Locomotion: movement types, muscle contraction
- Which of the following statements are correct regarding skeletal muscle?A. Muscle bundles are held together by collagenous connective tissue layer called fascicle.B. Sarcoplasmic reticulum of muscle fibre is a store house of calcium ions.C. Striated… Answer: 3. B and C only Key idea: Check each statement on skeletal muscle. A is wrong: the layer of collagenous connective tissue around bun... 1
- During muscular contraction which of the following events occur ?(a) ‘H’ zone disappears(b) ‘A’ band widens(c) ‘I’ band reduces in width(d) Myosine hydrolyzes ATP, releasing the ADP and Pi(e) Z-lines attached to actins are pulled inwardsChoose the co… Answer: 1. (a), (c), (d), (e) only During contraction, thin filaments slide over thick ones. (a) H zone disappears - true. (b) A band widens... 1
- Which of the following statements wrongly represents the nature of smooth muscle ? Answer: 3. Communication among the cells is performed by intercalated discs Smooth muscles are unstriated, involuntary and found in walls of... 1
- Which of the following muscular disorders is inherited ? Answer: 2. Muscular dystrophy Muscular dystrophy is a genetic (X-linked) disorder causing progressive degeneration of skeletal muscle. Tetan... 1
- Calcium is important in skeletal muscle contraction because it Answer: 1. binds to troponin to remove the masking of active sites on actin for myosin. Key idea: Ca²⁺ triggers muscle contraction. Calcium... 1
- Name the ion responsible for unmasking of active sites for myosin for cross-bridge activity during muscle contraction. Answer: 4. Calcium When a nerve signal reaches the muscle, Ca²⁺ is released from the sarcoplasmic reticulum. Ca²⁺ binds to troponin on the t... 1
- It is much easier for a small animal to run uphill than for a large animal, because : Answer: 2. Smaller animals have a higher metabolic rate. Smaller animals have a larger surface area to volume ratio and so a higher metaboli... 1
- Lack of relaxation between successive stimuli in sustained muscle contraction is known as : Answer: 3. Tetanus Sustained contraction caused by rapid successive stimuli, with no time to relax between them, is tetanus. Spasm: sudden i... 1