Phisioex 9 Skeletal Muscle

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hysioEx 9.0 – Exercise 2: Skeletal Muscle PhysiologyName:

Chart 1: Latent Period Results
VoltageActive force (g)Latent period (msec)
0.00.00XXXXXXXXXX
3.01.04XXXXXXXXXX
4.01.322.40
6.01.652.40
8.01.812.40
10.01.812.40

Chart 2: Effect of Stimulus Voltage on Skeletal Muscle Contraction VoltageActive force (g)
0.00.00
0.20.00
0.80.02
1.0.15
1.5.43
2.0.66
2.5.87
3.01.64
3.51.19
4.01.32
4.51.42
5.01.51
5.51.59
6.01.65
6.51.70
7.01.74
7.51.78
8.01.81
8.51.82
9.01.82
9.51.82
10.01.82

Chart 3: Effect of Stimulus Frequency on Skeletal Muscle Contraction VoltageStimulusActive Force (g)
8.5Single1.83
8.5Multi2.40
8.5Multi3.00
8.5Multi4.22
10Multi3.65
8.5Multi5.72

Chart 4: Tetanus in Isolated Skeletal Muscle
Stimuli/secActive Force (g)
505.12
1305.88
1405.91
1425.94
1445.94
1465.95
1485.95
1505.95

Chart 5: Fatigue Results
Rest PeriodActive Force (g)Sustained maximal force
(sec)
8.55.8610
8.55.8610
8.55.86.60
8.55.865.0

Chart 6: Skeletal Muscle Length-Tension Relationship
Length
(mm)Active
Force (g)Passive
Force (g)Total
force (g)

Chart 7: Isotonic Contraction Results
Weight (g)Velocity
(cm/sec)Twitch
duration
(msec)Distance
lifted (cm)

Activity 1: The Muscle Twitch and the Latent Period

1)Define the terms skeletal muscle fiber, motor unit, skeletal muscle twitch, electrical stimulus, and latent period. multinucleated contractile cells varying from less than 10–100 mcm in diameter and from less than 1 mm to several centimeters in length; the fiber consists of sarcoplasm and cross-striated myofibrils, which in turn consist of myofilaments; human skeletal muscles are a mixture of red, white, and intermediate type fibers

a single somatic motor neuron and the group of muscle fibers innervated by it.

The mechanical response to a single action potential.

The period of time that elapses between the generation of an action potential in a muscle cell and the start of muscle cell and the start of muscle contraction. Although no force is generated during the latent period, chemical changes (including the release of calcium from the sarcoplasmic reticulum) occur interacellularly in preparation for contraction.

2)What is the role of acetylcholine in a skeletal muscle contraction? The acetylcholine binds with receptors on the muscle membrane which are in close proximity to the neuron (the motor end plate). The binding of the acetylcholine to the muscle membrane allows for the initiation of an action potential (which promotes the passing of an electrical current) on the muscle membrane. A special enzyme, acetylcholinesterase, breaks down the released acetylcholine so that it cannot continue to bind to the muscle membrane. In this way, the nerve controls the action of the muscle such that the muscle can only generate a current when the nerve has first generated a current.

3)Describe the process of excitation-contraction coupling in skeletal muscle fibers. AP propagates along sarc olemma and down T- tubule
Release of Ca2 from SR into sarcoplasm
Ca2 binds to troponin which removes tropomyosin from actin binding sites Contraction begins

Calcium influx
Ca binds to Troponin, actin site exposed
Myosin binds to actin
Cross bridge/powerstroke
ATP binds to myosin CB disconnect
ATP splits into ADP & P
CB reenergized and repositions
Ca Removed

4)Describe the three phases of a skeletal muscle twitch.
Latent
The period of time that elapses between the generation of an action potential in a muscle cell and the start of muscle cell and the start of muscle contraction. Although no force is generated during the latent period, chemical changes (including the release of calcium from the sarcoplasmic reticulum) occur interacellularly in preparation for contraction....
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