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Central Nervous System, Spinal Nerves, And Cranial Nerves

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Chapter 10 Spinal Cord Structure Protection and Coverings Spinal cord in vertebral cavity- Surrounded by bone Wrapped in meninges- 3 layers of connective tissue ... – PowerPoint PPT presentation

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Title: Central Nervous System, Spinal Nerves, And Cranial Nerves


1
Central Nervous System, Spinal Nerves, And
Cranial Nerves
  • Chapter 10

2
Spinal Cord StructureProtection and Coverings
  • Spinal cord in vertebral cavity-
  • Surrounded by bone
  • Wrapped in meninges-
  • 3 layers of connective tissue
  • Spinal cord meninges are continuous with brain
    meninges

3
Spinal Meninges
  • Epidural space lined with fat
  • Dura mater- tough ,dense connective tissue
  • Extends to 2nd sacral vertebra
  • Well beyond spinal cord
  • Arachnoid mater- collagen and elastic fibers
  • Subarachnoid space-
  • cerebral spinal fluid circulates in this space
  • Pia mater- transparent layer
  • adheres to surface of brain spinal cord
  • Contains blood vessels

4
Figure 10.1
5
Gross Anatomy Of Spinal Cord
  • runs to 2nd lumbar vertebra
  • Roots of spinal nerves for lumbar, sacral
    coccygeal nerves in vertebral cavity before
    leaving Cauda Equina
  • Enlargements cervical lumbar
  • Include nerves for upper lower limbs
  • Each spinal segment gives rise to a spinal nerve
    31 pairs

6
Figure 10.2
7
Internal Structure Of Spinal Cord
  • Two grooves- left right halves
  • Anterior median fissure posterior median sulcus
  • Gray matter- 3 horns on each side
  • Anterior, posterior, lateral
  • Anterior- somatic motor neurons
  • Posterior- sensory neurons
  • Lateral- autonomic motor neurons

8
Internal Structure Of Spinal Cord (cont)
  • White matter- organized into columns
  • Anterior, posterior lateral white columns
  • Each column contains one or more tracts having a
    common destination
  • Sensory ascending tracts
  • Carry information toward brain
  • Motor descending tracts
  • Carry information down spinal cord

9
Figure 10.3
10
Spinal Nerves
  • Serve particular area of body
  • Contain 2 bundles of axons roots
  • Dorsal root- only sensory axons
  • Swelling called dorsal root ganglion
  • Contains Cell bodies of sensory neurons
  • Ventral root- axons of somatic autonomic motor
    neurons

11
Spinal Nerves (cont)
  • Named and numbered according to level of vertebra
    they emerge from
  • C1-8, T1-12, L1-5, S1-5 1 coccygeal
  • C1 from above atlas
  • Rest through intervertebral foramina

12
Spinal Nerve Composition
  • Roots unite to form nerve at foramina
  • Mixed sensory motor axons
  • Each axon wrapped in endoneurium
  • Axons grouped in fascicles wrapped in perineurium
  • Outer covering epineurium

13
Figure 10.4
14
Distribution Of Spinal Nerves
  • After leaving vertebra nerves branch
  • Some join with axons from neighboring nerves to
    form plexuses
  • Names then relate to area they are in or region
    innervated
  • Spinal nerves T2-T11 do not form plexuses
    intercostal nerves
  • Supply abdominal muscles, skin of chest back
    and muscles between robs.

15
Plexuses
  • Cervical plexus- posterior head, neck, shoulders
    diaphragm
  • Brachial plexus-upper limbs some neck
    shoulder muscles
  • Lumbar plexus- abdominal wall, external genitals
    part of lower limbs
  • e.g. ilioinguinal, femoral, obdurator nerves
  • Sacral plexus- buttocks, perineum lower limbs
  • e.g. Gluteal, sciatic pudendal nerves

16
Figure 10.2
17
Spinal Cord Functions
  • Routes signals along pathways
  • Gray matter integrates signals
  • Reflex fast involuntary sequence of actions in
    response to a stimulus
  • Inborn reflex e.g. withdrawal reflex
  • Can also have learned reflexes,
  • e.g. driving skills
  • Can be spinal or cranial integration

