Test 3- Ch. 12 Part 2

spinal nerves

______ consits of

1. axon bundles

2. Schwann cells

3. connective tissue (3 types of CT)

Endoneurium

type of connective tissue in spinal nerves that surrouds individual neurons

Perineurium

type of connective tissue in spinal nerves that surrounds axon groups to form fascicles

Epineurium

type of connective tissue in spinal nerves that surrounds the entire nerve

first

the _____ pair of spinal nerves exit the vertebral column between the skull and atlas

exit

the last 4 pairs of spinal nerves ____ via the sacral foramina

intervertebral

the rest of the spinal nerves (excluding the first and last 4) exit through the _______ foramina

Dermatomal Map

• skin area supplied with sensory innervation by spinal nerves

• spinal nerves indicated by capital letter and number (C1)

• important because they can be used to help locate nerve damage

Rami

another word for BRANCHES of spinal nerves

Dorsal Ramus

innervate deep muscles of the trunk responsible for movements of the vertebral column and the CT and skin near the midline of the back

Ventral Ramus

what they innervate depends upon which part of the spinal cord is considered

• these wrap to the front of the body

• consists of the thoracic region and form 5 plexuses

thoracic region

the _____ is part of the ventral ramus that form intercoastal nerves that innervate the intercoastal muscles and the skin over the thorax

• also form nerve plexuses

roots of the plexus

remaining spinal nerves in the ventral rami (_______) after the thoracic region is considered: form 5 plexuses (intermingling of nerves)

1. cervical plexus- C1-C4

2. brachial plexus- C5-T1

3. lumbar plexus- L1-L4

4. sacral plexus- L4-S4

5. coccygeal plexus- S5

C1

the only spinal nerve that doesn’t have a specific cutaneous sensory distribution

Cutaneous Sensory Innervation

where the specific nerves fuel the skin. For example, if you touch someone’s foot sole, they feel it because the tibial nerve supplies that area of skin

Communicating Rami

branch that communicates with sympathetic chain of ganglia

Cervical Plexus

C1-C4

innervates superficial neck structures, skin of neck, and posterior portion of the head

Ansa Cervicalis: loop between C1 and C3 that serves the infrathyroid muscles

has the Phrenic nerve

ansa cervicalis

loop between C1 and C3 that serves the infrathyroid muscles

Phrenic nerve

• from C3-C5 (cervical and brachial plexuses)

• innervates diaphragm

Brachial Plexus

• originates from C5-T1

• five ventral rami form 3 trunks that separate into 6 divisions then form cords that give rise to 5 branches/nerves

Branches of the Brachial Plexus

1. Axillary nerve

2. Radial nerve

3. Musculocutaneous nerve

4. Ulnar nerve

5. Median nerve

Axillary nerve

origin: posterior cord of brachial plexus C5-C6

movements: laterally rotates arm, and abducts arm

cutaneous (sensory) innervation: inferior lateral shoulder

radial nerve origin

origin is the posterior cord of the brachial plexus C5-T1

radial nerve movements

1. extends and flexes elbow

2. extends, adducts, and abducts wrist

3. supinates forearm and hand

4. extends fingers

5. abducts and extends thumb

cutaneous innervation: posterior surface of arm and forearm; lateral 2/3rds of dorsum of hand

Musculocutaneous nerve origin

originates in lateral cord of brachial plexus, C5-C7

Musculocutaneous nerve movements

1. flexes shoulder

2. flexes elbow

3. supinates forearm and hand

Cutaneous innervation: lateral surface of the forearm

Ulnar nerve origin

origin: medial cord of brachial plexus; C8-T1

Ulnar nerve movements

1. flexes and adducts wrist

2. flexes, abducts, and adducts fingers

3. adducts thumb

4. controls hypothenar muscles

5. flexes metacarpophalangeal joints and extends interphalangeal joints

Cutaneous innervation: medial third of hand, little finger, and medial half of ring finger

median nerve origin

origin: medial and lateral cords of brachial plexus; C5-T1

median nerve movements

1. pronates forearm and hand

2. flexes and abducts wrist

3. flexes fingers

4. controls thumb and thenar muscles

5. flexes metacarpophalangeal joints and extends interphalangeal joints

median nerve cutaneous innervation

lateral two-thirds of palm and hand, thumb, index and middle fingers, and the lateral half of the ring ringer and dorsal tips of the same fingers

• innervates all but 1 flexor muscle

Lumbar and Sacral Plexus

• lumbar plexus: ventral rami of L1-L4

• sacral plexus: ventral rami of L4-S4

• usually considered together because of their close relationship

• 4 major nerves: Obturator, femoral, tibial, common fibular

Obturator nerve origin

lumbosacral plexus; L2-L4

Obturator nerve movements

1. rotates thigh laterally

2. adducts thigh

3. adducts thigh and flexes knee

cutaneous innervation: superior medial side of the thigh

Femoral Nerve origin

lumbosacral nerve; L2-L4

(not the obturator one)

femoral nerve movements

1. flexes hip

2. flexes hip and flexes knee

3. extends knee and flexes hip

Cutaneous innervation: anterior and lateral branches supply the anterior and lateral thigh; saphenous branch supplies the medial leg and foot

• innervates iliopsoas and sartorius muscles

Tibial and Common Fibular Nerves

called the peroneal nerves.

