whole muscle topics

Question 1

an action potential in a muscle fiber lasts

Answer 1

1-2 msec

Question 2

fiber contraction may take

Answer 2

100 msec or more

Question 3

the muscle that takes the longest to contract is

Answer 3

soleus

Question 4

a given motor neuron innervates

Answer 4

several muscle fibers

Question 5

a given muscle fiber is innervated by

Answer 5

only one motor neuron

Question 6

motor unit

Answer 6

one motor neuron plus all the muscle fibers it innervates

Question 7

multiple fiber summation

Answer 7

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

Question 8

tension

Answer 8

is the force exerted on an object by a muscle

Question 9

load

Answer 9

is the force exerted on a muscle by the weight of the object

Question 10

for a fiber to shorten, tension must

Answer 10

exceed load

Question 11

isotonic contraction

Answer 11

muscle shortens while the load on it remains constant

Question 12

isometric contraction

Answer 12

muscle develops tension but doesn’t shorten

Question 13

twitch

Answer 13

contraction of a single muscle fiber in response to a single action potential

Question 14

frequency summation

Answer 14

increased muscle tension that occurs when successive action potentials occur rapidly enough that the fiber has not completely relaxed from the prior twitch

Question 15

treppe

Answer 15

a period of summation in which the strength of contraction rapidly increases as the rate of stimulation rises

“staircase effect”

Question 16

unfused tetanus

Answer 16

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

Question 17

fused tetanus

Answer 17

maintained contraction at even higher stimulation rates in which no oscillations occur

Question 18

muscle tone

Answer 18

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

Question 19

tone results from

Answer 19

a low baseline rate of action potentials to the muscle coming from the spinal cord

Question 20

a tetanically stimulated individual muscle fiber stretched to various lengths develops different

Answer 20

levels of tension

Question 21

if a sarcomere is stretched so much that there is no overlap between actin and myosin,

Answer 21

no cross bridges can form (thus no tension)

Question 22

if a sarcomere is stretched to the point that the amount of overlap between the myosin filament and the actin filament allows essentially all myosin heads to find binding sites on actin, then

Answer 22

there are maximal cross bridges pulling on actin, which means maximal tension produced

Question 23

in a sarcomere, when actin filaments begin to overlap each other, this

Answer 23

interferes with the myosin head’s ability to find binding sites and exert force

Question 24

at short sarcomere lengths, the Z lines collide with the ends of

Answer 24

myosin filaments and may even crumple it; resulting in tension dropping to very low levels