Chapter 13: The Spinal Cord, Spinal Nerves, and Spinal reflexes

dermatome

A bilateral region of skin that is innervated by a single pair of spinal nerves is a ____________

tendon reflex

a weight lifter is straining to life a 200-kg barbell above his head. shortly after he lifts it to chest height, his muscles appear to relax and he drops the barbell. which reflex has occurred?

lumbar plexus and sacral plexus

arise from the lumbar and sacral segments of the spinal cord -innverates the pelvic girdle and lower limbs

posterior gray horns

contain somatic and visceral sensory nuclei

lumbar plexus

contains axons from the ventral rami and the spinal nerves T12 - L4

sacral plexus

contains axons from the ventral rami of spinal nerves I4-S4

superficial white matter

contains large numbers of myelinated and unmyelinated axons

ventral roots

contains the axons of motor neurons that extend into the periphery to control somatic and visceral effectors

visceral reflexes

control the activities of other systems -control actions of smooth and cardiac muscles, glands, and adipose tissue -also called autonomic reflexes

somatic motor nuclei

controls 1) muscles that position the pectoral girdle 2) muscles that move the arm 3) muscles that move the forearm and hand 4) muscles that move the hand and fingers

descending tracts

convey motor commands to the spinal cord

peripheral nervous system

cranial nerves and spinal nerves

central canal and subarachnoid space

in the spinal cord the cerebrospinal fluid is found within the ________

convergence

in what pattern of neural processing do several neurons synapse on one neuron?

central canal

gray mater forms an H or butterfly shape and surrounds the narrow...

cauda equina

gross dissection -the filum terminale and the long ventral and dorsal roots to the conus medullaris -resemble a horses tail

plantar reflex

in adults, stroking the lateral sole of the foot produces a curling of the toes..

divergence

in what pattern of neural processing does one neuron synapse with several other neurons?

stretch reflex

increasing the length of a muscle and will cause that muscle to contract -example of somatic reflex - knee-jerk

meningitis

inflammation of the meningeal membranes -can disrupt the normal circulation of cerebrospinal fluid

serial processing

information is relayed in a stepwise fashion, from one neuron to another. -sensory information is relayed from one part of the brain to another

cervical plexus

injury to which of the nerve plexuses would interfere with the ability to breathe?

cervical plexus

injury to which plexus would interfere with your ability to breathe?

pia mater

inner most meningeal layer -consists of a meshwork of elastic and collagen fibers that is firmly bound to the underlying neural tissue.

brachial plexus

innervates the pectoral girdle and the upper limb -C5 - T1 also have fibers C4 and T2

highest level of motor control

involves a series of interactions that occur in centers of the brain that can modulate or build on reflexive motor patterns

motor nuclei

issue motor commands to peripheral effectors

trunks

large bundles of axons from several spinal nerves

anterior white columns

lie between the anterior gray horns and the anterior median fissure

posterior white columns

lie between the posterior gray horns and the posterior median sulcus

cranial reflexes

localized reflex responses comparable in organization and complexity to those of the spinal cord

lateral gray horns

locates only in the thoracic and lumbar segments -contain visceral motor nuclei

axillary nerve and radial nerve

posterior cord forms two nerves..

sympathetic nervous system

prepares the body for intense physical activity and is often referred to as the fight-or-flight response.

autonomic nervous system (ANS)

processing centers in the brain, spinal cord, and peripheral nervous system - responsible for the control of visceral effectors, such as smooth muscles, cardiac muscles, glands, and adipose tissue.

somatic reflexes

provide a mechanism for the involuntary control of the muscular system -control skeletal muscle contractions -include superficial and stretch reflexes

lumbar enlargement

provides innervation to structures of the pelvis and lower limbs

reflexes

quick, automatic responses triggered by specific stimuli

sensory nuclei

receive and relay sensory information from peripheral receptors

peripheral neuropathies

regional losses of sensory and motor function most often resulting from nerve trauma or compression

lateral white column

the white matter between the anterior and the posterior columns on each side makes up the...

columns

the white matter on each side of the spinal cord can be divided into three regions called...

