Flashcards in Lecture 6 Deck (21)
_______ 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
an alpha motorneuron and the muscle fibers it innervates
the ______ motor unit shows the largest drop in force with time (fatigue).
fastest and strongest
the _____ motor unit does not show fatigue at all
slowest and smallest
Small Motor Unit
slow twitch, fatigue resistant
Larger Motor Unit
fast twitch, fatigue reistant
Largest Motor Unit
fast twitch, fatiguable
Small motor units recruit _______
first at low muscle forces
An increase in muscle force leads to recruitment of ________ motor units.
To increase muscle force, the CNS may _____
recruit new motor units and/or increase the frequency of already recruited motor units
In motor unit rotation, the muscle force ______.
is kept constant
Motor Unit Rotation- A change in the number of recruited motor units correlates _______ with their mean frequency of firing
the electrical activity (action potentials) associated with a muscle contraction
Uses of EMG
measuring reaction time or muscle latency when muscles turn on and off
Also beneficial for reflex testing
A typical record with an intramuscular needle electrode reveals a few motor units with different shapes of the compound potentials: ___________.
MU1, MU2, & MU3
intramuscular electromyography records
the activity of individual MUs
intramuscular emg provides information about
excitation of a small volume within a muscle
surface electromyography uses a pair of electrodes that are placed on a ______.
A third electrode in surface electromyography is used ______
to reduce noise
averages the activity of many (all) MUs.
causes no discomfort
is not selective