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.

1. The operation of the sodium-potassium "pump" moves _____.(A) sodium and potassium ions into the cell (B) sodium and potassium ions out of the cell (C) sodium ions into the cell and potassium ions out of the cell (D) sodium ions out of the cell and potassium ions into the cell (E) sodium and potassium ions into the mitochondria

2. Light reflecting off an object in the environment is detected by photoreceptors after following which path? (A) lens ＞ cornea ＞ retina ＞ ganglion cell layer ＞ iris (B) cornea ＞ lens ＞ iris ＞ ganglion cell layer ＞ retina (C) retina ＞ ganglion cell layer ＞ lens ＞ iris ＞ cornea (D) cornea ＞ iris ＞ lens ＞ ganglion cell layer ＞ retina

3. How do myelin sheaths increase the speed with which action potentials are propagated along an axon? (A) They increase the permeability of Na+ ions in the plasma membrane. (B) They amplify the action potential by increasing sodium influx along the entire distance of the neuron. (C) They insulate the axon, preventing K+ ions from exiting the neuron. (D) They cause action potentials to "jump" down the axon rather than travel in a continuous path along every site on the axon.

4. A newborn who is accidentally given a drug that destroys the thymus would most likely _____ (A) lack class I major histocompatability (MHC) molecules on cell surfaces (B) lack innate immunity (C) be unable to genetically rearrange antigen receptors (D) be unable to differentiate and mature T cells (E) have a reduced number of B cells and be unable to form antibodies

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

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

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.