Chapter 14: Nervous System: Spinal Cord and Spinal Nerves Flashcards
A typical adult spinal cord is approximately ___ of an inch in diameter and ranges between 42 and 45 centimeters (_____ inches) in length.
3/4 of an inch in diameter
16 to 18 inches
The spinal cord extends inferiorly from the ____ of the brain through the vertebral canal and ends at the inferior border of the L1 vertebra.
medulla oblongata
The tapering inferior end of the spinal cord is called the ______ which marks the official “end” of the spinal cord proper.
conus medullaris
Two enlargements are visible in the surface view of the spinal cord because they are ____ than other areas of the cord due to the greater number of neurons that extend from these enlargements to ______ the upper and lower limbs.
wider
innervate
The ____ enlargement is an enlarged region of the inferior cervical part of the spinal cord that contains the neurons that innervate the upper limbs.
cervical enlargement
The ____ enlargement is an enlarged region of the mid-lumbar part of the spinal cord that contains the neurons that innervate the lower limbs.
lumbosacral enlargement
The spinal cord is subdivided into ___ parts.
5
Associated with each part of the spinal cord there are the rootlets that form the ____ pairs of spinal nerves.
31
The ___ part of the spinal cord is the supeiormost part of the spinal cord.
cervical
The cervical part contains neurons whose axons contribute to the __ pairs of cervical spinal nerves.
8 pairs
The cervical part is continuous with the ____.
medulla oblongata
The ___ part lies inferior to the cervical part. It contains the neurons for the ___ pairs of thoracic spinal nerves.
thoracic
12
The ____ part is a shorter segment of the spinal cord that contains the neurons for the ____ pairs of lumbar spinal nerves.
lumbar
5
The ____ part lies inferior to the lumbar part and contains neurons for the ____ pairs of sacral spinal nerves
sacral
5
The ____ part is the most inferior tip of the spinal cord which has ____ pair of cocygeal spinal nerves arising from this part.
coccygeal
1
Different parts of he spinal cord do not match up exactly with the vertebrae of the same name due to the fact that the vertebrae growth continued longer than the growth of the spinal cord resulting in the _____.
cauda equina
L2-L5, S1-S5, and Col extend inferiorly from the ____ forming the cauda equina.
conus medullaris
The nerve roots of the cauda equina get their name b/c they resemble a ____.
horses’s tail
The filum terminale within the cauda equina is a thin strand of ____ that helps anchor the conus medullaris to the ____.
pia mater
coccyx
The intervertebral foramina are lateral openings between vertebrae, which provide the passageway for each spinal nerve to extend from the spinal cord and exit the ____.
vertebral canal
Each spinal nerve is identified by the first letter of the spinal cord part to which it attaches combines with a ___.
number
Each side of the spinal cord contains ____ cervical nerves, ____ thoracic nerves, ___ lumbar nerves, ___ sacral nerves, and ___ coccygeal nerve.
8 cervical nerves 12 thoracic nerves 5 lumbar nerves 5 sacral nerves 1 coccygeal nerve
Spinal nerve names are different than cranial nerve names because cranial nerves are designated by ___ followed by a roman numeral.
CN
The spinal cord is roughly ____, but slightly flattened posteriorly and anteriorly.
cylindrical
There are 2 longitudinal depressions: a narrow groove, the posterior _____, dips internally on the posterior surface, and a slightly wider groove, the anterior or ventral _____.
median sulcus
median fissure
Both the size and shape of the spinal cord changes along its length because the amount of ___ and ____ reflects the function of that part of the spinal cord.
gray matter
white matter
The spinal cord parts that control the upper and lower limbs are larger because more _____ are located there and more space is occupied by ____ and ____.
neuron cell bodies
axons and dendrites
There are 8 pairs of cervical spinal nerves, but only ___ cervical vertebrae.
7
The atlas is the ___ cervical vertebrae.
1st
The spinal cord is protected and encapsulated by ____ which are continuous with the cranial _____.
spinal cord meninges
meninges
The meninges and spaces listed from innermost to outermost are as follows: pia mater, subarachnoid space, arachnoid mater, subdural space, dura mater, and ____.
epidural space
The ____ directly adheres to the spinal cord.
pia mater
The pia mater is the delicate, innermost meningeal layer, which is composed of elastic and ___ fibers that support that some of the blood vessels supplying the spinal cord.
collagen
____ ligaments are paired, lateral triangular extensions of the spinal pia mater that attach to the dura mater.
denticulate ligaments
The denticulate ligaments help suspend and anchor the ____ laterally.
spinal cord
The pia mater extends from the inferior end of the cord as the ____, which serves to anchor the spinal cord inferiorly to the coccyx.
filum terminale
The _____ mater lies external to the pia mater.
arachnoid mater
The arachnoid mater is partially composed of a delicate web of collage and elastic fibers termed the ____.
arachnoid trabeculae
Immediately deep to the arachnoid is the ___.
subarachnoid space
Cerebrospinal fluid circulates in the _____ space, both around the brain and the spinal cord.
subarachnoid
The subdural space is a potential space between the arachnoidspace and _____.
overlying dura mater
The outermost layer of meninges is the ____, which is composed of dense irregular connective tissue.
dura mater
The cranial dura mater has an outer periosteal layer and inner meningeal layer, the spinal dura mater consists of ____.
