ANATOMY AND PHYSIOLOGY OF PAEDIATRIC NERVOUS SYSTEM BY DR. ASOGWA INNOCENT KINGSLEY ML- 608 PEOPLES’ FRIENDSHIP 1
Jul 03, 2015
ANATOMY AND PHYSIOLOGY OF
PAEDIATRIC NERVOUS SYSTEM
BY
DR. ASOGWA INNOCENT KINGSLEY
ML- 608
PEOPLES’ FRIENDSHIP UNIVERSITY OF RUSSIA
1
PEDIATRIC ANATOMY/PHYSIOLOGY• Central Nervous System
–The brain at birth is 1/10 the body weight–Only ¼ of the neuronal cells that exist in
adults are present in the newborn–Neuronal development finishes as age 12–Myelination is not complete until age 3
• Primitive reflexes (Moro, grasp) disappear with myelination
Pediatric Anatomy/Physiology• Central Nervous System
–Autonomic nervous system is developed at birth, though immature
–Parasympathetic system is intact and fully functional
–Lower end of the cord is at L3 at birth•Recedes to L1 by 1 year of age
–Dural sac shortens from S3 to S1 by 1 y/o
4
Nervous System Subdivisions
5
11.2: Meninges
• The meninges• Membranes of CNS• Protect the CNS• Three (3) layers:
• Dura mater• “Tough mother”• Venous sinuses• Falx
• Arachnoid mater• “Spiderweb-like”• Space contains cerebrospinal fluid (CSF)
• Pia mater• “Faithful mother”• Encapsulates blood vessels
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Scalp
Cranium
Cerebrum
Cerebellum
Spinal cord
Meninges
Meninges
Cerebrum
(b)(a)
Gray matterWhite matter
Subarachnoid spaceFalx cerebri
Pia mater
Dura mater
Bone of skullSubcutaneous tissueSkin
Tentoriumcerebelli
Vertebra
Dural sinus Arachnoidgranulation
Arachnoidmater
6
Meninges of the Spinal Cord
Spinal cord
Spinal cord
Pia mater
Arachnoid mater
Dura mater
Dorsal root
Dorsal root
Spinal nerve
Epidural space
(a) (b)
Ventral root
Dorsal rootganglion
Thoracicvertebra
Spinalnerve
Dorsal rootganglion
Subarachnoidspace
Dorsal branch(dorsal ramus)
Ventral branch(ventral ramus)
Ventral root
Epiduralspace
Body ofvertebra
7
11.3: Ventricles and Cerebrospinal Fluid
• There are four (4) ventricles• The ventricles are interconnected cavities within cerebral hemispheres and brain stem• The ventricles are continuous with the central canal of the spinal cord• They are filled with cerebrospinal fluid (CSF)
• The four (4) ventricles are:• Lateral ventricles (2)
• Known as the first and second ventricles
• Third ventricle• Fourth ventricle
• Interventricular foramen• Cerebral aqueduct
Lateral ventricle
Third ventricle
Fourth ventricle
(a)
Interventricularforamen
Cerebralaqueduct
To central canalof spinal cord
Third ventricle
(b)
Cerebralaqueduct
To central canalof spinal cord
Fourthventricle
Lateralventricle
Interventricularforamen
8
Cerebrospinal Fluid
• Secreted by the choroid plexus• Circulates in ventricles, central canal of spinal cord, and the subarachnoid space• Completely surrounds the brain and spinal cord• Excess or wasted CSF is absorbed by the arachnoid villi• Clear fluid similar to blood plasma• Volume is only about 120 ml.• Nutritive and protective• Helps maintain stable ion concentrations in the CNS
Third ventricle
Fourth ventricleCerebral aqueduct
Subarachnoid space
Arachnoid mater
Dura mater
Pia mater
Pia materCentral canal of spinal cord
Subarachnoid space
Filum terminaleArachnoid mater
Dura mater
Arachnoidgranulations
Choroid plexusesof third ventricle
Blood-filleddural sinus
Choroid plexus offourth ventricle
9
11.1 Clinical Application
Cerebrospinal Fluid Pressure
10
11.4: Spinal Cord• Slender column of nervous tissue continuous with brain and brainstem• Extends downward through vertebral canal• Begins at the foramen magnum and terminates at the first and second lumbar vertebrae (L1/L2) interspace
Brainstem
Spinal cord
(a) (b)
Foramenmagnum
Cervicalenlargement
Vertebralcanal
LumbarenlargementConusmedullarisCaudaequina
Filumterminale
Conusmedullaris
Lumbarenlargement
Cervicalenlargement
11
Structure of the Spinal Cord
White matter
Gray matter
Lateral funiculus
Posterior funiculus
Gray commissure
Central canal
(a)
Posterior horn
Dorsal rootof spinal nerve
Dorsal rootganglion
Ventral rootof spinal nerve
Anteriorhorn
Anteriormedianfissure
Portion ofspinal nerve
Anteriorfuniculus
Posterior mediansulcus
12
Functions of Spinal Cord
• Center for spinal reflexes
• Conduit (pathway) for nerve impulses to and from the brain and brainstem
13
Reflex Arcs
• Reflexes are automatic, subconscious responses to stimuli within or outside the body
