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Physiology 1 > Lab 3 - Muscle > Flashcards

Lab 3 - Muscle Flashcards

1
Q

What is the SimMuscle program used for?

A

To examine the contraction properties of skeletal (striated) muscle.

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2
Q

When bone is cut and you want to prized the preparation, what do you put the sample into?

A

Ringer solution

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3
Q

What are the equipment of the virtual laboratory?

A

A stand for the preparation
A simulator
A transducer
Occilloscope

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4
Q

What does a Transducer do?

A

Converts the changes in muscle length and muscle tension into electrical signals.

It should be connected to the oscilloscope through a cable.

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5
Q

What is zero adjust

A

After changing anything in the experimental setup calibration is needed.

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6
Q

Expain Isotonic-isometric work

A

Muscle function can be examined under either isotonic “free” or isometric “lock” conditions

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7
Q

Electric stimulations, three types

A

Single - one stimuli (1 ms)
Twin - Two stimuli
Train - a set number - “counts” of stimuli

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8
Q

Electric stimulations, The intensity of the stimulus “amplitude” range

A

From 0 - 500 mV

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9
Q

Electric stimulations, the time interval between stimuli “delay”

A

Delay: 0-500 ms

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10
Q

What is the name of the screen that shows the signals=

A

Ocilloscope screen

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11
Q

What is connected to channel 1

A

Ocilloscope

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12
Q

What is connected to channel 2

A

Signals from the transducer are received through channel 2

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13
Q

What does the timebase button do

A

Setts the speed of the registration in ms per divisions (ms/Div)

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14
Q

What is muscle contraction based on?

A

Muscle contraction is based on sliding of contractile elements.
Actin and myosin.

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15
Q

What is all-or-none law?

A

A single muscle fibre reacts to adequate stimuli according to the all-or-nothing law by contracting maximally.

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16
Q

Threshold potential in different fibers

A

In the muscle tissue the threshold potential of the different fibers are different.

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17
Q

What is spatial (quantal) summation?

A

When stimulus strength is increasing, more and more fibers contract.
Finally all the fibers are activated and the muscle reaches its maximal contraction level.

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18
Q

What are the range of stimuli strength to determine the minimal and maximal stimulus

A

0-500 mV (in 20 mV steps)

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19
Q

What is minimal stimulus

A

The weakest stimulus strength that just elicits contraction

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20
Q

What is maximal stimulus

A

The weakest stimulus that just causes complete contraction.

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21
Q

Measuring contraction time

Upon reaching the muscle…..

A

The action potential increases myoplasmic calcium concentration.

Calium binds to troponin-C (TnC), shifting the tropomyosin-troponin complex to the groove of the actin filament.

As a result of this:

The myosin binding sites on the actin filament are freed to react with the myosin.

Activated myosin heads (angle of 90 * binding ATP) bind to the active site of the actin.

Binding allows the myosin heads to reach the resting stage.

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22
Q

How does the binding allow the myosin head to reach resting stage?

A

The myosin head first bends 40 *, then- after releasing ATP and P1 - a total of 45 *, result in the sliding filaments.

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23
Q

What is the Latency period?

A

The time period between the stimulation and the start of the contraction.

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24
Q

What is the process occurring during the latency period called?

A

Electro-mechanical coupling

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25
Q

What happens if ATP is available?

A

If ATP is available, it binds to the myosin, which dissociates from the actinm and the myosin head returns to the original activated position (90*, wound up state).

26
Q

What is the name of this cycle (starts with the formation of the actomyosin complex, followed by sliding filaments, and is completed by dissociation - The ATP dependent terminal phase)

A

Cross- the bridge cycle.

27
Q

What is Superposition

A

Muscle contraction can not only be increased by increasing the number of fibers that contract at one time (spatial or quantal summation)

But also by increasing the frequency of triggering of the contracting fibers

28
Q

Explane the phenomenon Superposition

A

If a fiber is stimulated repeatedly before the previous calcium transient has finished, the new stimulus elicits additional calcium release, thus contraction increases.

29
Q

How do we examine superposition?

A

To examine the superposition, the muscle iw stimulated with TWIN stimuli.
Begin with 200 ms delay, and then decrease the time interval between stimuli in 25 ms steps.

30
Q

Incompleated and completed tetany

A

New stimuli applied shortly after the end of a twitch may exclit new contractions whit gradually increasing amplitude

31
Q

New stimuli applied shortly after the end of a twitch may exclit new contractions whit gradually increasing amplitude, this is caused by what?

A

This is caused by intracellular calcium that has no time to be removed between stimuli
(Superposition)

32
Q

What is a complete tetany

A

Finally after the muscle relax but shows continuous tonic spasm.

The prodromal stage of complete tetany is termed partial or incomplete tetany

33
Q

What does the prodromal stage of complete tenant mean?

A

When different contractions can still be distinguished.

34
Q

Muscular fatigue

What causes it?

A

Primarly caused by the increasing contraction of metabolic by-products

35
Q

What inhibits the muscle function

A

Lack of energy leads to formation of lactic acid, which directly inhibits muscle function

36
Q

What are a reason of muscle fatigue, which can be found predominantly in experiments, but rarely in nature?

A

Lack of neurotransmitters as a reason for fatigue, but rarely on the nature.

