Flashcards in Chapter 10 Deck (63):
1
What does well coordinated or learned movement require?
a continuous integration of visual, somatosensory and vestibular information with motor processing
2
What is feedforward?
anticipatory use of sensory information to prepare for movement
3
What is feedback?
refers to the use of sensory information during or after movement to make corrections either to the ongoing movement or to future movements
4
What does neural activity begin with?
a decision made in the anterior part of the frontal lobe
5
What is the second step in motor planning?
motor planning areas are activated, followed by control circuits
6
What regulates the activity in upper motor neuron tracts?
control circuits, consisting of the cerebellum and basal ganglia
7
Where do upper motor neuron tracts deliver signals?
to spinal interneurons and lower motor neurons (LMN)
8
What does the LMNs do?
signals directly to skeletal muscles, eliciting the contraction of muscle fibers that move the upper limbs and fingers
9
How is voluntary movement controlled?
from the top down (the brain, to the spinal cord, to the muscle)
10
What four systems make essential and distinct contributions to motor control:
1. local spinal and brainstem circuits
2.Descending control pathways
3. the cerebellum
4. basal ganglia
11
Motor cortex
planning, initiating, and directing voluntary movements
12
Brainstem centers
basic movements and postural control
13
Basal ganglia
gating proper initiation of movement
14
Cerebellum
sensory motor coordination of ongoing movement
15
When is muscle contraction produced?
when actin slides relative to myosin
16
What does the resistance to stretch muscles depend on?
the length
17
What determines the total resistance to muscle stretch?
active contraction, titin and weak actin-myosin bonds
18
What is muscle tone?
resistance to a passive stretch in a resting muscle
19
How is muscle tone assessed clinically?
passive rotation of a limb through a range of motion
20
What happens when muscle tone is normal?
resistance to passive stretch is minimal
21
What is normal resting muscle tone provided by?
weak actin-myosin bonds
22
When do sarcomeres disappear from the ends of myofibrils?
when healthy innervated muscle is continuously immobilized in a shortened position
23
When will the muscle add new sacromeres?
if the muscle is immobilized in a length position
24
What is cocontraction?
refers to the simultaneous contraction of antagonist muscles, increasing the joint’s resistance to movement
25
What does cocontraction do?
stabilizes joint
26
What does cocontraction do in the upper limbs?
enables precise movements
27
What does cocontraction do in the lower limbs?
allows an individual to stand on an unstable surface
28
What are two types of LMSs
alpha and gamma
29
What do alpha and gamma neurons do?
only neurons that convey signals to extrafusal and intrafusal skeletal muscle fibers
30
Where do axons of alpha motor neurons project?
extrafusal skeletal muscle, branching into numerous terminals as they approach muscle
31
Where do axons of gamma motor neurons project?
to intrafusal fibers in the muscle spindle
32
What to gamma motor neurons consist of?
medium sized myelinated axons
33
What is alpha-gamma coactivation?
alpha and gamma motor neurons function simultaneously
34
Why does alpha-gamma coactivation occur?
-sources of input to alpha MN have collaterals MN
-less excitation needed to reach threshold gamma MN
35
Motor unit:
An alpha motor neuron AND the muscle fibers it innervates”, constituting a functional entity
36
Features of Motor units:
vary in degree of fatigability
in speed of contraction
in size
37
How are motor units classified:
slow-twitch fibers
fast-twitch fibers
38
Slow twitch fibers:
innervated by smaller-diameter, slower-conducting alpha motor neuron; involved in standing
39
Fast twitch fibers:
innervated by larger-diameter, faster-conducting motor neuron; involved in walk and run etc
40
In most movements, which fibers are activated first?
slow twitch fibers are activated first due to smaller cell bodies
41
What is the Size Principle?
The order of recruitment from smaller to larger motor neurons
42
When are movements generated?
when somatosensory information is integrated with descending motor commands in the spinal cord
43
What are LMN pools?
groups of cell bodies in the spinal cord whose axons project to a single muscle
44
What do medially located pools innervate?
axial and proximal muscles
45
What do laterally located pools innervate?
distal muscles
46
What do anteriorly located pools in ventral horn innervate?
extensors
47
What do posteriorly located pools innervate?
flexors
48
What is reciprocal inhibition?
the inhibition of antagonist muscles during agonist contraction
49
How is reciprocal inhibition achieved?
by interneurons in the spinal cord that link lower motor neurons into functional group
50
What is central pattern generators?
basic pattern of coordinated rhythmical activity (walking) wired into the spinal cord circuits
51
What is a stretch reflex?
a mechanism to monitor and maintain muscle length
52
What does a stretch reflex stimulate?
stretch of the muscle
53
What is the senor of a stretch reflex?
spindles
54
What does a stretch reflex involve?
alpha (and gamma) motor neurons, local circuit interneurons, and afferent somatic sensory input
55
What is the golgi tendon organ reflex?
a system that monitors and maintains the muscle force
56
What is the stimulus of the golgi tendon organ reflex?
tension due to muscle contraction
57
What is sensor for the golgi tendon organ reflex?
golgi tendon organ
58
What is a flexion withdrawal reflex?
a system for withdrawing the limb from a harmful stimulus
59
What is the activation of the flexion withdrawl reflex?
activation of nociceptor
60
What is the sensor of flexion withdrawal reflex?
sensor endings in skin, etc
61
How is the golgi tendon organ reflex a negative feedback?
Functionally, the system can protect potential damage and prevent muscle fatigue
62
What is the Hoffman or H-reflex?
Are monosynaptic reflexes elicited by electrically stimulating a nerve
63