• Simple reflex arc (sensory – motor)• Most common reflex arc (sensory – association – motor)
Receptor
(a)
Sensory orafferent neuron
Motor orefferent neuronCentral
NervousSystem
Effector(muscle or gland)
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Reflex Arcs
15
General Components of a Spinal Reflex
Receptor
Sensory neuron
Motor neuron
White matter
Gray matter
Spinal cord
DorsalInterneuron
4
5
3
2
1
(b)
Cell bodyof sensoryneuron
Effector(muscleor gland)
Centralcanal
Ventral
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Reflex Behavior
• Example is the knee-jerk reflex• Simple monosynaptic reflex• Helps maintain an upright posture
Spinal cord
Patella
Patellar ligamentDirection of impulse
Axon of sensoryneuron
Cell body ofsensory neuron
Cell body ofmotor neuron
Axon of motorneuron
Effector (quadriceps femorismuscle group)
Receptor associated withdendrites of sensory neuron
17
Reflex Behavior• Example is a withdrawal reflex (flexor reflex)• Prevents or limits tissue damage
Interneuron
Spinal cord
Axon of sensory neuron
Cell body of sensory neuron
Dendrite ofsensoryneuron
Painreceptorin skin
Directionof impulse
Cell body ofmotor neuron
Axon ofmotor neuron
Effector (flexormuscle contractsand withdraws partbeing stimulated)
Tack
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Reflex Arc
• Example crossed extensor reflex• Crossing of sensory impulses within the reflex center to produce an opposite effect
=Stimulation
= Inhibition
Interneuron
Flexor contracts
Sensory neuron
+
++
–
––
Motorneurons
Extensorcontracts
Flexorrelaxes
Motorneurons
Extensorrelaxes
19
11.2 Clinical Application
Uses of Reflexes
20
Tracts of the Spinal Cord
• Ascending tracts conduct sensory impulses to the brain• Descending tracts conduct motor impulses from the brain to motor neurons reaching muscles and glands
Posterior spinocerebellar tract
Lateral corticospinal tract
Lateral reticulospinal tract
Rubrospinal tract
Anterior spinocerebellar tract
Lateral spinothalamic tract
Anterior reticulospinal tract
Medial reticulospinal tract
Fasciculus cuneatus
Fasciculus gracilisDorsal column
Anterior spinothalamic tractAnterolateralsystem
Anteriorcorticospinaltract
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Ascending Tracts
• Major ascending (sensory) spinal cord tracts:
• Fasciculus gracilis and fasciculus cuneatus• Spinothalamic tracts
• Lateral and anterior• Spinocerebellar tracts
• Posterior and anterior
Midbrain
Pons
Medulla
Thalamus
Sensorycortex ofcerebrum
Cerebrum(frontalsection)
Brainstem(transversesections)
Spinal cord(transverse section)
Sensory fiberscross over
Spinothalamictract
FasciculusCuneatus tract
Sensory impulsefrom skin temperatureor pain receptors
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Descending Tracts
• Major descending (motor) spinal cord tracts:
• Corticospinal tracts• Lateral and anterior
• Reticulospinal tracts• Lateral, anterior and medial
• Rubrospinal tract
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Midbrain
Pons
Brainstem(transversesections)
Spinal cord(transverse section)
Motor cortexof cerebrum
Cerebrum(frontalsection)
Corticospinaltract
Medullaoblongata
Motor fiberscross over
Motor impulse toSkeletal muscle
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Nerve Tracts of the Spinal Cord
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11.3 Clinical Application
Spinal Cord Injuries
25
11.5: Brain
• Functions of the brain:• Interprets sensations• Determines perception• Stores memory• Reasoning• Makes decisions• Coordinates muscular movements• Regulates visceral activities• Determines personality
• Major parts of the brain:• Cerebrum
• Frontal lobes• Parietal lobes• Occipital lobes• Temporal lobes• Insula
• Diencephalon• Cerebellum • Brainstem
• Midbrain• Pons• Medulla oblongata
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Major Parts of the Brain
27
The BrainCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebrum
Diencephalon
MidbrainPons
Medulla oblongata
Spinal cord
Cerebellum
Fornix
(b)
Skull
Meninges
Cerebrum
Diencephalon
Brainstem
(a)
SulcusGyrus
Fornix
Cerebellum
Spinal cord
Midbrain
Pons
Medullaoblongata
Corpuscallosum
Corpuscallosum Transverse fissure
© Martin M. Rotker/Photo Researchers, Inc.