epidural space

- a region that contains areolar tissue, blood vessels, and a protective padding of adipose tissue

anterior white commissure

-a region where axons cross from one side of the spinal cord to the other -the anterior white columns are interconnected by these

four major plexuses

-cervical plexus -brachial plexus -lumbar plexus -sacral plexus

spinal nerve

-classified as mixed nerves -they contain both afferent (sensory) and efferent (motor) fibers

ventral root of a spinal nerve

-contains both visceral and somatic motor fibers -if damaged - would interfere with motor function

dorsal root ganglia

-every spinal segment is associated with a pair -contain the cell bodies of sensory neurons

dorsal roots

-formed by the axons of the neurons -bring sensory information into the spinal cord

innate reflex

-genetically or developmentally acquired reflexively removing a hand from a hot stove and blinking when the eyelashes are touched are examples of ________

babinski sign

-stroking an infants foot produces a fanning of the toes -should disappear as motor pathways develop -if the higher center or the descending tracts are damaged it will reappear

endoneurium

-surrounding each spinal nerve is a series of connective tissue layers -innermost layer -extend from the perineurium and surround individual axons

epineurium

-surrounding each spinal nerve is a series of connective tissue layers -outermost layer -consists of a dense network of collagen fibers

perineurium

-surrounding each spinal nerve is a series of connective tissue layers -the middle layer -extend inward from the epineurium

classification of reflexes

-their development -the nature of the resulting motor response -the complexity of the neural circuit involved -the site of information processing

extrafusal muscle fibers

-these fibers are responsible for the resting muscle tone and contraction of muscles the muscle spindle is surrounded by larger skeletal muscle fibers called...

columns in the white matter

A disease that damages myelin sheaths would affect which portion of the spinal cord? -composed of bundles of myelinated axons

anterior gray horns of the spinal cord

A person with polio has lost the use of his leg muscles. In which area of his spinal cord would you expect the virus- infected motor neurons to be? -where the cell bodies of of somatic motor neurons are located

CNS; PNS

Anatomically, the spinal cord is part of the ______________, and the spinal nerves are part of the ______________

through dorsal roots of spinal nerves

Sensory information from the lower portion of your body will be conducted to the spinal cord by sensory neurons. how do sensory neurons enter the spinal cord?

endoneurium

The delicate connective tissue fibers that surround individual axons of spinal nerves compose a layer called _______

pain receptors

____________ are the dendrites of sensory neurons

tract

a bundle of axons in the CNS that is somewhat uniform in diameter, myelination, and propagation speed

anterior median fissure

a deeper grove along the anterior (ventral) surface

myelography

a diagnostic procedure in which a radiopaque dye is introduced into the cerebrospinal fluid to obtain an x-ray image of the spinal cord and cauda equina

nerve growth factor

a peptide that promotes the growth and maintenance of neurons. other factors that are important to neuron growth and repairs include BDNF, NT-3, NT-4, GAP-43

spinal reflex

a rapid, automatic response triggered by specific stimuli that is controlled in the spinal cord

negative feedback

a reflex generally removes or opposes the original stimulus. this is an example of...

visceral reflex

a reflex, like urination, that involves smooth muscle contraction of the bladder, is what kind of reflex?

flexor reflex

a representative withdrawal reflex -affects the muscles of a limb

spinal meninges

a series of specialized membranes surrounding the spinal cord, provide the necessary physical stability and shock absorption.

areflexia

absence of reflexes

cerebrospinal fluid (CSF)

acts as a shock absorber and a diffusion medium for dissolved gases, nutrients, chemical messengers, and wastes

higher centers or descending tracts are damaged

after injuring he back, tina exhibits a positive babinski reflex. what does this imply about tinas injury?

the skin and muscles of the back of the neck and of the shoulders

an anesthetic blocks the function of the dorsal rami of the cervical spinal nerves. which areas of the body will be affected

reinforcement

an enhancement of spinal reflexes

central nervous system

brain and spinal cord

Ascending tracts

carry sensory information toward the brain

reverberation

collateral branches of axons somewhere along the circuit extend back toward the source of an impulse and further stimulate the presynaptic neurons -positive feedback loop

nerve plexus

complex interwoven network of nerves

sciatic nerve

compression of which nerve produces the sensation that your leg has "fallen asleep'?

cervical plexus

consists of the ventral rami of spinal nerves C1-C5 -innervate muscles of the neck and extend into the thoracic cavity -control diaphragmatic muscles

gray commisures

contain axons that cross from one side of the cord to the other before they reach an area in the gray matter

extended; extensor reflex

during a withdrawal reflex of the foot, what happens to the limb on the side opposite the stimulus? what is the response called?

