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Name: __________________________ Biology 449 - Animal Physiology Spring 2007 Midterm 2 – Key Fill in your scantron form as follows: Write and bubble in your name in the upper left (last name first). Follow any additional instructions provided in class. Sign your form on the upper right. By so doing you verify that you are abiding by Creighton’s policy on academic honesty. Multiple choice: As always, choose the best answer for each multiple-choice question. Answer on your scantron form. Each question is worth 3 points. 1. Paracrine agents reach their target cells via a. b. c. d. e. diffusion transport in vesicles. transport in the bloodstream. transport in the lymph. transport through ducts. 2. In which chemical category do most known hormones fall? a. b. c. d. e. Amines Glycoproteins Peptide hormones Prostaglandins Steroid hormones 3. Which of the following mechanisms can change the amount of hormone being released by a gland? a. b. c. d. e. Changes in the action potential frequency in neurons that innervate the gland. Changes in the levels of a tropic hormone that affects the gland. Detection by the gland itself of changes in the internal environment. Two of the above. All of the above. 4. The main response to cortisol (in natural animal populations) could best be described as helping to ensure that an animal a. b. c. d. e. can keep fueling cellular activity when it may have limited access to food. deposits large fat stores in case future access to food is limited. has increased its metabolic rate to a level that can support increased activity. has adequate blood flow to essential tissues when faced with dangerous conditions. does not get infected with a pathogen when it can least afford it. 1 5. Given what you know about thyroid hormones, which of the following is the most likely mechanism by which they help increase Na+/K+-ATPase activity? a. The hormones bind to and activate Na+/K+-ATPases already present in the cell membrane. b. The hormones activate G-protein complexes that directly activate Na+/K+-ATPases already present in the cell membrane. c. The hormones activate G-protein complexes that activate secondary messengers that activate Na+/K+-ATPases already present in the cell membrane. d. The hormones activate G-protein complexes that activate secondary messengers that promote the insertion of stored Na+/K+-ATPase into the cell membrane. e. The hormones cause the increased production of mRNA for Na+/K+-ATPase, which leads to the production and insertion of additional ATPase. 6. Which of the following terms best describes the general changes or activities promoted by growth hormone? a. b. c. d. e. Increased metabolic rate Decreased metabolic rate Increased catabolic activity Increased anabolic activity Increased sex hormone levels 7. In muscle fibers, the myofibrils are composed of the main functional units of contraction. These units are known as a. b. c. d. e. sarcolemmas. sarcomeres. sarcoplasms. sarcoplasmic reticuli. sarcotrons. 8. Cross-bridge cycling in muscles involves a. reversible binding between actin and myosin, and changes in conformation of the myosin. b. reversible binding between actin and myosin, and changes in conformation of the actin. c. reversible binding between myosin and tropomyosin, and changes in conformation of the myosin. d. reversible binding between myosin and tropomyosin, and changes in conformation of the tropomyosin. e. mysterious forces beyond the power of humankind to understand. 2 9. The dihydropyridine receptors in the T-tubules of skeletal muscle active ryanodine receptors as part of the process triggering muscular contraction. The dihydropyridine receptors themselves are triggered by a. b. c. d. e. neurotransmitter molecules. changes in the diameter of the T-tubules. changes in membrane potential. the presence of Ca2+. the absence of Ca2+. 10. In general, the heavier the load a muscle is lifting during a twitch contraction a. b. c. d. e. the less time it is able to lift the load. the more slowly it lifts the load. the less distance it lifts the load. Two of the above. All of the above. 11. In comparison to slow oxidative muscle fibers, fast glycolytic muscle fibers tend to have a. b. c. d. e. higher capillary density. slower rates of fatigue. more glycogen (the stored form of glucose). more mitochondria. more myoglobin. 12. To control the amount of sustained force they produce, muscles rely on a. b. c. d. e. the partial activation of each muscle fiber. alternation between twitch and tetanic contractions. opposing forces produced by antagonistic muscles. activation of only some muscle fibers in the muscle. reduced delivery of fuel to muscle fibers. 13. The blood vessels that experience the highest pressure are the a. b. c. d. e. systemic arteries. systemic arterioles. pulmonary arteries. pulmonary arterioles. capillaries. 3 14. Action potentials in the sinoatrial node of the heart would not occur without a. b. c. d. e. stimulation by the sympathetic nervous system. stimulation by the endocrine system. stimulation by action potentials that are triggered by the atrioventricular node. stimulation by action potentials from stretch receptors in the heart wall. The sinoatrial node depolarizes spontaneously, without the need for external stimulation. 15. Starling’s Law of the Heart states that a. b. c. d. e. The heart beats more quickly in response to decreased ventricular filling. The heart beats more quickly in response to increased ventricular filling. The heart ejects more blood in response to decreased ventricular filling. The heart ejects more blood in response to increased ventricular filling. If you hear a starling sing under a full moon, you are destined to meet your true love. 16. If the arterioles leading to the gastrointestinal tract were to dilate, which of the following patterns would you most likely see as a result? a. Increased bloodflow to the GI tract, and increased cardiac output and/or increased vasoconstriction elsewhere. b. Increased bloodflow to the GI tract, and decreased cardiac output and/or decreased vasoconstriction elsewhere. c. Decreased bloodflow to the GI tract, and increased cardiac output and/or increased vasoconstriction elsewhere. d. Decreased bloodflow to the GI tract, and decreased cardiac output and/or decreased vasoconstriction elsewhere. e. You would probably start vomiting up blood. 