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Brain Development
• Neural tube• Three primary vesicles:
• Forebrain(Prosencephalon)• Midbrain(Mesencephalon)• Hindbrain(Rhombencephalon)
• Five secondary vesicles:• Telencephalon• Diencephalon• Mesencephalon• Metencephalon• Myelencephalon
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Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)
Neural tube
(a)
Diencephalon
Mesencephalon
Myelencephalon
Metencephalon
Neural tube
(b)
Telencephalon
(c)
Diencephalon
Midbrain
Pons and Cerebellum
Spinal cord
Cerebralhemispheres
Medullaoblongata
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Brain Development
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Structure of the Cerebrum• Corpus callosum
• Connects cerebral hemispheres (a commissure)
• Gyri • Bumps or convolutions
• Sulci• Grooves in gray matter
• Central sulcus • Fissures
• Longitudinal: separates the cerebral hemispheres• Transverse: separates cerebrum from cerebellum• Lateral fissure of Sylvius
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Central sulcus
Gyrus
Sulcus
Frontal lobe
Lateral sulcus
Parietal lobe
Occipital lobe
Central sulcus
Parietal lobe
Occipital lobe
(a)
(b) (c)
Parietal lobe
Central sulcus
Occipital lobeFrontal lobe
Insula
Temporal lobe
Longitudinalfissure
Transversefissure
Cerebellarhemisphere
Retractedtemporal lobe
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Lobes of the Cerebrum
• Five (5) lobes bilaterally:• Frontal lobe• Parietal lobe• Temporal lobe• Occipital lobe• Insula aka ‘Island of Reil’
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(c)
Parietal lobe
Central sulcus
Occipital lobe
Frontal lobe
Insula
Retractedtemporal lobe
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Functions of the Cerebrum
• Interpreting impulses• Initiating voluntary movements• Storing information as memory• Retrieving stored information • Reasoning• Seat of intelligence and personality
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Functional Regions of theCerebral Cortex
• Cerebral cortex• Thin layer of gray matter that constitutes the outermost portion of cerebrum• Contains 75% of all neurons in the nervous system
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Frontal eye field
Central sulcus
Parietal lobe
Occipital lobe
Cerebellum
Brainstem
Interpretation of auditory patterns
Lateral sulcus
Auditory area
Sensory areas involved withcutaneous and other senses
Sensory speech area( Wernicke’s area)
Combining visual images,visual recognition of objects
Visual area
Temporal lobe
Motor speech area(Broca’s area)
Motor areas involved with the controlof voluntary muscles
Concentration, planning,problem solving
Front lobe
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Functions of the Cerebral Lobes
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Sensory Areas(post-central sulcus)
• Cutaneous sensory area• Parietal lobe• Interprets sensations on skin
• Visual area• Occipital lobe• Interprets vision
• Auditory area• Temporal lobe• Interprets hearing
• Sensory area for taste• Near base of the central sulcus
• Sensory area for smell• Arises from centers deep within the cerebrum
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Frontal eye field
Central sulcus
Parietal lobe
Occipital lobe
Cerebellum
Brainstem
Interpretation of auditory patterns
Lateral sulcus
Auditory area
Sensory areas involved withcutaneous and other senses
Sensory speech area( Wernicke’s area)
Combining visual images,visual recognition of objects
Visual area
Temporal lobe
Motor speech area(Broca’s area)
Motor areas involved with the controlof voluntary muscles
Concentration, planning,problem solving
Front lobe
36
Sensory AreasCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Parietal lobe
Sensory area
Central sulcus
Motor area
Frontal lobe
Swallowing
ForearmArm Pelvis
Thigh
Leg
Lips
Forearm ArmNeck Pelvis
Thigh
Leg
Genitals
(a) Motor area (b) Sensory area
Longitudinalfissure
SalivationVocalizationMastication
Facialexpression
Thumb,fingers,and hand
Trunk
Foot andtoes
Tongue andpharynx
Teeth andgums
Upperface
Hand, fingers,and thumb
Trunk
Foot andtoes
Longitudinalfissure
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Association Areas• Regions that are not primary motor or primary sensory areas• Widespread throughout the cerebral cortex• Analyze and interpret sensory experiences• Provide memory, reasoning, verbalization, judgment, emotions
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Frontal eye field
Central sulcus
Parietal lobe
Occipital lobe
Cerebellum
Brainstem
Interpretation of auditory patterns
Lateral sulcus
Auditory area
Sensory areas involved withcutaneous and other senses
Sensory speech area( Wernicke’s area)
Combining visual images,visual recognition of objects
Visual area
Temporal lobe
Motor speech area(Broca’s area)
Motor areas involved with the controlof voluntary muscles
Concentration, planning,problem solving
Front lobe
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Association Areas
• Frontal lobe association areas• Concentrating• Planning• Complex problem solving
