A&PII Chapter 13
What is the source of the sensory signals carried by the cuneate fasiculus?
Upper limbs & chest
____ fibers are nerve fibers that innervate blood vessels, glands & internal organs
Visceral
The nerve signals of the medial vestibulospinal tract help in controlling position of the ____
head
Define Spinal Meningitis
inflammation of spinal meniges
Spinal meningitis
inflammation of spinal meninges
The ___ center of a reflex arc is located within the gray matter of the spinal cord or brainstem
integrating
An ____ reflex arc is a reflex arc in which the input & output occur at different levels of the spinal cord
intersegmental
Fibers from the cuneate fasciculus end on the ___ side of the medulla oblongata
ipsilateral
Define cauda equina
is a bundle of spinal nerves and spinal nerve roots, consisting of the second through fifth lumbar nerve pairs, the first through fifth sacral nerve pairs, and the coccygeal nerve, all of which arise from the lumbar enlargement and the conus medullaris of the spinal cord.
3 functions of the spinal cord
reflexes, conduction, locomotion
The second-order neurons of the spinoreticular tract terminate in the ___ formation of the brainstem
reticular
The ___ tract originates in the reticular formation
reticulospinal
The ___ tracts carry signals that control muscles of the upper & lower limbs, especially for posture & balance
reticulospinal
Moving peripherally from the spinal cord, the anterior & posterior ___ form the spinal nerve
roots
In a sensory pathway, the ___ order neuron runs from the spinal cord or brainstem to the thalamus
second
A syndrome called spinal ____ occurs early after spinal injury. It involves absence of reflexes & flaccid paralysis of muscles below the injury
shock
In a sensory pathway, the ___ order neuron runs from the thalamus to the sensory cerebral cortex
third
4 regions of the spinal cord
thoracic, lumbar, sacral, cervical
Examples of a somatosensory stimulus
touch, pressure, stretch, temperature, pain
Define Gamma Motor Neuron
type of lower motor neuron that takes part in the process of muscle contraction, and represents about 30% of fibers going to the muscle
The vestibular nuclei of the brainstem receives input from the ___ of the inner ear
vestibule
Define Rabies
viral disease that spreads via somatic motor nerve fibers to the CNS & then to ANS fibers
Define Lumbar Plexus
web of nerves (a nervous plexus) in the lumbar region of the body which forms part of the larger lumbosacral plexus. It is formed by the divisions of the first four lumbar nerves (L1-L4) and from contributions of the subcostal nerve (T12), which is the last thoracic nerve.
All spinal nerves except C1 pass through which structure to emerge from the vertebral column?
Intervertebral foramen
Within a muscle, how are intrafusal fibers structurally different from extrafusal fibers?
Intrafusal fibers have sarcomeres at their ends; the middle lacks sacromeres
What ramus of a spinal nerve innervates the local muscles, joints, & skin of the back?
Posterior
What type of signal does the spinocerebellar tract carry?
Proprioception
Muscle spindles are classified as what type of receptor?
Proprioceptor
___ is a viral infection that spreads via somatic nerve fibers to the CNS
Rabies
What is a tangle of nerve endings entwined in collagen fibers?
Tendon organ
What does contralateral mean?
That 2 points are on opposite sides of the body
What does ipsilateral mean?
That 2 points are on the same side of the body
True of False: The neural pathway of a flexor reflex is more complex than that for the tendon reflex
True
True or False: The flexor reflex uses an ipsilateral reflex arc
True
In descending pathways, the which motor neurons have their somas in the cerebral cortex or brainstem?
Upper
Define paraplegia
paralysis of both lower limbs
Define Intercostal Nerve
part of the somatic nervous system, and arise from the anterior rami of the thoracic spinal nerves from T1 to T11
Inferior to the medullary cone, the ___ mater forms the terminal filum
pia
The third-order neurons of the spinoreticular tract runs from the ____ to the thalamus
pons
The ___ median sulcus is a longitudinal groove on the dorsal surface of the spinal cord
posterior
The ____ roots are the spinal nerve roots that carry sensory nerve signals
posterior
The cuneate fasiculus is located in the ___ column of the spinal cord
posterior
In a patellar reflex, the effector is the ___ ____ muscle group of the thigh
quadriceps femoris
4 properties of a reflex
quick, stereotyped, requires stimulation, involuntary
In some reflexes, ____ inhibition is used to inhibit the action of antagonists so they don't oppose the reflex response
reciprocal
Within a nerve, each fascicle is wrapped in which layer?