1 layer
The dura mater provides stability to the ____.
spinal cord
Each intervertebral foramen, the dura mater extends between adjacent vertebrae and fuses with the connective tissue layers that surround the ____.
spinal nerves
The ____ lies between the dura mater and the inner walls of the vertebra, and houses adipose and areolar connective tissue, and blood vessels.
epidural space
A lumbar puncture is used to obtain _____ to determine whether an infection or disorder of the central nervous system is present.
CSF
The spinal cord is partitioned into an inner _____ matter region and outer ____ matter region.
gray
white
The gray matter is dominated by neuron cell bodies, dendrites, glial cells, and _____ axons.
unmyelinated
White matter is composed primarily of myelinated axons that extend to and from the ____.
brain
The ___ matter in the spinal cord is centrally located, and its shape resembles a letter H, or a butterfly.
gray
The gray matter may be subdivided into the following components: anterior horns, lateral horns, posterior horns, and the ____.
gray commissure
___ horns are the left and right anterior masses of gray matter.
anterior
The anterior horns primarily house the cell bodies of ____ which innervate skeletal muscle.
somatic motor neurons
____ horns are found in the T1-L2 parts of the spinal cord only.
lateral
The lateral horns contain the cell bodies of ____ which innervate cardiac muscle, smooth muscle, and glands.
autonomic motor neurons
____ horns are the left and right posterior masses of gray matter.
posterior
Posterior horns contain the axons of ____ and the cell bodies of interneurons.
axons of sensory neurons
cell bodies of interneurons
The cell bodies of the sensory neurons are located in the _______.
posterior root ganglia, not the posterior horns
The ____ is a horizontal bar of gray matter that surrounds a narrow central canal.
gray commissure
The gray commissure primarily contains _____ axons and serves as a communication route between the right and left side of the gray matter.
unmyelinated
Within the gray comissure there are various functional groups of neuron cell bodies called _____.
nuclei
____ nuclei in the posterior horns contain interneuron cell bodies.
sensory nuclei
____ nuclei receive nerve signals from sensory receptors (pain or pressure receptors in the skin) whereas visceral sensory nuclei receive nerve signals from ____ and viscera.
Somatic sensory
blood vessels
Motor nuclei in the anterior and lateral horns contain _____ cell bodies that send nerve signals to muscles and glands.
motor neuron cell bodies
The somatic motor nuclei in the ____ horn innervate _____.
anterior
skeletal muscle
Autonomic motor nuclei in the ___ horns innervate smooth muscle, cardiac muscle, and glands.
lateral
The white matter of the spinal cord is external to the ____.
gray matter
White matter is partitioned into 3 regions, each called a _____.
funiculus
A ___ funiculus lies between the posterior gray horns and the posterior side of the cord and the posterior median sulcus.
posterior
The ___ funiculus is the white matter on each lateral side of the spinal cord.
lateral
The ____ funiculus is composed of white matter that occupies space on each anterior side of the cord between the anterior gray horns and the anterior median fissure.
anterior
The anterior funiculi are interconnected by the ___.
white commissure
The axons within each white matter funiculus are organized into smaller structural units called ____.
tracts or fasciculi
Individual ___ conduct sensory nerve signals or motor nerve signals (ascending tracts from the spinal cord to the brain or motor nerve signals (descending tracts from the brain to the spinal cord)>
tracts
The lateral and anterior funiculi contain both ascending and ___ tracts, and so they are composed of both motor and ____ axons.
descending tracts
sensory
The posterior funiculi contain ____ axons only, which extend in ___ tracts.
sensory
ascending
The CNS communicates with peripheral body structures through ____.
pathways
Poliomyelitis is an infection caused by one of the three strains of the poliovirus. In about __% of cases the virus spreads to the nervous system and attacks somatic motor neurons in the anterior horns of the spinal cord.
1%
In paralytic polio the ___ neurons are damaged or destroyed, resulting in paralysis of the muscles innervated by those segments of the spinal cord.
motor
Prompt use of ___ immediately after the injury appears to preserve some muscular function that might otherwise be lost.
steroids
These pathways conduct either sensory nerve signals from receptors to the CNS or ____ from the CNS to effectors; processing and integration occur along them.
motor nerve signals
Nervous system pathways are either ___ or ____ pathways.
sensory or motor
Sensory pathways are also called ___ pathways because the nerve signals transmitted from sensory receptors ___ through the spinal cord to the brain.
ascending
ascend
Motor pathways are also called ___ pathways because they transmit nerve signals that descend from the brain through the spinal cord to muscle or glands.
descending
Common location of neuron components
composed of 2 or more neurons
paired tracts
decussation
common characteristics of pathways
The neuron cell bodies are located in one of three places; glanlia within the PNS, gray horns within the spinal cord, or _____. In contrast the axons of these neurons extend through the spinal cord and brain ___.
nuclei within the brain along the pathway
as tracts
Most pathways are composed of a series of ___ or ___ neurons that work together.