• Parietal lobe association areas• Understanding speech• Choosing words to express thought
• Temporal lobe association areas• Interpret complex sensory experiences • Store memories of visual scenes, music, and complex patterns
• Occipital lobe association areas• Analyze and combine visual images with other sensory experiences
39
Motor Areas(pre-central sulcus)
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Frontal eye field
Central sulcus
Parietal lobe
Occipital lobe
Cerebellum
Brainstem
Interpretation of auditory patterns
Lateral sulcus
Auditory area
Sensory areas involved withcutaneous and other senses
Sensory speech area( Wernicke’s area)
Combining visual images,visual recognition of objects
Visual area
Temporal lobe
Motor speech area(Broca’s area)
Motor areas involved with the controlof voluntary muscles
Concentration, planning,problem solving
Front lobe
• Primary motor areas• Frontal lobes• Control voluntary muscles
• Broca’s area• Anterior to primary motor cortex• Usually in left hemisphere• Controls muscles needed for speech
• Frontal eye field• Above Broca’s area• Controls voluntary movements of eyes and eyelids
40
Motor AreasCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Parietal lobe
Sensory area
Central sulcus
Motor area
Frontal lobe
Swallowing
ForearmArm Pelvis
Thigh
Leg
Lips
Forearm ArmNeck Pelvis
Thigh
Leg
Genitals
(a) Motor area (b) Sensory area
Longitudinalfissure
SalivationVocalizationMastication
Facialexpression
Thumb,fingers,and hand
Trunk
Foot andtoes
Tongue andpharynx
Teeth andgums
Upperface
Hand, fingers,and thumb
Trunk
Foot andtoes
Longitudinalfissure
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Hemisphere Dominance
• The left hemisphere is dominant in most individuals
• Dominant hemisphere controls:• Speech• Writing• Reading• Verbal skills• Analytical skills• Computational skills
• Nondominant hemisphere controls:• Nonverbal tasks• Motor tasks• Understanding and interpreting musical and visual patterns• Provides emotional and intuitive thought processes
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Memory
• Short term memory• Working memory• Closed neuronal circuit• Circuit is stimulated over and over• When impulse flow ceases, memory does also unless it enters long-term memory via memory consolidation
• Long term memory• Changes structure or function of neurons• Enhances synaptic transmission
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11.4 Clinical Application
Traumatic Brain Injury
44
Basal Nuclei
• Masses of gray matter• Deep within cerebral hemispheres• Caudate nucleus, putamen, and globus pallidus• Produce dopamine• Control certain muscular activities
• Primarily by inhibiting motor functions
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Thalamus
Hypothalamus
Brainstem
Putamen
Cerebellum
Spinal cord
Longitudinalfissure
Right cerebralhemisphere
Caudatenucleus
Globuspallidus
Basalnuclei
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Diencephalon
• Between cerebral hemispheres and above the brainstem• Surrounds the third ventricle
• Thalamus• Epithalamus• Hypothalamus• Optic tracts• Optic chiasm• Infundibulum• Posterior pituitary• Mammillary bodies• Pineal gland
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Pyramidal tract
Pons
Optic nerve Optic chiasma
Thalamus
Spinal cord
Pituitary gland
Pineal gland
Optic tractMammillary body
(a) (b)
Olive
Corpora quadrigemina
Cerebralpeduncles
Superiorcolliculus
Inferiorcolliculus
Thirdventricle
Fourthventricle
Cerebellarpeduncles
Medullaoblongata
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Diencephalon
• Thalamus• Gateway for sensory impulses heading to cerebral cortex• Receives all sensory impulses (except smell)• Channels impulses to appropriate part of cerebral cortex for interpretation
• Hypothalamus• Maintains homeostasis by regulating visceral activities • Links nervous and endocrine systems (hence some say the neuroendocrine system
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Diencephalon
• Consists of:• Portions of frontal lobe• Portions of temporal lobe• Hypothalamus• Thalamus• Basal nuclei• Other deep nuclei
• Functions:• Controls emotions• Produces feelings• Interprets sensory impulses
The Limbic System
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11.5 Clinical Application
Parkinson Disease
49
Brainstem
Three parts:1. Midbrain2. Pons3. Medulla Oblongata
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Spinal cord
Thalamus
HypothalamusDiencephalon
Pons
Midbrain
Corpuscallosum
Corporaquadrigemina
Cerebralaqueduct
Reticularformation
Medullaoblongata
50
Midbrain
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Pyramidal tract
Pons
Optic nerve Optic chiasma
Thalamus
Spinal cord
Pituitary gland
Pineal gland
Optic tractMammillary body
(a) (b)
Olive
Corpora quadrigemina
Cerebralpeduncles
Superiorcolliculus
Inferiorcolliculus
Thirdventricle
Fourthventricle
Cerebellarpeduncles
Medullaoblongata
• Between diencephalon and pons• Contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain• Cerebral aqueduct• Cerebral peduncles (bundles of nerve fibers)• Corpora quadrigemina (centers for visual and auditory reflexes)