Perineurium
Which meninx is closely associated with the contours of the spinal cord?
Pia mater
What is a reflex involving one or more interneurons called?
Polysynaptic
Place the spinal cord regions in order from superior to inferior.
1. Cervical 2. Thoracic 3. Lumbar 4. Sacral
Place the meninges in order from superficial to deep.
1. Dura mater 2. Arachnoid mater 3. Pia mater
Place the components of a reflex arc in order.
1. Receptor 2. Afferent nerve fiber 3. Integration center 4. Efferent nerve fiber 5. Effector
Within the spinal cord, which tracts carry motor signals down from the brain?
Descending
The number of neurons in a descending pathway is ____
2
Sensory pathways consist of a particular number of neurons. Sensory pathways consist of a chain of ___ (what number?) neurons in sequence.
3
There are ___ pairs of spinal nerves.
31
How many spinal nerves are there in order from superior to inferior?
8 Cervical, 12 Thoracic, 5 Lumbar, 5 Sacral, 1 Coccygeal
What is the caudal equine?
A bundle of nerve roots occupying the vertebral canal from L2 to S5
What is a nerve?
A cord of nerve fiber bundles bound together by connective tissue
What is a region of the spinal cord supplied by a pair of spinal nerves called?
A segment
What is a reflex?
A stereotyped, involuntary response to a stimulus
During a crossed extension reflex, which nerve fibers cross to the contralateral side?
Afferent
Fact about tendon reflex
Alpha motor neurons are inhibited & the muscle does not contract as strongly
In which disease are motor neurons destroyed & sclerosis of the lateral spinal cord occurs?
Amyotropic lateral sclerosis
What is parathesia?
An abnormal sensation
The spinoreticular tract is found in which columns of the spinal cord?
Anterior & Lateral
The spinothalamic tract is found in which columns of the spinal cord?
Anterior & Lateral
Which spinal cord areas are composed of gray matter?
Anterior horn, Lateral horn, Posterior horn
What 2 things are considered a distal branch of a spinal nerve?
Anterior ramus & Posterior ramus
What are the 3 columns of white matter found in the spinal cord?
Anterior, Posterior, Lateral
Which meninx consists of simple squamous epithelium with a mesh of fibers in the adjoining space?
Arachnoid mater
Where do gamma motor neurons innervate a muscle spindle?
At the contractile end of each infrafusal fiber
Where are muscle spindles typically located?
At the ends of a muscle, near the tendons
Where does the spinal cord arise from the medulla oblongata?
At the foramen magnum
What are 4 names of a plexus?
Brachial, Cervical, Sacral, Lumbar
The first cervical spinal nerve emerges above vertebrae ____
C1
A spinal cord injury above which segment will lead to respiratory failure?
C4
Where do signals ascending through the spinocerebellar tract terminate?
Cerebellum
Which structure is formed from nerves C1-C5?
Cervical plexus
What ligament is formed by the fusion of the lumbar cistern & dura mater?
Coccygeal
Which rami connect the anterior rami to the sympathetic chain?
Communicating
Which rami of spinal nerves T1-T2 connect to the sympathetic chain ganglia?
Communicating
The spinal cord contains ascending & descending nerve fibers that send information between the CNS & the periphery. This illustrates which function of the spinal cord?
Conduction
In response to stretching, a muscle reflexively does what?
Contracts
____ is a term meaning "on the opposite side of the body"
Contralateral
In the spinoreticular tract, the second order neurons decussate to where?
Contralateral anterolateral system
In which reflex does a contralateral extensor muscle contract?
Crossed extension
What factor accounts for the fact that the right side of the brain communicates with the left side of the body, & vice versa?
Decussation
What is an area of skin innervated by a spinal nerve called?
Dermatome
What is the dural sheath around the spinal cord made of?
Dura mater
____ neurons carry information away from the CNS to an effector
Efferent
What carries the nerve signal to the effector in a reflex arc?
Efferent nerve fiber
True of False: Severing a sensory nerve root will completely deaden sensation from a dermatome
False
True or False: Reflex pathways always involve the cerebral cortex
False
What are meninges?
