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Human Physiology PB > Test 2 Chapter 8 Muscles cont. > Flashcards

Test 2 Chapter 8 Muscles cont. Flashcards

10.8.18

1
Q

What are the 8 muscle properties?

A
  1. Threshold
  2. Refractory Period
  3. Twitch
  4. All or Nothing Property
  5. Tension Regulation
  6. Length Tension Relationship
  7. Force Velocity Curve
  8. Leverage
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2
Q

How many times for cross bridge cycle?

A

40 times

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3
Q

Upon calcium being released what happens to the filaments?

A

filaments slide pass each other and there is an overlap of filaments

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4
Q

What Happens to the filaments
A-band
I-Band
H-Zone

A

A-Band does not change length -stays the same.

I-Band-ACTIN becomes shorter

H-Band-Myosin-becomes significantly shorter

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5
Q

With maximal contraction what can happen to the H-Band?

A

The H-Zone can disappear

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6
Q

Relaxed Muscle

Contracted Muscle

A

Nothing has changed

  1. Sarcomere becomes shorter
  2. H-Zone, I band becomes shorter
    A-band same length
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7
Q

What is the Cross Bridge Cycle? (in the presence of Calcium)

1.
2.
3.
4.
5.
A
  1. ATP split by Myosin ATPase and ADP P attached to myosin (energy stored in cross bridge)
  2. Ca binds troponin removing tropomyosin from actin binding site so it can bind with cross bridge
  3. Power Stroke due to myosin and actin interaction. Pi released during and ADP released after power stroke
  4. Linkage between actin and binds to myosin cross bridge- cross bridge assumes original conformation-ATP hydrolyzed
  5. Returns to step 1: ATP split by Myosin ATPase
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8
Q

The exposure of active sites (actin binding sites) on myosin head is dependent upon what

A

Calcium

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9
Q

How is the cross bridge cycle stopped?

A

pumping calcium back where it came from into the sarcoplasmic reticulum which requires ATP. (using the pump)

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10
Q

Is relaxation an active or passive process?

A

Active Process…Requires ATP to contract and relax

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11
Q

What is the step wise shortening theory?

A

Another theory about muscle contraction that we do not have to worry about…something about a corkscrew

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12
Q
  1. Threshold Property of Muscle
A

Has a threshold but not a big issue because neuromuscular junction ALWAYS reaches threshold. (unlike nerve have to take graded potentials and summate them to get to AP)

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13
Q

Is muscle electrically excitable tissue?

A

Yes just like nerve

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14
Q

What is the basis of an AP in a muscle fiber? (Identical to AP in neuron)…

A
  1. Na channels open
  2. Sodium rushes in
  3. Sodium channels close
  4. K channels open
  5. K rushes out
  6. K channels close
  7. Action potential propagates across sarcolemma through the t-tubules
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15
Q
  1. Is there a refractory period for muscle?
  2. Can you put 2 action potentials on top of each other?
  3. Can you put 2 twitches on top of each other?
A

Yes-refractory period

No 2 action potentials cannot be on top of each other due to the refractory period

Yes two twitches can be on top of each other.

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16
Q

Refractory Period can you get another AP?

A

No because Na channels are deactivated. (electrical property)

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17
Q

3rd Muscle Property: What is Twitch?

A

A mechanical event that resolves from an action potential

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18
Q
  1. Mechanical Property?

the 2 Electrical Properties?

A
  1. TWITCH

2. Electrical properties: Action potential and threshold

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19
Q

Action Potential compared to muscle twitch

A

Action Potential

  1. Rapid event–>about 1-2 msec
  2. Depolarization and repolarization in 2 msec

TWITCH

  1. SLOW=about 100 msec
  2. Mechanical Event=Development of Tension
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20
Q

What is a twitch

A

TWITCH is the development of tension (becomes shorter) then less tension (longer)

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21
Q

What happens prior to mechanical event (Twitch) Happening?

A
  1. Stimulate muscle fiber
  2. Reach threshold
  3. Produce an Action Potential
  4. Propagates over sarcolemma surface
  5. to the tubule
  6. Stimulates mechanical event–>
  7. TWITCH
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22
Q

What Happens during a twitch (explain the graph) 3 phases

A
  1. Latent Period= The beginning phase
  2. Contraction Time
  3. Relaxation Time
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23
Q

Explain the Latent Period (1)

A

-Time of initiation of AP
-No tension being developed (flat) for a few millliseconds
-AP has to propagate over sarcolemma down t-tubules-stimulate DHP receptors in T-tubules
-stimulate RYR on lateral sacs which releases calcium-
-calcium diffuses out of SR into sarcoplasm
-interact with troponin-causing tropomyosin to move
-expose active sites
-cross bridges form
causing **TENSION=FIRST POWER STROKE

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24
Q

Until first power stroke how much tension is there?

A

ZERO

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25
Q

Latent Period represents what two things?

A

Excitation and coupling…takes time to develop tension

26
Q

Explain the Contraction Time (2)

A
  • Tension in fiber is increasing until it hits its peak

- concentration of calcium in the SR is increasing (more powerstrokes= more tension)

27
Q

Explain Relaxation Time (3)

A

Time in which calcium is put back into SR faster than it is being released.

