3 - More on Muscle (Skeletal Muscles) Flashcards
Duration of an AP in a muscle fiber.
1-2 msec
Duration of a muscle fiber contraction.
100 msec>
True/False: All muscle fibers contract at the same rate.
False; varies
A single motor neuron innervates […] muscle fibers, a given muscle fiber is innervated by […] motor neuron.
Several; One
One motor neuron plus all the muscle fibers it innervates.
Motor unit
Increased muscle tension caused by increasing the number of motor units contracting simultaneously.
Multiple fiber summation
Force exerted on an object by a muscle.
Tension
Force exerted on a muscle via an object.
Load
Conditions for a muscle fiber to shorten.
Tension > Load
When a muscle shortens while the load remains the same.
Isotonic contraction
When the muscle develops tension but does not shorten.
Isometric contraction
Contraction of a single muscle fiber in response to a single AP.
Twitch
Increased muscle tension that occurs when successive APs occur rapidly enough that the fber has not completely relaxed from the prior twitch.
Frequency summation
Period of summation in which the strength of contraction rapidly increases as the rate of stimulation rises.
Treppe
Maintained contraction at high stimulation rates in which muscle tension oscillates due to slight relaxations between stimuli.
Unfused tetanus
Maintained contraction at even higher stimulation rates in which no oscillations occur.
Fused tetanus
The tautness that remains when the muscle is not actively moving a body part.
Muscle tone
Causes tone.
Low rate of APs being sent to the muscle from the spinal cord
What would occur if the sarcomere is stretched so far that there is no overlap between actin and myosin?
No cross bridges would be able to form therefore there would be no tension (i.e. D on the chart)
What would occur is the overlap between the myosin and actin was near complete coverage?
All myosin heads would be able to bind, permitting maximal cross bridge formation therefore maximal tension is produced (i.e. B and C in the chart)
What would occur if actin was so close to each other it began to overlap?
Myosin would not be able to bind and therfore would not be able exert its force (i.e. A on the chart)
