Exercise called You correctly answered: c. an EPP

Exercise called You correctly answered: c. an EPP

Exercise 2: Skeletal Muscle Physiology: Activity 1: The Muscle Twitch and the Latent Period Lab Report 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: b. tendons. 2. Skeletal muscles are composed of hundreds to thousands of individual cells called You correctly answered: c.

fibers. 3. The term motor unit refers to You correctly answered: c. 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: d. he neuromuscular junction. 5. A twitch is You correctly answered: a. one contractile response to a single action potential. 010/08/11 page 1 Experiment Results Predict Question: Predict Question: Will changes to the stimulus voltage alter the duration of the latent period? Your answer : a. Yes, changing the stimulus voltage will change the latent period duration proportionately.

Stop & Think Questions: 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: c. he latent period What occurs during the latent period of these isometric contractions? You correctly answered: b. All the steps of excitation-contraction coupling occur. Experiment Data: Voltage 0. 0 3. 0 4. 0 6.

0 8. 0 10. 0 Length 75 75 75 75 75 75 Active Force 0. 00 1. 04 1. 32 1.

65 1. 81 1. 82 Passive Force 0. 00 0. 00 0. 00 0.

00 0. 00 0. 00 Total Force 0. 00 1. 04 1. 32 1. 65 1.

81 1. 82 Latent Period —-3. 20 2.

80 2. 40 2. 80 010/08/11 page 2 010/08/11 page 3 010/08/11 page 4 Post-lab Quiz Results You scored 85% by answering 6 out of 7 questions correctly. .

An action potential in a motor neuron triggers the release of which neurotransmitter? You correctly answered: b. acetylcholine 2. The term skeletal muscle fiber refers to You correctly answered: a. 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: c. an EPP (end-plate potential). 4. Which of the following is not a phase of a skeletal muscle twitch? You correctly answered: b. hyperpolarization phase 5.

A skeletal muscle twitch is You correctly answered: a. one contractile response to a single action potential. 6. Which of the following correctly matches the twitch phase with its definition? You correctly answered: d.

the contraction phase: the time between the end of the latent period and peak muscle tension 7. A sufficiently strong electrical stimulus applied to an isolated, mounted skeletal muscle induces the development of muscle force, or muscle tension. Which of the following statements concerning this observation is true? Your answer: d.As the strength of the electrical stimulus is increased, the amount of force each individual muscle fiber generates also increases. Correct answer: c. The electrical stimulus mimics acetylcholine release at a neuromuscular junction 010/08/11 page 5 Review Sheet Results 1. Define the terms skeletal muscle fiber, motor unit, skeletal muscle twitch, electrical stimulus, and latent period.

Your answer: Skeletal muscle fiber: Hundreds to thousands of individual skeletal muscle cells Motor unit: consist of a motor neuron Skeletal muscle twitch: The machanical response to a single action potential Electrical stimulus: An lectrical stimulator Latent period: Is the period of time that elapses between the generation of an action potential in a muscle cell and the start of muscle contraction. 2. What is the role of acetylcholine in a skeletal muscle contraction? Your answer: The role is of a neurotransmitter 3. Describe the process of excitation-contraction coupling in skeletal muscle fibers. Your answer: A motor neuron triggers the release of ACH from its terminal. ACH then diffuses onto the sarcolemma and bind to receptors in the motor end plate, initiating a change in ion permeability that results in a graded depolarization of the muscle plasma membrane.

The entire process is called excitation-contracting couplng. 4. Describe the three phases of a skeletal muscle twitch.

Your answer: Latent period: The period of time that elapses between the generation of an action potential in a muscle cell and the start of muscle contraction. Contraction phase: Starts at the end of the latent period and ends when muscle tension peaks. Relaxation phase: Is the period of time from peak tension until the end of the muscle contraction. 5.Does the duration of the latent period change with different stimulus voltages? How well did the results compare with your prediction? Your answer: My prediction was correct. With the higher voltage the latent period was less. When the voltage was 4.

0 the latent period was 3. 20. When the voltage was 10.

0 the latent period was 2. 80. 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: starts to move sodium ions into the cell 010/08/11 page 6

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