Graded Muscle Contractions & fibers

Question 1

What are the 2 criteria needed for contraction

Answer 1

ATP (will always have ATP unless death )

Calcium

Question 2

Terminal cisternae contain membrane bound foot protein that is called

Answer 2

Ryanodine Receptor (RyR)

Question 3

For a given set of Physiological conditions, a muscle fiber twitch always produces the same tension in response to an action potential — is called

A muscle twitch is an ______ response

Answer 3

All or None

Question 4

Progressive activation of muscles motor units to achieve desired contraction strength

Answer 4

Motor unit recruitment

Question 5

smaller motor neurons = small motor units

larger motor neurons= larger motor units

Smaller motor neurons have lower thresholds than larger motor neurons

Answer 5

size principal of recruitment

Question 6

what motor unit is recruited first in terms of recruitment

Answer 6

The smaller motor units with the smaller thresholds.

In order to recruit the large ones you need a high Action Potential frequency

Question 7

Which motor units are more fatigue resistant?

Answer 7

small motor units are slow and fatigue-resistant and are activated first and for longer periods of time than the large motor units that are fast and fatigable and recruited later and for shorter periods of time.

Question 8

What is fiber type of motor units recruited first vs. those recruited last?

Answer 8

smaller motor units with the smaller thresholds working our way up to the large motor units with the large thresholds

Question 9

What happens if you stimulate a muscle fiber again BEFORE the muscle relaxation is complete?

calcium levels spike

Answer 9

the second twitch is added on to the first twitch, resulting in wave summation

Question 10

When calcium levels are high - what starts to occur?

Answer 10

Cross bridge cycling

Question 11

if a muscle fiber is restimulated after it has COMPLETELY relaxed, what occurs?

Answer 11

The second twitch will be the same magnitude as the first twitch

Question 12

if a muscle fiber is stimulated so rapidly that it does not have an opportunity to relax at all between stimuli –

Answer 12

a maximal sustained contraction known as tetanus occurs

(when a graph is increased but then stays constant and levels out)

continuous cross bridge cycling

Question 13

How do you stop tetanus

Answer 13

either you stop stimulating it OR it begins to fatigue out

Question 14

Why does stimulating motor units at higher frequencies produce more tension than stimulating them at lower frequencies?

Answer 14

summation results in greater contraction of the motor unit

Question 15

Why is there an optimal resting length of a muscle?

Answer 15

enables skeletal muscles to generate the maximum force possible when contracted or stimulated

Question 16

when we took the frogs gastroc muscle out of the frog.. what did we ruin / take out?

Answer 16

we took out the frogs optimal resting length of the gastroc muscle (it was stretched in the body and now it is not)

Question 17

if the resting length is longer or shorter

Answer 17

the contractions are compromised. The length tension relationship is altered

Question 18

effect of resting fiber length on muscular contraction (term)

Answer 18

length-tension relationship

Question 19

what instrument did we use in the frog lab that recorded how much contraction occurred

Answer 19

force transducer

Question 20

what did we do to the frogs gastro muscle before stimulating it? we changed the …

Answer 20

resting length

Question 21

tension is generated in muscle, but no shortening occurs

Answer 21

Isometric contraction

Question 22

tension generated by muscle exceeds the resistance of object, muscle shortens and moves object

Answer 22

isotonic concentric contraction

Question 23

why do our skeletal muscles need ATP?

Answer 23

• myosin / actin. crossbridge cycling
• drive the SERCA pumps to return calcium into the SR

Question 24

if you are running a 50 m dash you want

Answer 24

available ATP

Question 25

creatine phosphate can donate phosphate group to ADP (catalyzed by the enzyme creatine Kinase)

location: cytoplasm of muscle fiber

Answer 25

Direct Phosphorylation

Question 26

if you run a whole lap of the track

Answer 26

Anaerobic glycolysis

Question 27

run a 1500M (4 laps around the track)

Answer 27

Aerobic pathwats

Question 28

which type of exercise is most likely to benefit from creatine supplement (100 meter dash or marathon)

Answer 28

100 meter dash

Question 29

which type of exercise would be more likely to induce increased capillary density (100 meter dash or marathon)

Answer 29

Marathon- you need oxygen supply

Question 30

what causes central fatigue?

Answer 30

-motor neurons no longer being adequately stimulated by the CNS

-Boredom

• Protective mechanism (muscles becoming sore or feeling pain – so you stop)

Question 31

exercising muscle no longer able to maintain contractile activity, DESPITE adequate stimulated by CNS or artificial stimulation

Answer 31

Muscle Fatigue