Concept explainers
(a)
To determine: The comparison between the skeletal and smooth muscle contraction with respect to signal for crossbridge activation
Introduction: The skeletal muscles perform the function of attaching bones with the skin. The skeletal muscles perform voluntary muscular movements. The smooth muscles are present along the walls of the internal organs. They are involved in performing the involuntary muscular movements.
(b)
To compare: The skeletal and smooth muscle contraction on the basis of the source(s) of calcium required for Ca2+ signal.
Introduction: Calcium plays an important role in facilitating contraction by reacting with regulatory proteins. The absence of calcium prevents the interaction of actin and filament. The smooth muscles contain the same contractile elements as smooth muscles. They both contain actin and myosin that interact through the crossbridge.
(c)
To determine: The comparison between the skeletal and smooth muscle contraction on the basis of signal that releases Ca2+ from the sarcoplasmic reticulum.
Introduction: The Ca2+ plays an important role in initiating contraction of the muscles. The sarcoplasmic reticulum provides a source of Ca2+ for both the skeletal muscles and the smooth muscles. In addition, extracellular fluid also provides the source of Ca2+ for smooth muscles.
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EBK HUMAN PHYSIOLOGY
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- Summation in a single muscle fibre means that Select one: a. the fibre increases the frequency of contraction b. the fibre stays contracted longer c. the fibre increases the force of the contraction and stays contracted longer d. the fibre increases the force of the contraction e. the fibre increases both the force and frequency of contractionarrow_forwardFor the following five events, which is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber? 1. Tropomyosin shifts, exposing the myosin-binding sites on actin. 2. Calcium is released from the sarcoplasmic reticulum and binds to the troponin complex. 3. An action potential is propagated down the transverse tubules. 4. Cycles of myosin cross-bridge formation and breakdown cause the thin filaments to slide toward the center of the sarcomere. 5. An action potential in a motor neuron causes the axon to release acetylcholine, which triggers an action potential in a muscle fiber. 1 → 2 → 3 → 4 → 5 3 → 2 → 4 → 1 → 5 2 → 1 → 3 → 5 → 4 5 → 3 → 2 → 1 → 4 4 → 3 → 1 → 2 → 5arrow_forwardWhich of the following step(s) about the excitation of skeletal muscle is/are incorrect? 1. Acetylcholine is released and binds to motor end plate receptors 2. An action potential is created and moves down T-tubules 3. Calcium is released from the sarcoplasmic reticulum 4. Calcium ions bind to tropomyosin to shift troponin off the binding sites for cross-bridging 5. Myosin forms cross-bridges and binds with actin to pull it towards middle of sarcomerearrow_forward
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