Lecture 6 Flashcards Preview

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Flashcards in Lecture 6 Deck (21):
1

_______ in the spinal cord send their axons through the ventral roots. The axons branch in a target muscle, and each axon innervates several muscle fibers

Alpha-Motoneuron

2

Motor Unit

an alpha motorneuron and the muscle fibers it innervates

3

the ______ motor unit shows the largest drop in force with time (fatigue).

fastest and strongest

4

the _____ motor unit does not show fatigue at all

slowest and smallest

5

Small Motor Unit

slow twitch, fatigue resistant

6

Larger Motor Unit

fast twitch, fatigue reistant

7

Largest Motor Unit

fast twitch, fatiguable

8

Small motor units recruit _______

first at low muscle forces

9

An increase in muscle force leads to recruitment of ________ motor units.

larger

10

To increase muscle force, the CNS may _____

recruit new motor units and/or increase the frequency of already recruited motor units

11

In motor unit rotation, the muscle force ______.

is kept constant

12

Motor Unit Rotation- A change in the number of recruited motor units correlates _______ with their mean frequency of firing

negatively

13

EMG measure

the electrical activity (action potentials) associated with a muscle contraction

14

Uses of EMG

Clinical diagnosis
research studies
measuring reaction time or muscle latency when muscles turn on and off
Also beneficial for reflex testing

15

A typical record with an intramuscular needle electrode reveals a few motor units with different shapes of the compound potentials: ___________.

MU1, MU2, & MU3

16

intramuscular electromyography records

the activity of individual MUs

17

intramuscular emg provides information about

excitation of a small volume within a muscle

18

surface electromyography uses a pair of electrodes that are placed on a ______.

muscle belly.

19

A third electrode in surface electromyography is used ______

to reduce noise

20

Surface EMG

averages the activity of many (all) MUs.
causes no discomfort
is not selective

21

intramuscular emg

record the activity of individual MUs
is uncomfortable
provides information about excitation of a small volume within a muscle