9. Functionally, what is a muscle fiber's fundamental unit of contraction?
(A) Z line.
(B) thin filament.
(C) thick filament.
(D) sarcomere.

5. Suppose a person's AV node in their heart suddenly stopped sending signals to the rest of the heart. How would this person's EKG differ from normal? (A) The EKG would have a taller P region. (B) The EKG would not have a QRS region. (C) The EKG would have a shorter T region (D) The EKG would not have a gap between the S and T regions.

6. Oxygen-poor blood is carried from the heart of a mammal to the lungs via the (A) pulmonary arteries. (B) pulmonary veins. (C) superior vena cava. (D) inferior vena cava.

7. Which of the following hormones is made by the hypothalamus and released by the posterior pituitary? (A) estrogen. (B) anti-diuretic hormone (ADH). (C) insulin. (D) calcitonin.

8. During ventricular systole, the semilunar valves _____ and the AV valves _____ (A) open; open. (B) close; open (C) open; close. (D) close; close

10. Arrange in the correct sequence these components of the mammalian immune system as it first responds to a pathogen. I. Pathogen is destroyed. II. Lymphocytes secrete antibodies.  III. Antigens from the pathogen bind to receptors on lymphocytes. IV. Lymphocytes specific to antigens from the pathogen become numerous. V. Only memory cells remain. (A) I → III → II → IV → V (B) III → II → I → V → IV (C) III → I → IV → II → V (D) IV → II → III → I → V (E) III → IV → II → I → V

11. The essential amino acids (A) must be obtained from the food we eat. (B) are found only in green, leafy vegetables. (C) are essential as an energy source. (D) are required for making nucleic acids.

12. For a neuron at rest with a membrane potential of -65 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in the _____. (A) depolarization of the neuron (B) hyperpolarization of the neuron (C) replacement of potassium ions with sodium ions (D) replacement of potassium ions with calcium ions (E) neuron switching on its sodium-potassium pump to restore the initial conditions

13. Most gastric ulcers are caused by (A) overuse of aspirin and/or ibuprofen. (B) excessive mental stress. (C) bacteria. (D) overconsumption of alcohol.

14. Which gland requires iodine to produce its hormones? (A) adrenal medulla. (B) pineal. (C) pituitary. (D) thyroid.

15. The activity of acetylcholine in a synapse is terminated by its_____ . (A) active transport across the presynaptic membrane (B) diffusion across the presynaptic membrane (C) active transport across the postsynaptic membrane (D) diffusion across the postsynaptic membrane (E) degradation on the postsynaptic membrane