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Pons
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Pyramidal tract
Pons
Optic nerve Optic chiasma
Thalamus
Spinal cord
Pituitary gland
Pineal gland
Optic tractMammillary body
(a) (b)
Olive
Corpora quadrigemina
Cerebralpeduncles
Superiorcolliculus
Inferiorcolliculus
Thirdventricle
Fourthventricle
Cerebellarpeduncles
Medullaoblongata
• Rounded bulge on underside of brainstem• Between medulla oblongata and midbrain• Helps regulate rate and depth of breathing• Relays nerve impulses to and from medulla oblongata and cerebellum
52
Medulla Oblongata
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Pyramidal tract
Pons
Optic nerve Optic chiasma
Thalamus
Spinal cord
Pituitary gland
Pineal gland
Optic tractMammillary body
(a) (b)
Olive
Corpora quadrigemina
Cerebralpeduncles
Superiorcolliculus
Inferiorcolliculus
Thirdventricle
Fourthventricle
Cerebellarpeduncles
Medullaoblongata
• Enlarged continuation of spinal cord• Conducts ascending and descending impulses between brain and spinal cord• Contains cardiac, vasomotor, and respiratory control centers• Contains various nonvital reflex control centers (coughing, sneezing, swallowing, and vomiting)
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Reticular Formation
• Complex network of nerve fibers scattered throughout the brain stem• Extends into the diencephalon• Connects to centers of hypothalamus, basal nuclei, cerebellum, and cerebrum• Filters incoming sensory information • Arouses cerebral cortex into state of wakefulness
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Spinal cord
Thalamus
HypothalamusDiencephalon
Pons
Midbrain
Corpuscallosum
Corporaquadrigemina
Cerebralaqueduct
Reticularformation
Medullaoblongata
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Types of Sleep
• Slow wave• Non-REM sleep • Person is tired• Decreasing activity of reticular system• Restful• Dreamless• Reduced blood pressure and respiratory rate• Ranges from light to heavy• Alternates with REM sleep
• Rapid Eye Movement (REM)• Paradoxical sleep • Some areas of brain active• Heart and respiratory rates irregular• Dreaming occurs
55
Cerebellum
• Inferior to occipital lobes• Posterior to pons and medulla oblongata• Two hemispheres• Vermis connects hemispheres• Cerebellar cortex (gray matter)• Arbor vitae (white matter)• Cerebellar peduncles (nerve fiber tracts)• Dentate nucleus (largest nucleus in cerebellum)• Integrates sensory information concerning position of body parts• Coordinates skeletal muscle activity• Maintains posture
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Thalamus
Superior peduncle
Middle peduncle
Inferior peduncle
Pons
Medulla oblongata
Cerebellum
Corpus callosum
Longitudinalfissure
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11.6 Clinical Application
Brain Waves
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Nervous System Subdivisions
58
11.6: Peripheral Nervous System
• Cranial nerves arising from the brain• Somatic fibers connecting to the skin and skeletal muscles• Autonomic fibers connecting to viscera
• Spinal nerves arising from the spinal cord• Somatic fibers connecting to the skin and skeletal muscles• Autonomic fibers connecting to viscera
59
Structure of a Peripheral NerveCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Peripheral nerve
Epineurium
Axon
Neurilemma
Myelin sheath
Schwann cell
Node of Ranvier
Endoneurium
Perineurium
Fascicle
Sensory receptor
Motor neuronending
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Nerve and Nerve Fiber Classification
• Sensory nerves• Conduct impulses into brain or spinal cord
• Motor nerves• Conduct impulses to muscles or glands
• Mixed (both sensory and motor) nerves• Contain both sensory nerve fibers and motor nerve fibers• Most nerves are mixed nerves• ALL spinal nerves are mixed nerves (except the first pair)
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Nerve Fiber Classification
• General somatic efferent (GSE) fibers• Carry motor impulses from CNS to skeletal muscles
• General visceral efferent (GVE) fibers• Carry motor impulses away from CNS to smooth muscles and glands
• General somatic afferent (GSA) fibers• Carry sensory impulses to CNS from skin and skeletal muscles
• General visceral afferent (GVA) fibers• Carry sensory impulses to CNS from blood vessels and internal organs
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Nerve Fiber Classification
• Special somatic efferent (SSE) fibers• Carry motor impulses from brain to muscles used in chewing, swallowing, speaking and forming facial expressions
• Special visceral afferent (SVA) fibers• Carry sensory impulses to brain from olfactory and taste receptors
• Special somatic afferent (SSA) fibers• Carry sensory impulses to brain from receptors of sight, hearing and equilibrium
63
Cranial NervesCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Olfactory bulb
Hypoglossal (XII)
Optic tract
Olfactory tract
Olfactory (I)
Optic (II)