• together they’re referred to as the sciatic (ischiadic) nerve since they are bound together within the same sheath of the thigh

Tibial Nerve

Origin: lumbosacral plexus; L4-S3

Movements:

1. extends hip and flexes knee

2. extends hip and adducts thigh

3. plantar flexes foot

4. flexes knee

5. flexes toe

Cutaneous innervation: none

Additional info of tibial nerve

• it also innervates the posterior portion of the thigh, leg, and foot

• ex: used when dancer points toes (flexes toe movement)

Medial and Lateral Plantar Nerves of Tibial Nerve

origin: tibial nerve

movement: flex and adducts toe

cutaneous (sensory) innervation: sole of the foot

Sural nerve of Tibial nerve

origin: tibial nerve

movement/muscle innervation: none

cutaneous (sensory) innervation: lateral and posterior 1/3rd of the leg and lateral side of the foot

Fibular Nerve Areas

1. common fibular (peroneal) nerve

2. deep fibular (peroneal) nerve

3. superficial fibular (peroneal) nerve

Common fibular nerve

origin: lumbosacral plexus; L4-S2

movement/muscle innervation: extends hip and flexes knee

cutaneous innervation: lateral surface of the knee

ex: innervates anterior and lateral muscles of the leg and foot, skin of anterior and lateral leg and dorsum of the foot

Deep Fibular Nerve

origin: common fibula (peroneal) nerve

movement: dorsiflexes and extends foot

cutaneous innervation: great and second toe

Superficial Fibular Nerve

origin: common fibular nerve

movement: plantar flexes and everts foot

cutaneous innervation: dorsal anterior third of the leg and dorsum of the foot

Coccygeal Plexus

• S5

• muscles of the pelvic floor

• sensory information from the skin over the coccyx

Spinal stenosis

Narrowing of spinal canal or area around nerve roots; leads to compression of

nerves; usually cervical (neck) or lumbar (lower back); can cause pain, numbness, or

weakness

Encephalitis

Inflammation of the brain caused by a virus and less often by bacteria or other

agents; symptoms include fever, coma, and convulsions

Meningitis

Inflammation of meninges caused by viral or bacterial infection; symptoms include

stiffness in the neck, headache, and fever; severe cases can cause paralysis, coma,

or death

Rabies

Viral disease transmitted by an infected animal; brain infection results in abnormal

excitability, aggression, paralysis, and death

Tetanus

Caused by bacterial neurotoxin; affects lower motor neurons in spinal cord and

brainstem, leading to muscle contraction; prevents muscle relaxation; body becomes

rigid, including “lockjaw”; death results from spasms in respiratory muscles

Multiple sclerosis

Autoimmune condition; may be initiated by viral infection; inflammation in brain and

spinal cord with demyelination and sclerotic (hard) sheaths results in poor conduction

of action potentials; symptoms include exaggerated reflexes, tremor, and speech

defects

Anesthesia

Loss of sensation; may be a pathological condition or may be induced temporarily to facilitate medical action

Neuritis

inflammation of a nerve from a number of causes; in motor nerves, can result in loss of motor function; in sensory nerves, can result in anesthesia or neuralgia

Neuralgia

Nerve pain; involves severe spasms of throbbing or stabbing pain along the pathway of a nerve; can result from inflammation, nerve damage, or an unknown cause

Sciatica

Neuralgia of the sciatic nerve, with pain radiating down the back of the leg; most common cause is a herniated lumbar disk

Leprosy

Bacterial disease that kills skin and PNS cells; characterized by disfiguring nodules and tissue necrosis

Herpes

Family of diseases characterized by skin lesions due to herpes viruses in sensory ganglia; different viruses cause oral lesions (cold sores), sexually transmitted disease with lesions on genitalia, or chickenpox in children (shingles in adults)

Poliomyelitis

Viral infection of the CNS, but primarily damages somatic motor neurons, leaving muscles without innervation; leads to paralysis and atrophy

Diabetic neuropathy

Damage to nerves occurs in diabetic patients due to high blood sugar levels and decreased blood flow; occurs in over half of diabetics; symptoms develop slowly, often including pain or numbness in extremities but can be manifested in every organ system

Charcot-Marie-Tooth disease

One of the most common hereditary neurological disorders (named for three neurologists who described it); different forms caused by mutations that generally lead to damage of the myelin sheath; characterized primarily by muscle weakness, dysfunction, atrophy, and loss of sensation primarily in lower extremities

Neurofibromatosis

Genetic disorder; neurofibromas (benign tumors along peripheral nerve tract) occur in early childhood and result in skin growths

Myasthenia gravis

Autoimmune disorder affecting acetylcholine receptors; makes the neuromuscular junction less functional; muscle weakness and increased fatigue lead to paralysis