Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Neuroanatomy Exam 1 > Spinal Reflexes > Flashcards

Spinal Reflexes Flashcards

(72 cards)

Start Studying
1
Q

Lower motor neuron cell bodies reside in

A

ventral horn of spinal cord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Lower motor neuron axons run in

A

peripheral nerves that terminate in skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Relexes involve what kind of neurons

A

alpha motor and gamma motor neurons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Alpha motor neurons

A

Largest neurons residing in ventral horn of spinal cord
Innervate typical skeletal muscle fibers (extrafusal) which when stimulated cause contraction of the gross muscle to produce movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Gamma motor neurons

A

Smaller neurons in the ventral horn of spinal cord

Inenrvate the contractile (polar) portions of intrafusal fibers enclosed within muscle spindles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Reflex Definition

A

a simple stereotyped response to a specific sensory stimulus

  • Involuntary
  • Protective
  • Confined to spinal cord (nonconcious)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Reflex consists of:

A
  1. Receptor
  2. Afferent limb
  3. Interneuron
  4. Efferent limb
  5. Effector
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Receptor

A

in skin, skeletal muscle, tendon, or joint capsule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Afferent Limb

A

formed by sensory (pseudounipolar) neuron whose cell body is housed in DRG
Peripheral process is in skin, skeeltal muscle, tendon or joint capsule
Central process synapses in spinal cord gray metter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Interneurons

A

may or may not be a component of the reflex arc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Efferent limb

A

formed by motor neuron whose cell body is usually located in the ventral horn of spinal nerve
Axon synapses in skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Effector

A

skeletal muscle that responds to stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Reflexes can be

A

Intrasegmental
Intersegmental
Suprasegmental

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Intrasegmental

A

involve or affect only a single spinal cord level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Intersegmental

A

involve or affect numerous spinal cord levels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Suprasegmental

A

are influenced by neurons residing in cerebral hemisphere or brainstem and through their connections influence reflex activity occuring at the spinal cord level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Biceps reflex

A

C5 C6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Triceps reflex

A

C6 to C8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Quadriceps Reflex

A

L2 to L4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Gastrocnemius Reflex

A

S1 to S2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Muscle Stretch Reflex

A

consists of 2 neurons (one sensory and one motor)

May be elicited by tapping a large tendon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Ex of muscle stretch reflex

A

Quadriceps stretch reflex (patellar tendon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Tapping of the patellar tendon does what

A

Displaces the patella slightly which then stratches the extrafusal fibers and also stretches the muscle spindles of the quadriceps muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Receptors in patellar tendon reflex =

