Exercise 2: Skeletal Muscle Physiology: Activity 1: The Muscle Twitch and the Latent Period Lab Report Pre-lab Quiz Results You scored 40% by answering 2 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 Your answer : d. myofilaments. Correct answer: c. fibers. 3. The term motor unit refers to Your answer : a. all of the motor neurons that innervate one skeletal muscle. Correct answer: 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. the neuromuscular junction. 5. A twitch is Your answer : b. one contractile response to a series of action potentials. Correct answer: a. one contractile response to a single action potential.

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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? Your answer : b. the contractile period Correct answer: c. the latent period What occurs during the latent period of these isometric contractions? Your answer : a. The length of the muscle fiber is sliding into an optimal length. Correct answer: 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 ----2.80 2.80 2.80 2.80

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Post-lab Quiz Results You scored 85% by answering 6 out of 7 questions correctly. 1. 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 Your answer: a. an EPSP (excitatory postsynaptic potential). Correct answer: 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? You correctly answered: c. The electrical stimulus mimics acetylcholine release at a neuromuscular junction

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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 : long, cylindrical cells that contain many peripherally located nuclei. Motor Unit: consists of one motor neuron and all the muscle fibers it innervates, or supplies. Skeletal Muscle Twitch: a