3- Spinal Nerves, Dermatomes, and Myotomes

dorsal root

sensory branch of each spinal nerve

ventral root

motion (efferent info)

spinal nerve

a nerve that emerges from the spinal cord; _____ once they leave vertebrae; both motor/sensory

dorsal primary ramus (DPR)

innervates deep muscles of the back, skin (posterior) of head, neck, and back

ventral primary ramus (VPR)

innervates anterior trunk and makes up plexuses to the extremities; legs, anterior trunk, and limbs

dorsal root ganglion

contains cell bodies of sensory neurons

sympathetic chain ganglion

What ganglion receives preganglionic sympathetic fibers from T1 to L1-2 and innervates smooth muscle, cardiac muscle, glands, head, thoracic viscera, and blood vessels of the body wall and limbs?

general somatic efferent (GSE)

carry motor impulses from CNS to skeletal muscles

general somatic afferent (GSA)

mediates sensory innervation from somatic muscles, skin, ligaments, and joints; sensory info from the body (hot/cold)

general visceral efferent, general visceral afferent

Types of autonomic information carried by nerves

general visceral efferent

innervates smooth (non-voluntary) muscle, glands, organs; movement in digestive

general visceral afferent

what is sensory information that is conscious and unconscious?

true

t/f All spinal nerves carry some form of motor and sensory information

yes, except cranial nerves

Do typical spinal nerves innervate nearly all the body wall, extremities, and most of the muscles?

muscles

Where do motor commands go?

CNS

Where does sensory information go?

dermatomes

-A band or region of skin supplied (innervated) by a single sensory nerve

-Can be described in 2 ways: with reference to a dorsal nerve root and with reference to a given cutaneous nerve

What are the ways dermatomes can be described?

With reference to a dorsal nerve root and with reference to a given cutaneous nerve

cutaneous nerve

-nerve that innervates the skin

-body sensation is attributed to/described by the _____________ that innervates a given area

-more localized

opthalmic nerve

maxillary nerve

mandibular nerve

trigeminal nerve

opthalmic nerve, maxillary nerve, mandibular nerve

great auricular nerve, innervates the skin of the neck and posterior ear

transverse cervical nerve

supraclavicular nerves

intercostal nerves

anterior cutaneous rami, lateral cutaneous rami

anterior cutaneous rami

lateral cutaneous rami

axillary nerve

medial brachial cutaneous nerve

intercostobrachial nerves

innervation of the skin on medial surface of the arm are called what?

inferior lateral brachial cutaneous nerve

medial antebrachial cutaneous nerve

lateral antebrachial cutaneous nerve

radial nerve

ulnar nerve

median nerve

ilioinguinal nerve

iliohypogastric nerve

arises from L1, gives motor functino to the naterolateral abdominal wall msucles and innervates sensory fro skin in the pubic region. Injury to the anterior branch can occur during appendectomy causing decreased sensation at the suprapubic region.

lateral femoral cutaneous nerve

a cutaneous nerve that innervates the skin on the lateral part of the thigh.

L3

obturator nerve

passes through obturator foramen to innervate adductor muscles

anterior femoral cutaneous nerve

branches of femoral nerve to serve anterior and medial surfaces of thigh

may be subdivided into intermediate and medial branches

lateral sural cutaneous nerve

from dorsal divisions of ventral rami L-5, S-1 & S-2; arises in the popliteal fossa and passes into the superficial fascia over the lateral calf region to supply the superior part of the lateral aspect of the leg

saphenous nerve

superficial peroneal nerve

sural nerve

deep peroneal nerve

fibular nerve

-Also known as anterior tibial nerve; it extends down the front of the leg, behind the muscles. It supplies impulses to these muscles and also to the muscles and skin on the top of the foot and adjacent sides of the first and second toes.

-superficial peroneal nerve, sural nerve, deep peroneal nerve

greater occipital nerve

lesser occipital nerve

greater auricular nerve

transverse cervical nerve

posterior cutaneous rami of thoracic spinal nerves

lateral cutaneous rami of thoracic spinal nerves

posterior brachial cutaneous nerve

medial brachial cutaneous nerve

lower lateral brachial cutaneous nerve

lateral antebrachial cutaneous nerve

iliohypogastric nerve

cluneal nerves

perforating cutaneous nerve

lateral femoral cutaneous nerve

posterior femoral cutaneous nerve

lateral sural cutaneous nerve

medial sural cutaneous nerve

calcaneal nerve

sural nerve

Nerve of the lower leg that supplies impulses to the skin on the outer side and back of the foot and leg.

lateral plantar nerve

medial plantar nerve

yes

Are dermatomes more CNS?

peripheral

What kind of injury are cutaneous nerves?

myotomes

a group of muscles receiving innervation from a single spinal cord segment or spinal nerve; the muscle equivalent of dermatome testing

motor neuron pools

-clusters of motor neurons in longitudinal columns

-correlate to muscle spinal level innervation

yes

Are some muscles most associated with 1 spinal level?

C1/2 myotome

cervical flexion

C3 myotome

cervical sidebending

C4 myotome

scapular elevation (shrug)

C5

what myotome is shoulder abduction?

C6 myotome

elbow flexion, wrist extension

C7 myotome

elbow extension, wrist flexion

C8 myotome

thumb extension or finger flexion

T1 myotome

5th finger abduction

L2

what myotome is hip flexion (adduction)?

L3

what myotome is knee extension?

L4 myotome

ankle dorsiflexion

L5 myotome

great toe MTP extension

s1

what myotome is eversion or plantarflexion?

S2 myotome

plantarflexion or knee flexion

action potentials

How do neurons transmit information?

The target of the information

What must be considered regarding neurons?

yes

Do the action potentials for motor commands or sensory info look the same?

true

t/f one nerve is composed of many neurons and one nerve can carry several types of information

autonomic nervous system

-the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.

-motor system that innervates smooth muscle, cardiac muscle, glands, organs

sensory (afferent)

What other component does it have?

heart rate, digestion, body temperature, pupillary dilation or constriction, dilation or constriction of arteries/arterioles, salivation and secretion of glands, bowel and bladder function, sexual response

What does the ANS influence?

general somatic afferents (GSA)

-Sensations from skin, skeletal muscle, tendon, and connective tissue

-feeling cold results in contraction of smooth muscle in superficial arteries to conserve body heat

general visceral afferent

what is sensory feedback to the ANS?

cortical inputs from hypothalamus

fight or flight response; arousal

special sensory afferents

seeing and smelling food cooking, resulting in increased salivation