muscle twitches

Question 1

muscle mechanics principles

Answer 1

same principles apply to contraction of a single muscle fiber and a whole muscle
Contraction produces tension, the force exerted on the load or object to be moved

Question 2

Isometric contraction

Answer 2

no shortening; muscle tension increases but does not exceed the load

Question 3

Isotonic contraction

Answer 3

muscle shortens because muscle tension exceeds the load

Question 4

Motor unit

Answer 4

a motor neuron and all (a least four but up to several hundred) muscle fibers it supplies

Question 5

smaller vs larger motor units

Answer 5

Small motor units in muscles that control fine movements (fingers, eyes)
Large motor units in large weight-bearing muscles (thighs, hips)

Question 6

muscle twitch

Answer 6

Response of a muscle to a single, brief threshold stimulus

Question 7

myogram

Answer 7

a graph of twitch tension development

Question 8

three phases of a isometric twitch

Answer 8

latent period
period of contraction
period of relaxtion

Question 9

latent period of twitch

Answer 9

events of excitation-contraction coupling

Question 10

period of contraction of twitch

Answer 10

cross bridge formation; tension increases

Question 11

period of relaxtion of twitch

Answer 11

Ca2+ reentry into the SR; tension declines to zero

Question 12

Different strength and duration of twitches are due to

Answer 12

variations in metabolic properties and enzymes between muscles

Question 13

motor unit in a muscle usually contract…

Answer 13

asynchronously (some turn off while others turn on) helps prevent fatigue unless load too big

Question 14

Graded Muscle Responses

Answer 14

Variations in the degree of muscle contraction

Required for proper control of skeletal movement

Question 15

graded muscle responses are graded by

Answer 15

Changing the frequency of stimulation

Changing the strength of the stimulus

Question 16

A single stimulus results in

Answer 16

a single contractile response—a muscle twitch

Question 17

Response to Change in Stimulus Frequency

Answer 17

Increase frequency of stimulus (muscle does not have time to completely relax between stimuli)

Question 18

If another stimulus is applied before the muscle relaxes completely

Answer 18

then more tension results. This is temporal (or wave) summation and results in unfused (or incomplete) tetanus. (low stimulation frequency)

Question 19

If stimuli are given quickly enough

Answer 19

fused (complete) tetany results

high stimulation frequency

Question 20

Threshold stimulus

Answer 20

stimulus strength at which the first observable muscle contraction occurs

Question 21

as stimulus strength is increased above threshold

Answer 21

Muscle contracts more vigorously

Question 22

Contraction force is precisely controlled by

Answer 22

recruitment (multiple motor unit summation), which brings more and more muscle fibers into action

Question 23

Size principle

Answer 23

motor units with larger and larger fibers are recruited as stimulus intensity increases

Question 24

what helps prevent fatigue

Answer 24

fibers are contracting asynchronously

Question 25

recruitment principle

Answer 25

Can control strength of contraction to meet the needs of the moment

Question 26

muscle tone

Answer 26

Constant, slightly contracted state of all muscles | Keeps muscles firm, healthy, and ready to respond

Question 27

muscle tone due to

Answer 27

spinal reflexes that activate groups of motor units alternately in response to input from stretch receptors in muscles

Question 28

Isotonic contractions two types

Answer 28

concentric contractions or eccentric contractions

Question 29

Concentric contractions

Answer 29

the muscle shortens and does work

Question 30

eccentric contractions

Answer 30

the muscle contracts as it lengthens

Question 31

isotonic contractions

Answer 31

Muscle changes in length and moves the load

Question 32

Isometric Contractions

Answer 32

The load is greater than the tension the muscle is able to develop Tension increases to the muscle’s capacity, but the muscle neither shortens nor lengthens

Question 33

what is the only source used directly for contractile activities

Answer 33

ATP

Question 34

For contraction, Available stores of ATP are depleted in

Answer 34

4-6 seconds

Question 35

ATP is regenerated by three ways

Answer 35

``` Direct phosphorylation of ADP by creatine phosphate (CP) (1st 14-16 seconds – turbo boost) Anaerobic pathway (glycolysis) (30-40 seconds) Aerobic respiration (95%) ```

Question 36

Anaerobic Pathway At 70% of maximum contractile activity

Answer 36

Bulging muscles compress blood vessels Oxygen delivery is impaired Pyruvic acid is converted into lactic acid

Question 37

Anaerobic Pathway lactic acid

Answer 37

Diffuses into the bloodstream Used as fuel by the liver, kidneys, and heart Converted back into pyruvic acid by the liver

Question 38

Aerobic Pathway

Answer 38

Produces 95% of ATP during rest and light to moderate exercise

Question 39

Aerobic Pathway fuels

Answer 39

stored glycogen, then bloodborne glucose, pyruvic acid from glycolysis, and free fatty acids

Question 40

short duration exercise 6 seconds

Answer 40

ATP stored in muscles is used first

Question 41

short duration exercise 10 seconds

Answer 41

ATP is formed from creatine phosphate and ADP

Question 42

short duration exercise 30-40 seconds to end of exercise

Answer 42

glycogen stored in muscles is broken down to glucose, which is oxidized to generate ATP

Question 43

prolonged duration exercise hours

Answer 43

ATP is generated by breakdown of several nutrient energy fuels by aerobic pathway. this pathway uses oxygen released from myoglobin or delivered in the blood by hemoglobin. when it ends, the oxygen deficit is paid back

Question 44

muscle fatigue

Answer 44

Physiological inability to contract

Question 45

muscle fatigue two types

Answer 45

nervous fatigue and metabolic fatigue

Question 46

Nervous fatigue

Answer 46

Nerve ion imbalance can’t send same intensity of signal anymore

Question 47

Metabolic fatigue

Answer 47

Either lack of fuel (ATP – very rare) or some metabolic waste product (lactic acidocis) interferes with calcium function in sarcomere

Question 48

Extra O2 needed after exercise for

Answer 48

Replenishment of (Oxygen reserves Glycogen stores ATP and CP reserves) and Conversion of lactic acid to pyruvic acid, glucose, and glycogen

Question 49

40% of the energy released in muscle activity is

Answer 49

useful for work

Question 50

how much energy in muscle activity is given off as heat

Answer 50

60%

Question 51

Dangerous heat levels are prevented by

Answer 51

radiation of heat from the skin and sweating