18
Reflex arc (patellar reflex)
  • Sensory receptor- responds to stimulus
  • Tap below patella
  • Sensory neuron- to dorsal horn brain
  • Integrating center- e.g. single synapse
  • Sensory to motor neurons
  • Motor neuron- from center to effector
  • Via ventral horn
  • Effector- responder (muscle or gland)
  • Patellar reflex- rectus femoris contracts

19
Figure 10.5
20
Brain-major parts
  • Brain stem- continuous with spinal cord
  • Medulla oblongata, pons, midbrain
  • Diencephalon- above brain stem
  • Thalamus, hypothalamus pineal gland
  • Cerebrum- at top and largest part
  • Surface covered with gray matter- cortex
  • Beneath is cerebral white matter
  • Cerebellum- back of brain stem
  • Means little brain
  • Cranial meninges- dura mater, arachnoid mater
    pia mater

21
Figure 10.6a
22
Figure 10.6b
23
Brain blood supply
  • Requires 20 bodys oxygen supply
  • 4 min lack gt permanent damage
  • Requires continuous glucose supply
  • Protected by Blood-brain barrier
  • Allows lipid soluble materials O2, CO2, alcohol,
    anesthetic agents but controls entry of other
    materials
  • Created by tight capillaries and glial cells

24
Cerebral Spinal Fluid (CSF)
  • Circulates through ventricles of brain and the
    subarachnoid space.
  • 4 ventricles 2 lateral, third fourth
  • Formed in choroid plexuses
  • Specialized capillary networks in wall of
    ventricles covered by ependymal cells
  • Flows through ventricles then from 4th to
    central canal of spinal cord subarachnoid cells
  • Reabsorbed through arachnoid villi into superior
    saggital sinus

25
Figure 10.7
26
Brain Stem- Medulla
  • Medulla Oblongata- inferior part of brainstem
  • white matter extending between spinal cord
    other parts of brain
  • several nuclei cardiovascular center
  • (heart rate)
  • Medullary rhythmicity area
  • (respiratory rhythm)
  • Other sensory reflex motor areas
  • Some related to cranial nerves

27
Brain Stem- Pons
  • Pons (bridge)- nuclei tracts
  • Connect left right of cerebellum
  • Ascending descending tracts
  • Nuclei motor relays from cerebrum to cerebellum
    , respiration cranial nerves V, VI, VII, VIII

28
Figure 10.8
29
Brain Stem- Midbrain
  • Connects pons to Diencephalon
  • Large tracts cerebral peduncles (motor)
  • Nuclei substantia nigra, red nuclei, cranial
    nerves III IV
  • Superior colliculi nuclei involved in tracking
    visual stimuli
  • Inferior colliculi auditory input startle
    reflex

30
Reticular formation
  • Netlike arrangement of gray and white mater
  • Ascending part Reticular Activating System
    (RAS)
  • Projects to cerebral cortex helps maintain
    consciousness
  • Inactivation gt sleep

31
Figure 10.9
32
Diencephalon
  • Thalamus- critical relay for sensory input
  • Transmits motor information from cerebellum
    basal nuclei to cerebrum
  • Hypothalamus- important for homeostasis
  • Control of ANS-regulation of many activities
  • Control of pituitary and hormone production
  • Regulation of emotional behavior patterns
  • Regulation of eating drinking
  • Control of body temperature
  • Regulation of circadian rhythms states of
    consciousness
  • Pineal gland- secretes melatonin

33
Figure 10.10
34
Cerebellum
  • Two cerebellar hemispheres
  • Posterior to medulla and pons, below cerebrum
  • Cerebellar cortex gray matter
  • Tree like white matter nuclei
  • Attached to brain stem via cerebellar peduncles

35
Cerebellar function
  • Gets wide range of sensory input
  • Compares with programmed motor activity from
    cerebral cortex
  • Smoothes coordinates complex activities
  • Regulates posture balance
  • Required for skilled motor activities

36
Cerebrum- Structure
  • Cerebral cortex
  • Internal white mater
  • Deep gray nuclei
  • Surface folds gyri
  • Grooves between sulci
  • Longitudinal Fissure- divides it into left
    right hemispheres
  • Connected by corpus collosum

