Ch 13 the peripheral nervous system and nervous activity

1. The Peripheral Nervous
System and Reflex Activity
Lecture 13

2. ーー デ ェ
===

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Figure 13.1

3. Figure 13.2

4. トーーー Axon

Myelin sheath

Endoneurium

Perineurium

Epineurium

Fascicle

(a)

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Figure 13.3

5. Fine axon sprouts.

|-Droplets
of myelin

| site of,
nerve damage

‘Schwann cell

‘Schwann
cell

‘Schwann coll

Macrophage (2)

| aligning

Pr Et
Este om
Nw axon edo
amont

(ey

Schwann.
call
Schwann Site of now
call myelin sheath
formation
Now axon:
filament
Single
enlarging
axon flament
Schwan

cell

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Figure 13.4

6. Fragmented
axon Droplets
of myelin

Endoneurium

Myelin
droplet

Site of
nerve damage

Schwann cell

Schwann
cell

Macrophage

Schwann cell |

Macrophage (b)
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Figure 13.4a, b

7. Fine axon sprouts
or filaments

New axon
filament

Schwann

semana! |

Schwann
cell

New axon
filament

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Aligning
Schwann
cells form
regeneration
tube

Endoneurium

Site of new
myelin sheath
formation

+ Single

enlarging
axon filament

Figure 13.4c, d

8. Filaments of
olfactory
nerve (1)
Olfactory bulb

Infundibulum と Oculomotor
Facial nerve fi)
nerve (Vil)
Vestibulo-
cochlear
poe . nerve (V)

Glosso- Abducens
nerve (VI)

Accessory nerve (XI)

Hypoglossal nerve (XII)

fa)

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Figure 13.5

9. Filaments of
Frontal lobe & 『 olfactory
À, 4 À nerve (1)
f we À Olfactory bulb
i=l Olfactory tract

Optic nerve (II)
YA

NY (PS À Optic chiasma

Temporal lobe

/ —— Optic tract
Infundibulum Oculomotor
Facial A 는 7 nerve 01)
nerve (VII) | ~ PR Trochlear

IT

0901 EA nee
nerve (VIII) y 一 | em
Glosso- : Abducens

pharyngeal nerve (IX)!
Vagus nerve (X)
Accessory nerve (XI)

Hypoglossal nerve (XII)

= AU ADA nerve (VI)

AL A 1 Cerebellum
= Medulla

(a) >
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Figure 13.5a

10. I Olfactory Yes (smell)

Il Optic Yes (vision)

Il Oculomotor No

IV Trochlear No

V Trigeminal Yes (general
sensation)

VI Abducens No

Yes
Yes

Yes

No
No
Yes
No
No

No

VII Facial Yes (taste)
VIII Vestibulocochlear Yes (hearing
and balance)

IX Glossopharyngeal Yes (taste)

X Vagus Yes (taste)
XI Accessory No
XII Hypoglossal No

Yes
Some

Yes
Yes
Yes
Yes

Yes
No

Yes
Yes
No
No

(b) “PS = parasympathetic

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Figure 13.5b

11. Cervical peus |
Brachial wm

Cervical
enlargement

Intercostal
nerves

Lumbar plexus

Sacral plexus

Cauda equina

‘Copyright 2006 Pearson Esueation, Ic. publishing as Benjamin Cummings
Figure 13.6

12. Ventral root White matter
Dorsal root: Gray matter

Dorsal root Dorsal and ventral
ganglion à rootlets of spinal
Dorsal ramus 0

of spinal nerve

Ventral ramus.
of spinal nerve

Spinal nerve
Rami communicantes.

‘Sympathetic trunk
(chain) ganglion

Dorsal ramus
Ventral ramus
sr nerve! Intercostal nerve
Rami communican

Dorsal root ganglion

‘Sympathetic trunk
(chain) ganglion

Dorsal root

Thoracie cavi
id Lateral cutaneous

Branches of
Anterior cutaneous] intercostal

nerve

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Figure 13.7

13. White matter

Ventral root:

Dorsal root Gray matter
Dorsal root Dorsal and ventral
ganglion rootlets of spinal

Dorsal ramus nerve
of spinal nerve

Ventral ramus
of spinal nerve

Spinal nerve
Rami communicantes

Sympathetic trunk
(chain) ganglion

(a)

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Figure 13.7a

14. Dorsal ramus

Ventral ramus

Spinal nerve

" " Intercostal nerve
Rami communicante:

Dorsal root ganglion

Ventralreot Sympathetic trunk
(chain) ganglion

Dorsal root

Thoracic cavity

Anterior cutaneous| intercostal
nerve

Lateral cutaneous
Branches of
IS

Sternum —
(b)

