39. What is the primary function of the transverse tubules?
(A)Form cross-bridges between actin and myosin during muscle contraction.
(B)Attach troponin to tropomyosin.
(C) Attach muscle fibers to skeletal elements to exert force.
(D)Conduct action potentials from the surface of muscle fiber to internal regions near myofibrils.
(E)Act as a channel for Ca²⁺ ions during excitation-contraction coupling.

35. Which of the following is an example of positive feedback control in homeostasis? (A)During the birth process, stretch receptors in the uterus stimulate the release of oxytocin from the pituitary gland. This hormone stimulates uterine muscle contraction that increases stimulation of the stretch receptors. (B)Blood volume and pressure drop due to bleeding. This decreased pressure causes the kidneys to increase water reabsorption to increase blood volume and pressure. (C) Glucose levels rise following consumption of a big dessert, triggering release of insulin which causes glucose levels to fall. (D)Blood levels of glucose fall during sustained exercise, causing the release of glucagon which stimulates the release of glucose into the blood.

36. The sodium-potassium pump of neurons pumps (A)Na+ and K+ out of the cell. (B)Na+ and K+ into the cell. (C) Na+ into the cell and K+ out of the cell. (D)Na+ out of the cell and K+ into the cell.

37. Which of the following are not important in chemical synapses? (A)gap junctions(B)secretory vesicles(C)neurotransmitters(D)specific neurotransmitter receptors (E)voltage-gated Ca2+ channels 

38. You turn on the shower and check the water temperature with your hand. Your brain is able to monitor increasing temperature because the thermosensitive neurons in your skin (A)gradually adapt to the stimulus. (B)transmit action potentials to different brain regions. (C) transmit bigger action potentials to the brain when the water warms up. (D)transmit action potentials at a greater rate when the water warms up.

40. Which of the following is not a reason respiration in water is challenging? (A)Water is very dense relative to air. (B)Water holds relatively little oxygen compared to air. (C) Water moving over thin respiratory epithelial surfaces can create osmotic challenges. (D)Dessication of respiratory surfaces is a significant problem.

41. Diving mammals like whales and seals experience frequent periods when they are not able to breathe air. Which of the following is a muscle adaptation they show to this challenge? (A)increased capillary densities (B)increased myoglobin concentrations (C) increased amounts of sarcoplasmic reticulum (D)increased expression of acetylcholine receptors

42. Consider a tadpole becoming a toad. You would expect to find it changing its form of nitrogenous waste from ______ to______. (A)ammonia, urea(B)urea, ammonia(C)urea, uric acid(D)uric acid, urea(E)uric acid, ammonia

43. All of the following are functions of the mammalian kidney except (A)water retention(B)filtration of blood(C)excretion of nitrogenous waste(D)regulation of salt balance in the blood (E)production of urea

44. Which of the following has both endocrine and exocrine activity? (A)the pituitary gland(B)parathyroid glands(C)salivary glands(D)the pancreas(E)adrenal glands

45. Sexual reproduction (A)only occurs in vertebrates. (B)allows more offspring to be produced per individual. (C) allows a parent to pass on 100% of their genes to offspring. (D)increases genetic variation.