Oculomotor (III)
Abducens (VI)
Facial (VII)
Glossopharyngeal (IX)
Accessory (XI)
Trochlear (IV)
Trigeminal (V)
Vestibulocochlear (VIII)
Vagus (X)
64
Cranial Nerves
• Remember:
• Cranial nerves are designated ‘CN’
• Cranial nerves are designated with Roman numerals (I – XII)
65
Cranial Nerves I and II
• Olfactory nerve (CN I)• Sensory nerve• Fibers transmit impulses associated with smell
• Optic nerve (CN II)• Sensory nerve• Fibers transmit impulses associated with vision
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Cranial Nerves III and IV
• Trochlear nerve (CN IV)• Primarily motor nerve• Motor impulses to muscles that move the eyes• Some sensory
• Proprioceptors
• Oculomotor nerve (CN III)• Primarily motor nerve• Motor impulses to muscles that:
• Raise eyelids• Move the eyes• Focus lens• Adjust light entering eye
• Some sensory• Proprioceptors
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Cranial Nerve V
• Trigeminal nerve (CN V)• Mixed nerve• “Three (3) sisters”• (1) Ophthalmic division
• Sensory from surface of eyes, tear glands, scalp, forehead, and upper eyelids
• (2) Maxillary division• Sensory from upper teeth, upper gum, upper lip, palate, and skin of face
• (3) Mandibular division• Sensory from scalp, skin of jaw, lower teeth, lower gum, and lower lip• Motor to muscles of mastication and muscles in floor of mouth
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Lacrimal nerve
Eye
Maxilla
Mandible
Lacrimalgland
Infraorbitalnerve
Tongue
Mentalnerve
Ophthalmicdivision
Maxillarydivision
Mandibulardivision
Lingualnerve
Inferioralveolarnerve
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Cranial Nerves VI and VII
• Abducens nerve (CN VI)• Primarily motor nerve• Motor impulses to muscles that move the eyes• Some sensory
•Proprioceptors
• Facial nerve (CN VII)• Mixed nerve• Sensory from taste receptors• Motor to muscles of facial expression, tear glands, and salivary glands
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Zygomatic nerve
Buccal nerve
Facial nerve
Mandibular nerve
Cervical nerve
Temporal nerve
Posterior auricularnerve
Parotid salivarygland
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Cranial Nerves VIII and IX
• Vestibulocochlear nerve (CN VIII)• A.k.a acoustic or auditory nerve• Sensory nerve• Two (2) branches:
• Vestibular branch• Sensory from equilibrium receptors of ear
• Cochlear branch • Sensory from hearing receptors
• Glossopharyngeal nerve (CN IX)• Mixed nerve• Sensory from pharynx, tonsils, tongue and carotid arteries• Motor to salivary glands and muscles of pharynx
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Cranial Nerve X
• Vagus nerve (CN X)• Mixed nerve• Somatic motor to muscles of speech and swallowing• Autonomic motor to viscera of thorax and abdomen• Sensory from pharynx, larynx, esophagus, and viscera of thorax and abdomen
Meningeal branchAuricular branchPharyngeal branch
Palate
Cardiac nerves
Heart
Liver
Kidney
Nerve XINerve XII
Carotid body
Large intestine
Lung
Stomach
Spleen
Pancreas
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Superior laryngealnerve
Recurrent laryngealnerve
Superior ganglionof vagus nerve
Inferior ganglionof vagus nerve
Left vagusnerve
Smallintestine
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Cranial Nerves XI and XII
• Accessory nerve (CN XI)• Primarily motor nerve• We called this “Spinal” Accessory because:
• Cranial branch• Motor to muscles of soft palate, pharynx and larynx
• Spinal branch • Motor to muscles of neck and back• Some sensory
• Proprioceptor
• Hypoglossal nerve (CN XII)• Primarily motor• Motor to muscles of the tongue• Some sensory
• Proprioceptor
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Functions of Cranial Nerves
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Spinal Nerves
• ALL are mixed nerves (except the first pair)• 31 pairs of spinal nerves:
• 8 cervical nerves• (C1 to C8)
• 12 thoracic nerves• (T1 to T12)
• 5 lumbar nerves• (L1 to L5)
• 5 sacral nerves• (S1 to S5)
• 1 coccygeal nerve• (Co or Cc)
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Cauda equina
C1C2C3C4C5C6C7C8T1T2T3T4T5T6
T7
T8T9T10T11
T12L1L2L3L4L5
S2S3
S4
S1
S5Co
Posteriorview
Cervicalnerves
Thoracicnerves
Lumbarnerves
Sacralnerves
Coccygealnerve
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Spinal Nerves
• Dorsal root (aka posterior root)
• Sensory root• Axons of sensory neurons are in the dorsal root ganglion
• Dorsal root ganglion • Aka DRG• Cell bodies of sensory neurons whose axons conduct impulses inward from peripheral body parts
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Lateral horn
Ventral root(a)
(b)
Dorsal root
Dorsal root
Spinal nerve
Dorsal rootganglion
Posteriormedian sulcus
Posteriorhorn
Anteriorhorn
Centralcanal
Anterior median fissure
Dorsal branchof spinal nerve
Ventral branchof spinal nerve
Visceral branchof spinal nerve
Paravertebralganglion
Ventral branchof spinal nerve (ventral ramus)Dorsal branchof spinal nerve (dorsal ramus)
Paravertebralganglion
Visceral branchof spinal nerve
Ventral root