Fibrous connective tissue membranes covering the central nervous system
Which order neuron of the spinothalamic tract ends in the posterior horn at the point of entry to the spinal cord?
First
Define Posterior Spinocerebellar Tract
Flechsig's fasciculus, Flechsig's tract) conveys proprioceptive information from proprioceptors in the skeletal muscles and joints to the cerebellum.
What are the 4 possible effectors of a reflex?
Gland, Skeletal Muscle, Cardiac Muscle, Smooth Muscle
Where do the nerve fibers of the gracile fasciculus terminate in the medulla oblongata?
Gracile nucleus
Both somatic & autonomic reflexes are exaggerated in what?
Hyperreflexia
Which nerve tracts do not decussate & have their origin & destination on the same side of the body?
Ipsilateral
In the spinothalamic tract, where do the second order neurons decussate?
Just after the synapse between the first-order & second-order neuron
In an adult, the spinal cord ends at vertebrae ____
L1
In descending tracts, which motor neuron innervates the target organ?
Lower
The second-order neurons from the gracile & cuneate nuclei from what?
Medial Lemniscus
Which branch of a spinal nerve innervates the meninges?
Meningeal
Where are nerve signals carried by the gracile fasciculus from?
Midthroacic & lower parts of the body
What are intrafusal fibers?
Modified muscle fibers within a muscle spindle
The pollovirus destroys which neurons in the brainstem & anterior horn of the spinal cord?
Motor
What do muscle spindles monitor?
Muscle length & body movements
What is a type of stretch receptor embedded in skeletal muscle?
Muscle spindle
Where do the first-order neurons of the spinocerebellar tract originate?
Muscles & Tendons
Muscle spindles would be more abundant in what?
Muscles that require fine control
What is the term used to describe nerve pain?
Neuralgia
What is a drop in blood pressure due to loss of sympathetic stimulation to the blood vessels called?
Neurogenic shock
What are 2 examples of nerves that carry only sensory information?
Optic nerve & Olfactory nerve
What is quadriplegia?
Paralysis of all 4 limbs
What is hemiplegia?
Paralysis on one side of the body
Which of these structures is closest to the spinal cord?
Rootlet
Nerve fibers of peripheral nerves are encased in ___ cells
Schwann
____ cells form a neurilemma & the myelin sheath around axons in the PNS
Schwann
Within the sensory pathway that ascends via the cuneate fasiculus, which order neuron is the one that decussates?
Second
The posterior root of a spinal nerve carries what type of nerve fibers?
Sensory
The somas of which neurons are found within the posterior root ganglion?
Sensory
Within the spinal cord, which tracts carry information up to the brain?
Sensory
Which disease results from herpes virus residing in a posterior root ganglion?
Shingles
A somatic fiber innervates which of the following?
Skin, skeletal muscles, bones & joints
_____ reflexes use receptors located in the skin, muscle, & tendons
Somatic
The anterior root of a spinal nerve contain axons of which neurons?
Somatic motor
___ fibers are nerve fibers that innervate more localized organs in the head (eyes, ears, olfactory & taste receptors, etc.)
Special
What is responsible for the inhibition of antagonistic contraction during a reflex response?
Spinal cord interneurons inhibit alpha neurons to the antagonists
What is an inflammation of the spinal meninges due to infection called
Spinal meningitis
The patellar reflex is an example of which type of reflex?
Stretch
____ reflexes are important in stabilizing joints because they balance the tension between extensors & flexors
Stretch
Where does the cerebrospinal fluid circulate?
Subarachnoid space
In the spinal cord, where is the white matter in relation to the gray matter?
Superficial
The lateral gray horns of the spinal cord are found in which segments of the spinal cord?
T2 to L1
What is the cervical enlargement of the spinal cord?
The area of the spinal cord that gives ride to the nerves of the upper limbs
Stretch reflexes are mediated primarily by what?
The brain
What is peripheral neuropathy?
The loss of sensory or motor function due to nerve injury
Into what cavity is an epidural anesthetic delivered?
The space between the vertebral bones & dural sheath
Define Lateral Reticulospinal Tract
This tract is divided into two parts, the medial (or pontine) and lateral (or medullary) reticulospinal tracts (MRST and LRST). The MRST is responsible for exciting anti-gravity, extensor muscles
What is a bundle of nerve fibers within the white matter of the spinal cord called?