2 or 3
Sensory pathways have primary neurons, secondary neurons, and sometimes ___ neurons that facilitate the pathway’s functioning.
tertiary
Motor pathways use an upper motor neuron and ___ motor neuron.
lower
All pathways are composed of __ tracts.
paired
Most pathways ____ from one side of the body to the other side at some point along the pathway. This means that the left side of the brain processes sensory input from the motor output on the right side of the body and vice versa.
decussate (cross over)
The term ___ is used to indicate the relationship to the opposite side, whereas the term ipsilateral means the same side.
contralateral
Over 90% of pathways decussate however, the point at which decussation occurs can ___ among pathways.
vary
Pathways and tracts are generally named according to their origin and __.
termination
Motor pathways begin with either cortico, indicating an origin in the cerebral cortex or with the name of a brainstem nucleus such as ___ indicating an origin within the red nucleus of the midbrain.
rubro
Sensory pathways are ascending pathways that relay sensory input from ___ in the brain.
receptors
Sensory pathways are organized into two categories that are dependent upon the type of ___ involved.
receptor
Somatosensory pathways process stimuli received from receptors within the skin, muscles and ___.
joints
Viscerosensory pathways process stimuli received from the ___.
viscera
Sensory pathways use a series of 2 or 3 neurons to transmit nerve signals from the body to the brain. The first neuron in this chain is the ____ neuron which resides in the _____ of a spinal nerve, and the axons extends to a secondary neuron.
primary
posterior root ganglion
The secondary neuron is an interneuron that extends from the primary neuron to either the ____ neuron or the ___.
tertiary neuron or cerebellum
The tertiary neuron is also an interneuron and extends from the secondary neuron to the ___ (specifically the primary somatosensory cortex of the parietal lobe).
cerebrum
Pathways that lead to the cerebellum do not have a ___.
tertiary neuron
There are __ major types of somatosensory pathways.
3
The posterior funiculus medial lemniscal pathway projects from a somatic receptor to the primary ____ of the cerebral cortex.
primary somatosensory cortex
Its name derives from two components: the tracts within the spinal cord, collectively called the posterior funiculus, and the tracts within the brainstem, collectively called the _____.
medial lemniscal
The posterior funiculus medial lemniscal pathway transmits ___ input concerned with proprioceptive (posture and balance) info about limb position, as well as discriminative touch, precise pressure, and vibration sensations from the __.
sensory
skin
The posterior funiculus medial lemniscal pathway uses a series of __ neurons to signal the brain about a specific stimulus.
3
Axons of the primary neurons reside in spinal nerves and reach the CNS through the posterior roots of the ___. Upon entering the spinal cord, these axons ascend within a specific posterior funiculus, either the fasciculus cuneatus or the fasciculus ____.
spinal nerves
gracillis
Sensory axons ascending within the posterior funiculi synapse on secondary neuron cell bodies housed within the nucleus cuneatus or nucleus gracilis, respectively. The axons of these secondary neurons then project to the _____ on the opposite side of the brain through the medial lemniscus.
thalamus
_____ occurs after secondary neuron axons exit their specific nuclei within the medulla oblongata and before they enter the medial lemniscus.
decussation
The axons of the secondary neurons synapse on cell bodies of the tertiary neurons within the thalamus, where the sensory info is sorted according to the ____ involved (somatotopically).
part of the body
axons from the tertiary neurons transmit nerve signals to a specific location of the primary somatosensory cortex housed within the _________.
postcentral gyrus
The _____ pathway or spinothalamic pathway is located in the anterior and lateral white funiculi of the spinal cord.
anterolateral pathway
The anterolateral pathway or spinothalamic pathway is composed of the anterior spinothalamic tract and the ____ tract.
lateral spinothalamic tract
Axons within these pathways (anterolateral) relay ___ input related to crude touch and ____ as well as pain and temp.
sensory
pressure
Typically, sensations that require us to ______ to the stimulus (such as an itch making us want to scratch) are relayed through the anterolateral pathway.
act in response
The anterolateral pathway uses a chain of ___ neurons to signal the brain about a specific stimulus.
