Fourth Examination - KEY

Bios 201

December 3, 2003

Part I. Each multiple choice question is worth 3 points.

1. Which one of the following statements concerning arousal and orgasm is FALSE?

(__X__) a. Nitric oxide release causes smooth muscle contraction, leading to erection.

(_____) b. The parasympathetic nervous system mediates the early phase of arousal.

(_____) c. Return to the nonaroused state after orgasm (satiety) is correlated with a rise in the hormone prolactin.

(_____) d. The sympathetic nervous system increases heart rate and helps induce orgasm.

(_____) e. Contraction of the epididymis and vas deferens helps propel sperm forward during ejaculation.

2. Which one of the following is NOT a property of photoreceptor cells in the retina?

(_____) a. Generate contrast by regulating horizontal cells.

(__X__) b. Release more neurotransmitter in the light.

(_____) c. Have light-regulated G protein-coupled receptor.

(_____) d. Continuously make more photoreceptor protein to replace that damaged by light.

(_____) e. Fovea has many cone cells, few rod cells.

3. Which one of the following statements concerning mammalian fertilization is FALSE?

(_____) a. Both sperm and eggs have vesicles just under their plasma membrane.

(_____) b. Enzyme-induced changes in the extracellular matrix (the zona pellucida) of the egg permit or retard entry of sperm.

(__X__) c. Mammalian sperm and egg each have a single haploid nucleus.

(_____) d. Movement of sperm is facilitated by beating of its flagella; movement of the egg is facilitated by beating of cilia on epithelial cells of the fallopian tube.

(_____) e. Fusion of sperm with egg triggers a rise in intracellular Ca²⁺ in the egg.

4. Which one of the following pairs is INCORRECT?

(_____) a. hypothalamus - regulation of hunger and thirst

(_____) b. thalamus - input/output center for nerves entering/leaving cerebrum

(__X__) c. reticular formation - regulation of swallowing, vomiting, digestion

(_____) d. corpus callosum - communication between right and left cerebral hemispheres

(_____) e. boundary between frontal and parietal lobe of cerebrum - primary motor and somatosensory areas

5. Which one of the following statements concerning sensory reception is INCORRECT?

(__X__) a. Taste (gustatory) receptors each respond to just one specific molecule.

(_____) b. Receptors are used to sense electrical fields.

(_____) c. The muscle spindle senses the length (stretch) of a muscle.

(_____) d. Some pain receptors respond to heat, others to chemicals released by damaged tissue.

(_____) e. Touch receptors are found in modified dendrites of sensory neurons.

6. Which one of the following hormones is NOT properly paired with the response it induces (directly or indirectly)?

(_____) a. glucagon - increase in blood sugar

(__X__) b. ANF (atrial natriuretic factor) - increase in blood pressure

(_____) c. parathyroid hormone - increase in blood calcium

(_____) d. leptin - decrease in appetite

(_____) e. ACTH - increase in blood glucose

7. Which one of the following associations is FALSE?

(_____) a. long-term memory - hippocampus

(__X__) b. long-term depression - induced by repeated strong stimulation

(_____) c. short-term memory - frontal lobes of cortex

(_____) d. long-term potentiation - increase in glutamate receptors in hippocampus

(_____) e. memorization of phone numbers - rapid changes in strength of existing synapses

8. Which one of the following statements concerning neural integration is INCORRECT?

(_____) a. Most of the brain synapses are inhibitory.

(_____) b. EPSPs and IPSPs are graded potentials.

(__X__) c. At inhibitory synapses, neurotransmitters increase K⁺ permeability or decrease Cl^- permeability.

(_____) d. A synapse at the axon hillock typically has a greater influence on action potential formation than a synapse on a dendrite.

(_____) e. Most nerve cells have multiple input synapses whose post-synaptic potentials can summate in time or space.

9. Which one of the following mechanisms is NOT used to turn off an excitatory synapse just after its activation?

(__X__) a. Closing of K⁺ channel.

(_____) b. Plasma membrane Ca²⁺ pump activity.

(_____) c. Inactivation of neurotransmitter receptor.

(_____) d. Transport of neurotransmitter into nearby glial cells.

(_____) e. Degradation of neurotransmitter by enzymes in extracellular matrix in the synaptic cleft.

10. Which one of the following statements concerning the peripheral nervous system is FALSE?

(__X__) a. Most of the spinal and cranial nerves have processes from either sensory or motor neurons, but not both.

(_____) b. Not all of the somatic nervous system is "voluntary" because of spinal cord-mediated reflexes.

(_____) c. For motor neurons of the autonomic nervous system, their cell bodies are found in ganglia outside the spinal cord.

(_____) d. Sympathetic and parasympathetic nerves often innervate the same peripheral organ.

(_____) e. Sensory nerves are afferent, motor nerves are termed efferent.

11. Which one of the following statements about the proximal tubule and the loop of Henle is FALSE?

(_____) a. Cortical nephrons have a shorter loop of Henle than juxtamedullary nephrons.

(_____) b. Transport of Na⁺ out of the filtrate occurs at a higher rate in the proximal tubule than in the next segment, the descending limb of the loop of Henle.

(_____) c. The proximal tubule secretes acid into the filtrate.

(__X__) d. Water reabsorption by the proximal tubule requires a large osmotic gradient between the filtrate and the extracellular fluid next to nearby blood vessels.

(_____) e. Glucose and amino acids in the glomerular filtrate are reabsorbed primarily by the proximal tubule.

12. Which one of the following statements concerning action potential in nerve cells is FALSE?

(_____) a. The rising phase of an action potential is mediated by the opening of voltage-dependent Na⁺ channels.

