Anatomy: Chapter 14

The brachial plexus

-innervates the shoulder girdle and upper extremities -is formed from the ventral rami of spinal nerves c5-T1 -source of the musculocutaneous, radial, median, and ulnar nerves

Why are dermatomes clinically important?

Damage to either a spinal nerve or dorsal root ganglion will produce a characteristic loss of sensation in specific areas of the skin

What prevents side to side movements of the spinal cord?

Denticulate ligaments

Femoral nerve

Formed by ventral rami of L2-L4 Innervates quadriceps, Sartorius, pectineus, and iliopsoas muscles Recieves sensory info from skin of anteromedial surface of thigh and medial surface of leg and foot

Role of meninges in protecting the spinal cord

Protection, stability, space for the CSF

ulnar nerve

flexor carpi ulnaris muscle adductor pollicis muscle small digital muscles sensory from skin over medial surface of hand

median nerve

flexor muscles of forearm digital flexrrs sensory from skin over anterolateral surface of hand

musculocutaneous nerve innervates

flexor musles on the arm sensory skin over lateral surface of forearm

Innate reflexes

genetically determined

Axons crossing from one side of the spinal cord to the other within the gray matter are found in the

gray commissures

a bundle of postganglionic sympathetic nerve fibers that go to a spinal nerve for distribution to effectors in the body wall, skin, and extremities

gray ramus

function of reflex

help preserve homeostasis by making rapid adjustments in the function of organs or organ systems

projections of gray matter toward the outer surface of the spinal cord are called

horns

If the dorsal root of the spinal cord were damaged what would be affected?

incoming sensory info

Pia mater

innermost meningeal layer elastic and collage fibers of pia mater are interwoven with those of the arachnoid trabeculae firmly bound

Brachial plexus

innervates pectoral girdle and upper limb axillary nerve radial nerve musculocutaneous nerve median nerve ulnar nerve

Sciatic nerve

largest nerve in human body formed by ventral rami of L4-S3 Innervates the semimembranosus, semitendinosus, and adductor magnus muscles

acquired reflexes

learned

polysynaptic reflex

longer delay between stimulus and response length of delay is proportional to number of synapses involved produce complicated responses because interneurons can control several muscle groups

The __ ___ provides innervation to structures of the pelvis and lower limbs

lumbosacral

radial nerve innervates

many extensor muscles of m and the arm

arachnoid mater

middle meningeal mater consists of simple squamous epithelium

__ nuclei issue motor commands to peripheral effectors, such as skeletal muscles

motor

Ventral root

motor neuron axons

Reflex vs. voluntary muscle movement

muscle movements are under conscious control and are voluntary. reflexes are automatic and immediate. Not under conscious control

The cell bodies of neurons in the gray matter of the spinal cord are organized into groups called

nuclei

Each peripheral (spinal) nerve contains three layers of connective tissue:

outer epineurium central perineurium inner endoneurium

The middle layer of the CT that surrounds each peripheral nerve is the

perineurium

dorsal ramus of each spinal nerve

receives sensory innervation from and sends motor innervation to a specific segment of the skin and muscles of the neck and back

immediate involuntary motor response to a specific stimulus

reflex

involuntary motor response

reflex

the neural wiring of a single reflex is called a

reflex arc it begins at a receptor and ends at a peripheral .

__ nuclei receive and relay sensory information from peripheral receptors

sensory

Phrenic nerve

sensory innervation from and motor innervation to the diaphragm originates from C4

patellar reflex

sharp rap on patellar ligament stretches muscle spindles in quadriceps

stretch reflex

simple monosynaptic reflex provides automatic regulation of skeletal muscle length

monosynaptic reflex

simplest reflex arc sensory neuron synapses directly on a motor neuron only one synapse so minimized delay

The posterior (dorsal) gray horns contain

somatic and visceral sensory nuclei

The anterior (ventral) gray horns contain

somatic motor neurons

CSF is contained in the

subarachnoid space

___ space separates the dura mater from the deeper meningeal layers

subdural space

Cervical enlargement

supplies nerves to the pectoral girdle and upper limbs

The adult spinal cord extends from the foramen magnum to

the first lumbar vertebrae

describe a nerve plexus

the ventral rami of adjacent spinal nerves blend their fibers to produce a series of compound nerve trunks; a complex of interwoven network of nerves

