SECOND MIDTERM EXAM November 15, 2011 BILD 2. Nasha 10. (10 points) Josh 2. (10 points) Josh 3. (10 points) Mary 4. (5 points) 8.

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1 SECOND MIDTERM EXAM November 15, 2011 BILD 2 WRITE YOUR NAME ON ALL 7 PAGES. ANSWER ALL 10 QUESTIONS (100 POINTS). CONFINE YOUR ANSWERS TO THE SPACE ALLOWED. If you would like to write on the back of the exam ask to have a TA initial that page. Pen or Pencil is acceptable, but answers must be legible to be corrected. Pen is required for a regrade submission. Answer only the exact questions asked, but provide all the detail possible in those cases (be sure to use the correct vocabulary, describing by name the key players, structures, and processes). Nasha 1. (10 points) Josh 2. (10 points) Josh 3. (10 points) Mary 4. (5 points) Sam 5. (10 points) Kaivan 6. (10 points) Hien 7. (10 points) Aivi 8. (10 points) Mary 9. (15 points) Nasha 10. (10 points) 100 total TOTAL POINTS By signing this waiver I give permission for this exam to be left for me to pick up in the boxes outside the elevators on the third floor of Pacific Hall. I realize that this procedure may expose my grade to public scrutiny. If I do not sign this waiver, I acknowledge that my exam will be available for pick up only between 8:00 and 11:00 AM, Monday-Friday in 3100E Pacific Hall. Signature Date 1 P age

2 Question 1 (10 points). Define the two components of gastric juice that carry out chemical digestion. Where are they produced, what is their role in digestion, and why don t they destroy the stomach cells that make them? Hydrochloric acid (HCL) and Pepsin carry out chemical digestion that beigns in the lumen of the stomach. HCL is a strong acid that kills most bacteria and denatures proteins. Pepsin is a protease that cleaves proteins into smaller polypeptides (or unfolds proteins). Despite their role in digestion they do not destroy stomach cells because they are made from inactive building blocks that are first secreted into the stomach lumen where they are subsequently made or activated. Parietal cells secrete hydrogen and chloride ions, which form HCL in the lumen. Chief cells secrete pepsinogen, the inactive form of pepsin. HCL acid or already active pepsin can cleave pepsinogen to expose its active site to make pepsin. The stomach cells are further protected by mucus secreted by mucus cells. Question 2 (10 points). a) Describe the essential role of ATP in muscle contraction. Muscle contraction occurs when myosin filaments (thick filament) pulls the adjacent actin filaments (thin filament) toward the middle of the sacromere, causing it to shorten. This process depends on ATP. When ATP is bound to a myosin head it hydrolyzes the ATP to change into a high energy state allowing the myosin head to bind to actin and form a cross-bridge. The shift back to a low energy state causes the shape of the myosin head to change and pulls the actin filament forward. ATP is needed to start a new cycle. b) What other regulated factor must be present in a muscle fiber in order for muscle contraction to take place? Calcium ions (CA2+) c) What event regulates the availability of the factor you listed in (b)? Action potential from a motor neuron results in the release of Ca2+ into the cytosol of the muscle fiber. 2 P age

3 Question 3. (10 points) Briefly define or identify each of the following: a) Motor Unit: A single motor neuron and all the muscle fibers it controls. b) Cecum: Component of the large intestine important for fermenting ingested food. More developed in animals that eat large amounts of plant material. c) Residual Volume: Oxygen depleted air that remains in the lungs after a forced exhalation. d) Stroke Volume: The amount of blood pumped by a ventricle in a single contraction. e) Tetanus: A smooth sustained muscle contraction that is a sum of many muscle twitches. Question 4 (5 points). Describe how the same hormone can elicit different responses from multiple target cells (provide at least two explanations). (two of the following) Target cells may have different receptors that bind the same hormone. The hormone may bind to receptors that elicit different signal transduction pathways with in the target cells. If different signal transduction pathways are induced then different proteins will be targeted to carryout the response in the target cell. 3 P age

