Physio Ex Exercise 2 Activity 1 PDF

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11/4/2020

PhysioEx Exercise 2 Activity 1

PhysioEx Lab Report Exercise 2: Skeletal Muscle Physiology Activity 1: The Muscle Twitch and the Latent Period Name: Dana M. Paolino Date: 4 November 2020 Session ID: session-50f6b048-fe90-434d-33e0-1787d8b29969

Pre-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1 Skeletal muscles are connected to bones by You correctly answered: tendons. 2 Skeletal muscles are composed of hundreds to thousands of individual cells called You correctly answered: fibers. 3 The term motor unit refers to You correctly answered: one motor neuron and all of the skeletal muscle fibers it innervates. 4 The motor neuron and muscle fiber intersect at what is called You correctly answered: the neuromuscular junction. 5 A twitch is You correctly answered: one contractile response to a single action potential.

Experiment Results Predict Question 1 Predict Question: Will changes to the stimulus voltage alter the duration of the latent period? Your answer: No, changing the stimulus voltage will not change the latent period duration. Stop & Think Questions 1 What is the period of time that elapses between the generation of an action potential and the start of muscle tension development in a muscle fiber? You correctly answered: The latent period. 2 What occurs during the latent period of these isometric contractions? https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex2/act1/

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PhysioEx Exercise 2 Activity 1

You correctly answered: All the steps of excitation-contraction coupling occur. Experiment Data Voltage (v)

Length (mm)

Active Force Passive Force

Total Force

Latent Period (msec)

0

75

0

0

0

----

3

75

1.04

0

1.04

----

4

75

1.32

0

1.32

3.20

6

75

1.65

0

1.65

3.20

8

75

1.81

0

1.81

3.20

10

75

1.82

0

1.82

3.20

Voltage = 0 V

Voltage = 3 V

Voltage = 4 V i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex2/act1/

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PhysioEx Exercise 2 Activity 1

Voltage = 6 V

Voltage = 8 V

Voltage = 10 V i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex2/act1/

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PhysioEx Exercise 2 Activity 1

Post-lab Quiz Results You scored 100% by answering 6 out of 6 questions correctly. 1 An action potential in a motor neuron triggers the release of which neurotransmitter? You correctly answered: acetylcholine. 2 The term skeletal muscle fiber refers to You correctly answered: an individual skeletal muscle cell. 3 The graded depolarization in the skeletal muscle fiber that is elicited in response to one action potential from the motor neuron is called You correctly answered: an EPP (end-plate potential). 4 Which of the following is not a phase of a skeletal muscle twitch? You correctly answered: hyperpolarization phase. 5 A skeletal muscle twitch is You correctly answered: one contractile response to a single action potential. 6 Which of the following correctly matches the twitch phase with its definition? You correctly answered: the contraction phase: the time between the end of the latent period and peak muscle tension.

Review Sheet Results i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex2/act1/

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PhysioEx Exercise 2 Activity 1

1 Define the terms skeletal muscle fiber, motor unit, skeletal muscle twitch, electrical stimulus, and latent period. Your answer: A skeletal muscle fiber refers to an individual skeletal muscle cell - long, cylindrical, and multinucleated with obvious striations. A motor unit consists of a motor neuron (a nerve cell that conducts impulses) and all the muscle fibers it innervates. A skeletal muscle twitch is a contractile, or mechanical, response to a single action potential. An electrical stimulus causes muscle contractions. The latent period refers to the period of time, in which no force is generated, that elapses between the generation of an action potential and the beginning of muscle contraction. 2 What is the role of acetylcholine in a skeletal muscle contraction? Your answer: When acetylcholine is released, it diffuses onto the muscle fiber's sarcolemma and binds to receptors in the motor end plate. This binding initiates a change in ion permeability which results in a graded depolarization of the muscle plasma membrane, or end-plate potential, triggering events that lead to contraction. 3 Describe the process of excitation-contraction coupling in skeletal muscle fibers. Your answer: Excitation-contraction coupling in skeletal muscle fibers is a process resulting in muscle contraction. This process begins at the neuromuscular junction and leads to the end-plate potential. A motor neuron is responsible for releasing acetylcholine from its terminal, which is triggered by an action potential. When acetylcholine is released, it diffuses onto the muscle fiber's sarcolemma and binds to receptors in the motor end plate. This binding initiates a change in ion permeability which results in a graded depolarization of the muscle plasma membrane, or end-plate potential, triggering events that lead to contraction. 4 Describe the three phases of a skeletal muscle twitch. Your answer: The three phases of a skeletal muscle twitch include the latent period, the contraction phase, and the relaxation phase. The latent period refers to the period of time, in which no force is generated, that elapses between the generation of an action potential and the beginning of muscle contraction. The contraction phase begins at the end of the latent period and ends at the peak of muscle tension. The relaxation phase refers to the period of time from peak muscle tension to the end of contraction. i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex2/act1/

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5 Does the duration of the latent period change with different stimulus voltages? How well did the results compare with your prediction? Your answer: I predicted the latent period duration would not change with a change of the stimulus voltage; thus, my prediction was correct. The stimulus voltage was adjusted to 4 volts, 6 volts, 8 volts, and 10 volts during the experiment. The latent period remained, unchanged, at 3.20 msec during each of these four scenarios. 6 At the threshold stimulus, do sodium ions start to move into or out of the cell to bring about the membrane depolarization? Your answer: At the threshold stimulus, sodium ions start to move into the cell to bring about membrane depolarization.

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