The ventral ramus supplies

the ventrolateral body surface, structures in the body wall, and the limbs

Each column contains

tracts, whose axons share functional and structural characteristics

What nerve transmit if you receive an injection into the deltoid region of the arm?

upper lateral cutaneous nerve of the arm

Sensory and motor innervation of the skin of the lateral and ventral surfaces of the body are provided by the

ventral ramus

Lateral gray horns contain

visceral motor neurons

Bundles of fibers, known as __ __, extend from the inner surface of the arachnoid mater to the outer surface of the pia mater.

arachnoid trabeculae

____ tracts carry info toward the rain

ascending

The gray commisures contain

axons crossing from one side of the cord to the other

The ventral root leaves the spinal cord and contains

axons of somatic motor neurons

Extended area of the spinal cord that supplies nerves to the pectoral girdle and upper limbs

cervical enlargement

The white matter is divided into regions, or

columns

Spinal nerves are called mixed nerves because they

contain both motor and sensory fibers

visceral (autonomic) reflexes

control actions of smooth and cardiac muscles and glands

somatic reflexes

control skeletal muscle contractions includes superficial and stretch reflexes adjusts muscle tone

The spinal cord tapers into a conical tip called

conus medullaris

cervical plexus contains

cutaneous and musculocutaneous branches of the ventral rami of spinal nerves C1-C4

All axons within a tract relay info in the same

direction

__ ___ ganglia contain cell bodies of sensory neurons

dorsal root

The paired structures that contain cell bodies of sensory neurons and are associated with each segment of the spinal cord are the

dorsal root ganglia

Outermost covering of spinal cord and brain Consists of a layer of dense irregular tissue Inner and outer surfaces are covered by simple squamous epithelium

dura mater

a single bundle of axons is known as a

fasicle

single bundle of axons

fasicle

A slender strand of fibrous tissue, the ___ ___, extends from the inferior tip of the conus medullaris to the coccyx.

filum terminale

Strand of fibrous tissue that provides longitudinal support as a component of the coccygeal ligament

filum terminale

5 steps of a neural reflex

1. arrival of stimulus ad activation of receptor 2. activation of a sensory neuron 3. Information processing in the CNS 4. Activation of a motor neuron 5. Response by effector

Why is it important that a spinal tap be done between the third and 4th lumbar vertebrae?

An adults spinal cord only goes down to L1 or L2. By doing it at L3 and 4, you ensure there is no risk for spinal cord injury

Why is the rectus abdominus always retracted laterally and never medially?

It's innervated by nerves from T7-T12. They enter laterally so muscles must be retracted the same way the nerves are positioned. If they are retracted medially, the nerves would be cut, causing paralysis.

Why is response time in a monosynaptic reflex much faster than response time in a polysynaptic fiber?

Polysynaptic: totals several synapses, resulting in a delay Monosynaptic: only 1 synapse so it has a faster response time

Why are there 8 cervical spinal nerves but only 7 cervical vertebrae?

The first pair of spinal nerve are located above the atlas. This "extra" pair is the reason there are 8 pair instead of 7

The deep crease on the ventral surface of the spinal cord is the

anterior median fissure

The filum terminale and long ventral and dorsal roots form the

cauda equina

The gray matter of the spinal cord is dominated by:

cell bodies of neurons and glial cells

axillary nerve innervates

deltoid and teres minor muscles, sensory from skin of shoulder

Each pair of spinal nerves monitors a specific region of the body surface, known as

dermatomes

___ tracts convey motor commands to the spinal cord

descending

Function of filum terminale

provides longitudinal support to the spinal cord as a component of the coccygeal ligament

Preganglionic axons are myelinated, so the branch carrying them is light in color and is known as the

white ramus

Spinal nerves T1-L2 have four branches:

white ramus and gray ramus (ramus communicans) dorsal ramus and ventral ramus