37
Q

What happens during muscle fatigue?

A

The amplitude of contraction decreases and the contraction time increases

38
Q

What happens during muscle fatigue?

A

The amplitude of contraction decreases and the contraction time increases

39
Q

Why does muscle fatigue happen?

A

White (glycolytic) muscles that contain fast-twich fibers exhaust faster, while red (oxidative) muscles with slow-twich fibers exhaust slower.

40
Q

How do you measure muscle fatigue

A
  1. Stimulate the muscle with a single supra maximal stimulus
  2. Elicit tetany (in order to exhaust the muscle)
  3. Stimulate the muscle the same way as the first time.

The observations shown at the oscilloscope screen shall be drawn. There will be two obvious sign of muscle fatigue.

41
Q

What does the length-tension diagram consist of?

A

Passive strength curve
Isotonic maximum curve
Isometric maximum curve

*Remmember zero adjust

42
Q

To make the length-tension diagram, you will first need to?

A

First register the passive strength curve.
For each different load applied to the relative length of the muscle should be plotted in as a function of CORRESPONDING passive strength.

43
Q

When making the length-tension diagram - You need to determine?

A

Relative length of the muscle at rest (L0) and the passive strength in compensation to the L0 by applying 50g weights repeatedly until reaching 300 g.

*remember zero adjust

44
Q

During isotonic contraction, how does the muscle tone/length change

A

During isotonic contraction the muscle tone does not change, but the muscle length decreases as a result of muscle contraction elicited by the stimulation.

45
Q

What is Isometric maximumcurve

A

In case of the muscle is passively stretched with different loads, providing isometric conditions and stimulating it with supra maximal single stimuli.

46
Q

How do you obtain the isometric maximum curve for the muscle?

A

By plotting data on a length-tension diagram

47
Q

What is the optimal work range for each muscle?

A

Stiaded muscle - require medium tension (preload)

48
Q

What is Electromyography

A

Action potentials that elicits muscle contraction can be detected on the surface of the skin as a potential differences. The method for measuring those differences is called electromyography.

49
Q

What is called when the potential difference are measured in a function of time

A

Electromyogram (EMG)

50
Q

Why does the skeletal muscle show many curves with a EMG?

A

Because skeletal muscles are isolated and are often large units, the EMG is not a single curve but is a average picture of overlapping action potentials.

51
Q

What can you determine based on a EMG recording?

A

Neural or muscular origin of a disease

52
Q

Is there normally a measurable potential difference from a resting muscle.

A

No, but during a contraction electrical signals can be recorded.

As a contraction gets stronger , more and more muscle fibers are activated. It results in more frequent and larger potential differences.

53
Q

How do you attach the electrodes for the EMG?

A
  1. Small amount of electrode cream on the concave side of each disc electrode.
  2. Place the Black and Yellow electrodes with their concave side onto the skin overlying the belly of the m.biceps brachii.
    (Electrodes should be 2-5 cm apart and aligned with the long axis of the arm.)
  3. Fasten electrodes with a piece of adhesive tape.
  4. In similar way, the blue and red electrodes should be placed over m. triceps brachii.
  5. Atache the dry earth strap around the wrist of the volunteer. (fuzzy side in contact with skin)
  6. The volunteer should sit in a relaxed position , with his/ or her elbow bend 90 degrees with the palm facing upwards.
    START BUTTON, record eating EMG for 30 sec.
  7. Next the volunteer should to is to perform a contraction of biceps muscle, and then the triceps muscle.

To be repeated with dif weights

54
Q

Minimal and maximal stimulus strength in humans

Electrical signals from the hand dynamometer, chanel 1?

A

Electrical signals dispalyed in channel 1 is Force

55
Q

Minimal and maximal stimulus strength in humans

Electrical signals from the hand dynamometer, chanel 2?

A

Electrical signals dispalyed in channel 1 is Stimulus

56
Q

Witch risks/procaution has to be taken during measuring of min/max stimulus in humans

A

Not people with cardiac or neurological disorder
Remove jewlery, watches etc.
Small amount of electrode cream before you place the electrode on the ulnar nerve.
During the experiment the hand dynamometer should be held loosely.

57
Q

How do you determine the threshold potential?

A

By applying single stimuli (Number of pulses) by clicking the stimulate button.

Increase the stimuli strength (pulse current (mA)) gradually and determine the min stimuli strength which just elicits contraction.

By increasing the stimulus strength further, determine the weakest stimuli needed that just elicits a maximal contraction.

58
Q

What do we measure when measuring contraction time in humans?

A
  • zoom view to determine the duration of dif parts of a complete cycle.

Latency perion
Contraction time
Relaxation time
Compleete system

59
Q

Super positions in humans

A

Stimulate the ulnar nerve with supra maximal stimuli. (pulse current: 15 mA, Number of pulses: 2)

By changing “frequency” determine the time interval needed to elicit superposition

60
Q

Incompleete tetany in humans

A

Apply supramaximal (pulse current: 15 mA) Trainstimulation. (Number of pulses: 8) over the ulnar nerve. Frequenzy should be equal to that needed for eliciting superposition.

61
Q

Muscle fatigue in humans

When determine the muscle power as a percentage of maximal contraction?

A

After the fifth cycle

Physiology 1 (42 decks)

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