Peripheral Nervous System

Peripheral Nervous System

Anything leaving the spinal cord

Sensory neurons =...

Afferent neurons

Motor neurons =...

Efferent neurons

Associative =...

Interneurons

Dorsal =...

Sensory

Ventral =...

Motor

Ganglia

Cluster of neuron cell bodies

Nerve

Bundle of axons

Free nerve endings

Unencapsulated dendrites

Most common receptor type

Nocireceptors and thermoreceptors

Nocireceptors

Pain

Thermoreceptors

Temperature

Mechanoreceptors

Pressure receptors

Meissner's Corpuscles

Pacinian Corpuscles

Meissner's Corpuscles

Light pressure

Pacinian Corpuscles

Deep pressure

Propioreceptors

Awareness of position, movement, balance

Neuromuscular spindles

Golgi tendon organs

Vestibular system of inner ear

Chemoreceptors

Response to chemicals

Olfactory nerve (smell)

Taste buds (flavor)

Carotid body & sinus (blood CO2 and pressure)

Photoreceptors

Rods and cones in retina detect light

Spinal nerves

Pass through intervertebral foramina throughout spine

Dermatomes

Map of sensory innervation of the skin

T4 - nipple

T10 - umbilicus (aka belly button)

How do you lose sensation?

Damage the level above and below

Ex. losing sensation of belly button

- damage T9, T10, and T11

Referred pain

Pain in organs is perceived as pain elsewhere

Visceral sensory

from organs

Somatic sensory

from skin

Nerve plexuses

Motor and sensory fibers of each ventral ramus combine to form major nerve networks

4 major plexuses

Cervical, brachial, lumbar, sacral

Where do all nerve plexuses arise from

Ventral rami

Cervical plexus

C1 - C4

Muscles of skin and neck

Phrenic nerve

Innervates diaphragm

C3, C4, C5 (phrenic nerve) Keep you alive!

Brachial plexus

C5 - T1

Motor: Muscles of shoulders and upper limb

Sensory: Skin of shoulder and upper limb

Axillary nerve

Innervates deltoid muscle

Sensory: Skin of shoulder

Motor deficit: Abduction

Musculocutaneous nerve

Innervates biceps brachii and brachialis

Sensory: Lateral skin of forearm

Motor Deficit: Weak supination, arm flexion

Radial nerve

Innervates triceps, extensors of forearm

Sensory: Portions of posterior and lateral arm and forearm

Motor deficit: Arm, wrist, and digit extension

Wrist drop

Ulnar nerve

Innervates flexor carpi ulnaris, flexor digitorum, lumbricals (4-5)

Sensory: Medial skin of hand

Motor deficit: Claw hand, cannot flex digits

Median nerve

Innervates flexors of wrist, thenar eminence, lumbricals (1-3)

Motor deficit at carpal tunnel: Everything suffers

Motor deficit to thenar eminence: Ape hand (loss of opposition)

Lumbosacral plexus

L1-S4

Sciatic nerve

Innervates hamstrings

Motor deficit: Inability to flex leg, weakened thigh extension

Tibial nerve

Innervates gastrocnemius, soleus, and tibialis posterior

Motor deficit: Reduced ability to plantarflex, flex digits, invert

Common peroneal (fibular) nerve

Common = branches out into deep and superficial branch

Damage at common: Unable to dorsiflex AND evert your foot

Damage at deep branch: Unable to dorsiflex (foot drop)

Damage at superficial branch: Unable to evert

Femoral nerve

Innervates quadriceps

Motor deficit: Inability to extend knee (kick)

Obturator nerve

Innervates adductor muscles

Motor deficit: Inability to adduct

Pudendal nerve

Innervates pelvic diaphragm

Motor deficit: Damage to pudendal nerve can cause incontinence