Tract
What is severance of the spinal cord called?
Transection
When are tendon organs stimulated?
When a muscle contracts
____ matter is composed of myelinated & unmyelinated axons & is superficial to the gray matter of the spinal cord
White
Define Anterior Spinocerebellar Tract
a bundle of fibers originating in the base of the posterior horn and zona intermedia throughout lumbosacral segments of the spinal cord, crossing to the opposite side and ascending in a peripheral position in the ventral half of the lateral funiculus.
Define Posterior Ganglion
a cluster of nerve cell bodies (a ganglion) in a posterior root of a spinal nerve. The dorsal root ganglia contain the cell bodies of sensory neurons (afferent).
Define Terminal Filum
a delicate strand of fibrous tissue, about 20 cm in length, proceeding downward from the apex of the conus medullaris. It is one of the modifications of pia mater.
Define Lateral Corticospinal Tract
a descending motor pathway that begins in the cerebral cortex, decussates in the pyramids of the lower medulla
Define sensory nerve
a nerve containing only fibers carrying incoming nerve signals to the CNS
Define Tectospinal Tract
a nerve pathway that coordinates head and eye movements
Define sacral plexus
a nerve plexus which provides motor and sensory nerves for the posterior thigh, most of the lower leg and foot, and part of the pelvis
Define Fascicle
a small bundle of nerve fibers, enclosed by the perineurium
Define Rootlets
a small root 1 of the ultimate divisions of a nerve root.
Define Guilliain-Barre syndrome
actue demyelinating nerve disorder
A ____ nerve is a peripheral nerve carrying nerve signals to the CNS
afferent
An ____ peripheral fiber is a nerve fiber carrying nerve signals toward the central nervous system
afferent
Define Spinoreticular tract
an ascending pathway in the white matter of the spinal cord, positioned closely to the lateral spinothalamic tract. The tract is from spinal cord—to reticular formation— to thalamus. It is responsible for automatic responses to pain, such as in the case of injury.
The ___ ramus of a spinal nerve innervates the anterior end & lateral skin & muscles of the trunk & gives rise to the nerves of the limbs
anterior
The ____ horns of the spinal cord contain the cell bodies of outgoing somatic motor neurons
anterior
The ____ median fissure is a longitudinal groove on the ventral surface of the spinal cord
anterior
The intercostal nerves arise from the ___ rami of the ____ spinal nerves
anterior; thoracic
The _____ mater is just below (deep to) the dura mater.
arachnoid
The middle layer of the meninges is the ___ mater
arachnoid
The neural pathway that mediates a reflex is called a reflex ____, consisting of a receptor, afferent nerve fiber, interneurons, efferent nerve fiber, & effector
arc
The term "nerve fiber" refers to the ____ of a neuron
axon
Define Posterior Ramus
refers to the posterior division of a spinal nerve
A quick, involuntary, stereotyped response to a stimulus is called a _______
reflex
Define Cuneate Fasciculus
bundle of axon fibers in the posterior column-medial lemniscus pathway of the spinal cord and carries information from the middle thoracic and lower limbs of the body
Define Gracile Fasciculus
bundle of axon fibers in the posterior column-medial lemniscus pathway of the spinal cord and carries information from the middle thoracic and lower limbs of the body
The lumbar cistern is the name of the hollow space that contains the ____ _____ & cerebrospinal fluid
cauda equina
In the spinal cord, the ____ canal is lined with ependymal cells & contains cerebrospinal fluid
central
The central canal of the spinal cord contains _____ fluid
cerebrospinal
The left & right sides of the gray matter in the spinal cord are connected by the gray ____
commissure
Define Communicating Rami
communicating branch between a spinal nerve and the sympathetic trunk
Since the corticospinal tracts decussate, innervation to the muscles will be across the body or _____
contralateral
The ___ tract carries signals for precise, finely coordinated limb movements
corticospinal
The ____ tract is also called the pyramidal tract
corticospinal
The nerve fibers of the ______ tract from ridges called pyramids on the anterior surface of the medulla
corticospinal
What are extensions of the pia mater that anchor the spinal cord?
