Aged erythrocytes normally meet their end in the spleen when they are engulfed by ______ that recognize which erythrocytes are worn out by the...

16. Aged erythrocytes normally meet their end in the spleen when they are engulfed by ______ that recognize which erythrocytes are worn out by the ________ on the erythrocyte plasma membrane.

a. macrophages, oxidized sugars

b. neutophils, proteins

c. T killer cells, antigen fragments

d. Plasma B cells, antigen

e. reticulocytes, ribosomes

17. When blood is spun in a centrifuge, T cell receptors are found in the:

a. plasma

b. hematocrit

c. buffy coat

d. globin

e. erythrocyte

18. During the production of lymph, ____________ generates a ___________ force to move fluid to the interstitial (extracellular) space.

a. protein in plasma, osmotic

b. protein in plasma, hydrostatic

c. the heart, hydrostatic

d. the heart, osmotic

e. a and c are correct

19. Erythropoietin is a ________ that increases the rate of cell division and survival of _______.

a. steroid hormone, mature erythrocytes in the red marrow

b. glycoprotein hormone, aged erythrocytes in the spleen

c. glycoprotein hormone, proerythrocytes in the red marrow

d. glycoprotein, mature erythrocytes in the red marrow

e. c and d are correct.

20. In Starling's law of the heart, stroke volume increases when:

a. sarcomere length increases during diastole.

b. more Ca2+ is released from the sarcoplasmic reticulum during systole.

c. pressure to open the aortic valve increases.

d. the end diastolic volume increases.

e. a and d are correct.

21. Contractile cardiomyocytes and skeletal muscle cells perform similar functions. Which of the following statements is NOT true?

a. The structure of the DHP receptors found in contractile cardiomyocytes differs from DHP receptors in skeletal muscle fibers.

b. The Ryanodine receptor in contractile cardiomyocytes requires Ca2+ influx from the extracellular space.

c. Voltage-gated sodium channels present in skeletal muscle cells are absent from contractile cardiomyocytes.

d. After Ca2+ flows into the cytoplasm it binds troponin C in both contractile cardiomyocytes and skeletal muscle cells.

e. Contractile cardiomyocytes contain a single nucleus whereas skeletal muscle cells contain numerous 

22. Ivabaradine is a drug that blocks Na+ influx through HCN channel. You would expect this drug to:

a. increase the heart rate.

b. decrease heart rate.

c. increase the strength of muscle contraction.

d. increase the rate of rise of the ramp potential.

e. a and d are correct.