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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

What is the purpose of the Hoffman or H-reflex?

to quantify the level of alpha motor neuron facilitation or inhibition