Reflexes Flashcards
1
Q
Motor output can be…
A
voluntary or involuntary
2
Q
Motor system conveys information to…
A
muscles
3
Q
Voluntary muscle responses:
A
- conscious
- initiated at motor cortex
4
Q
Signal flow for voluntary motor responses:
A
motor cortex -> brain stem -> spinal cord -> skeletal muscle
5
Q
Involuntary motor response are also known as…
A
reflexes
- unconscious and subconscious mechanisms
6
Q
Involuntary motor response is initiated at…
A
- spinal cord level
- brain stem
- cerebellum
- cortex
7
Q
Reflex arc is the basic unit of…
A
involuntary neural activity
8
Q
Reflex arc is an…
A
unlearned, built-in response
- can be modified by learning
9
Q
Components of reflex arc:
A
- sense organ/receptor
- afferent neuron
- central connection: one or more synapses occurring in the CNS
- efferent neuron
- effector tissue (skeletal, cardiac, or smooth muscle, glands)
10
Q
Reflexes can be…
A
basic (monosynaptic) or complex (polysynaptic)
11
Q
Autonomic reflexes:
A
- viscera reflexes
- polysynaptic
- has tonic activity
12
Q
Somatic reflexes can be…
A
monosynaptic or polysynaptic
13
Q
Monosynaptic reflexes:
A
- has a single synapse between the afferent and efferent neurons
- simplest reflex
- don’t need interneurons
14
Q
Polysynaptic reflexes:
A
- more than one synapse between the afferent and efferent neurons
- need interneurons
15
Q
Spinal reflexes:
A
reflex mediated by the spinal cord
- ex: knee jerk
- has reflex arc
16
Q
Cranial reflexes:
A
controlled by small section of the brain
17
Q
Bulk of muscle fibers are…
A
contractile fibers (extrafusal fibers)
18
Q
What makes up the muscle spindle?
A
intrafusal fibers: thinner fibers found in belly of most muscles
19
Q
Intrafusal fibers:
A
- tension sensing fibers
- set up reflexes to set muscle tension
- monitor stretch of muscle
20
Q
Muscle spindle flow of information:
A
- registers excess stretch
- goes to afferent fiber
- synapse in spinal cord
- efferent fiber
- muscle contracts
21
Q
Afferent innervation of muscle spindle:
A
intrafusal fibers innervated by two types of fibers w/ modified dendritic receptors
22
Q
Two types of fibers w/ modified dendritic receptors:
A
- type 1a afferent fiber
- type 2 afferent fiber
23
Q
Type 1a afferent fiber has what kind of dendritic ends?
A
annulospiral rings on dendritic ends
nuclear bag fibers
24
Q
Type 1a afferent fiber transmits info about..
A
muscle length and velocity of contraction
25
Type 2 afferent fiber has what kind of dendritic ends?
flower spray dendritic ends
26
Type 2 afferent fiber transmits info about...
muscle length
27
Efferent motor output is associated with ____ activation
muscle spindle
28
Components of lower efferent output:
- A alpha motor neurons in ventral horn
| - A gamma efferent neurons
29
A alpha motor neurons:
- large myelinated neurons
- travels to NMJ of skeletal muscle
- produces contraction of muscle
30
Somatic motor unit of A alpha motor neurons:
alpha motor neuron and all the skeletal muscle fibers that its axon supplies
31
Renshaw cells:
- supplied by A alpha motor neurons
- transmits inhibitory signals to surrounding motor neurons, which sharpens motor signals
- is an interneuron
- in gray matter of spinal cord
32
A gamma efferent fibers:
- myelinated, but smaller than A alpha motor neurons
| - determines sensitivity of spindle to stretch
33
A gamma efferent fibers supply...
intrafusal fibers of spindle itself
34
Increased output from A gamma fibers leads to...
increased contraction of spindle, which increases the sensitivity to stretch
35
T/F: A gamma fibers doesn't allow the muscle to retain sensitivity of the reflex regardless of muscle length
F, it does allow it
36
T/F: A alpha motor neurons and gamma fibers activate at different times
F, they coactivate
37
What is the key reflex in maintenance of posture?
stretch/myotatic reflex
38
Stretch/myotatic reflex is mediated by...
muscle spindle when the muscle is stretched
39
Example of stretch/myotatic reflex:
knee-jerk: determines how much background info is coming from the brain
40
How to activate the knee-jerk reflex:
tap the patellar tendon below knee and it should stretch the quadriceps muscle
41
Components of stretch/myotatic reflex:
- type 1a fiber
- collateral synapses
- type 2 (alpha beta)
42
Type 1a fiber branch of stretch reflex directly synapses w/...