denticulate ligaments
Also known as a motor nerve fiber, a _____ fiber is a nerve fiber carrying nerve signals away from the central nervous system
efferent
External to the neurilemma of a nerve fiber is the layer of loose connective tissue that surrounds a nerve fiber called an _______
endoneurium
The ___ space is located between the vertebrae & the dural sheath around the spinal cord
epidural
The dense irregular connective tissue layer enclosing an entire nerve is called the ______
epineurium
The crossed ___ reflex is contralateral
extensor
Within a nerve, nerve fibers are gathered into bundles called ______
fascicles
A _____ is a tract of nerve fibers within column of the spinal cord
fasciculus
In a sensory pathway, the ___ order neuron detects the stimulus & transmits the signal to the spinal cord or brainstem
first
A quick contraction of flexor muscle in response to a painful stimulus is called a ___ reflex
flexor
A flexor reflex involves contraction of ____ muscles & reciprocal inhibition of ____ muscles
flexor; extensor
Within a muscle spindle, ___ motor fibers contract the ends of the intrafusal fibers
gamma
A ____ is a cluster of neuron cell bodies found outside of the CNS
ganglion
A ___ fiber innervates widespread organs such as muscles, skin, glands, viscera & blood vessels
general
The ___ matter of the spinal cord contains the synapse & therefore is the site of synaptic integration
gray
Where are the neuron cell bodies, dendrites, & synapses found in the CNS?
gray matter
A flexor reflex uses a ____ after-discharge neural circuit
parallel
Define Spinothalamic tract
is a sensory pathway from the skin to the thalamus. From the ventral posterolateral nucleus in the thalamus, sensory information is relayed upward to the somatosensory cortex of the postcentral gyrus.
Define Corticospinal Tract
is a small bundle of descending fibers that connect the cerebral cortex to the spinal cord
Conscious awareness of the stimulus ____ required for a reflex response to occur
is not
Define Brachial Plexus
is the network of nerves that sends signals from your spine to your shoulder, arm and hand. A brachial plexus injury occurs when these nerves are stretched, compressed, or in the most serious cases, ripped apart or torn away from the spinal cord.
Describe a muscle spindle
it contains 7 or 8 modified muscle fibers & a few nerve fibers enclosed in a fibrous capsule
Define Alpha Motor Neuron
large, multipolar lower motor neurons of the brainstem and spinal cord. They innervate extrafusal muscle fibers of skeletal muscle and are directly responsible for initiating their contraction
The anterior spinocerebellar tract is found in the ___ column of the spinal cord
lateral
In descending pathways, the upper motor neurons synapse with ___ motor neurons in the brainstem or spinal cord
lower
The ___ enlargement is the area of spinal cord that gives rise to the nerves of the lower limbs & pelvis
lumbar
The subarachnoid space inferior to the medullary cone is called the ____ ______
lumbar cistern
The _____ ______ is the tapered end of the spinal cord
medullary cone
A nerve containing both sensory & motor nerve fibers is called a ___ nerve
mixed
Spinal nerves are described as ___ nerves because they carry both afferent & efferent signals
mixed
Reflex pathways are more likely to be ____ than _____.
monosynaptic; polysynaptic
A _____ reflex arc consists of only one synapse between 2 neurons
monosynpatic
The anterior horns of the spinal cord contain somas of somatic ____ neurons
motor
Define extrafusal fibers
muscle fibers outside of a muscle spindle
The ____ tract carries signals for the sensation of pain resulting from tissue injury
spinoreticular
The space between the arachnoid mater & pia mater is called the ____ space
subarachnoid
The lateral horns of the spinal cord contain somas of ____ motor neurons
sympathetic
Define Medullary Cone
tapered, lower end of the spinal cord
A ____ reflex occurs in response to excessive tension on a tendon
tendon
Define Posterior Root
the 1 of the 2 roots of a spinal nerve that passes posteriorly to the spinal cord separating the posterior and lateral funiculi and that consists of sensory fibers
Define Anterior Ramus
the anterior division of a spinal nerve. The anterior rami supply the antero-lateral parts of the trunk and the limbs. They are mainly larger than the posterior rami.
Define Anterior Root
the efferent motor root of a spinal nerve. At its distal end, the ventral root joins with the dorsal root to form a mixed spinal nerve.
Define Perineurium
the sheath of connective tissue surrounding a bundle (fascicle) of nerve fibers within a nerve.