4 Question 5 (10 Points). a) List the primary function of parathyroid hormone (PTH). Describe the stimulus that would result in increased levels of PTH in the blood and the source of this hormone. PTH works to regulate blood calcium levels in mammalian blood. When blood calcium levels fall below 10 mg/100 ml the parathyroid gland releases PTH hormone. b) Define two direct and one indirect target of parathyroid hormone and list a response elicited from each in the presence of the hormone. Direct targets 1) Kidneys: reabsorption of Ca2+ from filtrate. 2) Bones: stimulates release of Ca2+ from decomposition of bone material Indirect target intestines are final target through PTH interacts in the liver which activate vitamin D: increases Ca2+ uptake during absorption in intestines. c) Do the responses listed in (b) exert negative or positive feedback on the initial stimulus? Negative feedback d) Name an antagonistic hormone to PTH. Which endocrine structure produces this hormone? Calcitonin, produced by the thyroid gland Question 6 (10 Points). How does protein entering the esophagus after ingestion end up as amino acids in the blood? (Be sure to list the sites where digestion and absorption take place as well as three critical digestive enzymes in the process). Chemical digestion of proteins begins in the stomach. The first digestive enzyme, pepsin, breaks down protein to smaller polypeptids in the lumen of the stomach. Stomach chyme is released to the small intestines where trypsin, chymotrypsin, and carboxypeptidase (produced by the pancreas) break polypeptides down further in the lumen of the small intestines. Epithelial cells of the villus in the small intestine actively transport amino acids and small peptides across their cell membrane, into the interstitial fluid and finally into local blood capillaries. 4 P age

5 Question 7 (10 points). For each hormone listed below: (1) define where it is produced, (2) what stimulus triggered the production, (3) one target site of action, and (4) an elicited response. a) Gastrin: Stimulus: bolus arrives to stomach, Produced: stomach, Target: stomach, response: stimulates production of gastric juices. b) Leptin: Stimulus: body fat increases, Produced: adipose cells, Target: hypothalmus, Response: suppresses appetite. c) Thyroid-stimulating hormone (TSH): Stimulus: High levels of thyrotropin-releasing hormone (TRH) in the blood, Produced: anterior pituitary, Target: thyroid gland, Response: production of thyroid hormone. d) Glucagon: Stimulus: blood glucose levels below 90 mg/100ml, Produced: Alpha cells of the pancreas, Target: Liver, Response: breaks down glycogen and releases glucose in blood. e) Oxytocin: Stimulus: suckling infant, Produced: hypothalamus, Target: mammary glands, Response: milk release. Question 8 (10 points). Explain why birds can function better than humans at high altitude. Be sure to indicate differences in anatomy that explain your reasoning. [This is a question about respiration and meeting gas exchange demands, not about modes of locomotion and movement] The maximum PO2 in the lungs is higher in birds than mammals as air is always renewed with every exhalation. Gas exchange in mammals occurs at alveoli, which are a dead end of the branching ducts in the lungs. Residual volume causes deoxygenate air to mix with fresh air decreasing the O2 available for gas exchange. Birds move air through the lungs in one direction using air sacs. The parabronchi (site of gas exchange in birds) continually receives fresh oxygenated air that does not mix with residual air as in mammals (therefore higher O2 content). At high altitudes, where the air is composed of less O2, the bird is able to exchange more O2 than mammals as a result of these anatomical differences. 5 P age

6 Question 9 (15 points). a) Label the anatomy of the mammalian cardiovascular system as indicated (10 sites), then proceed to parts (b) and (c) listed below. A) See figure 42.6 in both text versions. b) Which structure listed above is responsible for establishing systolic and diastolic pressure in the systemic arteries? Left Ventricle (#9) c) The pacemaker of the heart is located in which structure listed above? What is the name of this pacemaker and describe the first response of the heart after electrical impulses are generated from this site. Right Atrium (#3) Sinoatrial node (SA node) Electrical impulses from the SA node spread rapidly through heart tissue and cause both atria to contract together in unison. 6 P age

7 Question 10 (10 points). a) What two hormones are made by the adrenal medulla? Epinephrine and norepinephrine b) How does stress result in the release of the hormones listed in (a)? Stress causes the hypothalamus to send action potentials that target the adrenal medulla. At the response of the nerve signals the adrenal medulla releases the hormones into the blood stream. c) How does control of hormone release differ for adrenal medulla versus adrenal cortex? Stressful stimuli causes the hypothalamus to activate the adrenal medulla via nerve impulses. The adrenal cortex is activated indirectly through hormonal signals. In this case the hypothalamus producing releasing hormones that cause the anterior pituitary to release ACTH (adrenocorticotrophic hormone). ACTH in the blood targets the adrenal cortex which responds by releasing corticosteroids. END 7 P age