SEHH2233 Human Biology I Tutorial Answer Keys (Ch7 Muscular system) 2023-2024 Sem I PDF

SEHH2233 Human Biology I Tutorial Answer Keys (Ch7 Muscular system） 2023-2024 Sem I Section A Revision on Ch 6 and 7 True or False Question （Amend the false statements to make them true.） 1. fourteen =》twelve 2. sternum => scapulae...

SEHH2233 Human Biology I Tutorial Answer Keys (Ch7 Muscular system） 2023-2024 Sem I Section A Revision on Ch 6 and 7 True or False Question （Amend the false statements to make them true.） 1. fourteen =》twelve 2. sternum => scapulae 3. 11 & 12 => 1 to 7 4. synovial => fibrous/ synarthrosis Section B Ch7 The Muscular System I. Multiple-choice questions 1A 2D 3A 4C 5A 6A 7D 8B 9D 10C 11B 12D II. Study the diagram of a muscle fiber on the right and answers the following questions 1B 2A 3D 4C III Fill in the cells of the table - Energy for Muscle Contraction A. glycolysis B. very fast C. very slow D. very limited E. unlimited IV True / False Questions (Question with * is more challenging.) 1. TRUE 2. TRUE 3. FALSE During muscle contraction, calcium ions combine with tropomyosin troponin, and this exposes active sites for cross-bridge formation. 4. TRUE 5. FALSE The anaerobic aerobic phase of respiration occurs primarily in mitochondria. 6. FALSE Liver cells convert lactic acid to ATP glucose. 7. TRUE 8. FALSE The latent period is the time when the muscle is relaxed. stimulated but not yet contract. 9. FALSE *White Red muscles have an increased capacity to carry on aerobic respiration 10. TRUE 11. FALSE A neurotransmitter substance crosses the synaptic cleft between a nerve and muscle fiber, and stimulates the nerve to have an action potential muscle fiber to contract. 12. FALSE Motor unit recruitment refers to the fact that some motor neurons can recruit new more skeletal muscle fibers with which they connect. 13. TRUE Page 1 of 3 SEHH2233 Human Biology I Tutorial Answer Keys (Ch7 Muscular system） V Fill in the blanks 1. lactic acid 2. myoglobin 3. lactic acid 4. tetanic contraction 5. acetylcholine 6. peristalsis 7. synergists 8. summation 9. intercalated disks Section C Short Questions 1. Describe a neuromuscular junction. Each skeletal muscle fiber is connected to a fiber from a nerve cell called a motor neuron. The muscle fiber contracts only when stimulated by this specific fiber. At the connection point between the nerve fiber and the muscle fiber, the muscle fiber’s sarcolemma is tightly coiled and heavily concentrated with mitochondria. This region is known as the motor end plate. The branches of the motor nerve fiber project into recesses (synaptic clefts) of the motor end plates and the distal ends are filled with mitochondria and synaptic vesicles that store chemicals called neurotransmitters. This entire region is known as a neuromuscular junction. 2. Describe how an oxygen debt may develop. When skeletal muscles have been used where they have exceeded their oxygen reserves, anaerobic respiration must take over. Anaerobic respiration changes glucose into pyruvic acid, and due to the lack of oxygen, the pyruvic acid is converted into lactic acid. The lactic acid diffuses out of the muscles and is taken to the liver by the blood. The liver can change lactic acidback into glucose: however, this conversion also requires the use of ATP. During strenuous exercise, primarily the muscles and not the liver use the oxygen, so the lactic acid accumulates. Oxygen debt then, is defined as the amount of oxygen needed by the liver to convert the lactic acid back into glucose, plus the amount needed by the muscles to resynthesize ATP and creatine phosphate and return them to their original concentrations. Because the conversion of lactic acid into glucose is a slow process, it may take several hours to repay the oxygen debt. 3. Explain how muscles may become fatigued and how a person’s physical condition may affect tolerance to fatigue. If a muscle is exercised strenuously for a long period, it may lose its ability to contract. This is called muscle fatigue. This condition may result from an interruption in a muscle’s blood supply or from the depletion of acetylcholine in the motor nerve fibers. The most common cause of muscle fatigue is due to the accumulation of lactic acid from anaerobic respiration. The lactic acid causes factors, such as pH, to change so that the muscle fibers no longer respond. Page 2 of 3 SEHH2233 Human Biology I Tutorial Answer Keys (Ch7 Muscular system） Occasionally, a muscle becomes fatigued and develops a cramp simultaneously. A cramp is a painful condition in which the muscle contracts spasmodically, but does not completely relax. This may be caused by a lack of ATP. A person who exercises can stimulate new capillaries to grow within the muscles, supplying more oxygen and nutrients to the muscle fibers. This will allow more aerobic respiration to take place, thereby decreasing dependence on anaerobic respiration, which results in less lactic acid buildup. 4. Explain how a skeletal muscle can be stimulated to produce a sustained contraction. If a muscle is exposed to a series of stimuli increasing in frequency, a point is reached where the muscle is unable to complete its relaxation period before the next stimulus arrives. This stacking of twitches causes a sustained contraction. Section D Critical Thinking Questions 1. Warm-ups improve athletic performance by increasing body temperature. The majority of the benefits of warm-up are related to temperature-dependent physiological processes. An elevation in body temperature produces an increase in the dissociation of oxygen from haemoglobin and myoglobin, a lowering of the activation energy rates of metabolic chemical reactions, an increase in muscle blood flow, an increase in the sensitivity of nerve receptors, and an increase in the speed of nervous impulses. Warm-up also appears to reduce the incidence and likelihood of sports-related musculoskeletal injuries as it may help to improve flexibility of joints. Reference: Shellock FG, Prentice WE. (1985) Warming-up and stretching for improved physical performance and prevention of sports-related injuries. Sports Med:2(4):267-78. Page 3 of 3