CH 14

Which blood vessels have the lowest blood pressure?

• veins

• capillaries

• arteries

• venules

If the radius of a tube decreases by half, what will happen to the resistance to fluid flow?

• Resistance will decrease 16 times.

• Resistance will double.

• Resistance will increase 16 times.

• Resistance will decrease by half.

Which statement about hydrostatic pressure is FALSE?

• Force is not equal in all directions.

• Hydrostatic pressure does not include the dynamic component of a moving fluid.

• If a fluid is not moving, the pressure that it exerts is called hydrostatic pressure.

• The lateral component of moving fluid represents the hydrostatic pressure.

the sac around the heart

• pleural sac

• pericardium

• myocardium

• endocardium

at an intercaated disc

• t-tubules unite the membranes of the adjoining cells.

• the myofibrils are loosely attached to the membrane of the disc.

• the cell membranes of two cardiac muscle fibers are completely separated by a synapse.

• two cardiac muscle cells are connected by gap junctions.

Which valves have chordae tendineae?

• valves in veins

• coronary valves

• semilunar valves

• bicuspid (mitral) and tricuspid valves

The flattening of the action potentials of myocardial contractile cells, called the plateau phase, is due to a combination of ________ K⁺ permeability and ________ Ca²⁺ permeability.

The importance of the plateau phase of the action potential of myocardial cells is in

• in

  preventing tetanus.

• enhancing the efficiency of oxygen use by the cells.

• regulating Ca²⁺ availability to the cells.

• preventing overstretching of the cells.

Autorhythmic cells can generate action potentials spontaneously because they have

• unstable membrane potentials.

• L-type Ca²⁺ channels.

• channels for Na⁺ and K⁺ that are always open.

• prolonged Ca²⁺ influx.

Autorhythmic cells

• are also called pacemakers because they set the rate of the heartbeat.

• are the same size as myocardial contractile cells.

• have organized sarcomeres.

• contribute to the force of contraction.