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 connected to bones by You correctly answered: b. tendons. 2. Skeletal muscles are are composed of hundreds to thousands of individual cells called You correctly answered: c. fibers. 3. The term term motor unit refers 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. the neuromuscular junction. 5. A twitch is You correctly answered: 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 latent period? Your answer : b. No, changing the stimulus voltage will not change the latent period duration. 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. the 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
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Total Force 0.00 1.04 1.32 1.65 1.81 1.82
Latent Period ----2.00 2.00 2.00 2.00
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Post-lab Quiz Results You scored 100% by answering 7 out of 7 questions correctly. 1. An action potential potential in a motor neuron triggers the release of which neurotransmitter? You correctly answered: b. acetylcholine 2. The term skeletal muscle 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 to one action potential 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 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 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 to an isolated, mounted 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: muscle fiber: sel otot tunggal yang terdiri dari banyak miofibril. motor unit: satu serabut saraf yang menginervasi semua muscle fiber. muscle twitch: respon otot pada setiap satu potensial aksi. electrial stimulus: yang menyebabkan otot berkontraksi. latent period: periode diantara stimulus diberikan dan awal terjadinya kontraksi. 2. What is the role of acetylcholine in a skeletal muscle contraction? contraction? Your answer: asetilkolin akan menempel pada reseptor di motor end plate menyebabkan terbukanya Na channel sehingga Na masuk dan menyebabkan terjadiya potensial aksi di permukaan otot. 3. Describe the process of excitation-contraction coupling in skeletal muscle fibers. Your answer: asetilkolin yang keluar dari vesikel diikat oleh reseptor menyebabkan Na channel terbuka dan Na masuk sehinngga menimbulkan potensial aksi disepanjang permukaan otot yang kemudian memicu serangkaian peristiwa yang akan menyebabkan kontraksi. 4. Describe the three phases of a skeletal muscle twitch. Your answer: 1. Periode laten, merupakan proses sebelum terjadinya kontraksi, dari asetilkolin yang keluar dari vesikel hingga terbukanya Ca channel di terminal cisterna yang akan ditangkap oleh TnC 2. Periode kontraksi, proses terjadinya kontraksi, menempelnya kepala miosin pada sisi aktif aktin yang akan menarik kearah garis M, 3. Periode relaksasi, proses terjadinya relaksasi, saat kepala miosin terlepas dari sisi aktif aktin 5. Does the duration of the latent period change with different different stimulus voltages? How well did the results compare with your prediction? Your answer: Yang berubah adaah proses kontraksinya, sedangkan periode laten merupakan periode sebelum terjadinya kontraksi yang tidak akan berubah, dan prosesnya akan tetap terulang meskipun voltage dinaikkan 6. At the threshold stimulus, do sodium sodium ions start to move into into or out of the cell to bring bring about the membrane depolarization? Your answer: Ya. Ion sodium akan berpindah ke sel untuk mengasilkan depolarisasi membran.