3
____of the primary nersons reside in spinal nerves and reach the CNS through the posterior roots of spinal nerves. However, these axons synapse on secondary neurons within the posterior horns of the spinal cord.
axons
Axons of the secondary neurons in the anterolateral pathway decussate through the anterior ____ and relay nerve signals to the opposite side of the spinal cord before ascending toward the rain and synapsing on tertiary neurons located within the ___.
white commissure
thalamus
Axons from the tertiary neurons (anterolateral pathway) then transmit nerve signals to the appropriate part of the ____.
primary somatosensory cortex
The ______ pathway extends through the anterior and posterior white funiculi of the spinal cord.
spinocerebellar
The spinocerebellar pathway is composed of the anterior spinocerebellar tract and the ______.
posterior spinocerebellar tract
Axons within these pathways conduct (spinocerebellar) signals from proprioceptors related to postural input to the ____.
cerebellum.
Info conducted in spinocerebellar pathways is integrated and acted on at a _____.
subconcious level
The spinocerebellar pathway uses a chain of ___ neurons to signal the cerebellum about a specific stimulus.
2
There is no ____ neuron in the spinocerebellar pathways.
tertiary
Axons (spinocerebellar pathway) of the primary neurons reside in spinal nerves and reach the CNS through the posterior roots of spinal nerves synapsing on ____ with in the posterior horns of teh spinal cord.
secondary neurons
Some of the secondary neuron axons in the spinocerebellar pathway decussate through the anterior ____ and relay nerve signals to the opposite side of teh spinal cord before ascending toward the brain.
white commissure
In the spincerebellar pathway secondary neuron axons transmit nerve signals to the ___.
cerebellum
Motor pathways or descending tracts are descending pathways in the brain and spinal cord that control ___.
effectors
Motor pathways originate from the cerebral cortex, cerebral nuclei, or the ___.
brainstem
At least __ motor neurons are present in the motor pathway.
2
The cell body of the ___ motor neuron is housed either within the cerebral cortex, cerebral nuclei, or a nucleus within the brainstem.
upper
An axon of the upper motor neuron synapses either directly on the lower motor neuron, or on an interneuron that ultimately synapses directly on a ____.
lower motor neuron
Upper motor neurons either excite or ___ the activity of lower motor neurons.
inhibit
The cell body of a lower motor neuron is housed either within the anterior horn of the spinal cord or within a brainstem _____.
cranial nerve nucleus
An axon of the lower motor neuron exits the CNS and projects to the _____ to be innervated.
skeletal muscle
The lower motor neuron is always ____ because its axon connects directly to the skeletal muscle fibers.
excitatory
Motor neurons form tow types of motor pathways: the ___ pathway and the ____ pathway.
direct and indirect
The direct pathway (motor) is responsible for ___ control of skeletal muscle activity.
conscious
The indirect pathway (motor) is responsible for ____ or ____ control of skeletal muscle.
subconscious or reflexive
The direct pathway is also called the ____ pathway, originates in the primary motor cortex in the ___ lobe.
pyramidal
frontal
The name pyramidal is derived from the ____ like shape of the upper motor neuron cell bodies within this area.
pyramid
The axons of the pyramidal upper motor neurons descend through the internal capsule, enter the cerebral peduncles, and ultimately synapse in one of two locations: ______ or the spinal cord.
brain stem
The tracts (pyramidal upper) extend from the cerebral cortex and synapse in the _____ compose the corticobulbar tracts.
brainstem
The tracts (pyramidal upper) that extend from the cerebral cortex and synapse in the spinal cord compose the ____ tracts.
corticospinal
The corticobulbar tracts originate from the facial region of the motor homunculus within the primary ____.
motor cortex
The term bulbar means resembling a bulb and is used to indicate the embryonic rhombencephalon in the ___.
brainstem
Axons of these upper motos neurons extend to the brainstem, where they synapse with ____ cell bodies that are housed within the brainstem cranial nerve nuclei.
lower motor neuron
Corticobulbar tracts do not pass through the ___ and they involve cranial nerves and not ____ nerves.
spinal cord
spinal nerves
The corticospinal tracts descend from the ____ of the cerebrum through the medulla oblongata and into the spinal cord where they synapse on lower motor neurons in the _____ horn of the spinal cord.
primary motor cortex
anterior
The ___ tracts are composed of lateral and anterior corticospinal tracts.
corticospinal
The lateral and anterior corticospinal tracts differ in their point of ______, their location within the spinal cord, and the specific ____ that they innervate and control.
decussation
muscles
The lateral corticospinal tracts include about ___% of the axons of the upper motor neurons that decussate within the pyramids of the medulla oblongata and then form the lateral corticospinal tracts in the lateral _____ of the spinal cord.
85
funiculi
Axons (lateral corticospinal tracts) of the lower motor neurons innervate skeletal muscles that control skilled movements in the ___.
limbs
The anterior corticospinal tracts represent the remaining __% of the axons of upper motor neurons that extend through the medulla oblongata.
15%
The axons (anterior corticospinal tracts) of these neurons do not decussate at the level of the medulla oblongata, instead they decussate at the level of a spinal cord segment through the ____.
gray commissure
The axons of the anterior corticospinal tracts of the lower motor neurons innervate ______ muscle.
axial skeletal
Several nuclei within the brainstem initiate motor commands for activities that occur at a ___ or ____ level.
subconscious or reflexive
The ___ pathway is so named because upper motor neurons originate within brainstem nuclei and take a complex, circuitous route through the brain to the spinal cord.
indirect pathway
The indirect pathway ____ or helps control the pattern of somatic motor activity by exciting or inhibiting the lower motor neurons that innervate the muscles.
modifies
The different tracts of the indirect pathway are grouped according to their ____ fxn.
primary
The lateral pathway (indirect) regulates and controls ___, ___ movements and tone in flexor muscles of the limbs.
precise, discrete
The lateral pathway (indirect) consists of ____ tracts that originate in the red nucleus of the midbrain.
rubrospinal
The medial pathway (indirect pathway - motor) regulates reflexive muscle tone and ____ movements of the muscles of the head, neck, proximal parts of the ____, and trunk.
gross
limbs
The medial pathway consists of three groups of tracts.
reticulospinal
tectospinal
vestibulospinal
The reticulospinal (medial - indirect - motor) tracts originate from the ____ in the midbrain and help control ___ movements related to posture and maintaining balance.
reticular formation
reflexive
The tectospinal (medial - indirect - motor) tracts conduct motor output from the superior and inferior colliculi in the ____ of the midbrain to help regulate reflexive ____ of the upper limbs, eyes, head, and neck as a consequence of visual and auditory stimuli.
tectum
positional changes
The vestibulospinal (medial - indirect - motor) tracts originate within vestibular nuclei of the ____. Nerve signals conducted within these tracts regulate reflexive muscular activity that helps maintain balance during sitting, standing, and ___.
brainstem
walking
The 31 pairs of spinal nerves extend from the spinal cord to muscles and glands and from ___ to the spinal cord.
sensory receptors
A nerve typically is formed from the union of thousands of motor and sensory axons and is enveloped in the 3 successive connective tissue wrappings: epineurium, perineurium and ____.
endoneurium
The cervical nerves are called C1 - ___.
C8 - 8 pairs of cervical nerves
The thoracic nerves are called T1- ___.
T12 - 12 pairs
The lumbar nerves are called L1- __.
L5 - 5 pairs
The sacral nerves S1 - _____.
S5 - 5 pairs
The coccygeal nerve is called ____.
Col - 1 pair
Each spinal nerve is formed by __ roots.
2 - an anterior and posterior root
Each ____ root or ventral root contains motor axons only and is formed from the merging of multiple anterior rootlets.
anterior
The motor axons in the anterior root arise from cell bodies in the _____ horns of the spinal cord.
anterior and lateral horns
Motor axons conduct nerve signals from the CNS to _____ (muscles and glands).
effectors
The posterior or dorsal root contains ___ axons only is formed from the merging of multiple posterior rootlets.
sensory
The cell bodies of the posterior root sensory neurons are located in the ____ within the posterior root.
posterior or dorsal root ganglion
Sensory axons in the posterior root relay nerve signals from the receptors of the ____.
CNS
Each anterior and corresponding posterior root unite within the ____ to form a spinal nerve.
intervertebral foramen
All spinal nerves are ___ nerves because each spinal nerve contains both motor axons from the anterior root and sensory axons from the posterior root.
mixed
Each cervical spinal nerve exits the vertebral canal and travels through an Intervertebral foramen superior to the vertebra of the same ___.
number
The 8th cervical spinal nerve is the exception, it leaves the intervertebral foramen between the C7 and ___ vertebrae.
T1
The anterior and posterior roots of the lumbar, sacral, and coccygeal spinal nerves are much ____ than the roots of the other spinal nerves because they must extend inferiorly to reach their respective intervertebral foramina before they can merge and form a spinal nerve.
longer (cauda equina)
After exiting the intervertebral foramen, a typical spinal nerve almost immediately splits into branches termed, __.
rami
The posterior or dorsal ramus is the ____ of the two main branches.
smaller
The posterior or dorsal ramus innervates the ___ muscles of the back and the skin of the back.
deep
The anterior or ventral ramus is the ____ of the two main branches.
larger
The anterior ramus splits into multiple other branches, which innervate the anterior and lateral portions of the trunk, the upper limbs, and the ___.
lower limbs
Many of teh anterior rami go on to form ____.
nerve plexuses
Rami ____ contain axons associated with the autonomic nervous system (ANS).
communicantes
Each set of rami communicantes extends between the spinal nerve and a ball-like structure call the sympathetic trunk ____.
ganglion.
The sympathetic trunk ganglia are interconnected and form a beaded necklace like structure called the sympathetic trunk that extends parallel and lateral to the______.
vertebral column
A dermatome is a specific segment of ____ innervated by a single spinal nerve.
skin
All spinal nerves except for ___ innervate a segment of skin, and each area of the skin that is innervated by a specific spinal nerve has been mapped.