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Dermatome• An area of skin that the sensory nerve fibers of a particular spinal nerve innervate
C2C3
C4C5
C6
T1
C6C7
S2S3
C8
L1L2
L3
L4
L5
T12
T1
S1
(a) (b)
S5C0
S4S3S2S1
L5
L4
L3
L2
L1
L5
L1
C8T1
T12
C7C6
C5C4
C3
C2
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Spinal Nerves
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Lateral horn
Ventral root(a)
(b)
Dorsal root
Dorsal root
Spinal nerve
Dorsal rootganglion
Posteriormedian sulcus
Posteriorhorn
Anteriorhorn
Centralcanal
Anterior median fissure
Dorsal branchof spinal nerve
Ventral branchof spinal nerve
Visceral branchof spinal nerve
Paravertebralganglion
Ventral branchof spinal nerve (ventral ramus)Dorsal branchof spinal nerve (dorsal ramus)
Paravertebralganglion
Visceral branchof spinal nerve
Ventral root
• Ventral root (aka anterior root) • Motor root• Axons of motor neurons whose cell bodies are in the spinal cord
• Spinal nerve• Union of ventral root and dorsal roots• Hence we now have a “mixed” nerve
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Nerve Plexuses
• Nerve plexus• Complex networks formed by anterior branches of spinal nerves• The fibers of various spinal nerves are sorted and recombined• There are three (3) nerve plexuses:
• (1) Cervical plexus• Formed by anterior branches of C1-C4 spinal nerves• Lies deep in the neck• Supply to muscles and skin of the neck• C3-C4-C5 nerve roots contribute to phrenic nerves bilaterally
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Brachial Plexus• (2) Brachial plexus
• Formed by anterior branches C5-T1• Lies deep within shoulders• There are five (5) branches:• 1. Musculocutaneous nerve
• Supply muscles of anterior arms and skin of forearms
• 2. Ulnar and 3. Median nerves• Supply muscles of forearms and hands• Supply skin of hands
• 4. Radial nerve• Supply posterior muscles of arms and skin of forearms and hands
• 5. Axillary nerve• Supply muscles and skin of anterior, lateral, and posterior arms
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Musculo-cutaneous n.
Musculocutaneous n.
Humerus
Thoracodorsal n.Lower subscapular n.
Suprascapular n.Lateral pectoral n.Medial pectoral n.
Axillary n.
Axillary n.
Radial n.
Radial n.
Radius
Ulna
Ulnar n.
Ulnar n.Median n.Median n.
C5
C5
C6
C6
C7
C7
C8
C8
T1
T1
(a)
(b)
Ventral rami: C5, C6, C7, C8, T1
Anterior divisions
Posterior divisions
Trunks: upper, middle, lower
Dorsalscapular n.
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Lumbosacral Plexus• (3) Lumbosacral plexus
• Formed by the anterior branches of L1-S5 roots• Can be a lumbar (L1-L5) plexus and a sacral (S1-S5) plexus• Extends from lumbar region into pelvic cavity• Obturator nerve
• Supply motor impulses to adductors of thighs
• Femoral nerve• Supply motor impulses to muscles of anterior thigh and sensory impulses from skin of thighs and legs
• Sciatic nerve• Supply muscles and skin of thighs, legs and feet
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Sciatic n.
Saphenous n.
Femoral n.
Obturator n.
Tibial n.
Pudendal n.
(b) (c)(a)
Femoral n.
Obturator n.
Pudendal n.
Sciatic n.
L1
L2
L3
L4
L5
S1S2S3
S4
S5
Ventralrami
Anteriordivisions
Posteriordivisions
Lateralfemoralcutaneous n.
Superiorgluteal n.
Inferiorgluteal n.
Superiorgluteal n.
Inferiorgluteal n.
Sacralplexus
Common fibular(peroneal) n.
Posteriorcutaneous n.
Commonfibular(peroneal) n.Tibial n.
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Plexuses
C1C2C3C4C5C6C7C8T1T2T3T4T5T6
T8T9T10T11T12L1L2L3L4
L5
S2S3S4S5
Co
Posterior view
Cervical plexus(C1–C4)
Lumbosacral plexus(T12–S5)
Sciatic nerve
Brachial plexus(C5–T1)
Obturator nerve
Phrenic nerve
Ulnar nerveMedian nerveRadial nerveAxillary nerve
T7
S1
Cauda equina
Musculocutaneousnerve
Femoralnerve
Intercostalnerves
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11.7 Clinical Application
Spinal Nerve Injuries
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11.7: Autonomic Nervous System
• Functions without conscious effort• Controls visceral activities• Regulates smooth muscle, cardiac muscle, and glands• Efferent fibers typically lead to ganglia outside of the CNS
• Two autonomic divisions regulate:• Sympathetic division (speeds up)
• Prepares body for ‘fight or flight’ situations• Parasympathetic division (slows down)
• Prepares body for ‘resting and digesting’ activities
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Autonomic Nerve Fibers
• All of the neurons are motor (efferent)
• Preganglionic fibers• Axons of preganglionic neurons• Neuron cell bodies in CNS
• Postganglionic fibers• Axons of postganglionic neurons• Neuron cell bodies in ganglia
Interneurons
Spinal cord
Dorsal root ganglion
Viscera
(b) Somatic pathway
Skin
Somatic motor neuron
Dorsal rootganglion
Sensoryneuron
Autonomicganglion
Preganglionicfiber
Postganglionicfiber
Skeletalmuscle
Sensoryneuron
(a) Autonomic pathway
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Sympathetic Division
• Thoracolumbar division – location of preganglionic neurons
• Preganglionic fibers leave spinal nerves through white rami and enter paravertebral ganglia
