CARDIOLOGY

Question 1

Describe the wall of an artery

What is the volume of blood within an artery called?

Answer 1

1. Extensive elastic fibers and SM
2. Stressed Volume

Question 2

What is the importance of arterioles?

What component of the NS is it innervated by?

Answer 2

1. Site of highest resistance - drops the blood pressure.
2. Sympathetic NS:
   a) B1: the arterioles of the skeletal muscle. Dilatory.
   b) A1: the arterioles of the skin, splanchnic, and renal circulations. Constriction

Question 3

What is the importance of the veins?

What is volume of blood in the veins called?

Are veins innervated by the NS?

Answer 3

1. Store the majority of the blood.
2. Unstressed Volume
3. Yes, the Sympathetic NS. Have Alpha-1 receptors.

Question 4

What is the equation for:

Velocity of BF

Blood Flow

Resistance

Answer 4

1. Velocity of BF: v = Q (flow) / cross-sectional area
2. Q = (MAP - RAP) [pressure gradient] / TPR

The pressure is as follows: Arteries>Arteriole>Capillaries>Venules>Veins>RA

3. Resistance is proportional to viscosity and length but inversely proportional to radius^4.

Question 5

What is the importance of Reynold’s number?

Answer 5

Reynold’s number predicts whether the flow of blood is laminar or turbulent.

An increase in Reynold’s number reflects increased tendency for turbulence.

Depends on viscosity and velocity.

Viscosity: decrease viscosity = decrease in resistance = increase velocity

Velocity: decrease radius of BV = increase in velocity.

Question 6

What is Capacitance?

How does it differ per vessel?

What happens with age? What happens to the BP?

Answer 6

1. Capacitance: the distensibility of a blood vessels. Capacitance increases with: lower stiffness, lower elastance

Capacitance decreases with increased stiffness

2. Veins have a higher capacitance thus can store more volume without a change in pressure.
3. Capacitance decreases with age; vessels become stiffer; systole increases

Question 7

What is Pulse Pressure?

What’s the most important determinant of PP?

What is the relationship to capacitance?

Answer 7

1. PP = Systole P - Diastole P
2. SV
3. Decreasing capacitance -> increases vessel stiffness –> increases sytolic pressure–> increases PP

Question 8

What does an increased PP signify?

What does a decreased PP signify?

Answer 8

1. Systole is higher due to increased SV - aortic regurgitation, hyperthyroidism (ladder effect of increased HR), age
2. Systole is lower due to - aortic stenosis, cardiogenic shock, cardiac tamponade, HF

Question 9

What do the various components of the ECG mean?

Answer 9

1. P: Atrial Depolarization
2. PR - the conduction velocity through the AV node.
3. QRS: Ventricular Depolarization
4. QT: the time it takes for ventricular depolarization and repolarization.
5. ST segment: represents the period when the ventricles are depolarized.
6. T waves: represent ventricular repolarization.

Question 10

What are the phases of a cardiac muscle contraction?

Answer 10

Phase 0: Depolarization Phase; Na

Phase 1: K+ efflux, rapid activating K channels

Phase 2: Ca2+ influx

Phase 3: K+ efflux, slow activating K+ channels, Repolarization

Phase 4: RMP @ K Eq = -90mV

Question 11

What components of the heart rest at -90mV?

What component of the heart has the longest AP?

Answer 11

1. Ventricles, Atria, Purkinje Fibers
2. Purkinje Fibers

Question 12

What are the phases of the SA node?

Answer 12

Phase 0: upstroke due to Ca2+ influx

Phase 3: K+ efflux, repolarization

Phase 4: If : Na+

The resting MP: -65mV

Phase 4 is fastest in SA>AV>His/Purkinje

Question 13

What does chronotropic mean?

Whats a positive chronotrope/negative chronotrope?

Answer 13

Chronotropes produce changes in HR

Positive: Increased HR via increasing firing rate of SA node.

Question 14

What is a dromotropic effect?

What is a positive dromotropic effect?

Answer 14

Dromotropic effects produce changes in the conduction velocity; primarily throught the AV node.

1. Positive dromotrope; increases the conduction velocity through the AV node. Decreases PR interval.

Question 15

What is the effect of the PaNS on the heart?

Answer 15

1. SA, atria, and AV have muscarinic receptors.

Negative chronotropic effect: Decreases HR via slowing down phase 4 depolarization (decreased If flux)

Negative dromotropic effect: Decreases the conduction velocity through the AV node (decreased inward Ca2+, and increased K+ efflux)

Question 16

What is the effect of the SyNS on the heart?

Answer 16

B1 receptors

1. Positive chronotropic effect: increases HR by increasing the rate of phase 4 depolarization; Increased Na+ influx through the If.
2. Positive dromotropic effect: increased conduction velocity through the AV node. AP conducted faster to the ventricle - this may compromise the filling time of the ventricle. This occurs due to an increased Ca2+ influx.

Question 17

In what cell type is the mitochondria more abundant? Skeletal or Cardiac?

What are T-tubules continuous with?

Answer 17

1. Cardiac
2. The T-tubules are continuous with cell membrane and invaginate the Z-line. T-tubules are well developed in ventricles but not atria.

Question 18

What receptors are involved with excitation of the cardiac muscle?

Answer 18

1. Dihydropyridine R/L-type: the AP causes a conformational change that allows Ca2+ to influx into the cell.
2. Ryanodine R: the Ca2+ binds the the RR on the SR = Ca2+ efflux into the cell.

Question 19

What is inotropism?

What is +ve ionotropism?

Answer 19

1. Inotropism: the ability of the heart to contract according to the distension/length of fiber.
2. Agents that increase the contraction of the heart.

Can be done via: 1) Increase HR: increasing Ca2+ influx leads to more Ca2+ available for the SR to uptake. By taking up more Ca2+, more will be available for the next contraction. Ladder effect.

3. Sympathetic via B1: Increase Ca2+ influx during plateau phase.

Increase Ca2+ ATPase activity on SR via P of Phospholamban.

Cardiac glycoside.