37
Cerebrum- Structure (cont)
  • 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 sensory area
  • Deep gray basal nuclei (basal ganglia)
  • Globus palladus, putamen, caudate nucleus

38
Figure 10.11a
39
Figure 10.11b
40
Limbic System
  • Ring of structures on inner border of cerebrum
    and floor of diencephalon
  • emotional brain pain , pleasure, anger,
    affection, docility
  • Involuntary activity related to survival
  • Important in memory development

41
Figure 10.12
42
Function areas of Cortex
  • Specialized areas anatomically located
  • Sensory areas receive input and responsible for
    perception
  • Motor areas- initiate movements
  • Associative areas- complex integration e.g.
    memory, emotion, reasoning, etc.

43
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 area base of postcentral
    gyrus
  • Primary olfactory area- medial aspect of temporal
    lobe

44
Motor Areas
  • Mainly from anterior part of hemisphere
  • Primary motor area- precentral gyrus
  • Brocas speech area-
  • interacts with premotor area primary motor area
    to regulate breathing and speech muscles

45
Association Areas
  • Adjacent to sensory motor areas
  • connected with tracts- interpret information
  • E.g. somatosensory association area
  • Posterior to primary somatosensory area
  • Integrates sensation- exact shape texture of
    object compares with stored memories
  • Wernikes area- left temporal parietal lobes
  • Interprets meaning of speech
  • Right hemisphere adds emotional content

46
Figure 10.13
47
Sensory Pathways
  • Relay information from periphery to cerebral
    cortex
  • 3 neurons in each pathway.
  • Posterior column- medial lemniscus pathway
  • Fine touch- body location, texture, size
  • Proprioception- position motion of body parts
  • Vibratory sensations- fluctuating touch stimuli

48
Figure 10.14a
49
Sensory Pathways (cont)
  • Spinothalamic pathways-
  • anterior lateral spinothalamic tracts
  • Relay impulses for pain, tickle, itch thermal
    sensations.

50
Somatic Motor Pathways
  • Signals converge on lower motor neurons
  • Lower motor neurons stimulate muscles directly
  • Input comes from
  • Local interneurons- e.g. reflexes
  • Upper motor neurons- corticospinal tracts
  • Basal ganglia- help with muscle tone
  • Cerebellum- coordination

51
Figure 10.15
52
Lateralization
  • Left gets input from sends output to right side
    of body and vice versa
  • Left important for spoken written language,
    numerical scientific skills reasoning
  • Right more involved with spatial and pattern
    recognition and emotional content

53
Memory
  • Process for storing retrieving information
  • Involves structural functional changes
  • Involves association areas, parts of limbic
    system diencephalon
  • Skill memory also involves cerebellum basal
    ganglia

54
Cranial Nerves (table 10.2)
  • I Olfactory- special sensory
  • II optic- special sensory -eye
  • III oculomotor-Motor eye
  • IV trochlear- motor eye
  • V trigeminal- Mixed
  • sensory around eyes upper mouth motor to
    chewing
  • VI abducens- motor eye
  • VII facial- mixed
  • sensory to front of tongue motor to facial
  • expression, lacrimal and some salivary glands

55
Cranial Nerves
  • VIII vestibulocochlear- special senses- ear
  • IX glossopharyngeal-mixed
  • Sensory for rest of tongue, pharynx palate,
    blood pressure
  • Motor to pharyngeal muscles, parotid salivary
    gland
  • X vagus-mixed (major visceral nerve)
  • Sensory from pharynx, ear, diaphragm, visceral
    organs in ventral cavity
  • Motor to palatal pharyngeal muscles organs in
    ventral cavity

56
Cranial Nerves (Cont.)
  • XI Accessory-Motor to voluntary muscles including
    sternocleidomastoid and trapezius
  • XII hypoglossal.- motor to tongue

57
Aging
  • Rapid growth during first few years
  • Size of neurons proliferation of neuroglia
  • Increases development of dendritic branches
    synaptic contacts
  • Decline in brain mass from early adulthood on
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