C1
Dermatomes are clinically important because they can indicate potential ____ to one or more of the spinal nerves.
damage
If a patient experience anesthesia (sensation of numbness) along the medial side of the arm and forearm, the C8 spinal nerve may be ____.
damaged
Dermatomes are also involved in referred _____ pain, a phenomenon in which pain or discomfort from one organ is mistakenly referred to a dermatome.
visceral
Shingles is the result of the chickenpox virus invading the ______. The virus causes a rash and blisters along the dermatome.
posterior root ganglia
A nerve plexus is a network of interweaving anterior ___ of spinal nerves.
rami
The anterior rami of most spinal nerves form nerve _____ on both the right and left sides of the body.
plexuses
The main plexuses are the cervical plexuses, brachial plexuses, lumbar plexuses, and ___ plexuses.
sacral
Nerve plexuses are organized so that axons from each anterior rami extend to body structures through several different branches and each terminal branch of the plexus houses axons from several different ___.
spinal nerves
Damage to a single segment of teh spinal cord or damage to a single spinal nerve generally does not result in ____ of innervation to a particular muscle or region of the skin.
complete
Most of the thoracic spinal nerves as well as ___ to ___ do not form plexuses.
S5 to Col
The anterior rami of spinal nerves T1-T11 are called ___ nerves because they travel in the intercostal space sandwiched between two adjacent ribs.
intercostal nerves
T12 is called a ___ nerve because it arises inferior to the ribs, not between two ribs.
subcostal nerve
With the exception of ___ the intercostal nerves do not form plexuses.
T1
The intercostal nerves innervate much of the torso wall and portions of the ____.
upper limb
The left and right cervical plexuses are located deep on each side of the ____, immediately lateral to cervical vertebrae C1-C4.
neck
The __ cervical nerve is not considered part of the cervial plexus although it contributes some axons to one of the plexus branches.
c5
One important branch of the cervical plexus is the phrenic nerve, which is formed primarily from the C4 nerve and some contributing axons from C3 to ___. The phrenic nerve travels through the thoracic cavity to innervate the thoracic ____.
C5
diaphragm
The left and right brachial plexuses are networks of nerves that supply the ____.
upper limb
Each brachial plexus innervates the pectoral girdle and the entire ____ of one side.
upper limb
Each brachial plexus is more complex than a cervical plexus and is composed of anterior rami, trunks, division, and ____.
cords
the anterior rami sometimes called roots of the brachial plexus are simply the continuations of the anterior rami of spinal nerves _____.
C5-T1
C5-T1 unite in the posterior triangle of the neck to form the superior, middle, and inferior _____.
trunks
Nerves ___ and ___ unite to form the superior trunk.
C5 and C6
Nerve ___ remains the middle trunk.
C7
Nerves ____ to ___ unite to form the inferior trunk.
C8 and T1
Portions of each ____ divide deep to the clavicle into an anterior division and a posterior division.
trunk
The anterior and posterior division of portions of each trunk contain ___ that primarily innervate the anterior and posterior parts of the upper limb, respectively.
axons
The anterior and posterior trunk divisions converge at the axilla to form ___ cords.
3
The ____ cord is posterior to the axillary artery and is formed by the posterior divisions of the superior, middle and inferior trunks, therefore it contains portions of C5 through T1 nerves.
posterior
The ____ cord is medial to the axillary artery and is formed by the anterior division of the ____ trunk; it contains portions of nerves C8-T1.
medial
inferior
The ___ cord is lateral to the axillary artery and is formed from the anterior divisions of the superior and ___ trunks; it contains portions of nerves C5-C7.
lateral
middle
5 major terminal branches emerge from the 3 cords, the axillary nerve, median nerve, musculocutaneous nerve, radial nerve, and _____.
ulnar nerve
The axillary nerve transverses through the ____ and posterior to the surgical neck of teh humerus. It innervates both the deltoid and teres minor muscles.
axilla
The axillary nerve receives sensory nerve signals from the superolateral part of the __.
arm
The ____ nerve travels along the midline of the arm and forearm, and deep to the carpal tunnel in the wrist.
median
The median nerve receives sensory nerve signals from the ____ side of the lateral 3 and 1/2 fingers (thumb, index, middle, and the lateral 1/2 of the ring finger) and the dorsal tips of the same fingers.
palmar
The median nerve innervates most of teh anterior forearm muscles, teh thenar muscles, and teh lateral two ____.
lumbricals
The musculocutaneous nerve innervates teh anterior arm muscles which flex the ____ and or flex the forearm.
humerus
The musculocutaneous receives sensory info from the lateral surface of the ___.
forearm
The radial nerve travels along the posterior side of the arm and the along the radial side of the ____.
forearm
The radial nerve ______ the posterior arm muscles and the posterior forearm muscles.
innervates
The ___ nerve receives sensory nerve signals from the posterior arm and forearm surface and teh dorsolateral side of teh ___.
