PAS 313 Lecture 12 Peripheral Nervous System

PNS

the network of nerves (sensory and motor) that extends from the CNS to the rest of the body, relaying sensory information and controlling bodily functions

Photoreceptors

Sensory receptor that detects light

Ex: Rods and cones in retina

chemoreceptors

Sensory Receptor that responds to chemicals

Examples of chemoreceptors (respond to chemicals)

Olfactory nerve - smell

Taste buds - flavor

Carotid body & sinus - blood CO2 and pressure

Olfactory nerves

Chemoreceptor that reacts to smell.

Taste Buds

Chemoreceptor that reacts to tastes

carotid body and sinus

Chemorecptor that reacts to changes in blood carbon dioxide (CO2) levels and blood pressure.

Mechanoreceptor

Sensory Nerve that reacts to touching/pressure

Meissner’s corpuscle and Pacinian corpuscle

Meissner’s corpuscle

Light pressure aka tactile corpuscle

Pacinian corpuscle

Deep pressure aka lamellar corpuscle

Thermoreceptor

Sensory Nerve that reacts to Temperatures, free nerve endings

Nociceptors

Sensory Nerve that reacts to pain, free nerve endings

Proprioceptor

Sense of position in space where receptors detects changes is length, tension, and position

Neuromuscular Spindles

Proprioceptor that reacts to stretching

Golgi Tendon

Proprioceptor that reacts to muscle force

Vestibular System

Proprioceptor that controls Balance

>Inner ear

Spinal Nerves

31 pairs

C8, T12, L5, S5, C1

Rami

Sensory and Motor nerves that send impulses to different parts of the body

Dorsal Ramus

spinal nerve that carries both motor and sensory signals to the deep muscles and skin of the back

Ventral Ramus

spinal nerve that carries both sensory and motor information to the anterior (front) part of the body

Dermatones

"Map" of sensory innervation of skin

T4 Dermatome

Nipple

T 10 Dermatome

Belly Button

Key factor regarding Dermatomes

Dermatomes overlap above and below

>Ie: if Navel(T10) is affected T9 to T11 are affected

Referred Pain

Pain in organs results in perceived pain somewhere else, generalization of where the pain is not the actual location

Involves visceral (organs) and somatic (skin) sensory

Referred pain examples : Myocardial Ischemia

Poor or no blood supply to cardiac, pain in upper left limb, and pain can radiate to right limb,jaw, and neck

Nervous Plexuses

Both motor and sensory derived from ventral rami that are Intertwined network of nerves

What are the 4 major Plexuses

Cervical, Lumbar, Sacral, Brachial

Cervical Plexus

C1 to C4, arises from cervical enlargement, muscles and skin of neck (Ventral Remember)

Cervical Plexus Nerves

Phrenic Nerve C3 to C5

phrenic nerve

Cervical Plexus Nerve that controls the diaphragm from C3, C4, C5

Brachial Plexus

C5-T1

Motor: muscles of shoulder and upper limbs

Sensory: skin of shoulder and upper limb

Nerves found in the Brachial Plexus

C5-T1   AMMUR

Axillary

Musculocutaneous

Median

Ulnar

Radial

Axillary nerve

Brachial plexus C5-T1

Motor: deltoid muscle

Sensory: skin of shoulder

Damage to the Axillary Nerve

Limited arm abduction and loss of shoulder (Brachial Plexus)

Musculocutaneous Nerve

Brachial plexus

Motor: muscles of anterior arm (biceps brachii and brachialis)

Sensory: lateral skin of forearm

Damage to the Musculocutaneous Nerve (Brachial Plexus)

Reduced arm flexion, forearm supination, and numbness/pain in lateral forearm (Brachial Plexus)

Radial nerve

Brachial plexus C5-T1

Motor: extension of arm, forearm, wrist, and digits (Triceps, extensor carpi muscles, extensor digitorum)

Sensory: portions of posterior, lateral arm, and  forearm

Damage to the Radial Nerve

Inability to do arm, wrist, digit extension, and numbess/pain in posterior arm/forearm (Brachial Plexus)

Wrist drop

Radial nerve is damaged so inability to extend wrist

If wrist involuntary drops into flexion = nerve damaged

Ulnar nerve

Brachial plexus C5-T1

Motor: Intrinsic hand muscles (flexor carpi ulnaris, part of flexor digitorum profundus, hypothenar muscles, lumbricals III and IV)

Sensory: numbness/pain - medial skin of hand and half of digit IV

Claw Hand

Severe damage to ulnar nerve where the lumbricals are affected and the extensor digitorum extends the metacarpophalangeal joint

Funny Bone

Compression or damage to ulnar nerve at elbow

Median Nerve

Brachial plexus C5-T1

Motor: flexors of wrist, thenar muscles, lumbricals 1 and 2

Sensory: numbness/pain, skin of palm and digits, half of digit 4

Damage to the Median Nerve

Carpal Tunnel and Ape Hand

> Opposition can't occur (Brachial Plexus)

Lumbo-sacral Plexus

L1 to S4, ventral Rami that provides motor and sensory innervation to the lower limbs

Nerves found in Lumbo-sacral Plexus

Femoral Nerve

Obturator nerve

Sciatic nerve

Tibial Nerve

Common Fibular Nerve

Pudendal Nerve

(Find Our Silly Tiny Cat Paws)

Lumbo-sacral Plexus Mnemonic

Find Our Silly Tiny Cat Paws

Femoral nerve

Lumbosacral plexus L1-S4

Motor: quadriceps

Sensory: skin of anterior thigh and leg

Damage to the Femoral Nerve

Inability to extend knee and numbness/pain in skin of anterior lower leg Lumbo-Sacral)

Obturator nerve

Lumbosacral plexus

Motor: adductor muscles

Damage to the Obturator Nerve

Inability to adduct thigh (Lumbo-Sacral)

Sciatic nerve

Lumbosacral plexus

Motor: hamstring

Sensory: posterior thigh

Damage to the Sciatic Nerve

Weakened thigh extension and inability to flex leg (Lumbo-Sacral)

Gluteal injection

Able to inject in b/c not many nerves to damage and avoids sciatic nerve

Sciatica

Pain resulting from a pinched or compressed sciatic nerve

Results in: Posterior lower limb pain/numbness and possible weakness of posterior lower limb muscles

Tibial Nerve

Lumbosacral plexus L1-S4

Motor: all posterior leg muscles (gastrocnemius, soleus, tibialis, flexor hallucis longus)

Damage to the Tibial Nerve

Reduced ability to plantarflex, flex digits, or inverts (Lumbo-Sacral)

Common fibular nerve

Lumbosacral trunk and two branches: deep fibular nerve and superficial fibular nerve

Deep Fibular nerve

Lumbosacral trunk

Motor: muscles of anterior leg

Superficial fibular nerve

Lumbosacral trunk

Motor: muscles of lateral leg

Damage to the Deep Common-Fibular nerve

Reduced or absent dorsiflexion, digit flexion, inversion (Lumbo-Sacral)

Damage to the Superficial Common-Fibular nerve

Eversion (Lumbo-Sacral)

Foot drop

Damage to the Deep common fibular nerve causes an inability to dorsiflex, the foot automatically falls into plantarflexion

Pudendal Nerve

Lumbosacral plexus L1-S4

Motor and Sensory: pelvic floor/diaphragm

Damage to the Pudendal nerve

Incontinence and prolapse (Lumbo-Sacral)

Pudendal Nerve Block

a medical procedure that involves injecting a local anesthetic near the pudendal nerve to temporarily relieve pain in the genital, rectal, and pelvic areas