Random phys Q's

Question 1

Only organ not receiving blood from left side of heart?

Answer 1

Lungs

Question 2

In steady state, which ventricle has higher cardiac output (CO)? Venous return?

Answer 2

Neither - working together in series, so must have same CO and venous return in SS

Question 3

What is the relationship between CO and venous return during SS?

Answer 3

Equal

Question 4

What empties into the LV?

Answer 4

Pulm vein (oxygenated blood)

Question 5

During exercise, what two mechanisms allow increased blood flow to skeletal muscle?

Answer 5

1. Increased CO

2. Redistribution of blood flow by selective alteration of arteriolar resistance

Question 6

How much of its own CO does the heart receive?

Answer 6

5% to coronary arteries (which fill during diastole)

Question 7

What empties into RA?

Answer 7

SVC/IVC (deoxy blood)

Question 8

During SS, venous return to the ___ equals ___ from the left ventricle

Answer 8

RA

CO

Question 9

To efficiently pump blood, ventricles contract from __ to ___

Answer 9

Apex to base

Question 10

Complete path a conduction through heart

Answer 10

SA node –> atrial internodal tracts/AV node –> Bundle of His (common bundle) –> right and left bundle branches –> Purkinje fibers –> ventricular cells

Question 11

Which part of the conduction system has the longest AP duration?

Answer 11

Purkinje fibers (~300 msec)

Question 12

Which tissues are described: long APs, long refractory periods, stable resting membrane potential, and a plateau period

Answer 12

Ventricles, atria, and purkinje fibers

Question 13

What allows Na+ influx during depolarization?

Answer 13

Opening of activation gates on Na channels

Question 14

Why does an AP never reach the Na+ equilibrium potential of ~65 mV?

Answer 14

The inactivation gates on the Na channels close (more slowly than the activation gates open)

Question 15

Why does the plateau phase occur?

Answer 15

K+ outward current = Ca2+ inward current through L-type Ca2+ channels which open during this phase; causes sustained, depolarized membrane potential
(remember: Na+ channels are closed due to inactivation gates)

Question 16

(T/F): Decreased Ca2+ influx is solely responsible for the shift from plateau to hyperpolarization.

Answer 16

False - also an increase in K+ outward current

Question 17

Which ion’s conductance is highest at rest?

Answer 17

K+

Question 18

How can Ca2+ and Na+ inward current be equal to K+ outward current at resting MP if K+ conductance is high and Ca2+/Na+ conductance is low?

Answer 18

Current = driving force x conductance

Little driving force on K+ b/c resting MP is near equilibrium potential for K+, so outward current is low
High driving force on Ca/Na but conductance is low do inward current is also low

Question 19

During which phases of atrial/ventricular APs are inward and outward currents equal?

Answer 19

2. Plateau (K = Ca)

4. Resting MP (K = Ca & Na)

Question 20

How does SA node AP differ from A/V AP?

Answer 20

1. Automatic
2. Unstable resting MP
3. No plateau (phase 1 and 2 are absent)

Question 21

How does the upstroke of SA node AP differ from A/V AP?

Answer 21

1. Caused by Ca inward current through T-type Ca channels (AV = Na influx)
2. Not as rapid or as sharp

Question 22

Why is the SA node resting MP considered unstable?

Answer 22

Once repolarization occurs and RMP reaches ~65 mV, If opens and Na causes a slow depolarization until threshold is reached and T-type Ca channels open

Question 23

What ensures that each AP in the SA node will be followed by another AP?

Answer 23

If is turned on by the preceding AP

Question 24

What accounts for notch in A/V AP?

Answer 24

Opening of Ito