Lecture 6 Flashcards

1
Q

_______ 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

A

Alpha-Motoneuron

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2
Q

Motor Unit

A

an alpha motorneuron and the muscle fibers it innervates

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3
Q

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

A

fastest and strongest

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4
Q

the _____ motor unit does not show fatigue at all

A

slowest and smallest

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5
Q

Small Motor Unit

A

slow twitch, fatigue resistant

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6
Q

Larger Motor Unit

A

fast twitch, fatigue reistant

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7
Q

Largest Motor Unit

A

fast twitch, fatiguable

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8
Q

Small motor units recruit _______

A

first at low muscle forces

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9
Q

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

A

larger

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10
Q

To increase muscle force, the CNS may _____

A

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

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11
Q

In motor unit rotation, the muscle force ______.

A

is kept constant

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12
Q

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

A

negatively

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13
Q

EMG measure

A

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

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14
Q

Uses of EMG

A

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

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15
Q

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

A

MU1, MU2, & MU3

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16
Q

intramuscular electromyography records

A

the activity of individual MUs

17
Q

intramuscular emg provides information about

A

excitation of a small volume within a muscle

18
Q

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

A

muscle belly.

19
Q

A third electrode in surface electromyography is used ______

A

to reduce noise

20
Q

Surface EMG

A

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

21
Q

intramuscular emg

A

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