Concept explainers
To analyze:
The meaning of the statement “a whole muscle responds to a stimuli in graded fashion” and the two ways to increase the force of contraction.
Introduction:
The muscular system is the set of muscles that are present in the body adhered to the skeletal system. The muscles are divided into several types, namely cardiac muscles which are involuntary, smooth muscles and skeletal muscles which are voluntary. The muscles of the body help in the body's movement, circulate blood through the body and helps in maintaining the posture of the body. The skeletal muscle fibers and the motor neuron collectively form the motor unit. A single muscle contraction can be due to the result of the working of several motor units together.
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SEELEY'S ANATOMY+PHYSIOLOGY
- How do actin and myosin interact in a sarcomere to bring about muscle contraction? What roles do ATP and calcium play?arrow_forwardOne of the primary characteristics of all muscle tissue is contractility, the ability to shorten (contract) and lengthen (relax). You've identified the various components of a myofibril above. Now, use the table below to indicate what occurs to each band, line, or zone when the muscle contracts vs. relaxes. What occurs to this region / structure during contraction/relaxation? Region / Structure A-Band H-Band I-Band M-Line Z-Line Zone of Overlap Sarcomere No change Shortens Lengthens Muscle Contraction Muscle Relaxationarrow_forwardSkeletal muscle is described as striated. What are the lighter, thinner stripes noted under the microscope? Group of answer choices troponin actin myosin dystrophin Rather than innervating individual muscle fibers, motor neurons often innervate two or more muscle fibers. The motor neuron and the muscle fibers it innervates are together called a: Group of answer choices motor unit myofibril muscle fascicle motor fascia Fast glycolytic muscle fibers allow for relatively quick ATP energy production by splitting glucose (but eventually leads to fatigue), a process described as: Group of answer choices fermentation aerobic pathway anaerobic pathway ATP reserve usearrow_forward
- What does it mean to say that a whole muscle respondsto stimuli in a graded fashion? What are the two ways toincrease the force of contraction?arrow_forwardIn an isometric contraction, how can the muscle stay the same length when the muscle is contracting? Can choose more than one - The muscle is not able to generate more (or the same amount) force than the load, preventing shortening of the muscle. - Calcium stops entering the sarcoplasm when the desired length is reached. - Elastic elements of the muscle stretch in response to the contraction of the muscle, so that the muscle stays the same size despite shortening sarcomeres. - The myosin heads detach from actin when they reach the desired length.arrow_forwardDescribe the relationship between the resting muscle length and the strength of its contraction. What is summation of subthreshold stimuli and what ion is involved? Describe the effect of increasing the intensity (voltage) of the stimulus while keeping the frequency constant? Define maximal stimulus.arrow_forward
- Distinguish between skeletal, smooth, and cardiac muscle in terms of location and whether they have sarcomeres. Use the sliding filament model to draw how thin filaments, thick filaments, and Z lines move during muscle contraction. Predict how perturbations of acetylcholine release, reception, or breakdown will influence muscle contraction. Predict how perturbations of actin, troponin, tropomyosin, myosin, or calcium would influence muscle contraction. Distinguish between the sympathetic and parasympathetic nervous system. Predict how changes in stress levels or situations would affect activation of the sympathetic and parasympathetic nervous system, levels of epinephrine and norepinephrine, and blood pressure.arrow_forwardWhat trend do you notice between force generation capability of a muscle and its cross-sectional area? If a muscle has a large cross-sectional area, then its force-producing potential is?arrow_forwardWhat is the steps in the Sliding Filament theory of muscle cell contraction in correct order? Including steps in depolarization and repolarization.arrow_forward
- How is muscle contraction stopped? Which of the following is/are correct? A) The brain stops sending the nerve impulse that commands the muscle to contract, interrupting communication at the neuromuscular junction B) Acetylcholineesterase (AChE) is released into the synaptic cleft to destroy any remaining Acetylcholine C) No mechanism is necessary. When the antagonist begins to contract, it forces relaxation and stretch of the agonist muscle. D) Relaxation occurs as the myosin heads are "snapped" off of the thick filaments. This interrupts the crossbridge and allows for muscles to stretch E) Relaxation only occurs if the brain sends a "stop" signal to the musclearrow_forwardIn light of the “all or none” law of muscle contraction, how can you explain twitch recruitment (also called the graded response) when stimulating the muscle versus stimulating the nerve? Explain the difference in stimulation voltage required to elicit a maximum response when stimulating the nerve versus the muscle directly?arrow_forwardIn normal skeletal muscle contraction, which of the following represents the correct sequence of events? 1. Action potential 2. Ca2+ release into cytoplasm 3. Interaction between actin and myosin filaments 4. Ca2+ is pumped back to cisterns 5. Depolarization of T tubules Answers A-F A 1-2-5-3-4 B C 1-4-5-3-2 1-5-2-3-4 D 5-1-2-3-4 E F 5-4-3-1-2 5-4-1-3-2 Oarrow_forward
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