PCAT Biology Reinforcement Test 2A Explanations

PCAT Biology Reinforcement Test 2A Explanations - BIOLOGY...

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1 BIOLOGY REINFORCEMENT TEST 2A EXPLANATIONS 1. A A sharp peak in LH levels precedes ovulation; in fact, this “LH surge” is the event that causes ovulation. Choices B and C are incorrect because a decrease in both progesterone and estrogen secretion precedes menstruation, not ovulation. Choice D is incorrect because a decrease in LH and FSH occurs during the luteal phase, which takes place AFTER ovulation. 2. D The primary function of a Schwann cell is to myelinate axons only. Myelin, a layer of fatty material that surrounds a neuron’s axon, increases the rate of impulse conduction along the axon. Schwann cells are present only in the peripheral nervous system; within the central nervous system (brain and spinal cord), similar cells called oligodendrocytes fulfill the same purpose. Choices B and C are incorrect because Schwann cells myelinate axons ONLY; they don’t myelinate dendrites. Choice A is incorrect because myelination does not concern the cell body, only the axon. 3. B The parasympathetic division of the nervous system is responsible for functions that maintain and return the body to a constant state. A mnemonic for remembering parasympathetic function is that it is responsible for “resting and digesting.” Some examples of body functions for which the parasympathetic system is responsible are increased digestive activities, decreased heartbeat, and vasoconstriction of skeletal blood vessels. Choices A, C, and D are incorrect because stimulating the heart, decreasing gastrointestinal activity, and vasodilating blood vessels in the skeletal system are functions of the sympathetic nervous system. The sympathetic nervous system is responsible for innervating the “fight or flight” response. 4. A During force filtration in the nephron, arterial blood is pushed through the glomerular capillaries by the force of hydrostatic pressure. Blood pressure forces 20% of the blood plasma entering the glomerulus into the surrounding Bowman’s capsule. The fluid and small solutes entering the nephron are called the filtrate. Molecules too large to filter through the glomerulus or those repulsed by the filter’s negative charge (e.g., blood cells and albumin) remain in the circulatory system. Choice C is incorrect because reabsorption is the process by which substances are taken back into the body from the filtrate. Choice B is incorrect because secretion is the process by which material is produced and released from inside a cell where it is made. Choice D is incorrect because excretion only applies if the substance appears in the final urine. 5. B In a normal nephron, the majority of amino acids, sodium, chloride, water, and glucose in the filtrate is reabsorbed back into the body from the proximal convoluted tubule. Thus, if the proximal
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Kaplan PCAT Biology Reinforcement Test 2A Explanations 2 convoluted tubule is not functioning properly, the urine will exhibit an elevated glucose level. Thus, choice B is correct. In the nephron, glucose is ONLY reabsorbed from the proximal convoluted tubule.
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This note was uploaded on 09/21/2011 for the course BIOLOGY PCAT taught by Professor Mcfadden during the Spring '11 term at Kaplan University.

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PCAT Biology Reinforcement Test 2A Explanations - BIOLOGY...

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