17. Which of the following substances can diffuse straight through the cell membranes of the capillaries’ endothelium? a. b. c. d. e. glucose Na+ proteins oxygen None of the above can diffuse straight through the endothelial membranes. 18. What happens to the lymph formed by leakage from the circulatory system? a. b. c. d. e. It remains in the interstitial space. It is excreted by the kidneys. It is exuded from the skin as sweat. It leaks back into the circulatory system through the walls of the venules. It is returned to the circulatory system through a separate set of vessels. 4 19. At resting levels of ventilation, which of the following best describes what drives inhalation? a. b. c. d. e. Contraction of the external intercostal muscles. Contraction of the internal intercostal muscles. Contraction of the diaphragm. Relaxation of the diaphragm. Two of the above. 20. As inhalation proceeds, the intrapleural pressure a. b. c. d. e. becomes more negative. becomes less negative. reaches zero. becomes positive. stays constant. Short answer: Write a concise answer to each of the following questions. Your answers should fit in the spaces provided. Diagrams may be used but must be accompanied by written explanations. Each question is worth 8 points. 21. Complete the following table for the hypothalamic-pituitary system by filling in the blanks with the appropriate hormones. Be sure to provide the full name of each hormone, not the abbreviation. Hypothalamus Target Organ or Tissue and Effects Anterior Pituitary Corticotropin releasing h. → Adrenocorticotropic h. → Adrenal cortex Cortisol release Thyrotropin releasing h. → Thyroid stimulating h. → Thyroid hormone gland T3/T4 release Prolactin releasing h. → Prolactin → Breasts Development, milk production Growth h. releasing h. → Growth h. → General body tissues Growth and repair Liver IGF-1 release 5 22. Consider a twitch versus a tetanic isometric contraction and answer the following: a. What is the trigger or signal that causes a muscle to contract in a twitch versus tetanic manner? Twitch contractions are triggered by a single action potential. Tetanic contractions are triggered by a rapid train of action potentials. b. What is the difference in the contraction of a twitch versus tetanus? You are welcome to use a figure to illustrate your answer, but be sure to explain the pattern as well. Twitch contractions show relatively short force production, which increases and then decreases. In tetanic contractions, there is summation or “fusion” of force production, resulting in a smooth increase in force to a higher values (3-6 twitch) which can then be maintained, at least until fatigue occurs. c. Given what you know about how contraction is controlled, what is occurring inside the muscle cells that cause the differences you described in “b” above? This question obviously requires speculation, but within the muscle the main change is that calcium is present for a greater period of time under the influence of continuous action potentials. Continued “saturation” of the myofibril with Ca2+ allows for greater crossbridge formation between actin and myosin, and hence greater force production 23. The following questions relate to anatomical dead space (ADS) and pulmonary ventilation. a. What physical structures make up the ADS? This is the conductive zone: mouth or nose, pharynx, larynx, trachea, bronchi, and bronchioles. b. In a person with an ADS of 150 ml who is breathing by taking breaths of 550 ml at a rate of 10 breaths per minute, what is the person’s Tidal volume: Simply the 550ml breath size Alveolar ventilation rate: (TV-ADS)VF = (550ml – 150ml) 10/min = 4000ml/min Minute ventilation: TVVF = 550ml 10/min = 5500ml/min 6 24. Describe the three pathways or mechanisms that help to control arteriole diameter. Be clear about whether diameter is increased or decreased in each example. Two external control mechanisms: Sympathetic nervous system: Increased sympathetic stimulation causes increased vasoconstriction; decreased stimulation causes decreased vasoconstriction. Endocrine control: Epinephrine causes vasoconstriction in most arterioles, but vasodilation in skeletal muscle and heart. (Other hormones, like ADH and angiotensin II, can also cause vasoconstriction.) Local control: Active hyperemia occurs in response to low O2 and high CO2 and H+ levels within tissues. These factors cause the arteriole’s endothelium to release nitric oxide, which diffuses to the smooth muscle, triggering relaxation and hence vasodilation. 25. Describe the mechanical events that occur in the heart during ventricular diastole. Your discussion should cover pressure and flow of blood and valve activity, and should explain how these events are related. You do not need to discuss pacemakers, AP’s, etc. At the end of systole the atrioventricular valves are closed and the semilunar valves are open. Diastole represents ventricular relaxation, and as soon as this starts the pressure in the ventricle starts to drop. Once PV drops below Part, the SV valves close. Isovolemic relaxation follows, meaning no blood enters or leaves the ventricles, until PV drops below PAtr and the AV valves open. Once these valves open, blood enters the ventricles after passing through the atria from the venous system, which has a small pressure head relative to the ventricles. At the end of ventricular diastole, atrial contraction occurs, driving additional blood into the ventricles. 7