posterior bawahnya terdapat

dua nukleus di setiap sisi yang dikenali

sebagai nukleus grasilis dan kuneatus.

Pons Terletak di atas medula. Pons mengandungi jirim putih dan nukleus. Nukleus saraf kranial ke 5 hingga ke 8 dan

nukleus pernafasan berada di pons.

Otak Tengah Terletak di atas pons dan di bawah diensefalon. Dua unjuran iaitu pedunkel dan serebrum

terdapat di permukaan ventralnya. Unjuran ini berhubung dengan serebrum

selepas lencongan ke anterolateral. Empat tuberkel bulat iaitu dua di atas dan dua

dibawah terletak pada permukaan dorsalnya.

(ii) Diensefalon Antara otak tengah dan serebrum. Struktur utamanya- talamus dan hipotalamus. Fungsi talamus adalah sebagai stesen pemancar

untuk impuls deria, ke korteks serebrum. Talamus -pusat untuk mentafsir impuls deria

seperti sakit, suhu, sentuhan dan tekanan. Hipotalamus pula terdiri daripada banyak struktur. hipotalamus - di bawah talamus.

Hipotalamus Hipotalamus - mengawal suhu tubuh dan

aktiviti autonomik organ-organ bahagian dalam.

Selain itu, fungsi yang lain adalah mencetuskan reaksi emosi seperti

ketakutan dan kemarahan. Di hipotalamus juga terdapat pusat

makan, pusat kenyang dan pusat haus.

(iii) Serebrum Bahagian terbesar otak. Ia terbahagi kepada dua hemisfera yang

berwarna kelabu. Kedua-dua hemisfera ini dipercayai Mengawal aktiviti bagi sebelah tubuh sahaja. Deria tubuhsebelah kanan dikawal oleh

hemisfera kiri dan begitulah sebaliknya.

Figure 7.19 The motor nerve pathways: upper and lower motor neurones.

Copyright © Elsevier Ltd 2005. All rights reserved.

Fungsi serebrum adalah terlalu banyak dan kompleks.

Namun secara umum, korteks serebrum terbahagi kepada tiga DOMAIN.

Deria Berfungsi untuk menerima kederiaan dari

kulit, otot dan bahagian dalam tubuh. Ia juga menerima impuls dari berbagai-bagai

deria seperti deria rasa, lihat, hidu, dengar dan sentuh.

PUSAT DERIA

Motor Berfungsi mengawal atur pergerakan otot,

pertuturan dan sebagainya.

Asosiasi Menghubungkan kawasan motor dan deria

melalui traktusnya. Memainkan peranan penting dalam ingatan,

emosi, taakulan,personaliti dan kecerdikan.

(iv) Serebelum Ia merupakan bahagian kedua terbesar otak. Memainkan peranan dalam pergerakan

separa sedar pada otot rangka. Pergerakan separa sedar penting untuk

koordinasi, keseimbangan tubuh dan penetapan kedudukan tubuh.

(b) Korda Spina Korda spina mempunyai kepanjangan kira-

kira 45cm bagi orang dewasa. Kedudukan korda spina adalah bermula dari

dasar tengkorak turun ke bahagian servikal, torasik dan seterusnya ke bahagian lumbar atas.

Korda spina

adalah terdiri daripada segmen-segmen . pada setiap segmen terdapat sepasang

ganglion. Pasangan ganglion tersebut ialah ganglion

akar dorsal dan ganglion akar ventral.

Korda Spina

Pada akar dorsal terdapat akson neuron deria.

Membawa maklumat dari periferi ke korda spina.

Akar ventral mengandungi akson neuron motor visera dan somatik yang mengawal

organ efektor.

Saraf spina pula terbentuk daripada gabungan ganglion akar deria dan akar motor.

Saraf ini dikelaskan sebagai saraf campuran kerana mempunyai kedua-dua serat aferen dan eferen.

