The central nervous system presentation dawn part 2

CRANIAL NERVES AND THEIR FUNCTIONS.

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Nervous System Subdivisions

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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

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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

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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)

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Cranial Nerves

• Remember:

• Cranial nerves are designated ‘CN’

• Cranial nerves are designated with Roman numerals (I – XII)

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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

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

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

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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


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)


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


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

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

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


DISORDERS OF CNS.

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The central nervous system presentation dawn part 2

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