Whole Muscle Physiology

Question 1

Muscle twitch

Answer 1

A single, brief contraction and relaxation cycle in a muscle fiber

Question 2

3 phases of muscle contraction

Answer 2

lag phase - the gap between stimulus and beginning of contraction
contraction phase
relaxation phase

Question 3

Motor units

Answer 3

a single motor neuron and all the muscle fibers it innervates.

An action potential in the motor neuron > generates an action potential in each of the muscle fibers it innervates

Question 4

Motor unit number

Answer 4

Muscle performing delicate and precise movements have many motor units

Question 5

2 ways to increase the force of a contraction

Answer 5

Summation

Recruitment

Question 6

Summation

Answer 6

increasing the force of contraction of muscle fibers within the muscle

Question 7

Recruitment

Answer 7

increasing the number of muscle fibers contracting

Question 8

Treppe

Answer 8

Increase in tension when a muscle is repeatedly contracted

Possibly explained by an increase in Ca2+ levels around myofibrils

It’s why athletes warm-up before their main exercise

Question 9

Multiple-motor-unit summation

Answer 9

increased stimulus strength and increased number of contracting motor units

Force of contraction increases as more and more motor units are stimulated

Question 10

Tetanus

Answer 10

A period of sustained muscle contraction

Question 11

Incomplete tetanus

Answer 11

Muscle fibers partially relax between contractions

Question 12

Complete tetanus

Answer 12

Muscle fibers produce action potentials so rapidly that no relaxation occurs

Question 13

Multiple wave summation

Answer 13

The increased tension produced as a result of the increase in the frequency of the contractions

Question 14

Active tension & muscle length

Answer 14

length of a muscle has a strong influence on amount of active tension it produces

Question 15

Active tension curve

Answer 15

Length of muscle increases > active tension increase… to a point

If it stretches further than optimum length, active tension begins to decline

This is why weight lifters assume positions where muscles are stretched close to optimum length

Question 16

Passive tension

Answer 16

tension applied when a muscle stretches but is not stimulated - like an elastic band. Exists due to muscle elasticity

Question 17

Total tension

Answer 17

Sum of active and passive tension

Question 18

Types of muscle contractions (4)

Answer 18

1) isometric - length of the muscle does not change, but the number of tension increases // posture
2) isotonic - the amount of tension produced by the muscle is constant but the length of muscle changes // waving or using a keyboard
3) concentric - isotonic contraction where the tension in muscle overcome opposing resistance, shortening the muscle // lifting a backpack from the floor to table
4) eccentric - isotonic contraction where tension is maintained in a muscle but opposing resistance causes the muscle to increase in length // slowly lowering a heavy weight

Question 19

Slow-twitch muscle fibers (type 1)

Answer 19

contract more slowly
Have a better-developed blood supply
Have more mitochondria
More fatigue resistant
Respond slowly to nervous stimulation
Break down ATP more slowly 
Have large amounts of myoglobin
Functions - posture and endurance

Question 20

Fast-twitch muscles (type 2)

Answer 20

Respond rapidly to nervous stimulation
Break down ATP more rapidly than slow-titch
Less-well-developed blood supply
Fewer myoglobins
Smaller mitochondria
Large deposits of glycogen
Fatigue quickly
Functions - Rapid, intense movements of short duration

Question 21

Glycogen

Answer 21

The stored form of glucose. Body relies on glycogen for sustained exercise

Question 22

How can you increase the muscular strength and mass of fast-twitch muscles?

Answer 22

Weight lifting/ anaerobic exercise

Question 23

How can you increase the vascularity of muscles and en the size of slow-twitch muscles

Answer 23

aerobic exercise

Question 24

Can you convert a type 1 muscle fiber to a type 2 muscle fiber

Answer 24

No

Question 25

Can you convert a type 2a muscle fiber to a type 2b muscle fiber

Answer 25

Yes

Question 26

Anabolic steroids

Answer 26

Synthetic hormone taken to increase size and strength of muscles

Question 27

Beyond increasing muscle size, what else improved strength in a trained person?

Answer 27

1) Nervous system can recruit a larger number of motor units simultaneously
2) Metabolic enzymes increase in hypertrophied muscles, making ATp production easier and nutrient absorption easier