hand
The ulnar nerve descends along the medial side of teh ____.
arm
Reflexes are rapid, preprogrammed, _____ responses of muscles or glands to a stimulus.
involuntary
a ___ is required to initiate a reflex.
stimulus
a ____ requires that few neurons are involved and synaptic delay is minimal
rapid response
a ___ response occurs the same way every time.
preprogrammed
An ___ response requires no conscious intent or pre-awareness of the reflex activity. Thus reflexes are not usually supressed.
involuntary
A reflex is a ____ mechanism; it allows us to quickly response to stimulus that may be detrimental to our well-being without having to wait for the brain to process it.
survival
____ of the stimulus occurs after the reflex action has been completed, in time to correct or avoid a potentially dangerous situation.
awareness
A reflex arc includes a sensory receptor, an effector, and the ____wiring between the two.
neural
A reflex arc always begins at a ___ in the PNS, communicates with the CNS, and ends at a peripheral effector, either a muscle or gland.
receptor
The ___ of intermediate steps of a reflex arc vary depending upon the complexity of the reflex.
number
A stimulus activates a sensory receptor
the sensory neuron transmits a nerve signal to the CNS
Information from teh nerve signal is processed in teh integration center by interneurons
The motor neuron transmits a nerve signal to the CNS to an effector
The effector respons to the nerve signal from teh motor neuron
5 steps of a reflex
A stimulus activates a sensory _____ that is external such as temp, pressure, or tactile changes.
receptor
Proprioceptors are sensory receptors found in ____ and tendons, and a stimulus to a proprioceptor may initiate a reflex as well.
muscles and tendons
More complex reflexes may use a number of interneurons within teh CNS to inegrate and process incoming sensory nerve signals and transmit ifno to the ____ neurons.
motor
The nerve signal is transmitted through the ____ of a motor neuron.
aneterior root
An effector is a muscle or a ____ that responds to the nerve signal from the motor neuron. This response is intended to counteract or remove teh original stimulus.
gland
Specific components of a reflex can vary, some involve teh spinal cord, whereas others involve the ___.
brain
spinal reflex or cranial reflex
somatic reflex or visceral reflex
monosynaptic reflex or polysynaptic reflex
ipsilateral reflex or contralteral reflex
innate reflex or acquired reflex
classification of spinal reflexes
A relfex may be identified by the specific area of teh central nervous system that serves as the ___ site. Spinal reflexes involve the spinal cord and cranial involve the brain.
processing site
The type of effector that is stimulated by the motor neurons involved in the reflex determines if it is somatic which involves the ____ muscle or the ____ which involves the cardiac muscle, smooth muscle, or gland as teh effector.
somatic or visceral (autonomic)
A reflex may be classified by the number of ____ participating in the reflex. Monosynaptic have only a ___ neuron and a ___ neuron. A polysnaptic reflex has one or more interneurons positions between teh sensory and motor neurons.
neurons
motor and sensory
The monsynaptic reflexes are the ____..
simplest
A reflex may be classified based upon wheter you are ____ with it.
born
Stretch reflexes and golgi tendon reflexes are initiated by a stimulus that is detected by a specific sensory receptor called a ____.
proprioceptor
A proprioceptor resides in a muscle or tendon and detects any change to that structure, such as strectch or ___.
tension
The 2 principle proprioceptors are the muscle spindle and the _____ organ.
golgi tendon
A muscle spindle is a proprioceptor that detects changes in stretch of a muscle, for this reason a muscle spindle is also known as a stretch ____.
receptor
A muscle ___ is composed of intrafusal muscle fibers that are surrounded by a connective tissue capsue.
spindle
Intrafusal muscle fibers lack ___ in their central regions and are contractile only at their distal regions.
myofilaments
Intrafusal muscle fibers are innervated by ___ motor neurons that detect changes within the muscle.
gamma
Around teh muscle spindle are extrafusal muscle fibers, which are innervated by ____motor neurons. These motor neurons have the largest diameter axons.
alpha
A muscle spindle is associated with a type of reflex called a ___ reflex.
stretch
A golgi tendon organ is another type of ____ that detects change in tension in a muscle tendon when a muscle contracts.
proprioceptor
A golgi tendon organ is composed of sensory nerve endings within a ___ or near a muscle tendon junction.
tendon
A ___ relfex is a muscle reflexively contracting in respons to stretching of a muscle.
stretch
Stretch in a muscle is monitored by a ____.
muscle spindle
A muscle spindle may be stretched if either the entire muscle is stretched or lengthened or if a ___ of the muscle that contains the muscle spindle is lengthened.
portion
The biceps reflex is an example of a ____ reflex.
stretch
The sensory neurons (stretch reflex) transmit nerve signals to the spinal cord (CNS) where they synapse with the _____ motor neurons associated with that muscle. The alpha motor neurons then transmit nerve signals to the extrfusal muscle fibers which causes the muscle to _____ thus resist the stretch.