intrafusal muscle fibers

each muscle spindles consists of a bundle of small, specialized skeletal muscle fibers called...

subarachnoid space

filled with cerebrospinal fluid (CSF)

more quickly

for the patellar (knee-jerk) reflex, how would the stimulation of the muscle spindle by gamma motor neurons affect the speed of the reflex?

sacral

from which plexus does the sciatic nerve arise?

neuronal pools

functional groups of interconnected neurons

major nerves of lumbar plexus

genitofemoral nerve -lateral femoral cutaneous nerve -femoral nerve

brown-sequard syndrome

loss of sensation and motor function that results from unilateral spinal cord lesions. proprioception loss and weakness occur ipsilateral to the lesion while pain and temperature loss occur contralateral

intersegmental reflex arcs

many segments interact to produces a coordinated, highly variable motor response -complicated spinal reflexes called..

nuclei

masses of gray matter within the central nervous system

higher-order functions

memory, learning, consciousness, and personality.

tendon reflex

monitors the external tension produced during a muscular contraction and prevents tearing or braking of the tendons

acquired reflexes

more complex, learned motor patterns -learned

gamma motor neurons

motor neurons innervating intrafusal fivers are called -their axons are called gamma efferents.

convergence

motor pathways for the control of skeletal muscles, like the diaphragm and external intercostal muscles, and exhibit what kind of neuronal organization?

withdrawal refelxes

move affected parts of the body away from a stimulus

polysynaptic

multiple synapses (two to several hundred)

Erb's palsy

obstetric condition characterized by paralysis or weakness of a newborn's upper arm muscles caused by a stretch injury to the brachial plexus

parallel processing

occurs when several neurons process the same information simultaneously

innate reflex

one of the first somatic reflexes to develop is the suckling reflex. which types of reflex is this?

monosynaptic

one synapse

denticulate ligaments

originate along either side of the spinal cord -prevent lateral (side to side) movement

paralegia

paralysis involving a loss motor control of the lower, but not the upper, limbs

quadriplegia

paralysis involving the loss of sensation and motor control of the upper and lower limbs

sciatic nerve

passes posterior to the femur, deep to the long head of the biceps femoris muscle. -as it passes the knee it divides into two branches -fibular nerve tibial nerve

parasympathetic nervous system

relaxes the body and inhibits or slows many high energy functions. rest and digest

major nerves of sacral plexus

sciatic nerve -pudendal nerve

subdural space

separates the dura mater from deeper meningeal layers -doesn't exist in healthy people

convergence

several neurons synapse on single postsynaptic neuron -motor neurons can be subject to both conscious and subconscious control (hold your breath)

hemiparesis

slight paralysis or weakness affecting one side of the boy

tabes dorsalis

slow progressive degeneration of the myelin layer of the sensory neurons of the spinal cord that occurs in the tertiary (third) phase of syphilis. Common signs and symptoms are pain, weakness, diminished reflexes, unsteady gait, and loss of coordination.

cords

smaller branches that originate at trunks

dermatome

specific bilateral region of the skin surface monitored by a single pair of nerves -each pair of spinal nerves supplies its own...

cervical enlargement

supplies nerves to the shoulder and upper limbs -expanded segment

craninal meninges

surround the brain -have the same three layers -at the foramen magnum of the skull, the spinal meninges are continuous with these...

kernig's sign

symptom of meningitis where patient cannot extend the leg at the knee due to stiffness in the hamstring muscles

spinal shock

term applied to all phenomena surrounding physiological or anatomical transection of the spinal cord that results in temporary loss or depression of all or most spinal reflex activity inferior to the level of injury

nerve conduction study

test often performed along with electromyography; the test stimulates certain nerves and records their ability to send an impulse to the muscle; it can indicate where any blockage of the nerve pathway exists

gray matter

the area of the spinal cord that surrounds the central canal and is dominated by the cell bodies of neurons, neuroglia, unmyelinated axons, and glial cells

horns

the areas of gray matter on each side of the spinal cord

reflex arc five steps

the arrival of a stimulus and activation of a receptor -the activation of a sensory neuron -information processing in the CNS -the activation of a motor neuron -the response of a peripheral effector

