Peripheral Nerves and Arteries

Information IN

Sensory or “afferent” neurons carry information into the CNS from receptors

located throughout the body.

Information OUT

Motor or “efferent neurons” carry electrical impulses away from the CNS

to innervate “effector organs,” like muscles and glands.

Sensory Receptors in Skin

•They detect sensory input and convert them into electrical impulses that will travel up neurons along the spinal cord.

•Sensory input about touch, pain, heat, cold, pressure.

Proprioceptors•Sensory receptors that report on internal events in your muscles and joints.

•They report on muscle stretch and joint position.

•They generate electrical impulses that will travel up neurons to the CNS.

The Reflex Arc

Dorsal root ganglia contain cell bodies of sensory neurons

Upper and Lower Motor Neurons

Of course, the signal to initiate motor movement does not begin at the neuron cell body in the spinal cord; it begins in the brain.

The motor neuron whose cell body is in the brain is called an upper motor neuron.

It relays the signal to the motor neuron whose cell body is in the spinal cord, called the lower motor neuron.

The lower motor neuron synapses on a muscle, causing contraction.

Lower Motor Neurons “Innervate” Muscle Cells at the Neuromuscular Junction

Motor Neurons “Innervate” Muscle Cells

Neuron “innervates” muscle and triggers it to contract by the release of a chemical neurotransmitter.

Order of Nerves Firing

To pick up an object, you wrap your hand around the object. This gives you a sensory input as you feel the object.

The sensory neuron sends the impulse to the spinal cord where it synapses on an interneuron.

The interneuron synapses on a motor neuron The motor neuron tells your muscles to

contract so you can pick up the object.

Upper and Lower Motor Neuron Diseases Some diseases only effect the UMN, and

some only effect the LMN. Lower motor neuron disorders:

Multiple Sclerosis Polio

Upper motor neuron disorder: Cerebral palsy

Autonomic Neuropathy

Autonomic neuropathy is damage to autonomic nerves.

The autonomic nerves are those that supply involuntary body functions, including heart rate, blood pressure, perspiration and digestion.

A common symptom in autonomic neuropathy is dizziness. Muscle twitches and lack of sensation are NOT symptoms, since they are not supplied by autonomic nerves.

XS of the Spinal Cord

Ventral median fissure

Dorsal median sulcus

Spinal Nerve

Rami

Roots

Spinal Nerve Plexi

A network of ventral rami

Interlacing network Each branch carries

fibers from several spinal nerves

Gives redundancy in case of nerve damage

C1-C4- Cervical plexus

C5-T1- Brachial plexus

L1-L4- Lumbar Plexus

L4-S4- Sacral Plexus

Cervical Plexus

Nerves innervate skin of neck, back of head and upper shoulder.

Phrenic nerve (important for breathing!) from C3, C4, C5. Carries afferent and efferent fibers to the respiratory diaphragm.

Brachial Plexus

ROOTS

TRUNKS

DIVISIONS

CORDS NERVES

Brachial Plexus

Brachial Plexus

Damage to Brachial Plexus Klumpke’s paralysis (brachial plexus damaged

during birth) Acquired Brachial Plexus injuries

Crutch paralysis (total upper extremity paralysis) Claw Hand / Ape hand Hand of benediction Wrist Drop (Waiter’s Hand)

Peripheral damage to the Brachial Plexus

“Funny Bone” damage

Carpal Tunnel

Major Nerves of the Upper

Extremity

Axillary

Musculocutaneus

Axillary Nerve

Deltoid Teres minor

Musculocutaneus Nerve

Supplies anterior muscles of the arm

Median Nerve

Supplies no muscles of the arm Supplies anterior forearm (except flexor carpi

ulnaris) Carpal Tunnel Syndrome Hand of benediction

Ulnar Nerve

Supplies flexor carpi ulnaris “Funny Bone” Damage can cause claw/ape hand

Radial Nerve

Supplies muscles on the posterior arm and forearm Triceps brachii Extensor carpi radialis Extensor digitorum communis

Damage can cause wrist drop

Lumbo-Sacral Plexus

• Lumbar: – Femoral nerve

• Sacral: – Sciatic nerve

Nerves of the Lower

ExtremityFemoral

Obturator

Obturator Nerve

Supplies adductor muscles

Sciatic Nerve

Supplies back of thigh Biceps femoris Semimembranosis Semitendonosis

Supplies leg and foot

Femoral Nerve

Anterior Thigh Quadriceps femoris

Tibial Nerve

Posterior leg and foot Gastrocnemius Soleus Tibialis Posterior

Common Peroneal Nerve

Superficial branch Lateral side of leg Supplies peroneal muscles

Deep branch Supplies anterior leg muscles Injury causes “Foot Drop”

Dermatomes

The area of skin innervated by a cutaneous branch of a spinal nerve at a particular level.

Arteries of the Upper Extremity

Arteries of the Upper Extremity

Subclavian (becomes axillary artery in armpit) Axillary (becomes brachial artery in arm)

Supplies triceps brachii Brachial (divides into radial and ulnar arteries

when it reaches the elbow) Supplies arm muscles except triceps brachii

Radial Ulnar

Arteries of the Lower Extremity

External Iliac artery

Arteries of the Lower Extremity

External iliac (becomes femoral artery) Femoral (becomes popliteal artery at knee)

Femoral artery supplies muscles of thigh (including adductor muscles)

Popliteal (becomes tibial artery in leg) Tibal

Leg muscles

Peripheral Vascular Disease (PVD)

Refers to the obstruction of large arteries, frequently in the lower extremity. Usually caused from atherosclerosis (fatty plaques).

Symptoms Claudication: pain, weakness, numbness, or cramping

in muscles due to decreased blood flow Sores, wounds, or ulcers that heal slowly or not at all Change in color (blueness or paleness) or temperature

(coolness) when compared to the other limb Diminished hair and nail growth on affected limb and

digits (shiny, hairless skin)