3 - More on Muscle (Skeletal Muscles)

Question 1

Duration of an AP in a muscle fiber.

Answer 1

1-2 msec

Question 2

Duration of a muscle fiber contraction.

Answer 2

100 msec>

Question 3

True/False: All muscle fibers contract at the same rate.

Answer 3

False; varies

Question 4

A single motor neuron innervates […] muscle fibers, a given muscle fiber is innervated by […] motor neuron.

Answer 4

Several; One

Question 5

One motor neuron plus all the muscle fibers it innervates.

Answer 5

Motor unit

Question 6

Increased muscle tension caused by increasing the number of motor units contracting simultaneously.

Answer 6

Multiple fiber summation

Question 7

Force exerted on an object by a muscle.

Answer 7

Tension

Question 8

Force exerted on a muscle via an object.

Answer 8

Load

Question 9

Conditions for a muscle fiber to shorten.

Answer 9

Tension > Load

Question 10

When a muscle shortens while the load remains the same.

Answer 10

Isotonic contraction

Question 11

When the muscle develops tension but does not shorten.

Answer 11

Isometric contraction

Question 12

Contraction of a single muscle fiber in response to a single AP.

Answer 12

Twitch

Question 13

Increased muscle tension that occurs when successive APs occur rapidly enough that the fber has not completely relaxed from the prior twitch.

Answer 13

Frequency summation

Question 14

Period of summation in which the strength of contraction rapidly increases as the rate of stimulation rises.

Answer 14

Treppe

Question 15

Maintained contraction at high stimulation rates in which muscle tension oscillates due to slight relaxations between stimuli.

Answer 15

Unfused tetanus

Question 16

Maintained contraction at even higher stimulation rates in which no oscillations occur.

Answer 16

Fused tetanus

Question 17

The tautness that remains when the muscle is not actively moving a body part.

Answer 17

Muscle tone

Question 18

Causes tone.

Answer 18

Low rate of APs being sent to the muscle from the spinal cord

Question 19

What would occur if the sarcomere is stretched so far that there is no overlap between actin and myosin?

Answer 19

No cross bridges would be able to form therefore there would be no tension (i.e. D on the chart)

Question 20

What would occur is the overlap between the myosin and actin was near complete coverage?

Answer 20

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)

Question 21

What would occur if actin was so close to each other it began to overlap?

Answer 21

Myosin would not be able to bind and therfore would not be able exert its force (i.e. A on the chart)