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