Peripheral Nervous System (PNS)

Peripheral Nervous System (PNS)

yes

All nervous structures outside of the CNS

no

All sensory and motor nerves including

Spinal nerves

Cranial nerves

Sensory ganglia

Sensory receptors

Motor nerves begins

Begin in ventral grey horn

Motor nerves

Innervate both voluntary skeletal muscles and involuntary

Somatic vs. visceral

Innervate muscles at neuromuscular junction

Sensory nerves

Receptors receive information from the world around us

Mechanoreceptors

Touch/pressure

Mechanoreceptors types

Meissner’s Corpuscle

Pacinian Corpuscle

Pacinian Corpuscle

Light pressure

AKA tactile Corpuscle

Meissner’s Corpuscle

Deep pressure

AKA Lamellar Corpuscle

Nociceptors

Pain

Thermoreceptors

temperature

Proprioceptors

Awareness of Position, movement, balance

Proprioception definition

Sense of position in space

Proprioception

Receptors in muscles, tendons, ligaments, skin, etc.

Detect changes in length, tension, and position

Proprioception examples

Neuromuscular spindles (stretch)

Golgi tendon organs (tension/muscle force)

Vestibular system of inner ear (balance, whole body position)

Chemoreceptors

Respond to chemicals

Olfactory nerve

Smell

Taste buds

Flavor

Carotid body & sinus

Blood CO2 and pressure

Photoreceptors

Rods and cones in retina detect Light

Dermatomes

“Map” of sensory innervation of skin

Dermatomes strips

Represented by specific spinal cord level

Pair of sensory nerves (left and right)

T4

Nipple

T10

Umbilicus (AKA navel, belly button)

Total sensation loss requires

Total sensation loss requires damage to THREE adjacent spinal nerve levels

Shingles

rash along entire dermatome

viruses

reside in dorsal root ganglion and travel along nerve axons

Referred Pain

Pain in organs results in perceived pain elsewhere

Referred Pain involves 

Visceral sensory (from organs)

Somatic sensory (skin)

visceral signals enter

spinal cord at same level as somatic, through same DRG

Because shared region in spinal cord, brain perceives additional pain in non -organ regions

Nervous plexuses

Intertwined network of nerves

Give off many branches that innervate bones, muscles, skin, etc.

4 Major plexuses

Cervical

Brachial

Lumbar

Sacral

ALL plexuses

Both motor & sensory

Derive from ventral rami

The Cervical Plexus C1-C4

Arises from cervical enlargement

Muscles and skin of neck

The Cervical Plexus

PHRENIC NERVE

C3, C4, C5

Diaphragm

The Brachial Plexus C5-T1

Motor

Sensory

The Brachial Plexus C5-T1 Motor

Muscles of shoulder & upper limb

The Brachial Plexus C5-T1Sensory

Skin of shoulder & upper limb

The Brachial Plexus: The Axillary Nerve

motor

Deltoid muscle

The Brachial Plexus: The Axillary Nerve

Sensory

Skin of shoulder

The Brachial Plexus: The Axillary Nerve

Damage to nerve

Limited arm abduction and loss of shoulder sensation

The Brachial Plexus Musculocutaneous Nerve

Motor

Muscles of anterior arm

Biceps brachii

Brachialis

The Brachial Plexus Musculocutaneous Nerve Sensory

Lateral skin of forearm

The Brachial Plexus Musculocutaneous Nerve

Damage to nerve

Greatly reduced Arm flexion, forearm supination

Numbness/pain in lateral forearm

The Brachial Plexus Radial Nerve

Motor

Extensors of arm, forearm, wrist, & digits

Ex. Triceps, extensor carpi muscles, extensor digitorum

The Brachial Plexus Radial Nerve

Sensory

Portions of posterior & lateral arm & forearm

The Brachial Plexus Radial Nerve

Damage to nerve

Arm, wrist, digit extension

Numbness/pain in posterior arm/forearm

Wrist drop

Radial nerve damage →Inability to extend wrist

If wrist involuntarily drops into flexion → radial nerve damage

The Brachial Plexus The Ulnar Nerve

motor

Flexor carpi ulnaris

Part of flexor digitorum profundus

Hypothenar muscles

Lumbricals III & IV (medial 2)

The Brachial Plexus The Ulnar Nerve

seonsory

Numbness/pain

Medial skin of hand

Ulnar nerve damage Funny bone

Compression or damage to ulnar nerve at elbow

Pain/numbness at site of damage and medial hand

Ulnar nerve damage Claw hand

Severe/chronic damage to nerve

Lumbricals affected

Extensor digitorum extends metacarpophalangeal joint

The Brachial Plexus Median Nerve

motor 

Flexors of wrist 

Thenar muscles

Lumbricals I & II

The Brachial Plexus Median Nerve

Sensory

Numbness/pain 

Skin of palm & digits

Carpal Tunnel Syndrome

Inflammation of tissue in carpal tunnel

All digit flexors pass through with median nerve

Damage/impingement of median nerve

Painful swelling, limited mobility, numbness of skin

Median Nerve Damage at wrist

Ape Hand

Loss of thumb opposition

Lumbosacral plexus Femoral Nerve

Motor

Quadriceps

Lumbosacral plexus Femoral Nerve

Sensory

Skin of anterior thigh and leg

Lumbosacral plexus Femoral Nerve

Damage to nerve

Inability to extend knee

Numbness/pain in skin of anterior lower limb

Lumbosacral plexus Obturator nerve

motor

Adductor muscles

Lumbosacral plexus Obturator nerve

Damage to nerve

Inability to adduct thigh

Lumbosacral plexus Sciatic nerve

Motor

Hamstrings

Lumbosacral plexus Sciatic nerve

Sensory

Posterior thigh

Lumbosacral plexus Sciatic nerve

Damage to nerve

Weakened thigh extension Inability to flex leg

Gluteal injection

Not many nerves to damage & avoids sciatic nerve

Sciatica

Posterior lower limb pain/numbness 

Possible weakness of posterior lower limb muscles

Lumbosacral Plexus Tibial Nerve

Motor

All posterior leg muscles

Gastrocnemius

Soleus

Tibialis Posterior

Flexor hallucis longus

Lumbosacral Plexus Tibial Nerve

Damage to nerve

Reduced ability to plantarflex, flex digits, invert

Lumbosacral Trunk Common Fibular Nerve

2 branches

Deep fibular nerve

superficial fibular nerve 

Deep fibular nerve

motor 

muscles of anterior leg

Deep fibular nerve

nerve damage 

Reduced or absent dorsiflexion, digit flexion, inversion

Superficial Fibular Nerve

Motor

muscles of lateral leg

Superficial Fibular Nerve

Nerve Damage

Eversion

Foot drop

Damage to deep fibular nerve: In ability to dorsiflex

Patient lifts foot off floor

If foot falls into plantar flexion  deep fibular nerve damage

The Lumbosacral Plexus The Pudendal Nerve

Motor & sensory to the Pelvic floor/ diaphragm Damage to the Pudendal Nerve can cause

The Lumbosacral Plexus The Pudendal Nerve

Incontinence

Cannot contain urine/feces

The Lumbosacral Plexus The Pudendal Nerve

Prolapse

Vagina and/or anal canal inverts outside of body

Pudendal Nerve Block

Can be used in obstetrics for pain relief during childbirth