PERIPHERAL NERVOUS
SYSTEM
PNS


Provides the relays to the central nervous system. It
picks up sensory information from the environment
and translates it to the CNS.
The stimulus received by the PNS can be classified
into five types.
Classification of stimulus

Mechanoreceptors respond to mechanical force
such as touch, pressure (including BP), vibration, and
stretch.

Thermo receptors- are sensitive to temperature
changes.

Photoreceptors- such as those of the retina and the
eye, respond to light energy.

Chemorecptors- respond to chemicals in chemical
solutions. (molecules that can be smelled, or tasted,
etc)

Noicreceptors- respond to stimulus that result from
pain. Such as loud noise, extreme cold, pressure,
and inflammatory chemicals.
Classification by location

Exteroceptors- sensitive to stimuli that occurs outside
of the body. Needless to say, these receptors are
found mostly on the body surface.

Interoceptors- respond to stimulus within the body.
They monitor everything from chemical change,
tissue stretch, and temperature. They can make us
feel pain, hunger, and discomfort, but we are
usually unaware of it.


Proprioceptors- Located in the skeletal muscles and
joints , tendons and ligaments, and in connective
tissue that covers the skeleton and muscle only.
They serve the same function as interoceptors.
Complexity


Most PNS structures are simple, meaning that they
are usually just a modified dendritic cell.
The Few that are complex however, are what we
associated as our sensory organs like the eyes.
Sensory Integration: from sensation to
perception


Human survival depends not only on sensation, but
the perception of that sensation.
For example If you get smacked on the arm, you
sense pressure, but you perceive that pressure as
pain.
General organization of the
somatosensory system

The somatosensory system is a system that serves
the limbs of the body. The three main levels at
which this is operated is as follows:
 Receptor
level: sensory receptors (tells you what)
 Circuit level: Ascending pathway (Sends impulse to
proper channel)
 Perceptual level: Neuronal circuits in the cerebral cortex
(tells you how to perceive the stimulus.)
Structural Classification of nerves

A nerve is a cordlike organ that is part of the
peripheral nervous system. The consist of parallel
bundles of peripheral axons, enclosed by
successive wrappings of connective tissue.
Regeneration of Nerve Fibers



1. When a nerve is severed or crushed, Wallerian
degeneration (cell destruction and the destruction of
cells around the severed cell) occurs.
2. After debris is disposed of, Shwann cells
proliferate and macrophages are released into the
injury site.
3. Then the regenerated axons will sprout across the
gap and to their original contacts.
Cranial nerves


There are 12 sets of nerves that associate themselves with the brain.
They are:












Olfactoral
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal
Cranial Nerves: Olfactory

Sensory nerves that
control smell. Runs
from the nasal mucosa
to the olfactoral bulb.
Cranial Nerves: Optic

Because the sensory
nerves of vision
develops outside the
brain, it is a brain
tract.
Cranial Nerves: Oculomotor

Sensory nerve that
supplies nerves that
innervate muscles that
control eye movement.
Cranial Nerves: Trochlear

Means “pulley” and
innervates muscles that
are in a pulley shaped
muscle in the orbit (eye
area).
Cranial Nerves: Trigeminal

Three branches that
supply sensory fibers
to the face and motor
fibers to the to the
chewing muscles.
Cranial Nerves: Abducens

Controls the muscles
that abduct the
eyeball (move it
laterally)
Cranial Nerves: Facial

A large nerve that
innervates the muscles
of the face. (and
other things as well)
Cranial Nerves: Vestibulocochlear

Sensory nerve for
hearing and balance.
A.K.A. the auditory
nerve.
Cranial Nerves: Glossopharyngeal

Means “tongue and
pharynx”. Innervates
the tongue and throat.
Cranial Nerves: Vagus

Means “wanderer” The
only cranial nerve that
extends to the thorax
and the abdomen.
Cranial Nerves: Accessory

An accesory (helper)
nerve that assists the
vagus nerve.
Cranial Nerves: Hypoglossal

Runs inferior to the
tongue and innervates
the tongue muscles.
Spinal nerves

There are 31 pairs of spinal nerves that innervate
the body. Each of those spinal nerves contain
thousands of nerves.
 There
are 8 pairs of cervical spinal nerves
 There are 12 pairs of thoracic spinal nerves
 There are 5 pairs of lumbar spinal nerves
 There are 5 pairs of sacral spinal nerves
 There is 1 pair of coccygeal nerves.
Nerve plexus

