10
Uni
t 1
Central Nervous System, Central Nervous System, Spinal Nerves, And Cranial Spinal Nerves, And Cranial
NervesNerves
Central Nervous System, Central Nervous System, Spinal Nerves, And Cranial Spinal Nerves, And Cranial
NervesNerves
Chapter 10
10
Uni
t 1
Spinal Cord StructureSpinal Cord StructureProtection and CoveringsProtection and CoveringsSpinal Cord StructureSpinal Cord Structure
Protection and CoveringsProtection 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
10
Uni
t 1
Spinal MeningesSpinal MeningesSpinal MeningesSpinal Meninges
• Epidural space lined with fat• Dura mater- tough ,dense connective
tissueExtends 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 cordContains blood vessels
Figure 10.1
10
Uni
t 1
Gross Anatomy Of Spinal Gross Anatomy Of Spinal CordCord
Gross Anatomy Of Spinal Gross Anatomy Of Spinal CordCord
• runs to 2nd lumbar vertebra• Roots of spinal nerves for lumbar,
sacral & coccygeal nerves in vertebral cavity before leaving = Cauda Equina
• Enlargements: cervical & lumbarInclude nerves for upper & lower limbs
• Each spinal segment gives rise to a spinal nerve – 31 pairs
Figure 10.2
10
Uni
t 1
Internal Structure Of Spinal Internal Structure Of Spinal CordCord
Internal Structure Of Spinal Internal Structure Of Spinal CordCord
• Two grooves- left & right halvesAnterior median fissure & posterior median sulcus
• Gray matter- 3 horns on each sideAnterior, posterior, lateral
•Anterior- somatic motor neurons•Posterior- sensory neurons•Lateral- autonomic motor
neurons
10
Uni
t 1
Internal Structure Of Spinal Internal Structure Of Spinal Cord (cont)Cord (cont)
Internal Structure Of Spinal Internal Structure Of Spinal Cord (cont)Cord (cont)
• White matter- organized into columnsAnterior, posterior & lateral white
columns
• Each column contains one or more tracts having a common destination
• Sensory = ascending tractsCarry information toward brain
• Motor = descending tractsCarry information down spinal cord
Figure 10.3
10
Uni
t 1
Spinal NervesSpinal NervesSpinal NervesSpinal 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
10
Uni
t 1
Spinal Nerves (cont)Spinal Nerves (cont)Spinal Nerves (cont)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
10
Uni
t 1
Spinal Nerve Spinal Nerve CompositionCompositionSpinal Nerve Spinal Nerve CompositionComposition
• 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
Figure 10.4
10
Uni
t 1
Distribution Of Spinal Distribution Of Spinal NervesNerves
Distribution Of Spinal Distribution Of Spinal NervesNerves
• 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 nervesSupply abdominal muscles, skin of chest
& back and muscles between robs.
10
Uni
t 1
PlexusesPlexusesPlexusesPlexuses
• Cervical plexus- posterior head, neck, shoulders & diaphragm
• Brachial plexus-upper limbs & some neck & shoulder muscles
• Lumbar plexus- abdominal wall, external genitals & part of lower limbse.g. ilioinguinal, femoral, obdurator nerves
• Sacral plexus- buttocks, perineum & lower limbse.g. Gluteal, sciatic & pudendal nerves
Figure 10.2
10
Uni
t 1
Spinal Cord FunctionsSpinal Cord FunctionsSpinal Cord FunctionsSpinal 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
10
Uni
t 1
Reflex arc (patellar Reflex arc (patellar reflex)reflex)
Reflex arc (patellar Reflex arc (patellar reflex)reflex)
1. Sensory receptor- responds to stimulusTap below patella
2. Sensory neuron- to dorsal horn & brain3. Integrating center- e.g. single synapse
Sensory to motor neurons
4. Motor neuron- from center to effectorVia ventral horn
5. Effector- responder (muscle or gland)Patellar reflex- rectus femoris contracts
Figure 10.5
10
Uni
t 1
Brain-major partsBrain-major partsBrain-major partsBrain-major parts
• Brain stem- continuous with spinal cordMedulla oblongata, pons, midbrain
• Diencephalon- above brain stemThalamus, hypothalamus & pineal gland
• Cerebrum- at top and largest partSurface covered with gray matter- cortexBeneath is cerebral white matter
• Cerebellum- back of brain stemMeans “little brain”
• Cranial meninges- dura mater, arachnoid mater & pia mater
Figure 10.6a
Figure 10.6b
10
Uni
t 1
Brain blood supplyBrain blood supplyBrain blood supplyBrain blood supply
• Requires ~20% body’s oxygen supply4 min lack => 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
10
Uni
t 1
Cerebral Spinal Fluid Cerebral Spinal Fluid (CSF)(CSF)
Cerebral Spinal Fluid Cerebral Spinal Fluid (CSF)(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 cellsReabsorbed through arachnoid villi into
superior saggital sinus
Figure 10.7
10
Uni
t 1
Brain Stem- MedullaBrain Stem- MedullaBrain Stem- MedullaBrain Stem- Medulla
• Medulla Oblongata- inferior part of brainstemwhite matter extending between spinal
cord & other parts of brain• several nuclei: cardiovascular
center (heart rate)
• Medullary rhythmicity area (respiratory rhythm)
• Other sensory & reflex motor areasSome related to cranial nerves
10
Uni
t 1
Brain Stem- PonsBrain Stem- PonsBrain Stem- PonsBrain Stem- Pons
• Pons (bridge)- nuclei & tractsConnect left & right of cerebellum
• Ascending & descending tracts• Nuclei – motor relays from