• Paraverterbral ganglia and fibers that connect them make up the sympathetic trunk
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Ventral root
Spinal nerves
Spinal cord
Dorsal root
Pia mater
Sympathetictrunk
Paravertebralsympatheticganglion
Transverseprocess
Vertebral notch(forms part ofintervertebralforamen)
Body ofvertebra
Duramater
Arachnoidmater
Dorsal rootganglion
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Sympathetic Division
• Postganglionic fibers extend from sympathetic ganglia to visceral organs
• Postganglionic fibers usually pass through gray rami and return to a spinal nerve before proceeding to an effector
• Exception: preganglionic fibers to adrenal medulla do not synapse with postganglionic neurons
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Spinal cord
Ventral root
Dorsal root
Sympathetic trunkPosterior horn
Lateral horn
Anterior horn
Preganglionicneuron
Postganglionicneuron
Dorsal rootganglion
Spinalnerve
Visceral effector(intestine)
Collateralganglion
To visceral effectors(smooth muscleof blood vessels,arrector pilimuscles, andsweat glands)
Grayramus
Whiteramus
Dorsal branch ofspinal nerve
Ventral branch ofspinal nerve
Paravertebralsympatheticganglion
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Sympathetic DivisionCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lacrimal gland
Skin
Eye
Blood vessels
Heart
Lungs
Adrenal glandKidney
UterusPenis
Liver
StomachGallbladder
Pancreas
Ovary
Scrotum
Small intestine
Large intestine
Trachea
Parotid gland,submandibular andsublingual glands
Urinarybladder
Preganglionicneuron
Postganglionicneuron
Sympatheticchain ganglia
Inferiormesentericganglion
Spinalcord
Superiormesentericganglion
Celiacganglion
Fibers toskin, blood vessels,and adipose tissue
Celiac andpulmonaryplexuses
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Parasympathetic Division
• Craniosacral division – location of preganglionic neurons
• Ganglia are near or within various organs
• Terminal ganglia
• Short postganglionic fibers
• Continue to specific muscles or glands
• Preganglionic fibers of the head are included in nerves III, VII, and IX
• Preganglionic fibers of thorax and abdomen are parts of nerve X
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Parasympathetic DivisionCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Heart
Trachea
Lung
GallbladderLiver
StomachSpleenPancreas
Small intestine
Large intestine
Kidney
UterusScrotum
Otic ganglion
Ciliary ganglion Eye
Penis Ovary
Sphenopalatineganglion
Cranialnerve III
CranialNerve VII
Submandibularganglion
Cranialnerve IX
Cranial nerve X(Vagus)
Cardiac andpulmonaryplexuses
Celiacplexus
Superiorhypogastricplexus
Inferiorhypogastricplexus
Spinalcord
Pelvicnerves Urinary
bladder
Parotidgland
Submandibularand sublingual glands
Lacrimalgland
Preganglionicneuron
Postganglionicneuron
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Autonomic Neurotransmitters
• Cholinergic fibers• Release acetylcholine• Preganglionic sympathetic and parasympathetic fibers• Postganglionic parasympathetic fibers
• Adrenergic fibers• Release norepinephrine• Most postganglionic sympathetic fibers
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Brain
Postganglionic fiber (axon)
Preganglionic fiber (axon)
Ganglion
Sympathetic neurons
ACh = acetylcholine (cholinergic)
NE = norepinephrine (adrenergic)
ACh
ACh
ACh
ACh
ACh ACh
NE
NE
Cranialparasympatheticneurons
Sacralparasympatheticneurons
Collateralganglion
Paravertebralganglion
Visceraleffectors
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Actions of AutonomicNeurotransmitters
• Result from binding to protein receptors in the membrane of effector cells:
• Cholinergic receptors• Bind to acetylcholine (Ach)• Muscarinic
• Excitatory • Slow
• Nicotinic• Excitatory• Rapid
• Adrenergic receptors• Bind to epinephrine and norepinephrine• Alpha and beta
• Both elicit different responses on various effectors
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Terminating Autonomic Neurotransmitter Actions
• The enzyme acetylcholinesterase rapidly decomposes the acetylcholine that cholinergic fibers release.
• Norepinephrine from adrenergic fibers is removed by active transport.
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Control of Autonomic Activity
• Controlled largely by CNS
• Medulla oblongata regulates cardiac, vasomotor and respiratory activities
• Hypothalamus regulates visceral functions, such as body temperature, hunger, thirst, and water and electrolyte balance
• Limbic system and cerebral cortex control emotional responses
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11.8: Lifespan Changes
• Brain cells begin to die before birth• Over average lifetime, brain shrinks 10%• Most cell death occurs in temporal lobes• By age 90, frontal cortex has lost half its neurons• Number of dendritic branches decreases• Decreased levels of neurotransmitters• Fading memory• Slowed responses and reflexes• Increased risk of falling• Changes in sleep patterns that result in fewer sleeping hours
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