Chapter 12 Spinal Cord and Spinal Nerves

spinal cord

Nerves that run up and down the length of the back and transmit most messages between the body and brain

dorsal horns

contain sensory axons that synapse with inter- neurons.

ventral horns

contain the neuron cell bodies of somatic motor neurons

lateral horn

contain the neuron cell bodies of autonomic motor neurons.

reflex arc

the functional unit of the nervous system.

Sensory receptors

respond to stimuli and produce action potentials in sensory neurons.

Muscle spindles

It is the sensory receptor of this reflex and detect the stretch of skeletal muscles and cause the muscle to shorten reflexively.

Golgi tendon reflex

prevents contracting muscles from applying excessive tension to tendons.

fasicles

group of axons

dorsal rami

innervate most of the deep muscles of the dorsal trunk responsible for moving the vertebral column.

ventral rami

are distributed in two ways. In the thoracic region, the ventral rami form intercostal (between ribs) nerves, which extend along the inferior margin of each rib and innervate the intercostal muscles and the skin over the thorax

Spinal nerves

supplies the upper limb.

axillary nerve

innervates the deltoid and teres minor muscles and the skin of the shoulder.

radial nerve

supplies the extensor muscles of the arm and forearm and the skin of the posterior surface of the arm, forearm, and hand.

musculocutaneous nerve

supplies the anterior arm muscles and the skin of the lateral surface of the forearm.

ulnar nerve

innervates most of the intrinsic hand muscles and the skin on the ulnar side of the hand.

median nerve

innervates the pronator

obturator nerve

supplies the muscles that adduct the thigh and the skin of the medial thigh.

femoral nerve

supplies the muscles that flex the thigh and extend the leg and the skin of the anterior and lateral thigh and the medial leg and foot.

tibial nerve

innervates the muscles that extend the thigh and flex the leg and the foot.

sciatic nerve

the tibial nerve and the common fibular nerve

Cervical Enlargement

where nerve fibers that supply the upper limbs enter and leave the spinal cord

lumbosacral enlargement

located in inferior thoracic, lumbar, and superior sacral regions is the site where the nerve fibers supplying the lower limbs enter or leave the spinal cord.

Conus Medularis

the spinal cord tapers to form a conelike region,

CAuda Equina

The numerous roots (origins) of spinal nerves extending inferiorly from the lumbosacral enlargement and conus medullaris resemble a horse's tail.

Meninges

connective tissue membranes that surround the spinal cord and brain.

what are the three layers that compose the meninges?

Dura Mater, Arachnoid Mater and Pia Mater

Dura mater

thick, outermost layer of the meninges surrounding and protecting the brain and spinal cord. Form a sac (thecal sac)

arachnoid mater

next deepest meningeal layer, very thin.

pia mater

deepest meningeal layer, bound very tightly to the surface of the spinal cord.

epidural space

space between the dura mater and the wall of the vertebral canal

epidural anesthesia

It is in the spinal nerves that is often administered in women during childbirth by injecting anesthetics into the epidural space of the spinal cord.

subdural space

space between dura mater and arachnoid mater

subarachnoid space

a space in the meninges beneath the arachnoid membrane and above the pia mater that contains the cerebrospinal fluid. It contains weblike strands of the arachnoid mater, blood vessels, and cerebrospinal fluid.

denticulate ligaments

e connective tissue septa extending from the lateral sides of the spinal cord to the dura mater, and it attach to the dura mater by toothlike processes between the exits of the cervical and thoracic spinal nerves

Denticulate

It refers to having small teeth.

filum terminale

a connective tissue strand that anchors the conus medullaris and the thecal sac to the first coccygeal vertebra, limiting their superior movement.

anterior median fissure and a posterior median sulcus

These are deep clefts partially separating the two halves of the cord.

What are the 3 columns in spinal cord?

ventral column, lateral column and dorsal column.

fascicles

Each column of the spinal cord is subdivided into this.

monosynaptic reflexes

involve simple neuronal pathways in which sensory neurons synapse directly with motor neurons without any interneurons.