cerebrum to cerebellum , respiration & cranial nerves V, VI, VII, VIII
Figure 10.8
10
Uni
t 1
Brain Stem- MidbrainBrain Stem- MidbrainBrain Stem- MidbrainBrain Stem- Midbrain
• Connects pons to DiencephalonLarge 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
10
Uni
t 1
Reticular formationReticular formationReticular formationReticular formation
• Netlike arrangement of gray and white mater
• Ascending part = Reticular Activating System (RAS)
• Projects to cerebral cortex & helps maintain consciousness
• Inactivation => sleep
Figure 10.9
10
Uni
t 1
DiencephalonDiencephalonDiencephalonDiencephalon
• Thalamus- critical relay for sensory inputTransmits motor information from cerebellum &
basal nuclei to cerebrum
• Hypothalamus- important for homeostasisControl of ANS-regulation of many activitiesControl of pituitary and hormone productionRegulation of emotional & behavior patternsRegulation of eating & drinkingControl of body temperatureRegulation of circadian rhythms & states of
consciousness
• Pineal gland- secretes melatonin
Figure 10.10
10
Uni
t 1
CerebellumCerebellumCerebellumCerebellum
• Two cerebellar hemispheresPosterior to medulla and pons,
below cerebrum
• Cerebellar cortex –gray matter• Tree like white matter & nuclei• Attached to brain stem via
cerebellar peduncles
10
Uni
t 1
Cerebellar functionCerebellar functionCerebellar functionCerebellar 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
10
Uni
t 1
Cerebrum- StructureCerebrum- StructureCerebrum- StructureCerebrum- 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
10
Uni
t 1
Cerebrum- Structure Cerebrum- Structure (cont)(cont)
Cerebrum- Structure Cerebrum- Structure (cont)(cont)
• Each hemisphere has 4 lobesFrontal, parietal, temporal, occipital
• Central sulcus separates frontal & parietalPrecentral gyrus anterior to sulcus= primary
motor areaPostcentral gyrus = primary sensory area
• Deep gray = basal nuclei (basal ganglia)Globus palladus, putamen, caudate
nucleus
Figure 10.11a
Figure 10.11b
10
Uni
t 1
Limbic SystemLimbic SystemLimbic SystemLimbic 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
Figure 10.12
10
Uni
t 1
Function areas of CortexFunction areas of CortexFunction areas of CortexFunction 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.
10
Uni
t 1
Sensory AreasSensory AreasSensory AreasSensory 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
10
Uni
t 1
Motor AreasMotor AreasMotor AreasMotor Areas
• Mainly from anterior part of hemisphere
• Primary motor area- precentral gyrus
• Broca’s speech area- interacts with premotor area &
primary motor area to regulate breathing and speech muscles
10
Uni
t 1
Association AreasAssociation AreasAssociation AreasAssociation Areas
• Adjacent to sensory & motor areas• connected with tracts- interpret
information• E.g. somatosensory association area
Posterior to primary somatosensory areaIntegrates sensation- exact shape & texture
of object compares with stored memories• Wernike’s area- left temporal &
parietal lobesInterprets meaning of speechRight hemisphere adds emotional content
Figure 10.13
10
Uni
t 1
Sensory PathwaysSensory PathwaysSensory PathwaysSensory Pathways
• Relay information from periphery to cerebral cortex
• 3 neurons in each pathway.• Posterior column- medial
lemniscus pathwayFine touch- body location, texture, sizeProprioception- position & motion of body
partsVibratory sensations- fluctuating touch
stimuli
Figure 10.14a
10
Uni
t 1
Sensory Pathways (cont)Sensory Pathways (cont)Sensory Pathways (cont)Sensory Pathways (cont)
•Spinothalamic pathways-• anterior & lateral spinothalamic
tracts• Relay impulses for pain, tickle,
itch & thermal sensations.
10
Uni
t 1
Somatic Motor PathwaysSomatic Motor PathwaysSomatic Motor PathwaysSomatic Motor Pathways
• Signals converge on lower motor neurons
• Lower motor neurons stimulate muscles directly
• Input comes from:Local interneurons- e.g. reflexesUpper motor neurons- corticospinal tractsBasal ganglia- help with muscle toneCerebellum- coordination
Figure 10.15
10
Uni
t 1
LateralizationLateralizationLateralizationLateralization
• 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
10
Uni
t 1
MemoryMemoryMemoryMemory
• Process for storing & retrieving information
• Involves structural & functional changes
• Involves association areas, parts of limbic system & diencephalon
• Skill memory also involves cerebellum & basal ganglia
10
Uni
t 1
Cranial NervesCranial Nerves (table 10.2) (table 10.2)Cranial NervesCranial Nerves (table 10.2) (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
10
Uni
t 1
Cranial NervesCranial NervesCranial NervesCranial 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 cavityMotor to palatal & pharyngeal muscles & organs in
ventral cavity
10
Uni
t 1
Cranial Nerves (Cont.)Cranial Nerves (Cont.)Cranial Nerves (Cont.)Cranial Nerves (Cont.)
• XI Accessory-Motor to voluntary muscles including sternocleidomastoid and trapezius
• XII hypoglossal.- motor to tongue
10
Uni
t 1
AgingAgingAgingAging
• 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