(_____) b. Voltage-dependent Na⁺ channels are faster to open than voltage-dependent K⁺ channels.

(__X__) c. All neurons generate action potentials.

(_____) d. Inactivation of Na⁺ channels is critically important to the falling phase of an action potential.

(_____) e. A major function of action potentials is to allow long-distance, rapid signaling in the nervous system.

13. Which one of the following is NOT a response mediated by a hormone from the thyroid or parathyroid glands?

(_____) a. metamorphosis of tadpoles

(__X__) b. circadian rhythms

(_____) c. skeletal growth in humans

(_____) d. regulation of the rate of O₂ consumption

(_____) e. regulation of blood calcium levels

14. A portal vessel carries blood from the hypothalamus directly to the

(_____) a. thyroid

(_____) b. pineal gland

(__X__) c. anterior pituitary

(_____) d. posterior pituitary

(_____) e. thymus

15. Fertilization of human eggs most often takes place in the

(_____) a. vagina

(_____) b. ovary

(_____) c. uterus

(__X__) d. oviduct (fallopian tube)

(_____) e. vas deferens

16. Which one of the following is NOT normally part of spermatogenesis in mammals?

(_____) a. supported by Sertoli cells

(_____) b. stem cells

(__X__) c. mitosis follows meiosis

(_____) d. protection from immune system by apoptosis-inducing ligands

(_____) e. construction of flagella

17. Which one of the following statements concerning thermoregulation is FALSE?

(_____) a. Most fishes have internal body temperatures that are within 1-2∞ of the surrounding water temperature.

(_____) b. Many flying insects such as bees and moths are endothermic.

(__X__) c. The hypothalamus acts as a thermostat, inducing thermoregulation, but does not itself contain thermosensors.

(_____) d. During hibernation, body temperature declines due in part to a decrease in metabolism.

(_____) e. Brown fat generates metabolic heat due to changes in mitochondrial metabolism.

Part II. Essay questions (best 5 of 7, 10 points each)

18. Birds and many reptiles excrete nitrogen waste as uric acid rather than as urea or ammonia. Describe the special advantages (2) and disadvantage (1) of excreting uric acid over other commonly used forms of nitrogenous waste.

Advantages:

1) minimization of water loss because uric acid is insoluble in water

2) insoluble wastes inside egg minimize toxicity to embryo

Disadvantage:

1) requires more energy (ATP) to synthesize than other types of nitrogen waste (ammonia, urea)

19. The plasma membrane Na⁺,K⁺-pump (aka Na⁺,K⁺-ATPase) is indirectly responsible for the resting membrane potential of mammalian cells. Explain how the resting potential is generated including details of the contribution of the Na⁺,K⁺-pump.

Na⁺,K⁺ pump creates a K⁺ gradient (high inside) and a Na⁺ gradient (low inside). A K⁺ channel allows K⁺ to leave the cell, down its concentration gradient. The loss of K⁺ creates a negative-inside membrane potential, which draws K⁺ back into the cell through the K⁺ channel. This sets up a dynamic equilibrium in which the K⁺ gradient is maintained and the cell sets a resting potential.

20. The official color for University of Texas is "burnt orange," a brownish orange. Briefly describe the major cellular and molecular mechanisms of the retina that are responsible for seeing this color and distinguishing this color from that of the University of Tennessee - which is "orange."

Cone type photoreceptors have photopsins that are sensitive to only part of the visible spectrum of light. There are three types of cones, each with their own unique photopsin turned to red, green or blue, respectively. Distinguishing specific colors (burnt orange from orange) is accomplished by determining the ratio of output from each of the three different cones.

21. Endocrine cells release hormones in response to appropriate signals. The adrenal cortex releases the steroid hormone cortisol in response to ACTH. The pancreatic beta cells release insulin in response to a rise in blood glucose. For both systems, a rise in cytosolic Ca²⁺ levels is the signal for hormone release, but the mechanism for Ca²⁺ action is different. Describe the two types of Ca²⁺ regulation of hormone release, one by steroid hormone-releasing cells, the other by peptide hormone-releasing cells.

In steroid hormone-releasing cells, Ca²⁺ stimulates the activity of steroid hormone synthesizing enzymes. In peptide hormone-releasing cells, Ca²⁺ stimulates the fusion of hormone-containing vesicles with the plasma membrane, thereby releasing hormone by exocytosis. Steroid hormones are hydrophobic; once made, they can readily diffuse out of the cell.

22. In mammals, estrogen is required for fertility of both males and females. Why is estrogen needed for fertility in males and females? In females, what cell type makes estrogen?

Estrogen is required for spermatogenesis and for survival of the maturing follicle.

Granulosa cells make estrogen.

23. Hereditary hypertension is often traced to changes in the renin-aldosterone-ADH system for increasing blood pressure. For each of these three hormones, name the tissue where the hormone is made and the immediate response induced by each hormone.

Renin - kidney (juxtaglomerular apparatus), generation of angiotensin

Aldosterone - adrenal cortex, Na⁺ retention by kidney (increase Na⁺ pumps/channels)

ADH - hypothalamus (posterior pituitary), water retention by kidney (increase water channels in collecting tubule)

24. Local regulators are chemical messengers that affect target cells adjacent to or near their point of secretion. A common type of local regulator is the family of chemicals called prostaglandins. Describe the chemical nature of prostaglandins (e.g., lipid, protein, modified amino acid or Š) and also two physiological responses in humans that are induced by a prostaglandin. Hint: One of these responses is blocked by the most commonly used over-the-counter drug.

Prostaglandins are modified lipids.

Responses:

Fever

Inflammation

Relaxation of smooth muscle

Contraction of smooth muscle (e.g., childbirth, labor)

Increased sensitivity to pain