Ch 13-2: Peripheral Nervous System

how many pairs of spinal nerves are there?

31

all spinal nerves are ______ nerves

mixed

spinal nerves supply all body parts except?

the head and part of the neck

how many pairs of cervical nerves are there?

8

how many pairs of thoracic nerves are there?

12

how many pairs of lumbar nerves are there?

5

how many pairs of sacral nerves are there?

5

which spinal nerves only have 1 pair?

coccygeal nerves (C0)

each spinal nerve is connected to the spinal cord via ____

roots

ventral roots contain ______ fibers

motor (efferent)

dorsal roots contain ______ fibers

sensory (afferent)

both ventral and dorsal roots start medially as _________ that then join laterally to form the spinal cord

rootlets

spinal nerves exit the vertebral column through the __________?

intervertebral foramina

branches of the spinal nerve include:

dorsal ramus and ventral ramus

smaller branch

dorsal ramus

larger branch

ventral ramus

what contains autonomic nerve fibers that join ventral rami in thoracic region?

rami communicantes

dorsal rami supply the _____ body trunk

posterior (back)

ventral rami supply the?

rest of the trunk and limbs

each root is purely _____?

sensory or motor

rami can carry ________?

both sensory and motor

all ventral rami except ____ form nerve plexuses

thoracic

interwoven nerve networks

nerve plexuses

_____ does not form nerve plexuses

dorsal rami

T2-T12 do not form plexuses, instead, they run separately as:

intercostal and subcostal nerves

the cervical plexus is formed by ?

ventral rami (C1-C4)

nerves that supply the skin of the neck, ear, back of head, and shoulders

cutaneous nerves

the main motor and sensory nerve of the diaphragm

phrenic nerve

phrenic nerve receives fibers from which cervical plexuses?

C3-C5

the brachial plexus is formed by which ventral rami?

C5-C8 and T1

the brachial plexus supplies nerves to the _______?

upper limb

brachial plexus: axillary nerve

(shoulder)- controls the deltoid muscle, teres minor and joint capsule of shoulder

brachial plexus: musculocutaneous nerve

controls the biceps brachii

brachial plexus: median nerve

controls forearm pronators, and thumb opposition muscles

brachial plexus: ulnar nerve

supplies wrist/finger flexion

brachial plexus: radial nerve

supplies all extensor muscles

a severe injury to the brachial plexus can?

weaken or paralyze entire upper limb

a severe injury to the median nerve can?

make it difficult to use pincer grasp to pick up small objects

carpal tunnel syndrome

when the median nerve is compressed as it passes the carpal tunnel in the wrist

the ulnar nerve is easily injured because it runs in a ______ position

superficial

severe or long-term damage to the ulnar nerve can cause?

sensory loss, paralysis, and muscle atrophy (wasting)

individuals who damage their ulnar nerve may have trouble doing what?

making a fist or gripping objects

which nerve injury results in “clawhand”?

ulnar nerve

which nerve injury results in “wrist drop”?

radial nerve

wrist drop

inability to extend the hand at the wrist

when a person falls asleep with their arm draped over a chair/sofa, cutting off circulation to the radial nerve

saturday night paralysis

which two plexuses overlap and serve the lower limb?

lumbar and sacral

the lumbosacral trunk carries fibers from the ______ to the _______

lumbar plexus to sacral plexus

the lumbosacral plexus provides motor and sensory innervation to?

lower limb as well as some parts of the abdomen, pelvis and buttocks

the lumbar plexus arises from?

L1-L4

the lumbar plexus innervates the?

thigh and abdominal wall

lumbar plexus: femoral nerve

moves front thigh muscles (quadriceps) and feels medial leg

lumbar plexus: obturator nerve

moves the inner thigh muscles (adductors)

the sacral plexus arises from?

L4 to S4

The sacral plexus serves the?

lower limb, pelvis structures, and perineum

longest and thickest nerve in the body?

sciatic nerve

sacral plexus: sciatic nerve

innervates hamstring muscles, adductor muscles, and most muscles in leg and foot

the sciatic nerve is composed of two nerves:

tibial and common fibular

sciatica

stabbing pain along the sciatic nerve

sciatica can be caused by?

falling, disc herniation or poorly places injection in the buttock

if the sciatic nerve is injured, what happens to your leg?

it is nearly useless and cannot be flexed due to paralyzed hamstrings

which nerve results in “footdrop”?

sacral nerve

footdrop

foot and ankle can not move at all

recovery from sciatic nerve is often?

slow and incomplete

parts of the PNS that activate effectors (muscles and glands) by releasing neurotransmitters

motor endings

motor endings innervate?

skeletal muscle, smooth muscle, and glands

motor endings occur at the?

neuromuscular junction

what is released when a nerve impulse reaches the axon terminal?

acetylcholine (ACh)

when Ach binds to receptors on the muscle cell it causes?

sodium and potassium ions to move across the membrane

action potentials lead to?

muscle contraction

quick, involuntary, predictable motor responses to a stimulus:

an inborn (intrinsic) reflex

developed through practice or repetition:

learned (acquired) reflexes

The site where the stimulus acts

receptor

Transmits afferent (incoming) impulses to the central nervous system (CNS)

sensory neuron

A region within the CNS, which can be either monosynaptic (one synapse) or polysynaptic (multiple synapses)

integration center

Conducts efferent (outgoing) impulses from the integration center to the effector organ

motor neuron

The muscle fiber or gland cell that responds to the efferent impulses by contracting (in muscles) or secreting (in glands)

effector

somatic reflexes activate ______

skeletal muscle

autonomic (visceral) reflexes activate _____?

visceral effectors (smooth or cardiac muscle or glands)