Polysynaptic reflexes

involve more complex pathways that have multiple synapses with interneurons between the sensory and motor neurons.

stretch reflex

is a reflex contraction of muscles in response to stretching of that same muscle

alpha motor neuron

It causes the muscle to contract. The stretch reflex is a monosynaptic reflex because there is no interneuron between the sensory neuron and the lower motor neuron.

knee-jerk reflex

The classic example of a stretch reflex

gamma motor neurons

innervate the ends of the muscle spindles.

gamma

it is refers to the small-diameter axons of these neurons compared to the large-diameter axons of alpha motor neurons.

Golgi tendon organs

The sensory receptors of the golgi receptor reflex.

withdrawal reflex

is to remove a limb or another body part from a painful stimulus

Reciprocal innervation

a phenomenon that allows opposing muscles to reinforce the efficiency of the withdrawal reflex. Reciprocal innervation allows the coordinated contraction of flexor muscles and relaxation of the opposing extensor muscles.

crossed extensor reflex

s another reflex associated with the withdrawal reflex. It occurs on the opposite side of the body from the stimulus.

What are the 3 layer of Connective Tissue?

Endoneurium, Perineurium, Epineurium

Endoneurium

It is a delicate connective tissue layer that surrounds each axon, or nerve fiber, and its Schwann cell sheath

Perineurium

which is a heavier connective tissue layer, that surrounds groups of axons to form nerve fascicles.

Epineurium

which is a third layer of dense connective tissue that binds the nerve fascicles together to form a nerve.

4 region of Vertibral Column

Lumbar, Sacral, Thoracic, Cervical

dermatome

It is the area of skin supplied with sensory innervation by a pair of spinal nerves.

roots

ventral rami of different spinal nerves and join with each other to form a plexus

ramus

is a major branch of a spinal nerve.

cervical plexus

It is a relatively small plexus originating from spinal nerves.

phrenic nerve

Nerves that is important for breathing.

What are the 5 major nerves emerging from the brachial plexus?

Axillary nerves, Radial nerve, ulnar nerve, musculocutaneous nerve, median nerve..

Axillary nerves

innervates the deltoid and teres minor muscles.

brachial plexus

It is originates from spinal nerves

Radial Nerve

innervates all of the extensor muscles of the upper limb, the supinator muscle, and the brachioradialis.

Musculocutaneous Nerve

provides motor innervation to the anterior muscles of the arm, as well as cutaneous sensory innervation to part of the forearm.

Ulnar Nerve

innervates two forearm muscles plus most of the intrinsic hand muscles, except some associated with the thumb.

Median Nerve

innervates all but one of the flexor muscles of the forearm and most of the hand muscles at the base of the thumb

carpal tunnel

This tunnel is created by the concave organization of the carpal bones and the flexor retinaculum on the anterior surface of the wrist.

lumbar plexus

originates from the ventral rami of spinal nerves L1-L4

sacral plexus

originates from L4-S4.

lumbosacral plexus

the two plexuses sacral and lumbar) are often considered together as a single what?

2 lumbosacral nerves?

Obturator Nerve and Femoral Nerve

Femoral Nerve

innervates the iliopsoas and sartorius muscles and the quadriceps femoris group.

Obturator Nerve

innervates the muscles that adduct the thigh.

tibial and common fibular nerves

originate from spinal segments L4-S3 and are bound together within a connective tissue sheath for the length of the pelvis and descends in the posterior thigh to the popliteal fossa, where the two portions of the sciatic nerve separate.

tibial nerve

innervates most of the posterior thigh and leg muscle. It branches in the foot to form the medial and lateral plantar nerves.

medial and lateral plantar nerves,

h innervate the plantar muscles of the foot and the skin over the sole of the foot.

sural nerve

supplies part of the cutaneous innervation over the calf of the leg and the plantar surface of the foot.

What are the Other Lumbosacral Plexus Nerves

o gluteal nerves, pudendal nerve,

episiotomy

a cut in the perineum that enlarges the opening of the birth canal.

coccygeal plexus

is a very small plexus formed from the ventral rami of spinal nerve S5 and the coccygeal nerve.