alpha
contract
The stretch reflex is indirectly involved in a process called ___ inhibition.
reciprocal
When the sensory nerve signal reach the CNS, some of the sensory axons synapse with interneurons. These interneurons synapse with alpha motor neurons that inhibit ____ muscle contraction.
antagonistic muscle contraction
As the biceps brachii is stimulated, reciprocal inhibition results in the triceps brachii contraction being dampened so the biceps movement will not be _____ by the tricpes brachii.
oppossed
The stretch reflex is a ___ relfex, but the corresponding reciprocal inhibition is ____ in nature because it uses interneuron within the circuit.
monsynaptic reflex
polysynaptic
The stretch reflex ____ muscles from stretching excessively.
prevents
The golgi tendon reflex prevents muscles from ____ or _____ excessively.
tensing or contracting
The golgi tendon reflex is _______ that results in muscle lengthening and relaxation in response to increased tension at a golgi tendon organ.
polysynaptic
As a muscle contracts, its associated tendon stretches, resulting in increased tension in the tendon and activation of the goldi tendon ___.
organ
Sensory neurons in the golgi tendon organ transmit nerve signals to interneurons in the ___, which in turn inhibit the alpha motor neurons in the smae muscle.
spinal cord
When the motor neurons are inhibited (golgi tendon organ), teh associated muscle is allowed to ____, thus protecting the muscle and tendon from excessive tension damage.
relax
Sensory neurons also communicate (golgi) with other interneurons in the spinal cord that stimulate alpha motor neurons for the _____muscles called the reciprocal activation.
antagonistic
An example of reciprocal activation is when the golgi tendon organ in teh quads detects excessive tension, the the golgi tendon reflex ultimately relaxes the quads muscle, and reciprocal activation results in teh hamstrings being stimulated to contract.
…
Golgi tendon reflexes help prevent a muscle or tendon from injury due to excessive tension and help ensue that the muscle contraction process occurs ____ and efficiently.
smoothly
In cases where the muscle is under extreme tension (weight lifting) a golgi tendon reflex may ____ a stretch reflex (the person drops the weights due to the excessive tension on the muscle)
nullify
A ___ reflex involves muscles contracting to withdraw the body part away from a painful stimulus.
withdrawal or flexor reflex
The ____ reflex involves pain receptors, termed nociceptors, which are painful stimulus such as touching something hot.
withdrawal or flexor reflex
This painful stimulation initaes a nerve signal that is transmitted by a sensory neuron to the spinal cord. Interneurons receive teh sensory nerve signal and stimulate motor neurons to the ____ to contract in response.
flexor muscles
With a withdrawal or flexor reflex a reciprocal ____ occurs with the extensor muscles, so the hamstrings can _____ unimpeded.
inhibition
The crossed-extensor reflex often occurs in conjunction with the ___ reflex., usually in the lower limbs.
withdrawal
When the _____ reflex is occuring in one limb, the crossed-extensor reflex occurs in the other limb
withdrawal
Sp, when the sensory neurons transmit nerve signals to the spinal cord, some sensory branches synapse with interneurons inolved in the stretch reflex, wheras other sensory branches synapse with interneurons inolves in the ______ relfex.
crossed-extensor reflex
These interneurons cross to the otehr side of the spinal cord through the gray commissure and synapse with motor neurons that control ____ muscles in the opposite limb and cause the antagonistic muscle to contract.
antagonistic
The crossed-extensor reflex helps us maintain ____ and shift body weigh accordingly.
balance
Clinicians use ___ to test specific muscle groups and specific spinal nerves or segments of the spinal cord.
reflexes
Some variations in reflexes is normal, a consistenly abnormal reflex response may indicate damage to the ___ or ____.
nervous system or muscles
A ___ reflex refers to a reflex response that is diminished or absent.
hypoactive
A hypoactive reflex may indicate damage to a segment of the spinal cord or it may suggest muscle ____ or ____ to the neuromuscular junction.
dmage or disease
A ____ reflex refers to an abnormally strong response that may indicate damage somewhere in either the brain or ____ especially is accompanied by clonus, rthymic oscillations between flexion and extension, when the muscle reflex is tested.
hyperactive
sprinal cord
A hollow ____ canal in the neural tube develops into the central canal of teh spinal cord. The ____ canal does not shrink in size rather the neural tube around it grows at a rapid rate.
neural
neural
The ____ plates lie anterior to the sulcus limitans and develop into the anterior and lateral horns, motor structures of the gray matter.
basal
The ___ plates lie posterio to the sulcus limitans ans by theninth week of development, the plates develop into posterior horns, sensory structures of the gray matter and form teh posterior part of teh gray commissure.
alar
By the 6th week of development a horizontal groove called the ___ forms in teh lateral walls of teh central canal which also represents a divving point in the neural tube as 2 specific regions become evident.
sulcus limitans