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Figure 13.7b

15. Hypoglossal
nerve (XII)

\ Ventral
Lesser occipital \ rami:
nerve

Greater auricular
nerve

Transverse cutaneous
nerve

Ansa cervicalis

Accessory nerve (XI)

Phrenic nerve

Supraclavicular:
nerves

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Figure 13.8

16. Key:
= roots
= Trunks
Es Upper
= Anterior Posterior
divisions Middle | Trunks
[a Posterior
division Lateral
Cords -| Posterior
Upper subscapular
reg Lower subscapular
incida Thoracodorsal
Medial cutaneous
Median nerves of the arm
(a) Ulnar and forearm
Major torminal Roots
branches Cords | Divisions | Trunks | (ventral
(peripheral norves) rami)
Musculocutaneous Ania Upper E
aera Posterior’ K
Median: ce
Medial, Vanterior. À
Uinar ; liddie ペーーーC。
1 Posterior
Radial: Y 도
가 Anterior /
Axillary \ Lower 5
“Posterior
(0)

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E

Musculo-
cutaneous
nerve

アル una

- Radius
Ulnar nerve
Median
nerve
Radial nerve
(superficial
branch)

Dorsal branch

of ulnar nerve

it ‘Superficial branch
of ulnar nerve
” Digital branch

of ulnar nerve

Median

nerve

Figure 13.9

17. Key:

[j= Roots
(= Trunks

= Anterior

division

a = Posterior

division

Cords — Posterior

Posterior
divisions Middle | Trunks

[Lateral ー
Lower

Long thoracic
Medial pectoral

| Medial
Lateral pectoral

Upper subscapular
Lower subscapular
Thoracodorsal

Medial cutaneous
nerves of the arm
and forearm

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Figure 13.9a

18. Major terminal Roots

branches Cords (ventral
(peripheral nerves) rami)
Musculocutaneous cuido Upper Cs
Lateral Posterior \
Median 1 (es
Medial } Anterior
Ulnar 1 ツーMidde <

| Posterior

Radial Y Ca
Posterior «-— Anterior 到
Axillary \ Lower T

1
‘Posterior
(b)

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Figure 13.9b

19. Trunks

nerve

Musculo-
cutaneous

nerve

Una
Radius
Ulnar nerve
Medi
nerve
Radial nerve
(superficial
branch)
Dorsal branch
of ulnar nerve
‘Superficial branch
of ulnar nerve
Digital branch
of ulnar nerve
Muscular
branch
Median
Digital
branch 그 "97e
(이

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デー ジロ
に ここ の
es

Figure 13.9c

20. liohypogastric

Nioinguinal
femoral
cutaneous
Genitofemoral

Obturator

Lateral femoral À Anterior:
cutaneous femoral
cutaneous

Saphenous:
Obturator

Femoral

Lumbosacral
trunk

(a)

Key:
= Ventral rami

(b)

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Figure 13.10

21. Ventral

Superior
gluteal

Lumbosacral
trunk

Inferior
gluteal

Common
fibular

Tibial

Posterior
femoral
cutaneous

Pudendal

Sciatic

= Ventral rami

Superior
gluteal

Inferior
gluteal
Pudendal

Sciatic

Posterior
femoral
cutaneous

Common
fibular

Tibial
Sural

Deep
fibular

Superficial
fibular

Plantar
branches

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Figure 13.11

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Figure 13.12

23. Figure 13.12a

24. Figure 13.12b

25. Control level Structures involved

| Cerebellum and basal nuclei

Internal
Feedback feedback

Motor cortex (pyramidal system)
and brain stem nuclei (vestibular,
red, reticular formation, etc.)

Spinal cord

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Figure 13.13

26. Figure 13.14

27. Efferent motor fiber to spindle

Secondary
sensory
endings
(type ll fiber)

ーー

Primary
sensory
endings
(type la fiber)

Muscle spindle

VAN ee
aña,

Connective
tissue capsule

Golgi tendon 一 |
organ

a Efferent
motor fiber
to extrafusal
muscle
fibers

Extrafusal
muscle
fiber

Intrafusal
muscle

— Sensory
E fiber

Tendon

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Figure 13.15

28. Interneuron Cell body of

(O Afferent impulses. se E sensory neuron
from stretch

receptor to
spinal cord

Initial
stimulus:
muscle
stretch

Muscle
spindle

(a)

Motor neuron
serving quadriceps

Motor neuron
serving antagonist
\ muscle group

\\ (hamstrings)

