2.1 struktur & fisiologi sistem saraf pusat
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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