  • Ryanodine Receptors close
  • *CALCIUM IS RESEQUESTERED**
28
Q

What events cause a twitch

A

AP–>Contraction–>Relaxation

29
Q

1 Action Potential on the alpha motor neuron does what

A

AP (electrical event)–>AP muscle fiber–> 1 Twitch (mechanical event)

30
Q

All or None Property (Muscle property 4) .Does it exist for muscle?

A

YES in skeletal muscle WITH EXCEPTIONS TREPPE

Yes with action potential (electrical event)

YES with twitch

31
Q

What is TREPPE?

A

Stimulate muscle fiber 1/sec, you get a twitch…

STAIRCASE effect you have to get past

32
Q

What 2 things can cause Treppe?

A

first few twitches may be substandard due to

  1. Temperature-Muscles move better with warmth
  2. Not enough calcium released
33
Q

How is Tension regulated?

A

converting a twitch into something that is useful

  1. Twitch Summation
  2. Motor Unit Recruitment
34
Q

What is Twitch (WAVE) Summation?

A

2nd twitch summating with the first

2 twitches from 2 Action Potentials summate (add together) to produce greater tension (similar to EPSPs)

35
Q

Refractory Period and Twitches

A

Increase frequency of AP and summate the twitches

Depends on frequency of nervous system stimulating muscle.

Muscle fiber being stimulated prior to Twitch being completed

36
Q

How long is a twitch?

A

about 100 milliseconds

37
Q

Increased frequency to a very high level 25-30Hz (stimuli/sec) can cause what?

A

calcium released at equivalent rate that it re enters SR…causing Tetanus

38
Q

What are two means of Tension Development?

A
  1. TWITCH SUMMATION=frequency

2. MOTOR UNIT RECRUITMENT

39
Q

What is Tetanus?

A

Stimulation Above 25-30 Hz

muscle is in a continual state of contraction

USEFUL HUMAN MOVEMENT occurs here

40
Q

How is normal voluntary movement produced?

A

TETANUS! Increased frequency causing calcium to be released at same rate of calcium channels being opened.

Calcium continuously in sarcoplasm

20-30x a second=stimulating muscle

41
Q

What is the most important means of regulating tension?

A

Motor Unit Recruitment

42
Q

What is Motor Unit Recruitment

A

Major Means of tension development…need more tension recruit more motor units

NERVOUS SYSTEM PROPERTY

43
Q

Smallest Motor Unit

Largest Motor Unit

A
  1. 3-4 fibers in extraoccular muscles of the eye

2. Quadriceps-activation thousands of fibers

44
Q

Synchronous Motor unit recruitment

A

Nervous System-stimulate all motor units together

  1. Enhances force
  2. Decreases endurance capacity (can’t sustain force)
45
Q

Asynchronous motor recruitment

A

Motor units not recruited at the same time-spreads the workload around

  1. Decreased force potential
  2. Increased endurance capacity

**Not fatiguing specific motor units

46
Q

Motor Unit

A

Alpha motor unit and the fibers it innervates (stimulates)

47
Q

Explain the Length Tension (RelationshipMuscle Property # 6)

A

The ability of a muscle to produce force is dependent upon its length

48
Q

What are the 2 aspects of length tension relationship?

A
  1. Passive force- Parallel and series elastic components

2. Active Force

49
Q

Passive force

Passive Tension Curve

A

due to parallel and series elastic components.

When stretched muscle stores energy and will snap back

Develops tension when stretched to longer lengths will snap back

(INCREASE LENGTH-INCREASE TENSION)

50
Q

Active Force (ACTIVE TENSION CURVE)

A

Stimulating & stretch…Muscle works best at resting muscle length ( in the middle)

51
Q

What length does muscle work best?

A

Resting Muscle Length

Power stroke->maximal # cross bridges formed = maximal overlap of actin & myosin

52
Q
  1. Force Velocity Relationship (Curve)
A

Muscle does not work well at all speeds.

Muscle works best (producing force) slow

At low velocity—>produce higher tension

Faster it shortens= less force produced

53
Q
  1. Leverage
A

Muscle works through a lever system

-Muscles connect to bones via lever systems

54
Q

What are the 3 classes of Levers?

A

1st class lever-teeter totter

2nd class lever- wheelbarrow

3rd class lever-

55
Q

Most levers in the body are which class?

A

3rd class levers

No 2nd class levers in the body

56
Q

Biceps attaching to radius is an example of what class lever

Elbow joint=?

Hand=?

A

3rd class lever

Elbow=fulcrum

Hand=Resistance

Force=

57
Q

Why do we use levers?

A

To gain mechanical advantage

-Long force arm & Short resistance arm

58
Q

What is mechanical disadvantage?

A

Force arm=short
resistance arm=long

50lb dumb bell * 7 =muscle producing 350 lb tension Have to increase tension

-large range of motion (Good thing)

59
Q

Angular velocity?

A

Gain speed due to angular velocity (increase speed of motion)

60
Q

Joint Angle with Poor leverage?

A

Develop more tension in the muscle

61
Q

Joint angle with Better leverage?

A

Muscle produces less force

62
Q

As joint angles change what else changes?

A

Levers change as well

Human Physiology PB (9 decks)

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