Are bundles of nerves that occur in the cervical,
thoracic, lumbar, and sacral regions that are
designed to innervate primarily the limbs.
Branches of the cervical plexus:
Cutaneous branches


Branch
Lesser occipital





C2, C3
Supraclavicular


C2, C3
Transverse Cervical


C2
Greater auricular


C3, C4

Structure served
Skin on posterolateral
aspect of neck
Skin of ear, skin over
parotid gland
Skin on the anterior
aspect of neck
Skin of the shoulder and
the clavicular region
Branches of the cervical plexus:
motor branches


Branch
Ansa Cervicalis




C1-C5
Phrenic


C1-C3
Segmental and other
muscular branches


C3-C5

Structure Served
Infrahyoid muscle of the
neck
Deep muscles of the
neck, portions of the
scalenes, levator,
scapulae, trapezius, and
sternonucleiodmastoid
muscles
Diaphragm
Branches of the brachial plexus


Nerve
Musculocutaneous




C5-C7
Median: (2) branches
MedialC8-T1
 lateral C5-C7



Structure served
Muscular branches;
flexor muscles in
anterior arm In
cutaneous branches:
controls skin on arm.
Flexor muscles of the
forearm. Digits of the
fingers.
Cutaneous: skin of 2/3
of hand and palm.


Nerve
Ulnar
 C8-T1


Structure served
Flexor muscles of the
anterior forearm;
interisitc muscles of the
lateral palm.
Cutaneous branches:
skin of the
posteriolateral surface
of the entire limb


Nerve
Radial
 C5-C8,


T1
Structure Served
Posterior muscles of
the arm and forearm;
most intrinsic muscles
of the hands.
Cutaneous:
posteriolateral surface
of the hand.


Nerve
Axillary


 C5,C6

Dorsal Scapular
 C5

Structure Served
Deltoid and teres
minor muscles.
Cutaneous: some skin
of the shoulder
Rhomboid muscles and
levator scapulae.


Nerve
Long Thoracic





C5, C6
Pectoralis


C5, C6
Suprascapular


Structure Served
Serratus anterior muscle
C5-C7
Subscapular


C5-T1

Teres major and
subscapularis muscle
Shoulder joint;
supraspinatus and
infraspinas muscles
Pectoralis major and
minor muscles
Branches of the Lumbar plexus


Nerve
Femoral



L2-L4
Obturator


L2-L4

Structure served
Skin of anterior and
medial thigh. Medial
leg and foot. Hip, knees,
and joints.
Motor to adductor
magnus, longus, and
brevis, obturator, skin
for medial thigh, and for
hip and knee joints


Nerve
Lateral femoral
cutaneous.
 L2,


L3


Iliohypogastric
 L1
Structure served
Skin of lateral thigh;
some sensory branches
to peritoneum.
Skin of lower
abdomen and hip;
muscles of
anterolateral
abdominal wall


Nerve
Ilioiguinal
 L1


Structure Served
Skin of external
genitalia, and
proximal medial
aspect of the thigh;
inferior abdominal
muscles


Nerve
Genitofemoral


Structure Served
Skin of scrotum in
males, of labia majora
in females, and of
anterior thigh; inferior
to middle portion of
inguinal region;
cremaster muscles in
males.
Branches of sacral plexus


Nerve
Sciatic nerve
(including sural,
medial and lateral
plantar, and medial
calcaneal branches)


 Tibial
 L4-S3

Structure Served
Cutaneous branches: to
skin of posterior
surface of leg and
sole of foot
Motor branches:
posterior of adductor
magnus, triceps surae,
tibulis
 Common
fibular
(superficial and deep
branches)

 L4-S2

Cutaneous: to skin of
anterior and lateral
surface of the leg and
dorsum of foot
Motor branches: short
head of biceps
femoralis of the thigh;
extensor muscles of the
toes.


Nerve
Superior Gluteal
 L4,



L5, S1
Inferior Gluteal
 L5-S2

Structure served
Motor branch to
gluteus medius and
minimus
Motor branch to
gluteus maximus

Posterior femoral
cutaneous

Skin of the buttock,
and posterior thigh
 S1-S3

Pudendal
 S2-S4

Supplies most of the
skin muscles, anus,
clitoris, labia, vaginal
mucosa (females),
scrotom and penis in
males.