@Efferent A

impulses to

alpha (0) motor’ ö
neurone cause >
contraction

of the stretched Spinel com
muscle that (La-La)
resists/reverses

the stretch

Muscle
spindle

© Efferent impulses | Hamstrings

| to antagonist (flexors)
| À muscles are
damped =
) {reciprocal Key:
> inhibition) ; + Excitatory synapse
y mn. | lt \ = Inhibitory synapse

(b)

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Figure 13.16

29. Figure 13.17

30. Golgi
tendon

内 organ
Quadriceps 9

(extensor)

Hamstrings
(flexor)

Spinal cord

Interneurons

Afferent fiber
from Golgi
tendon organ

Efferent fiber
to muscle
associated
with stretched
tendon

Key: Efferent fiber
+ Excitatory synapse to antagonisti
- Inhibitory synapse muscle

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Figure 13.18

31. Extensor 6 / Fe
inhibited (| "à r inhibited

Flexor ~ nen x >
e Extensor
stimulated stimulated

Key:
+ Excitatory synapse Right arm Left arm (site of
ー Inhibitory synapse (site of stimulus) reciprocal activation)

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Figure 13.19

32. General Sensory Rece]

STRUCTURAL CLASS

UNENCAPSULATED

FUNCTIONAL CLASSES
ACCORDING TO LOCATION (L)
ILLUSTRATION AND STIMULUS TYPE (S)

BODY LOCATION

Free nerve endings of
sensory neurons

Modified free nerve endings:

Merkel discs (tactile discs)

Hair follicle receptors

L: Exteroceptors, interocep-
tors, and proprioceptors

S: Thermoreceptors (warm
and cool), chemoreceptors
(itch, pH, etc.), mechano-
receptors (pressure),
nociceptors (pain, hot,
cold, pinch, and chemicals)

Exteroceptors
Mechanoreceptors
(light pressure); slowly
adapting

の ビ

: Exteroceptors
Mechanoreceptors (hair
deflection); rapidly
adapting

or

Most body tissues; most
dense in connective
tissues (ligaments,
tendons, dermis, joint
capsules, periostea)
and epithelia (epidermis,
cornea, mucosae, and
glands)

Basal layer of epidermis
of skin

In and surrounding hair
follicles

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Table 13.1.1

33. General Sensory Receptors Cl

STRUCTURAL CLASS

ILLUSTRATION

FUNCTIONAL CLASSES

ACCORDING TO LOCATION (L)
AND STIMULUS TYPE (S)

on (continued)

BODY LOCATION

ENCAPSULATED

Meissners corpuscles
(tactile corpuscles)

Pacinian corpuscles
(lamellated corpuscles)

Ruffini endings

Muscle spindles

Golgi tendon organs

Joint kinesthetic receptors

L: Exteroceptors

S: Mechanoreceptors (light
pressure, discriminative
touch, vibration of low
frequency); rapidly adapting

L: Exteroceptors, interocep-
tors, and some proprio-
ceptors

S: Mechanoreceptors (deep
pressure, stretch, vibration
of high frequency); rapidly
adapting

L: Exteroceptors and proprio-
ceptors

S: Mechanoreceptors (deep
pressure and stretch);
slowly or nonadapting

L: Proprioceptors

S: Mechanoreceptors (muscle
stretch, length)

L: Proprioceptors

S: Mechanoreceptors
(tendon stretch, tension)

L: Proprioceptors

S: Mechanoreceptors and
nociceptors

Dermal papillae of
hairless skin, particularly
nipples, external
genitalia, fingertips,
soles of feet, eyelids
Dermis and hypodermis;
periostea, mesenteı
tendons, ligaments,
capsules; most abundant
on fingers, soles of feet,
external genitalia, nipples

Deep in dermis,
hypodermis, and joint
capsules

Skeletal muscles,
particularly those of the

Joint capsules of
synovial joints

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Table 13.1.1

34. Cranial Nerves

I THE OLFACTORY NERVES (ol-fak’to-re)

Origin and course: Olfactory nerve fibers
arise from olfactory receptor cells located in
olfactory epithelium of nasal cavity and pass
through cribriform plate of ethmoid bone to
synapse in olfactory bulb. Fibers of olfactory
bulb neurons extend posteriorly as olfactory
tract, which runs beneath frontal lobe to

enter cerebral hemispheres and terminates in
primary olfactory cortex. See also Figure 15.21
Function: Purely sensory; carry afferent
impulses for sense of smell

Clinical testing: Person is asked to sniff
aromatic substances, such as oil of cloves

and vanilla, and to identify each.

