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 C 1 -C 4 - Cervical plexus C 5 -T 1 - Brachial plexus L 1 -L 4 - Lumbar Plexus L 4 -S 4 - 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

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 Extremity Femoral 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

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)