Cranial Nerves

12 CRANIAL NERVE

I. Olfactory: special sensory—smellII. Optic: special sensory—visionIII. Oculomotor: motor—control of eye

movementsIV. Trochlear: motor—control of eye

movementsV. Trigeminal: mixed

General sensory: touch, pain, pressure, hot, cold in face

Motor: to muscles used for chewing

VI. Abducens: motor—control of eye movements

VII.Facial: mixed Special sensory (taste) from anterior of tongue Motor to muscles of facial expression, tear

glands, and some salivary glands

VIII.Vestibulocochlear: special sensory—ear

IX. Glossopharyngeal: mixed Sensory for posterior of tongue, pharynx, and

palate; blood pressure Motor to pharyngeal muscles (swallowing),

salivary gland (parotid

X. Vagus: mixed (the major parasympathetic nerve)

Sensory from pharynx, ear, diaphragm, visceral organs in thoracic and abdominal cavities

Motor to palatal and pharyngeal muscles (swallowing and voice); to viscera in thoracic and abdominal cavities

XI. Accessory: motor to voluntary muscles including sternocleidomastoid and trapezius (move head, shoulders)

XII.Hypoglossal: motor to tongue (swallowing and speech)

Cerebrospinal Fluid (CSF)

Formed in the 4 ventricles of brain Lateral (#1 and 2) 3rd 4th ventricle Formed in choroid plexuses

By filtration and secretion of blood plasma In specialized capillary networks (covered by

ependymal cells) in walls of ventricles Pathway

Through 4 ventricles central canal of spinal cord and within subarachnoid space

Reabsorbed through arachnoid villi into blood in superior sagittal sinus

Cushions brain and provides nutrients

Brain Blood Supply and Blood-Brain Barrier Memerlukan 20% keperluan O2 tubuh.

4 min lack kerosakan kekal Memerlukan bekalan glukos secara

berterusan Dilindungi oleh darah-pelindung otak

Allows passage of lipid soluble materials: O2, CO2, alcohol, anesthetic agents

Mengawal kemasukan bahan2 merbahaya

Created by tight capillaries and astrocytes

TAMAT

SEKIAN TERIMA KASIH

Copyright 2010, John Wiley & Sons, Inc.

Gross Anatomy of Spinal Cord

Internal Structure of Spinal Cord Gray matter forms “H” (or “butterfly”)

Three horns on each side; sites of cell bodies Posterior gray horns: contain sensory neurons Anterior gray horns: contain somatic motor neurons Lateral: contain autonomic motor neurons

White matter (surrounds gray “H”) Consists of white columns

Posterior, anterior, and lateral columns Contain tracts (bundles of axons)

Sensory tracts: ascending to brain Motor tracts: descending from brain

Internal Structure of Spinal Cord

Spinal Nerves 31 pairs

Named according to level of vertebra C1-C8, T1-T12, L1-L5, S1-S5, 1 coccygeal Emerge from spinal cord through intervertebral

foramina

Nerves attached to spinal cord by 2 roots Dorsal root: made of axons of sensory neurons

Dorsal root ganglion: swelling containing cell bodies of sensory neurons

Ventral root: composed of axons of motor neurons Both somatic motor and autonomic motor

Spinal Nerve Composition Formed by 2 spinal nerve roots Are mixed:

Formed from dorsal root (sensory) and ventral root (motor) root

Connective tissue coverings Individual axons wrapped in endoneurium Axons grouped in fascicles wrapped in

perineurium Outer covering = epineurium

Spinal Nerve Composition

Distribution of Spinal Nerves Spinal nerves branch after pass through

intervertebral foramina Some join with branches from neighboring

nerves to form plexuses Nerve names relate to region innervated Spinal nerves T2-T12 do not form plexuses

Called intercostal nerves Supply abdominal muscles, skin of chest and

back, and muscles between ribs.

Plexuses Cervical plexus

Supplies posterior head, neck, shoulders, and diaphragm

Important nerves: phrenic to diaphragm Brachial plexus

Supplies upper limbs + some neck and shoulder muscles

Important nerves: radial, ulnar, axial, median to arm, forearm, hand

Plexuses Lumbar plexus

Supplies abdominal wall, external genitalia, and part of lower limbs

Important nerves: femoral (to anterior thigh: quads)

Sacral plexus Supplies buttocks, perineum, and most of lower

limbs Important nerves: gluteal, sciatic (to posterior

thigh and all of leg and foot)

Spinal Cord

Spinal Cord Functions Pathways for nerve impulses within tracts

Ascending (sensory). Example: spinothalamic Descending (motor). Example: corticospinal

Reflexes: fast, involuntary sequences of actions in response to stimuli Can be simple (withdrawal) or complex (learned

sequence such as driving car) Levels

Spinal (reflex arc): simple Cranial: more complex

Reflex Arc1. Sensory receptor: responds to stimulus

2. Sensory neuron: through dorsal root ganglion and root posterior horn

3. Integrating center: single synapse between sensory and motor neurons

4. Motor neuron: from anterior horn ventral root spinal nerve

5. Effector: muscle responds

Example of Reflex Arc: Patellar Reflex1. Sensory receptor is stimulated by tap on

patellar tendon

2. Sensory neuron: through dorsal root spinal cord

3. Integrating center: single synapse in spinal cord

4. Motor neuron: through ventral root spinal nerve femoral nerve

5. Effector: quads contract, extend leg

Example of Reflex Arc: Patellar Reflex

Brain: Major Parts Brain stem: continuous with spinal cord

Medulla oblongata, pons, midbrain Diencephalon: superior to brain stem

Thalamus, hypothalamus, and pineal gland Cerebrum: largest part and most superior