BS Homeostatic imbalance: Fracture of
ethmoid bone or lesions of olfactory fibers
may result in partial or total loss of smell, a
condition known as anosmia (an-oz'me-ah). @

Frontal lobe
of cerebral
hemisphere

Olfactory bulb

Olfactory
tract

Cribriform
plate of
ethmoid bone

Filaments of
olfactory
nerve (I)

Nasal mucosa

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Table 13.2.1

35. Cranial Nerves (continued)

11 THE OPTIC NERVES

Origin and course: Fibers arise from retina of

eye to form optic nerve, which passes through
optic canal of orbit. The optic nerves converge
to form the optic chiasma (ki-az'mah) where fibers
partially cross over, continue on as optic tracts,
enter thalamus, and synapse there. Thalamic
fibers run (as the optic radiation) to occipital
(visual) cortex, where visual interpretation occurs.
See also Figure 15.19.

Function: Purely sensory; carry afferent

impulses for vision

Clinical testing: Vision and visual field are
determined with eye chart and by testing the
point at which the person first sees an object
(finger) moving into the visual field, Fundus of
eye viewed with ophthalmoscope to detect
papilledema (swelling of optic disc, the site
where the optic nerve leaves the eyeball), as

well as for routine examination of the optic disc
and retinal blood vessels.

BS Homeostatic imbalance: Damage to optic
nerve results in blindness in eye served by nerve;
damage to visual pathway beyond the optic chiasma
results in partial visual losses; visual defects are
called anopsias (ah-nop'se-ahz). @

Eyeball
Retina
Optic nerve (il)

Optic chiasma

‘Optic tract

Lateral
geniculate
nucleus of
thalamus

Optic
radiation

Visual
cortex

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Table 13.2.2

36. Cranial Nerves (continued) 0

비 THE OCULOMOTOR NERVES (ok'u-lo-mo'tor)

Origin and course: Fibers extend from ventral midbrain
(near its junction with pons) and pass through bony orbit,
via superior orbital fissure, to eye.

Function: Chiefly motor nerves (oculomotor = motor to
the eye); contain a few proprioceptive afferents; each
nerve includes

= Somatic motor fibers to four of the six extrinsic eye
muscles (inferior oblique and superior, inferior, and
medial rectus muscles) that help direct eyeball, and to
levator palpebrae superioris muscle, which raises upper
eyelid

* Parasympathetic (autonomic) motor fibers to sphincter
pupillae (circular muscles of iris), which cause pupil to
constrict, and to ciliary muscle, controlling lens shape for
visual focusing; some parasympathetic cell bodies are in
the ciliary ganglia

= Sensory (proprioceptor) afferents, which run from same
four extrinsic eye muscles to midbrain

Clinical testing: Pupils are examined for size, shape, and
equality. Pupillary reflex is tested with penlight (pupils
should constrict when illuminated). Convergence for near
vision is tested, as is subject's ability to follow objects
with the eyes.

Superior
Medial rectus: orbital fissure

muscle

‘Superior rectus
muscle

Midbrain

Levator palpebrae
muscle

Inferior oblique
muscle

Ciliary
ganglion
Inferior:
rectus muscle

Parasympathetic Oculomotor Pons
motor fibers nerve (ill)

BS Homeostatic imbalance: In oculomotor nerve paral-
ysis, eye cannot be moved up, down, or inward, and at

rest, eye rotates laterally [external strabismus (strah-biz’ mus)]
because the actions of the two extrinsic eye muscles not
served by cranial nerve Ill are unopposed: upper eyelid
droops (ptosis), and the person has double vision and trouble

focusing on close objects. @
>

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Table 13.2.3

37. TT |

IV THE TROCHLEAR NERVES (trok’le-ar)

Origin and course: Fibers emerge from dorsal
midbrain and course ventrally around midbrain

to enter orbit through superior orbital fissure

along with oculomotor nerves.

Function: Primarily motor nerves; supply somatic motor
fibers to (and carry proprioceptor fibers from) one of the
extrinsic eye muscles, the superior oblique muscle
Clinical testing: Tested in common with cranial nerve Ill.

‘= Homeostatic imbalance: Trauma to, or paralysis of,
a trochlear nerve results in double vision and reduced
ability to rotate eye inferolaterally. @

