BIOLOGY:CONCEPTS+APPL.(LOOSELEAF)
10th Edition
ISBN: 9781305967359
Author: STARR
Publisher: CENGAGE L
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Chapter 32, Problem 2SA
Summary Introduction
Introduction:
A mature skeletal muscle consists of thousands of muscle fibers which are known as myofibrils. These are threadlike proteins which are arranged in identical contractile units called sarcomeres. The thick filament of the sarcomere has a motor protein called myosin and the thin filament has actin as a motor protein.
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At low intracellular Ca2+ concentration, _________________ the active sites on the thin actin filament.
a. troponin blocks
b. troponin exposes
c. tropomyosin blocks
d. tropomyosin exposes
e. a and c
The Sarcomere 2
Thin filaments are often named for which protein?
a. actin
b. myosin
c. troponin
d. tropomyosin
Mark the following statements as true for smooth muscle tissue, cardiac muscle tissue, and/or skeletal muscle tissue. a. _____ Actin attaches to dense bodies. b. _____ Cells are joined by intercalated discs. c. _____ The thick and thin filaments are arranged into sarcomeres. d. _____ The thick filaments contain myosin heads along their entire length. e. _____ The cells depolarize and contract as a unit. f. _____ Calcium ions binding to troponin is the initiating event of contraction. g. _____ Calcium ions binding to calmodulin is the initiating event of contraction. h. _____ The sarcolemma has a distinct motor end plate.
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- Which of the following is the site of calcium ion storage within muscles? a. T tubules b. sarcoplasmic reticulum c. actin filaments d. myosin filamentsarrow_forwardRigor mortis occurs following death because a. tropomyosin remains over the myosin binding sites of actin. b. myosin heads attach to actin and are not released due to lack of ATP. c. the myosin becomes misshapen. d. all of the Ca2+ remains within the sarcoplasmic reticulum.arrow_forwardThe sliding filament mechanism describes the process during which: a. actin and myosin slide relative to each other b. sarcomeres slide relative to each other c. troponin and tropomyosin slide relative to each other d. muscle fibers slide past each otherarrow_forward
- The______ is the basic unit of contraction. a. osteoblast c. myofibril b. sarcomere d. myosin filamentarrow_forwardWhat role (function) does calcium have within a muscle fiber? a. trigger muscle potentials along t-tubules b. trigger contraction by causing the formation of cross bridges c. trigger exocytosis of ACh across the synaptic space d. trigger action potentials along axons e. open voltage gates within the sarcoplasmic reticulum 2. Which of the following are regulatory proteins that allow a muscle fiber to contract when calcium is present? (select all that apply) dystrophin troponin myosin tropomyosin actin 3. During this phase of an action potential, potassium ions exit the cell through voltage gated potassium channels. a. depolarization b. repolarization c. glycolysis d. cross bridge formationarrow_forwardMovement of sarcomeres is dependent upon the motor protein ______ attached to and moving along _______ . Select one: a. Myosin, actin b. ATP, actin c. Microtubulin, actin d. Myosin, microtubules e. Dynein, ATP Clear my choicearrow_forward
- Skeletal muscle cells are a. large multinucleate cells that arise by growth. b. large multinucleate cells that arise by fusion of smaller cells. C. small cells connected by many gap junctions. d. large cells with a single nucleus.arrow_forwardThe functions of tropomyosin in skeletal muscle include A. releasing calcium ions after initiation of contraction. B. generating ATP which it passes to the contractile mechanism. C. binding to myosin during contraction. D. acting as a relaxing protein at rest by covering up the sites where myosin binds to actin. E. sliding on actin to produce shortening.arrow_forwardMuscle relaxation occurs when ________. a. calcium ions are actively transported out of the sarcoplasmic reticulum b. calcium ions diffuse out of the sarcoplasmic reticulum c. calcium ions are actively transported into the sarcoplasmic reticulum d. calcium ions diffuse into the sarcoplasmic reticulumarrow_forward
- 1. Calcium triggers the contraction of a muscle fiber. Where in the muscle fiber is this calcium stored? A. nucleus B. calcium vesicles C. sarcoplasmic reticulum D. Golgi apparatus E. mitochondriaarrow_forwardWhich of the following statements are true of the neuromuscular junction? (Read carefully and select all the correct statements.) A. A synapse is the space between two muscle fibers. B. Acetylcholine is released from vesicles in the sarcolemma. C. The axon terminal is the end of a sensory neuron. D. Acetylcholine makes the sarcolemma more permeable to calcium ions. E. Cholinesterase is an enzyme that destroys acetylcholine so that the impulse will continue at the same strength. F. The receptors for acetylcholine are in the sarcolemma.arrow_forwardWhat event causes a troponin-tropomyosin complex to regain its original shape in muscle relaxation? a. stimulation of ACh receptors b. diffusion of Na+ back into transverse tubules c. return of Ca2+ into the sarcoplasmic reticulum d. breaking of the bond with tropomyosinarrow_forward
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