A

muscle spindles that are mebedded in the muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Muscle stretch will trigger
the sensory endings on intrafusal fibers to fire
26
The central process (axon) will synapse with
alpha motor neuron and stimulates in reflex is monosynaptic Quad will contract slightly causing extension of the leg at the knee joint Reflex induced contraction
27
What does the muscle stretch reflex compensate for
muscle stretch
28
What does the muscle stretch reflex protect
the muscle fibers from overstretching
29
Reciprocal Inhibition
An extension of and enhances the stretch reflex
30
Receptor in reciprocal inhibition
muscle spindle at peripheral end of a fiber
31
In reciprocal inhibiton central process of sensory neuron...
bifurcates One branch forms excitatory synapse with an alpha mtoor neuron (stimulates quad to contract) Other branch forms excitatory synapse with inhibitory interneuron which inhibits another alpha motor neuron that innervates the hamstring muscle
32
So how does the reciprocal inhibition work?
As one muscle is stimulated to compensate for the stretch, another muscle is simultaneously inhibited
33
Autogenic Inhibition
Enhances the stretch reflex to prevent overcontraction
34
Receptor with autogenic inhibition
GTO When quad contracts, it exerts tension on its tendon which in turn stretched and activates the GTOs Muscle contraction triggers the sensory endings innervating tendons to fire
35
When sensory neurons peripheral process innervating the tendon is activated,
the central process stimulated an inhibitory interneuron which will inhibit an alpha motor neuron that innervated the quad
36
What does autogenic inhibtion limit
muscle overcontraction
37
What does autogenic inhibition protect
tendon
38
Stimulation of GTO plays a role in
muscle relaxation
39
Flexor Reflex
Withdrawal, Nociceptive
40
Receptors for flexor reflex
cuteneous | lightly myelinated Adelta fibers or unmyelinated C fibers of sensory neurons whose cell bodies are in DRG
41
Peripheral process of flexor reflex is located in
skin or in subcutaneous connective tissue
42
Stimulus with flexor reflex is
painful or causes tissue injury
43
The flexor reflex occurs in the
affected limb
44
Central process in flexor reflex enters
dorsolateral tract where it branches into short ascedning and short descending fibers and they form excitatory synapses with interneurons in gray matter of the spinal cord
45
The ___ interneurons synapse with the alpha motor neurons that innervate ___ muscles of the lower lib, stimulating their ___ and withdrawal of the lower limb
Excitatory Flexor Contraction
46
The ____ interneurons synapse with the alpha motorneurons that innervate the ___ of the same limb to inhibit them causing _____
Inhibitory Extensors Relaxation
47
Flexor reflex involves how many spinal cord levels
many
48
Crossed Extension Reflex Receptors
Cutaneous | Lightly myelinated A delta of unmyelinated C fibers
49
When would the crossed extension reflex happen?
When standing or walking and one of the limbs contacts a noxious stimulus
50
The crossed extension reflex occurs in which limb?
the unaffected limb so that the weight of the body can be shifted
51
The crossed extension reflex involves
commissural interneurons whose axons cross the midline to synapse with excitatory and inhibitory interneurons located in the ventral horn of the spinal cord on the opposite side
52
What does the excitatory interneuron do in crossed extension reflex
stimulates an alpha motor neuron that causes contraction of the limb extensors
53
What does the inhibitory interneuron do in crossed extension reflex
inhibits an alpha motor neuron that innervates the limb flexors
54
Muscle tone
tension created by variable contraction of skeletal muscle fibers
55
Muscle tone results from
stimulation of gamma motor neurons and the stretch reflex
56
Gamma motor neurons are a component of
gamma loop and are associated with maitenece of muscle tone
57
Gamma motor neurons are under ___ control
supraspinal | NOT under control of the sensory fibers innervating the intrafusal fibers
58
There are no signals relayed back from the muscle spindles to the gamma motor neurons
say it :)
59
Gamma motor neurons stimulate
polar (contractile) portions of the intrafusal fibers --> they contract --> pull away from midline --> stretching the central (nonctractile region) of intrafusal fibers --> annulospiral endings of the Ia sensory fibers are stretched and fire
60
The central processes of Ia fibers enter the spinal cord and synapse with
alpha motor neurons that innervate the skeletal muscle (extrafusal fibers)
61
Stimulation of gamma motor neurons does what
increases muscle tone
62
Inhibition of gamma motor neurons does what
decreases or inhibits muscle tone
63
Antigravity muscles do what
neutralize the effect gravit has on the body so that we are able to stand upright
64
The gamma loop includes what 5 components
1. Gamma motor neurons 2. Intrafusal fibers 3. Ia fibers 4. Alpha motor neurons 5. Extrafusal fibers
65
Alpha Gamma co-activation
during voluntary movement, the axons of descending motor tracts converge on both alpha and gamma motor neurons to simulate simultaneously
66
Stimulation of the alpha motor neurons cause
the extrafusal fibers of the gross muscle to contract and simultaneously the stimulation of the gamma motor neurons cause the polar (contactile) ends of the intrafusal fibers to contract
67
Alpha Gamma co activation is a way via which
as the length of the gross muscle changes during voluntary movement (stimulation of alpha) there is a corresponding adjustment of intrafusal fibers (via gamma) so that the muscle spindles sensitivity to stretch is maintained regardless of muscle length
68
Muscle spindles are
stretch receptors that must detect changes in muscle length at all times
69
As a gross muscle contracts, it becomes
shorter | but there is no corresponding shortening of muscle spindles
70
During voluntary movement the ____ modulates the sensitivity of the intrafusal fibers
alpha gamma coactivation
71
Alpha gamma coactivation 4 steps
1. Gamma motor neurons stimulate the polar ends of the intrafusal fibers 2. Polar ends contract, pulling away from the middle of the intrafusal fibers 3. Stretched the central (non contractile) portion of intafusal fibers 4. The stretching keeps the central part of the intrafusal fibers tight so even the slightest additional stress placed on it when the gross muscle stretches from the contracted side, will stimulate the sensory fibers
72
Lesion involving alpha and gamma motor neurons would result in
1. Flaccid paralysis (muscles limp and can't contract) 2. Atrophy 3. Hypotonia (reduced tone) 4. Hyporeflexia (dminished reflexes) or Areflexia (absence of reflexes)

Neuroanatomy Exam 1 (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions