supply other cells with the amino acids needed for protein synthesis.

Transcription

1 1. Fight or flight responses are a coordinated set of physiological changes that result in increased heart rate, breathing rate, and neuromuscular activity. The diagram below shows how a certain hormone, released during this response, affects a liver cell by causing it to rapidly release glucose into the bloodstream, preparing the body for immediate motion. The hormone affects nearly every cell in the body. Based on the information in the diagram, which statement describes how this hormone most likely affects the cells in a different organ? (A) The hormone stimulates heart cells to contract more rapidly in order to supply other cells with increased glucose and oxygen. This answer suggests the student understands that a hormone that increases the release of glucose in liver cells will increase the rate at which heart cells contract in order to supply the rest of the body with glucose and oxygen so that the body can move quickly when needed. (B) The hormone causes cells in the small intestine to absorb more nutrients in order to supply other cells with the amino acids needed for protein synthesis. This answer suggests the student may understand that nutrients are absorbed via cells in the small intestine, but does not understand that this hormone releases glucose to supply muscles and increases circulation and respiration to be able to move quickly, and that there is no data in the diagram concerning digestion, digestion would be impeded because digestion diverts blood away from systems that need it more. Page 1 of 7

2 (C) The hormone causes smooth muscle cells in the lungs to constrict in order to decrease the rate at which oxygen is exchanged with the environment. This answer suggests the student may understand that lung function requires the contraction of muscles but does not realize that the glucose will be used by the muscles to produce usable energy (ATP) and this will require an increase in oxygen exchange with the environment. (D) The hormone inhibits release of insulin from the pancreas which reduces the ability of the body cells to take in glucose. This answer suggests the student may understand that pancreatic cells release insulin and that insulin reduces blood glucose levels, but does not understand that this hormone prepares the body for immediate movement, and insulin is needed to encourage muscle cells to uptake glucose to use as fuel needed to do work to move the body quickly. 2. Human growth hormone (HGH) is produced in the pituitary gland and has many effects on the body. In children and adolescents, HGH signals the liver to release insulin-like growth factors (IGFs) into the blood, which stimulate bone and cartilage growth. In adults, HGH stimulates the release of fatty acids from fat tissue, stimulates the uptake of amino acids in cells, stimulates protein synthesis in cells, and directs cells to use fatty acids as an energy source during periods of fasting. The diagram below shows the organs targeted by HGH in the body. Page 2 of 7

3 Which statement predicts the most likely time when the pituitary gland would be stimulated to release HGH in an adult individual? (A) When the individual has eaten excess fat, because more fatty acids are available to use as an energy source This answer suggests the student may understand that HGH stimulates fat tissue to release fatty acids (metabolizes fat), but does not understand that the body does not release HGH just because abundant fatty acids are present, or that the body would release HGH when the body has an increased need for protein synthesis in cells. (B) During a period of rest after exercise, because the body must produce more proteins to repair damaged muscles This answer suggests the student understands that HGH will likely rise during a rest period after exercise because HGH stimulates cells to synthesize proteins, and proteins are used to repair damaged muscles. (C) When the individual s blood sugar levels are high, because cells are stimulated to use fatty acids as an energy source Page 3 of 7

4 This answer suggests the student may understand that HGH stimulates cells to use fatty acids rather than sugar for energy, but does not understand that HGH raises blood sugar by preventing cells from using sugar in the bloodstream, and would be produced when blood sugar levels are low, or during a time when the body has an increased need to synthesize proteins. (D) After eating a meal rich in protein, because the small intestine can absorb more amino acids and send them directly to cells This answer suggests the student may understand that meals rich in proteins are broken down into amino acids and absorbed by the small intestine, but does not understand that HGH would not be produced because there is an abundance of amino acids in the small intestine, and would be produced only when the body has an increased need to synthesize proteins. 3. Muscle contractions are produced by the interaction of actin and myosin filaments in response to the neurotransmitter acetylcholine (ACh). The nervous system regulates muscle contraction by controlling which motor units are stimulated as well as the rate at which the muscles are stimulated. If the motor neuron increases the rate of stimulation, the contractions add together. When the rate is so high that the muscle cannot relax between stimuli, the contractions fuse into one sustained contraction. Tetanus bacteria produce a toxin that affects the neuromuscular junction, the synapse between a motor neuron and the muscle it stimulates. When introduced into muscular tissue, the tetanus toxin increases the chemical signal from the nerve to the muscle so that ACh is continuously released by the motor neuron. Which statement best explains the effect of tetanus bacteria on muscle cells? (A) Muscle cells are unable to contract because binding sites for the actin and myosin filaments are occupied by ACh, and this results in permanent muscle paralysis. This answer suggests the student may understand that actin and myosin filaments are required for muscle contractions and that some types of paralysis are the result of noncontracting muscle cells, but does not understand that the presence of ACh would result in a prolonged muscle contraction. Page 4 of 7

5 (B) Muscle cells contract very slowly because there is not enough ATP available until the ACh is removed, and this results in delayed reflexes. This answer suggests the student may understand that ATP is required for muscle contractions and may delay reflexes, but does not understand that ATP production is unaffected by the tetanus toxin and that tetanus toxin results in longer muscle contractions and prolonged muscle spasms. (C) Muscle cells remain contracted for a longer period of time because actin and myosin filaments remain bound together until the ACh is removed, and this results in prolonged muscle spasms. This answer suggests the student understands that the tetanus toxin causes an extended release of ACh into the neuromuscular junction, and that the extended release of ACh results in longer muscle contractions and prolonged muscle spasms. (D) Muscle cells remain contracted because the motor neuron is prevented from sending another signal to the muscle while ACh is present in the synapse, and this results in delayed muscle movement. This answer suggests the student may understand that ACh is required for muscle contraction, but does not understand that the immediate response to ACh is a longer muscle contraction and prolonged muscle spasms. Page 5 of 7

6 4. Countercurrent flow is a physiological adaptation found in many animals. Two examples of countercurrent flow are found in fish gills and whale fins. Fish gills are made up of gill filaments, and the filaments are comprised of structures called lamella. The lamellas contain capillaries and are the site of gas exchange, as shown below in diagram 1. The countercurrent flow helps fish remove the maximum amount of oxygen from the water. Whales and sea lions in cold water have arteries and veins aligned in their fins to reduce heat loss to the environment, as shown below in diagram 2. Which changes could be made to these diagrams to best show the physiological advantage of the two countercurrent systems? (A) Diagram 1 could show the oxygen concentration in the capillaries slowly increasing from near 0% O 2 saturation as oxygen enters the capillaries to near 100% O 2 saturation as oxygen exits the capillaries. Diagram 2 could show the blood getting colder as it flows away from the body as heat is lost to the environment. This answer suggests the student may understand that blood increases in oxygen concentration as it passes through capillaries and blood loses heat to the environment as it moves toward the tip of a fin, but does not understand how countercurrent flow increases gas exchange and reduces heat loss. (B) Diagram 1 could show the oxygen concentration in the capillaries increasing while the water flowing over the lamella shows a steady decrease, which provides a concentration gradient for O 2 to move into the blood. Diagram 2 could show the blood flowing in the artery decreasing in temperature as the blood that is returning in the veins slowly increases due to heat exchange with the warmer blood in the arteries. Page 6 of 7

7 This answer suggests the student understands how countercurrent systems increase efficiency of gas exchange in fish gills and decrease heat loss in whale fins and knows that representing the concentration gradient and changes in temperatures are necessary to show the physiological advantage of countercurrent systems. (C) Diagram 1 could show the ph of the blood slowly increasing as the blood flows through the capillaries, because carbonic acid is being converted in CO 2 and diffuses out of the lamella. Diagram 2 could show that as the blood flows toward the tip of the fin, it loses heat to the environment and has a decrease in kinetic energy and velocity. This answer suggests the student may understand that movement of carbon dioxide into and out of the blood modifies ph and that lowering the temperature of a substance decreases kinetic energy, but does not understand that these processes are not related to countercurrent flow. (D) Diagram 1 could show the concentration of salt ions in the capillaries increasing in concentration while the water flowing over the lamella shows a steady decrease in salt ion concentration as salt ions diffuse through the lamella. Diagram 2 could show that when blood temperature gets too low, constriction of veins and arteries reduces blood to extremities and thereby reduces heat loss to the environment. This answer suggests the student may understand that movement of salt ions across gills may occur and that vasoconstriction of vessels in extremities reduces heat loss, but does not understand that these processes are not related to countercurrent flow. Page 7 of 7