innate reflexes

the connections that form between neurons during development -genetically determined

perineurium

the connective tissue that wraps bundles of axons into fascicles in the ______________

spinal meninges three layers

the dura mater -the arachnoid mater -the pia mater

coccygeal ligaments

the dura mater attaches itself as it base to the skeletal system through what structure

a response by an effector

the final step involved in a neural reflex is ___________

equinovarus

the foot is plantar flexed, inverted, and adducted; also called talipes equinovalgus

polysynaptic reflexes characterisitics

the involve pools of interneurons -they are intersegmental in distribution -they involve reciprocal inhibition -they have reverberating circuits -several reflexes may cooperate to produce a coordinated, control response.

musculocutaneous nerve

the later cords form the.....

phrenic nerve

the major nerve of the cervical plexus -left an right nerves supply the diaphragm -distributed to the skin of the neck and the superior part of the chest

median nerve

the medial cord and lateral cord form...

arachnoid mater

the middle meningeal layer -includes epithelium ( arachnoid membrane and the arachnoid trabeculae) a delcate network of collagen and eslastic fibers that extends between the membrane and outer surface

reflex arc

the nerve impulses to produce a reflex is called a reflex arc

ulnar nerve

the other major nerve of the medial cord

posterior median sulcus

the posterior (dorsal) surface of the spinal cord has a shallow longitudinal groove called the

muscle spindles

the sensory receptors in the stretch reflex are ________

muscle spindles

the sensory receptors involved in the stretch reflex are...

sacral 2

the skin on the posterior thigh and leg is innervated by which pair of spinal nerves

divergence

the spread of information from one neuron to several neurons -broad distribution of a specific input

the spinal meninges

the three membranous layers that surround the spinal cord are called..

cervical

the trapezius muscle in innervated by nerves from which plexus?

dura mater

tough, fibrous -the layer that forms the outermost covering of the spinal cord -contains dense collagen fibers that are orientated along the longitudinal axis of the cord

superficial reflexes

triggered by stimuli at the skin or mucous membranes

stretch reflexes

triggered by the sudden elongation of a tendon -regulates skeletal muscle length

gray ramus

unmyelinated fibers that innervate glands and smooth muscles in the body wall or limbs form the ____________

receptor, sensory neuron, interneuron, motor neuron, effector

what is the correct sequence of the structures involved in a simple neural reflex?

stimulus arrival & receptor activation

what is the first step of a reflex?

a sensory and motor relay, or synapse area

what is the function of gray matter in the spinal cord?

2

what is the minimum number of neurons in a reflex arc?

reinforcement

what is the name for enhanced facilitation of a reflex

reciprocal inhibition

what is the name for preventing the contraction of an antagonistic muscle that opposes the muscle involved in a withdrawal reflex?

postural reflex

what is the name of the stretch reflex that maintains your balance?

monosynaptic reflex

what is the term for a reflex in which the sensory neuron synapses directly on the motor neurons?

brachial plexus

what plexus includes the ulnar nerve?

withdrawal reflex

what reflex causes the movement of a body part away from a stimulus?

sensory neuron cell bodies

what structures are found the dorsal root ganglion?

ventral ramus of the spinal nerves

what structures carries sensory information from and motor commands to the ventrolateral body surface and the limbs?

parallel processing

what type of neuronal organization is involved where multiple responses occur at the same time?

reciprocal inhibition

when one set of motor neurons is stimulated, those neurons that control antagonistic muscles are inhibited.

brain and spinal cord

where are reflex centers found

the ventral root

where do somatic motor commands to skeletal muscles of the upper and lower appendages exit from the spinal cord

spinal cord

where does the information processing occur in a spinal reflex?

subarachnoid space

where is the cerebrospinal fluid that surrounds the spinal cord located?

femoral nerve

which nerve arises from the lumbar plexus and innervates the anterior thigh muscles?

cervical plexus

which nerve plexus contains nerves that innervate the muscles of the neck and the diaphragm?

anterior gray horns

which portion of the spinal cord is the control area for somatic motor neurons that stimulate skeletal muscles?

crossed extensor reflex

will cause a motor response on the side opposite the stimulus

spinal tap

withdrawal of cerebrospinal fluid involves the insertion of a needle into the subarachnoid space in the inferior lumbar region