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Table 13.2.4

38. Cranial Nerves (continued)

V THE TRIGEMINAL NERVES

Largest of cranial nerves; fibers extend from pons to face, The mandibular division also contains motor fibers that
and form three divisions (trigemina = threefold): innervate chewing muscles.
ophthalmic, maxillary, and mandibular divisions. As major Dentists desensitize upper and lower jaws by injecting
general sensory nerves of face, transmit afferent impulses local anesthetic (such as Novocain) into alveolar branches
from touch, temperature, and pain receptors. Cell bodies of of maxillary and mandibular divisions, respectively; since
sensory neurons of all three divisions are located in large this blocks pain-transmitting fibers of teeth, the
trigeminal (also called semilunar or gasserian) ganglion. surrounding tissues become numb.
Maxillary division (V2) Mandibular division (Va)
Origin and course — Fibers run from face to pons Fibers run from face to pons Fibers pass through skull via
via superior orbital fissure via foramen rotundum foramen ovale
Function Conveys sensory impulses from Conveys sensory impulses from Conveys sensory impulses from
skin of anterior scalp, upper nasal cavity mucosa, palate, anterior tongue (except taste
eyelid, and nose, and from na- upper teeth, skin of cheek, buds), lower teeth, skin of chin,
sal cavity mucosa, cornea, upper lip, lower eyelid temporal region of scalp; supplies
and lacrimal gland motor fibers to, and carries

proprioceptor fibers from,
muscles of mastication

Clinical testing Corneal reflex tested: touching Sensations of pain, touch, and Motor branch assessed by asking
cornea with wisp of cotton temperature are tested with person to clench his teeth, open
should elicit blinking safety pin and hot and cold mouth against resistance, and

objects move jaw side to side

IFS Homeostatic imbalance: Tic douloureux (tik doo'loo- stimulus, such as brushing teeth or even a passing breeze

100"; tic = twitch, douloureux = painful), or trigeminal hitting the face. It seems to be caused by pressure on the

neuralgia (nu-ral'je-ah), caused by inflammation of trigeminal nerve root, Analgesics and carbamazepine (an

trigeminal nerve, is widely considered to produce most anticonvulsant) are only partially effective. In severe cases,
excruciating pain known; the stabbing pain lasts for a few nerve is cut proximal to trigeminal ganglion; this relieves
seconds to a minute, but it can be relentless, occurring a the agony, but also results in loss of sensation on that side
hundred times a day. Usually provoked by some sensory of face. @ >

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Table 13.2.5

39. TABLE 13.2 Cranial Nerves continued | EEE É
V THE TRIGEMINAL NERVES

‘Superior orbital fissure
Ophthalmic division (V,)
Trigeminal (semilunar
or gasserian) ganglion

Trigeminal nerve (V)

Pons
Maxillary division (V。)

Mandibular division (V。)
Foramen ovale ibution of sensory
Foramen rotundum fibers of each division

‘Anterior trunk to Mandibular
‘chewing muscles division (V.)
Mandibular foramen

Temporalis Lateral
muscle pterygoid

muscle
Medial

pterygoid
muscle

Masseter
muscle

Mental foramen Anterior belly of
digastric muscle

Inset shows motor branches
of the mandibular division (V,) >

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Table 13.26

40. Cranial Nerves (continu

VI THE ABDUCENS NERVES (ab-du'senz)

Origin and course: Fibers leave inferior pons and enter
orbit via superior orbital fissure to run to eye.

Function: Primarily motor; supply somatic motor fibers to
lateral rectus muscle, an extrinsic muscle of the eye; convey
proprioceptor impulses from same muscle to brain.
Clinical testing: Tested in common with cranial nerve Ill.

FS Homeostatic imbalance: In abducens nerve paralysis,
eye cannot be moved laterally; at rest, affected eyeball
rotates medially (internal strabismus). @

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Table 13.2.7

41. 개 ㅣ.

Vil THE FACIAL NERVES

IR;

Origin and course: Fibers issue from pons, just lateral to
abducens nerves (see Figure 13.5), enter temporal bone
via internal acoustic meatus, and run within bone (and
through inner ear cavity) before emerging through
stylomastoid foramen; nerve then courses to lateral

ms

aspect of face. branch (asta)

Function: Mixed nerves that are the chief motor nerves Stylomastoid foramon

of face; have five major branches: temporal, zygomatic, REN

buccal, mandibular, and cervical (see e) rer

nerve teers

= Convey motor impulses to skeletal muscles of face ‘Sublingual gland:

(muscles of facial expression), except for chewing muscles Submandbular gland:

served by trigeminal nerves, and transmit proprioceptor
impulses from same muscles to pons (see b)

= Transmit parasympathetic (autonomic) motor impulses to
lacrimal (tear) glands, nasal and palatine glands, and
submandibular and sublingual salivary glands. Some of the
cell bodies of these parasympathetic motor neurons are in
pterygopalatine (ter’eh-go-pal’ah-tin) and submandibular
ganglia on the trigeminal nerve (see a)

= Convey sensory impulses from taste buds of anterior

two-thirds of tongue; cell bodies of these sensory neurons
are in geniculate ganglion (see a)

(6) Motor branches to muscles of
facial expression and sealp muscles >

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Table 13.2.8

42. LME Cranial Nerves (continued)

VII THE FACIAL NERVES (continued)

Clinical testing: Anterior two-thirds of tongue is tested for
ability to taste sweet (sugar), salty, sour (vinegar), and bitter
(quinine) substances. Symmetry of face is checked. Subject
is asked to close eyes, smile, whistle, and so on. Tearing is
assessed with ammonia fumes.