Surface covered with gray matter: cortex Deep to cortex is cerebral white matter

Cerebellum: posterior and inferior Means “little brain”

Cranial meninges: dura mater, arachnoid mater, and pia mater

Brain: Major Parts

Brain: Major Parts

Brain Blood Supply and Blood-Brain Barrier Requires 20% of the body’s O2 supply

4 min lack permanent damage Requires continuous glucose supply Protected by blood-brain barrier

Allows passage of lipid soluble materials: O2, CO2, alcohol, anesthetic agents

But controls entry of most harmful materials

Created by tight capillaries and astrocytes

Cerebrospinal Fluid (CSF) Formed in the 4 ventricles of brain

Lateral (#1 and 2) 3rd 4th ventricle Formed in choroid plexuses

By filtration and secretion of blood plasma In specialized capillary networks (covered by ependymal

cells) in walls of ventricles Pathway

Through 4 ventricles central canal of spinal cord and within subarachnoid space

Reabsorbed through arachnoid villi into blood in superior sagittal sinus

Cushions brain and provides nutrients

Cerebrospinal Fluid (CSF)

Brain Stem: Medulla Oblongata Most inferior part of brainstem

White matter connects spinal cord and other parts of brain

Contains vital nuclei Cardiovascular center

Regulates heart rate, blood pressure Medullary rhythmicity area

Adjusts respiratory rhythm Other sensory and reflex motor areas Cranial nerves VIII-XII attached here

Brain Stem: Pons Serves as a “bridge”

Connects medulla to midbrain and above Contains ascending and descending tracts Connects left and right sides of cerebellum

Contains nuclei Motor relays from cerebrum to cerebellum Helps control breathing Cranial nerves V-VIII attached here

Brain Stem

Brain Stem: Midbrain Connects pons to diencephalon

Large tracts: cerebral peduncles Nuclei:

Substantia nigra: related to Parkinson disease Red nuclei: help coordinate movements Origin of cranial nerves III and IV (control eye

movements) Superior colliculi: nuclei involved in

Scanning eye movements Responses to visual stimuli

Inferior colliculi: responses to auditory input

Reticular Formation Netlike arrangement of gray and white matter Contains ascending and descending tracts Ascending part = reticular activating system

(RAS) Carries sensory pathways to cerebral cortex Helps maintain consciousness Helps induce sleep

Reticular Formation

Diencephalon Thalamus: major sensory relay center

Also motor, autonomic, and consciousness functions

Hypothalamus: lies inferior to thalamus Control of pituitary and hormone production Works with ANS regulating many viscera Involved with feelings and behavior patterns Regulation of eating, drinking, fluid levels Control of body temperature Regulation of circadian rhythms, sleep, waking

Pineal gland: secretes melatonin Controls sleep, biological clock

Diencephalon

Cerebellum Location: posterior to medulla and pons,

inferior to cerebrum Attached to brain stem by cerebellar peduncles

Structure: Two cerebellar hemispheres Cerebellar cortex: gray matter Tree-like appearance (seen in sagittal section) of

white matter and gray nuclei

Cerebellum Functions

Receives wide range of sensory input from muscles, joints, tendons, eyes, inner ears

Compares actual movements with intended ones Helps produce smooth, coordinated movements Helps execute skilled motor activities Regulates posture and balance

Cerebrum: Structure Cerebral cortex Internal white mater Deep gray nuclei Surface folds of cerebral cortex: gyri Grooves between gyri: sulci Longitudinal fissure: divides cerebrum into

left and right hemispheres Hemispheres connected by corpus collosum

Cerebrum: Structure

Each hemisphere has 4 lobes Frontal, parietal, temporal, occipital Central sulcus separates frontal, parietal Precentral gyrus anterior to sulcus: primary motor

area Postcentral gyrus: primary somatosensory area

Deep gray nuclei: basal ganglia Globus pallidus, putamen, caudate nucleus

Cerebrum

Cerebrum

Limbic System Ring of structures on inner border of

cerebrum and floor of diencephalon Called “emotional brain”: plays primary role in