A alpha efferent fibers in ventral horn
43
T/F: type 1a fiber branch of stretch reflex is polysynaptic
F, it's monosynaptic
44
Upon stimulation, type 1a fiber branch of stretch reflex produces...
contraction of stretched muscle
45
Type 1a fiber branch of stretch reflex has a _____ response to _____
dynamic, rapid rate of length change
46
Collateral synapses synapse on...
interneurons (polysynaptic)
47
Collateral synapses in the stretch reflex only inhibits...
alpha motor neurons to antagonist muscles
| - produces IPSPs at level of cord
48
Collateral synapses participate in..
reciprocal innervation b/c accompanies stimulation of type 1a fiber branches
49
Some of the type 2 fibers branch to...
alpha and gamma efferents
50
Majority of type 2 fibers...
ascend to join DCML pathway
51
There is a ______ response to slow prolonged spindle stretch
static
52
Inverse myotatic reflex is also known as...
negative stretch reflex
53
Inverse myotatic reflex is mediated by...
golgi tendon organs
54
Golgi tendon organs in the inverse myotatic reflex responds to...
muscle tension relayed to tendon produced by excess muscle contraction
55
Golgi tendon organs in the inverse myotatic reflex have...
modified dendritic ends w/ sensory somatic afferent type 1b fibers
56
Type 1b fibers in the inverse myotatic reflex travel in...
DCML to cortex
57
Collateral branches in the inverse myotatic reflex has two branches that do different things:
- one sends IPSP to inhibit alpha motor neuron of the muscle initiating the response
- other stimulates the alpha motor neurons of antagonistic muscles
58
What happens when collateral branches send IPSP?
muscle relaxation
59
What happens when collateral branches stimulates the alpha motor neurons of antagonistic muscles?
- contraction of antagonist
| - helps equalize the muscle load and can stabilize muscles across a joint
60
Flexor withdrawal reflex is also known as...
- pain reflex
- withdrawal reflex
- nociceptive reflex
61
Flexor withdrawal reflex has a _____ response
prepotent: preempts spinal pathways from any other reflex activity taking place at that moment
62
Flexor withdrawal reflex stimulates...
a variety of sensory receptors
| - most strongly stimulated by pain
63
Flexor withdrawal reflex is a ______ reflex
polysynaptic
64
Flexor withdrawal reflex has what type of fiber?
A delta fiber from nociceptor synapses in dorsal horn of gray matter
65
A delta fiber in the flexor withdrawal reflex synapse w/...
2nd order neuron carrying pain via LST to thalamus
66
Collaterals in the flexor withdrawal reflex synapse w/ _____ and causes...
series of interneurons, flexion of the ipsilateral limb and extension of contralateral limb
- has double reciprocal innervations to help equalize balance loads and stabilizes muscles across joint
67
Flexion of ipsilateral limb has reciprocal innervations that...
inhibits extensors of ipsilateral limb (flexion reflex)
68
Extension of contralateral limb has reciprocal innervations that...
inhibits activity of contralateral flexors (crossed-extensor reflex)
69
Damage to the spinal cord will interfere with...
spinal reflexes
70
If one suffers damage to spinal cord, he/she will first get...
spinal shock that lasts 3-4 weeks
71
Spinal shock is characterized by...
- flaccid paralysis
- loss of autonomic function
- loss of all sensation below injury site
- joint has no resistance to being passively moved
72
What happens when the spinal shock eventually wears off?
- reflexes return gradually and become hyperactive
- provides greater resistance at joints
- voluntary movement and sensation might not ever return