Homeostatic imbalance: Bells palsy, characterized by
paralysis of facial muscles on affected side and partial loss of
taste sensation, may develop rapidly (often overnight). Most
often caused by herpes simplex | viral infection, which causes
swelling and inflammation of facial nerve. Lower eyelid
droops, corner of mouth sags (making it difficult to eat or
speak normally), tears drip continuously from eye and eye
cannot be completely closed (conversely, dry-eye syndrome
may occur). Condition may disappear spontaneously without
treatment. @

(c) A simple method of remembering the courses
of the five major motor nerves of the face

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Table 13.29

43. 70616 13.2 Cranial Nerves (continued): — . a

Vill THE VESTIBULOCOCHLEAR NERVES (ves-tib'u-lo-kok'le-ar)

Origin and course: Fibers arise from hearing and ‘Vestibular
equilibrium apparatus located within inner ear of ganglia
temporal bone and pass through internal acoustic Semicircular
meatus to enter brain stem at pons-medulla border.
Afferent fibers from hearing receptor in cochlea form

the cochlear division; those from equilibrium receptors

in semicircular canals and vestibule form the vestibular
division (vestibular nerve); the two divisions merge to form
vestibulocochlear nerve. See also Figure 15.27.

Function: Mostly sensory, Vestibular branch transmits
afferent impulses for sense of equilibrium, and sensory
nerve cell bodies are located in vestibular ganglia.
Cochlear branch transmits afferent impulses for sense of
hearing, and sensory nerve cell bodies are located in spiral
ganglion within cochlea. Some motor fibers from the pons
innervate the outer hair cells of the cochlea. See also Cochlea
Figure 15.28c (containing Vestibulocochlear nerve (VIII)
Clinical testing: Hearing is checked by air and bone spiral ganglion)

conduction using tuning fork.

Internal acoustic
meatus

Vestibular nerve
‘Cochlear nerve

ES Homeostatic imbalance: Lesions of cochlear nerve or
cochlear receptors result in central or nerve deafness,
whereas damage to vestibular division produces dizziness,
rapid involuntary eye movements, loss of balance, nausea,
and vomiting. @

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Table 13.2.11

44. Cranial Nerves (continued)

IX THE GLOSSOPHARYNGEAL NERVES (glos"o-fah-rin'je-al)

Origin and course: Fibers emerge from medulla and
leave skull via jugular foramen to run to throat.

Function: Mixed nerves that innervate part of tongue and
pharynx. Provide somatic motor fibers to, and carry
proprioceptor fibers from, a superior pharyngeal muscle
called the stylopharyngeus, which elevates the pharynx in
swallowing, Provide parasympathetic motor fibers to
parotid salivary glands (some of the nerve cell bodies of
these parasympathetic motor neurons are located in

otic ganglion).

Sensory fibers conduct taste and general sensory (touch,
pressure, pain) impulses from pharynx and posterior
tongue, from chemoreceptors in the carotid body (which
monitor O, and CO; levels in the blood and help regulate
respiratory rate and depth), and from baroreceptors of
carotid sinus (which monitor blood pressure). Sensory
neuron cell bodies are located in superior and inferior
ganglia.

Clinical testing: Position of the uvula is checked, Gag and
swallowing reflexes are checked. Subject is asked to speak
and cough. Posterior third of tongue may be tested for taste.

BS Homeostatic imbalance: Injury or inflammation of
glossopharyngeal nerves impairs swallowing and taste. @

Parotid gland
Parasympathetic

fibers

Glossopharyngeal
nerve (IX)

Jugular foramen
‘Superior ganglion
Inferior ganglion

Oti ganglion

Stylopharyngeus
Carotid sinus

Pharyngeal
muscles
‘Common carotid
artery

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Table 13.2.12

45. Cranial Nerves (continued) | y

X THE VAGUS NERVES (va'gus)

Origin and course: The only cranial nerves to extend
beyond head and neck region. Fibers emerge from
medulla, pass through skull via jugular foramen, and
descend through neck region into thorax and abdomen,
See also Figure 14.4.

Function: Mixed nerves; nearly all motor fibers are
parasympathetic efferents, except those serving skeletal
muscles of pharynx and larynx (involved in swallowing).
Parasympathetic motor fibers supply heart, lungs, and
abdominal viscera and are involved in regulation of heart
rate, breathing, and digestive system activity. Transmit
sensory impulses from thoracic end abdominal viscera,
from the aortic arch baroreceptors (for blood pressure) and
the carotid and aortic bodies (chemoreceptors for
respiration), and taste buds of posterior tongue and
pharynx. Carry proprioceptor fibers from muscles of larynx
and pharynx.

Clinical testing: As for cranial nerve IX (IX and X are tested
in common, since they both innervate muscles of throat
and mouth).

IFS Homeostatic imbalance: Since nearly all muscles of
the larynx ("voice box") are innervated by laryngeal
branches of the vagus, vagal nerve paralysis can lead to
hoarseness or loss of voice; other symptoms are difficulty
swallowing and impaired digestive system motility. Total
destruction of both vagus nerves is incompatible with life,
because these parasympathetic nerves are crucial
maintaining normal state of visceral organ acti
their influence, the activity of the sympathetic nerves, which
mobilize and accelerate vital body processes (and shut
down digestion), would be unopposed. @

Pons:

Ganglia inferior
and superior)

Medalla
cblongata

Vagus nerve (x)

Jugular foramen
Pharyngeal nerve branches
Carotid sinus

and body

Laryageal branches:

Aortic arch baroreceptor
and aortic body

Lung:

Coton:
{proximal portion)

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Table 13.2.13

46. TABLE 13.2 Cranial Nerves (continued) SO

XI THE ACCESSORY NERVES

Origin and course: Unique in that they are formed by
union of a cranial root and a spinal root. Cranial root

emerges from lateral aspect of medulla of brain stem;
spinal root arises from superior region (Ci-C of spinal Medulla

cord. Spinal portion passes upward along spinal cord, | | oblongata
enters skull via foramen magnum, and temporarily joins E

a x ranial root
cranial root; the resulting accessory nerve exits from skull
through jugular foramen. Cranial and spinal fibers then ( = Spinal root
diverge; cranial root fibers join vagus nerve, and spinal root | Foramen
runs to the largest neck muscles. diverges and magnum
Function: Mixed nerves, but primarily motor in function. Joins vagus ‘Cervical region
Cranial division joins with fibers of vagus nerve (X) to supply | of spinal cord

motor fibers to larynx, pharynx, and soft palate. Spinal root 2 / C-C)
supplies motor fibers to trapezius and sternocleidomastoid ei
muscles, which together move head and neck, and conveys Ala or
proprioceptor impulses from same muscles.

Clinical testing: Sternocleidomastoid and trapezius
muscles are checked for strength by asking person to
rotate head and shrug shoulders against resistance.

cleidomastoid
muscle

BS Homeostatic imbalance: Injury to the spinal root of

one accessory nerve causes head to turn toward injury side

as result of sternocleidomastoid muscle paralysis; shrugging
of that shoulder (role of trapezius muscle) becomes difficult. @

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Table 13.2.14

47. ER cani Nerves cnn nh:

XII THE HYPOGLOSSAL NERVES (hi"po-glos‘al)

Origin and course: As their name implies (hypo
beneath; glossal = tongue), hypoglossal nerves mainly
serve the tongue. Fibers arise by a series of roots from
medulla and exit from skull via hypoglossal canal to travel
to tongue. See also Figure 13.5.

Function: Mixed nerves, but primarily motor in function.
Carry somatic motor fibers to intrinsic and extrinsic
muscles of tongue, and proprioceptor fibers from same
muscles to brain stem. Hypoglossal nerve control allows
not only food mixing and manipulation by tongue during
chewing, but also tongue movements that contribute to
swallowing and speech.

Clinical testing: Person is asked to protrude and retract
tongue. Any deviations in position are noted.

BS Homeostatic imbalance: Damage to hypoglossal
nerves causes difficulties in speech and swallowing; if both
nerves are impaired, the person cannot protrude tongue;

if only one side is affected, tongue deviates (points) toward
affected side; eventually paralyzed side begins to atrophy. @

nerve (XII)

Extrinsic
muscles of
the tongue

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Table 13.2.15

48. 13-T03CervicalPlex_TAB
Table 13.3

49. Branches of the Brachial Plex

CORD AND SPINAL ROOTS
NERVES (VENTRAL RAMI) STRUCTURES SERVED
Musculocutaneous Lateral cord (Cs-C;) Muscular branches: flexor muscles in anterior arm (biceps brachii,
brachialis, coracobrachialis)
Cutaneous branches: skin on anterolateral forearm (extremely variable)

Median By two branches, one Muscular branches to flexor group of anterior forearm (palmaris longus,
from medial cord (Ca, Ty) flexor carpi radialis, flexor digitorum superficialis, flexor pollicis longus,
and one from the lateral lateral half of flexor digitorum profundus, and pronator muscles); intrinsic
cord (Cs-C)) muscles of lateral palm and digital branches to the fingers

Cutaneous branches: skin of lateral two-thirds of hand, palm side and
dorsum of fingers 2 and 3

Ulnar Medial cord (Ca, Ty) Muscular branches: flexor muscles in anterior forearm (flexor carpi
ulnaris and medial half of flexor digitorum profundus); most intrinsic
muscles of hand
Cutaneous branches: skin of medial third of hand, both anterior and
posterior aspects

Radial Posterior cord Muscular branches: posterior muscles of arm, forearm, and hand (triceps
(Cs-C Ti) brachii, anconeus, supinator, brachioradialis, extensors carpi radialis
longus and brevis, extensor carpi ulnaris, and several muscles that
extend the fingers)

Cutaneous branches: skin of posterolateral surface of entire limb
(except dorsum of fingers 2 and 3)

Axillary Posterior cord (Cs, Ce) Muscular branches: deltoid and teres minor muscles
Cutaneous branches: some skin of shoulder region
Dorsal scapular Branches of Cs rami Rhomboid muscles and levator scapulae
Long thoracic Branches of Cs-Cy Serratus anterior muscle
rami
Subscapular Posterior cord; branches Teres major and subscapular muscles
of Cs and Cs rami
Suprascapular Upper trunk (Cs, Ca) Shoulder joint; supraspinatus and infraspinatus muscles
Pectoral (lateral Branches of lateral and Pectoralis major and minor muscles
and medial) medial cords (CT

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Table 13.4

50. SPINAL ROOTS

# Branches of the Lumbar Plexus (See Figure 13.10) E

NERVES (VENTRAL RAMI) STRUCTURES SERVED

Femoral La Skin of anterior and medial thigh via anterior femoral cutaneous branch;
skin of medial leg and foot, hip and knee joints via saphenous branch;
motor to anterior muscles (quadriceps and sartorius) of thigh and to
pectineus, iliacus

Obturator Lely Motor to adductor magnus (part), longus, and brevis muscles, gracilis
muscle of medial thigh, obturator externus; sensory for skin of medial
thigh and for hip and knee joints

Lateral femoral cutaneous Lo, La Skin of lateral thigh; some sensory branches to peritoneum

lliohypogastric L Skin of lower abdomen, lower back, and hip; muscles of anterolateral
abdominal wall (obliques and transversus) and pubic region

ilioinguinal iy Skin of external genitalia and proximal medial aspect of the thigh; inferior
abdominal muscles

Genitofemoral Lulz Skin of scrotum in males, of labia majora in females, and of anterior thigh

inferior to middle portion of inguinal region; cremaster muscle in males

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Table 13.5

51. Branches of the Sacral Plexu:

SPINAL ROOTS

NERVES (VENTRAL RAMI) STRUCTURES SERVED
Sciatic nerve La, bs, Si-S3 Composed of two nerves (tibial and common fibular) in a common sheath;
they diverge just proximal to the knee
= Tibial (including sural, La-S3 Cutaneous branches: to skin of posterior surface of leg and sole of foot Motor
medial and lateral branches: to muscles of back of thigh, leg, and foot [hamstrings (except
plantar, and medial short head of biceps femoris), posterior part of adductor magnus, triceps
calcaneal branches) surae, tibialis posterior, popliteus, flexor digitorum longus, flexor hallucis
longus, and intrinsic muscles of foot]
= Common fibular Li-S2 Cutaneous branches: to skin of anterior surface of leg and dorsum of foot
(superficial and Motor branches: to short head of biceps femoris of thigh, fibular muscles of
deep branches) lateral compartment of leg, tibialis anterior, and extensor muscles of toes
{extensor hallucis longus, extensors digitorum longus and brevis)
Superior gluteal La, bs, St Motor branches: to gluteus medius and minimus and tensor fasciae latae
Inferior gluteal Ls-S2 Motor branches: to gluteus maximus
Posterior femoral 51-53 Skin of buttock, posterior thigh, and popliteal region; length variable; may
cutaneous also innervate part of skin of calf and heel
Pudendal SS, Supplies most of skin and muscles of perineum (region encompassing

external genitalia and anus and including clitoris, labia, and vaginal mucosa
in females, and scrotum and penis in males); external anal sphincter

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Table 13.6

52. Enkephalin- Descending

releasing serotonin- or
interneuron NE-releasing
From fiber
periphery = 을

Afferent
primary
nociceptive __
fiber
(type AS
and C
fibers)

Lateral
spinothalamic
pathway

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Figure UN 13.1