Muscle Physiology 2

Question 1

Definition:

Isotonic

Answer 1

Tension is constan while muscle length changes

Question 2

Definition:

Angle of joint decreases

Answer 2

Concentric

Question 3

Definition

Eccentric

Answer 3

Angle of joint increases

Question 4

Definition:

Isometric

Answer 4

muscle contracts but does not change length

Question 5

T/F: visible shortening occurs during the isometric tension phase (first phase of skeletal muscle contraction)

Answer 5

False, cross bridges shorten but tension added to series elastic components

Question 6

When are visible changes in length of the muscle first seen during a contraction?

What phase?

Answer 6

isotonic shortening phase

Question 7

What happens does parallel elastic fibres (PEC) = during the isotonic shortening phase?

Answer 7

PEC=SEC=load

Question 8

T/F: Tension is constant during the isotonic shortening phase

Answer 8

true

Question 9

Definition:

Muscle tone

Answer 9

Even at rest, a skeletal muscle exhibits a samll amount of tension

Question 10

How is tone established?

Answer 10

By alternating, involuntary activation of small groups of motor units in a muscle

Question 11

Definition:

Motor unit

Answer 11

Motor neuron and the muscle fibres it innervates

Question 12

What does the strength of a muscle contraction depend on?

Answer 12

number of motor units activated

Question 13

T/F: stongest motor units are recruited first

Answer 13

False, weak ones then stronger ones

Question 14

T/F: motor units contract alternately to sustain contractions for longer periods of time

Answer 14

true!

Question 15

Definition:

Movement using muscle with few muscle fibres/motor unit

Answer 15

Precise and delicate movements

Question 16

T/F: muscles producing powerful and coarsely controlled movements have large numbers of muscle fibres/MU

Answer 16

true

Question 17

Definition:

Delay between the arrival of the AP and intitaion of a contraction

Answer 17

Latent period

Question 18

Definition

Contraction period

Answer 18

When calcium binds to troponin and the actin-myosin cross-bridges are formed

Question 19

Definition

Relaxation period

Answer 19

When calcium is actively pumped into the SR, myosin heads detach from actin and muscle tension decrease

Question 20

Definition

Period of time when teh muscle tissue is unable to respond to a subsequent AP

Answer 20

refractory period

Question 21

What produces passive force?

Answer 21

tendons and elastic properties of the muscle

Question 22

What happens when a muscle is stretched beyond its optimal length?

Answer 22

titin acts as a spring and tries to pull the sarcomeres back towards their optimal length

Question 23

What does the active force of a muscle depend on?

Answer 23

The length of the sarcomeres in a muscle prior to contraction

Question 24

T/F: the number of active cross bridges is the least when the muscle is at the optimum length

Answer 24

False, it is at its greatest

Question 25

What happens to the # of active cross bridges as the muscle is stretched beyond its optimal length?

Answer 25

decrease b/c the pverlap between actin and myosin fibers decreases

Question 26

As the velocity of a concentric muscle action is increased...

Answer 26

less force is capable of being generated during that contraction as it takes a certain amount of time for cross-bridges to attach and detach

Question 27

As the velocity of a eccentric muscle action is increased...

Answer 27

more force is capable of being generated due to greater strain placed on the myosin heads allow the attachment of the second head more frequently

Question 28

T/F: force production increases as velocity of the contraction increases

Answer 28

false, it force decrease as velocity increases

Question 29

When is power maximized?

Answer 29

At submaximal force and velocity

Question 30

T/F: Type I fibres generate more peak power than type II fibres

Answer 30

false

Question 31

What is the continum for power and velocity of muscle fibre types?

Answer 31

IIbx > IIa > I