pain, pleasure, anger, affection and in behavior

Involuntary activity related to survival Important in memory development

Limbic System

Functional Areas of Cerebral Cortex Specialized areas in specific regions of

cerebral cortex Sensory areas receive input perception Motor areas initiate movements Associative areas complex integration:

memory, emotion, reasoning, judgment

Sensory Areas Primary somatosensory area: postcentral

gyrus Input includes: touch, proprioception, pain, itching, tickle,

temperature

Primary visual area: occipital lobe Primary auditory area: temporal lobe Primary gustatory (taste) area: base of

postcentral gyrus Primary olfactory (smell) area: medial

aspect of temporal lobe

Motor Areas Located anterior to central sulcus Primary motor area: precentral gyrus Broca’s speech area

Interacts with premotor area and primary motor area to regulate breathing and speech muscles

Is in left hemisphere in 97% of persons

Association Areas Adjacent to sensory and motor areas and

connected via association tracts Integrate and interpret information Examples

Somatosensory association area Posterior to primary somatosensory area Integrates sensation: exact shape and texture of object

compared with stored memories Wernike’s area: left temporal, parietal lobes

Interprets meaning of speech: words thoughts Right hemisphere adds emotional content

Cerebrum: Functional Areas

Somatic Sensory Pathways Relay sensory information from periphery to

cerebral cortex 3 neurons in each pathway

Cell body #1 in dorsal root ganglion Cell body #2 in spinal cord or brain stem Cell body #3 in thalamus; axon extends to

cerebral cortex (somatosensory area in postcentral gyrus)

Most sensory input to right side of body reaches left side of brain (and vice versa)

Somatic Sensory Pathways Posterior column - medial lemniscus pathway

senses Fine touch: body location, texture, size Proprioception: position and motion of body parts Vibrations: fluctuating touch stimuli

Spinothalamic pathways Anterior and lateral spinothalamic tracts Relay impulses for pain, tickle, itch, hot, and cold

sensations

Somatic Sensory Pathways

Somatic Motor Pathways Signals come from

Upper motor neurons: via corticospinal tracts Basal ganglia: help with muscle tone Cerebellum: coordination Sensory neurons or interneurons via reflexes

Impulses activate lower motor neurons Cell bodies in anterior gray of spinal cord Axons ventral root spinal nerve muscle

voluntary movements

Somatic Motor Pathways

Somatic Sensory and Motor PathwaysInteractions Animation

Somatic Sensory and Motor Pathways

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Lateralization Brain controls opposite side of the body: all

sensory and motor pathways cross in CNS Left side of the brain controls right side of body Right side of brain controls left side of body

Left hemisphere important for spoken and written language, numerical and scientific skills, and reasoning

Right side more involved with spatial and pattern recognition and emotional content

Memory Process for storing and retrieving information Involves structural and functional changes Involves association areas, parts of limbic

system, and diencephalon Skill memory also involves cerebellum and

basal ganglia

Cranial Nerves (Table 10.2)

I. Olfactory: special sensory—smellII. Optic: special sensory—visionIII. Oculomotor: motor—control of eye

movementsIV. Trochlear: motor—control of eye movementsV. Trigeminal: mixed

General sensory: touch, pain, pressure, hot, cold in face

Motor: to muscles used for chewing

Cranial NervesVI. Abducens: motor—control of eye

movementsVII.Facial: mixed

Special sensory (taste) from anterior of tongue Motor to muscles of facial expression, tear

glands, and some salivary glands

VIII.Vestibulocochlear: special sensory—ear

Cranial Nerves

IX. Glossopharyngeal: mixed Sensory for posterior of tongue, pharynx, and

palate; blood pressure Motor to pharyngeal muscles (swallowing),

salivary gland (parotid

Cranial Nerves

X. Vagus: mixed (the major parasympathetic nerve)

Sensory from pharynx, ear, diaphragm, visceral organs in thoracic and abdominal cavities

Motor to palatal and pharyngeal muscles (swallowing and voice); to viscera in thoracic and abdominal cavities

Cranial Nerves

XI. Accessory: motor to voluntary muscles including sternocleidomastoid and trapezius (move head, shoulders)

XII.Hypoglossal: motor to tongue (swallowing and speech)

Aging Rapid brain growth during first few years of

life Due to increase in size of neurons and

proliferation of neuroglia Increase in development of dendritic branches

and synaptic contacts

From early adulthood through old age: Decline in brain mass Fewer synaptic contacts brain function Some decrease in brain function