muscle physiology : Mechanism of Force Generation Flashcards Preview

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Flashcards in muscle physiology : Mechanism of Force Generation Deck (23)
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1
Q

ATP used by muscles for:

A
  1. CROSSBRIDGE CYCLE

2. active transport of calcium back into sarcoplasmic reticulum (relaxation)

2
Q

Muscle Metabolism

the 3 metabolic pathways

A
  1. Creatine Phosphate
  2. Glycolysis
  3. Oxidative Phosphorylation
3
Q
  1. Creatine Phosphate (and ATP) system

formula

A

……………………………………….creatine kinase……………………………
Creatine Phosphate + ADP <———–>. creatine + ATP

…………………. ATPase…………………………………………..
ATP + H20. <———>. ADH + Pi+ H+. + energy

4
Q

1.Creatine Phosphate (and ATP) system

features

A

creatine phosphate = first source of ATP
can provide 4-5 times the amount of ATP in cell at rest

one step process, very rapid
very limited amount, used up rapidly

5
Q
  1. Anaerobic or Non-Oxidative Glycolysis

used when

A

-when oxygen supply to muscle is limited (during intense excersize) …
Anaerobic Glycolysis=primary source of ATP

high intensity excersize : 20-120 seconds

this is the breakdown of glucose ,02 absent

6
Q
  1. Anaerobic or Non-Oxidative Glycolysis
    formula
    source of ATP
A

Glucose——–> 2 lactic acid + 2 ATP

rapid source of ATP:
Only two ATP/glucose
Limited glucose availability
Build up lactic acid (burning sensation)

7
Q
  1. Oxidative Phosphorylation
    energy source…
    oxygen supply
    occurs in
A

//Primary energy source for Light / Moderate exercise (> 2 minutes)
• Muscle stores limited amount of glucose as glycogen
‒ Substrate of oxidative phosphorylation up to 30 mins
• Glucose and fatty acids delivered to muscle by blood
‒ Dominant after 30 mins

//adequate

// mitochondria

8
Q

The Mechanics of Contraction:

twitch contraction

A

a single action potential from a motor nueron will produce a single isolated contraction in a muscle fiber

this single isolated contraction is known as a twitch

9
Q

Phases of a Muscle Twitch

A
  1. latent period
  2. contraction phase
  3. relaxation phase
10
Q

Latent period

A

Time from action potential in muscle cell to onset of contraction (few msec)

Excitation-contraction coupling

11
Q
  1. Contraction phase
A

Tension is increasing (10–100 msec)

Crossbridge cycles take place repeatedly

12
Q
  1. Relaxation phase
A

Tension is decreasing back to zero (longer than contraction phase)
Calcium reuptake

13
Q

isotonic vs isometric contraction

A

isotonic = load remains constant as muscle changes length

isometric= muscle is prevented from shortening so tension develops at constant muscle length

14
Q

Isometric Twitch Contraction

A
  • length constant
  • contractile elements generating tension
  • Stretches series elastic elements
  • muscle doesn’t shorten, load not lifted
15
Q

Isotonic Twitch Contraction

A
  • constant tension

- load is lifted as muscle shortens

16
Q

Normal Muscle Activity:

purely isometric contractions occur…
purely isotonic contractions occur…

A
  • in some daily situations

- rare

17
Q

Normal Muscle Activity:

Even load is constant..

A

isometric precedes isotonic phase of contraction

as tension ↑ the isometric contraction continues until tension exceeds than load

THEN isotonic contraction begins

tension remains constant as muscle shortens

18
Q

Graded Muscle Contractions:

The level of force generated by muscle depends on:

A

(Factors affecting the force or tension generated by individual muscle fibers )

  • -frequency of stimulations
  • -fiber diameter
  • -changes in fiber length
  • -extent of fatigue

(Regulation of the force/tension generated by whole muscle)
-number of fibers contracting

19
Q

Graded Muscle Contraction: Frequency of Stimulation

A

⇧frequency of action potentials in muscle fibers….⇧ tension

in 2 ways:
– Treppe
– Summation and tetanus

20
Q

what is a twitch

A

the. period of contraction and relaxation of a muscle after a single action potential

21
Q

what is summation
what
what happens

A

When multiple electrical stimuli are applied to a muscle at a high frequency,

twitches merge into higher force contractions.

22
Q

Twitch summation or treppe
what
results

A

addition of a second twitch, resulting in greater tension,

it results from stimulating the muscle before it has a chance to relax completely.

23
Q

Tetanus
what
results from

A

prolonged contraction without relaxation

results from repeating stimulation before the muscle has a chance to relax at all.