anatomy and physiology of paediatric nervous system by dr asogwa innocent kingsley

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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)

14

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

16

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

18

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


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

21

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

22

Descending Tracts

• Major descending (motor) spinal cord tracts:

• Corticospinal tracts• Lateral and anterior

• Reticulospinal tracts• Lateral, anterior and medial

• Rubrospinal tract


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

24


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

26

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


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


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’


(c)

Parietal lobe

Central sulcus

Occipital lobe

Frontal lobe

Insula

Retractedtemporal lobe

32

Functions of the Cerebrum

• Interpreting impulses• Initiating voluntary movements• Storing information as memory• Retrieving stored information • Reasoning• Seat of intelligence and personality

33

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


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

34

Functions of the Cerebral Lobes

35

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


Frontal eye field

Central sulcus

Parietal lobe

Occipital lobe

Cerebellum

Brainstem


Lateral sulcus

Auditory area




Visual area

Temporal lobe




Front lobe

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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


Frontal eye field

Central sulcus

Parietal lobe

Occipital lobe

Cerebellum

Brainstem


Lateral sulcus

Auditory area




Visual area

Temporal lobe




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

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Motor Areas(pre-central sulcus)


Frontal eye field

Central sulcus

Parietal lobe

Occipital lobe

Cerebellum

Brainstem


Lateral sulcus

Auditory area




Visual area

Temporal lobe




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

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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

41

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

43


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


Thalamus

Hypothalamus

Brainstem

Putamen

Cerebellum

Spinal cord

Longitudinalfissure

Right cerebralhemisphere

Caudatenucleus

Globuspallidus

Basalnuclei

45

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


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

46

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

47

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

48


Parkinson Disease

49

Brainstem

Three parts:1. Midbrain2. Pons3. Medulla Oblongata


Spinal cord

Thalamus

HypothalamusDiencephalon

Pons

Midbrain

Corpuscallosum

Corporaquadrigemina

Cerebralaqueduct

Reticularformation

Medullaoblongata

50

Midbrain


Pyramidal tract

Pons


Thalamus

Spinal cord

Pituitary gland

Pineal gland


(a) (b)

Olive


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)

51

Pons


Pyramidal tract

Pons


Thalamus

Spinal cord

Pituitary gland

Pineal gland


(a) (b)

Olive


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


Pyramidal tract

Pons


Thalamus

Spinal cord

Pituitary gland

Pineal gland


(a) (b)

Olive


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)

53

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


Spinal cord

Thalamus

HypothalamusDiencephalon

Pons

Midbrain

Corpuscallosum

Corporaquadrigemina

Cerebralaqueduct

Reticularformation

Medullaoblongata

54

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


Thalamus

Superior peduncle

Middle peduncle

Inferior peduncle

Pons

Medulla oblongata

Cerebellum

Corpus callosum

Longitudinalfissure

56


Brain Waves

57

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)

61

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

66

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

67

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


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


Zygomatic nerve

Buccal nerve

Facial nerve

Mandibular nerve

Cervical nerve

Temporal nerve

Posterior auricularnerve

Parotid salivarygland

68

69

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

70

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


Superior laryngealnerve

Recurrent laryngealnerve

Superior ganglionof vagus nerve

Inferior ganglionof vagus nerve

Left vagusnerve

Smallintestine

71

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

73

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)


Cauda equina

C1C2C3C4C5C6C7C8T1T2T3T4T5T6

T7

T8T9T10T11

T12L1L2L3L4L5

S2S3

S4

S1

S5Co

Posteriorview

Cervicalnerves

Thoracicnerves

Lumbarnerves

Sacralnerves

Coccygealnerve

74

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


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)



Ventral root

75

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


76

Spinal Nerves


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



Ventral branchof spinal nerve (ventral ramus)Dorsal branchof spinal nerve (dorsal ramus)



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


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


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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Spinal Nerve Injuries

82

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


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


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


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

88

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


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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


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


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

THANK YOU

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anatomy and physiology of paediatric nervous system by dr asogwa innocent kingsley

Health & Medicine

spinal cord excess

ventricle b cerebral

lateral ventricles

nervous system subdivisions

cerebral hemispheres

meninges membranes of

dural sinus choroid

year of age dural sac