Physiology- Cardiology

What is the function of the cardiovascular system?

to circulate blood at a rate that is consistent with metabolic demand while also maintaining low filling pressure and adequate perfusion pressure

What is perfusion pressure?

pressure needed to push blood to vital organs and other body systems

What is filling pressure?

a combination of the blood entering the heart and blood left over in the heart after a pump

What four things can blood carry?

1. nutrients
2. gas
3. waste
4. electrolytes

What is oxygen bound to?

hemoglobin

How do gas/nutrients/waste get exchanged in the blood?

capillaries

What are the two types of circulation?

Systemic and pulmonary

What is stroke volume?

the amount of blood that leaves the heart during systole

What is cardiac output?

the amount of blood that leaves one side of the heart in one minute

What is the equation for cardiac output?

stroke volume x heart rate

What are the pulmonary and aortic valves also known as?

Semilunar valves

What happens to pressure when a ventricle constricts?

pressure increases in comparison to atrial pressure

When do the AV valves close?

When ventricular pressure increases greater than atrial pressure

When do AV valves open?

when atrial pressure is higher than ventricular pressure

When do semilunar valves open?

when ventricular pressure exceeds great artery pressure

When do semilunar valves close?

when arterial pressure exceeds ventricular pressure

What is diastole?

when atria and ventricles are relaxed

What is sytole?

When atria or ventricles are contracted (ventricular contraction occurs shortly after atrial contraction)

What is the right AV valve also known as?

the tricuspid valve

What is the left AV valve also known as?

mitral valve

What is the difference in shape between the left and right ventricles?

Right ventricle is crescent shaped while the left ventricle is cylindrical

What is the shape of the right ventricle?

Crescent

What is the shape of the left ventricle?

cylindrical

What is the important physical difference between right and left ventricles?

Left ventricle is thick walled while the right ventricle is thin walled

Which ventricle is considered a pressure pump?

left ventricle because it is systemic circulation

Which ventricle is considered a volume pump?

right ventricle

Where does blood in veins go?

to the heart

Where does blood in arteries go?

away from the heart

What term can be used to describe the pattern of blood vessels around/on the heart

fractal branching

What are capillaries made of?

single layer of endothelial cells

What are large arteries made of?

elastin

What do veins not usually contain?

elastin because they dont need stretch (want to increase pressure)

How is blood flow to tissues controlled?

Local vasoconstriction and vasodilation

What is the fibrous skeleton responsible for?

electrically isolating the atria and ventricles

What is the difference between a working cardiomyocyte and a special cardiomyocyte?

Working cardiomyocytes do not spontaneously depolarize while special cardiomyocytes do

Where can you find working cardiomyocytes?

fibrous skeleton

When do working cardiomyocytes depolarize?

When their neighbors do

Why is low filling pressure important?

to avoid congestion

What are the components of the conduction system?

1. special cardiomyocytes
2. AV node
3. SA node
4. Bundle of His
5. Purkinje Fibers

Where is the AV node located?

Atrial septum

Where is the SA node located?

Right atrium

What gives rise to purkinje fibers?

bundle of his

What is the electrical connection between the atria and ventricles?

bundle of his

What is the bundle of his?

electrical connection between atria and ventricles

What gives rise to the Bundle of His?

AV node

What makes special cardiomyocytes so special?

automaticity/ spontaneous depolarization

What is the purpose of the conduction system?

allow communication between atria and ventricles with slight pause

What is Ohm's law?

pressure difference= cardiac output x resistance

What is resistance?

forces that must be overcome to establish flow

What is current equivalent to?

cardiac output

What is voltage equivalent to?

pressure difference

What does Poiseuille's Law relate?

Radius and distance

What happens to resistance when radius is increased?

resistance is decreased

What happens to resistance when radius is decreased?

resistance is increased

What is laminar flow?

smooth flow

What is turbulent flow?

unorganized flow

What factors are related to laminar flow becoming turbulent flow?

tube diameter, viscosity, density (all affect reynold's number)

What kind of pressure system is systemic circulation?

high pressure

What kind of pressure system is pulmonary circulation?

low pressure

What kind of oxygen system is systemic circulation?

high O2

What kind of oxygen system is pulmonary circulation?

low O2

What kind of resistance system is systemic circulation?

high resistance

What kind of resistance system is pulmonary circulation?

low resistance

What is heart rate?

number of cardiac cycles in one minute

What is normal membrane potential?

negative interior, positive exterior

Why are cardiomyocytes excitable?

membrane potential

What leads to an initial depolarization in the heart?

Excitation of cardiomyocytes

What is a depolarization?

momentary reversal of the membrane potential (becomes more positive inside)

What does an initial depolarization lead to?

Action potential

What is the formula for conductance?

reciprocal of resistance

What is conductance?

How easily ions flow

How does membrane potential change?

ions flow in and out via special channels

What part of the conduction system has the highest inherent rate of automaticity?

SA node

What part of the conduction system has the lowest inherent rate of automaticity?

bundle of his

What is pressure?

Force over a given area

Where is the most blood found at any given time?

Systemic veins

What are the units for pressure?

mmHg

What determines venous return?

intravascular blood volume and venous tone

Where is the greatest vascular resistance found?

Arterioles because they are more rigid

How is tendency for laminar flow to turn into turbulent flow determined?

Factors that impact Reynold's number

What factors impact reynold's number?

density, velocity, density, viscosity, diameter of vessel

What is impedence?

forces that oppose pulsatile flow

How does the heart contract?

myocardial shortening

What are the most important ions involved in heart conductance?

calcium, sodium, potassium

What controls cardiac rhythm?

SA node

Why is working cardiomyocytes considered a functional syncitium?

intercalated discs and gap junctions allow it to function as one unit

What are the three ways resting membrane potential is created?

1. ATPase
2. Donnan Effect
3. Selective permeability of membrane (leaky K but not permeable to Na)

What are the two types of potassium channels?

1.voltage-gated channels
2. inward rectifier

What are voltage-gated K+ channels for?

repolarization

What are inward rectifiers (K+) for?

maintaining resting potential

How does the duration of a cardiac action potential compare to that of a nerve cell?

It is much longer than that of nerve cell AP

Why does a cardiac AP have a plateau?

to avoid tetanus

What does inward Na+ flow cause during phase 0?

Initial depolarization of purkinje and working myocardium

What does slow Ca channels inward flow cause?

phase 2 plateau of specialized cardiomyocytes AND upstroke of working cardiomyocytes in phase 0

What ion causes initial depolarization of working cardiomyocytes?

sodium

What causes initial depolarization of specialized cardiomyocytes of nodes?

calcium

What cells DO NOT spontaneously depolarize?

atrioventricular cells (working cardiomyocytes)

What is overdrive supression?

spontaneous depolarization is suppressed if depolarization rate is higher than inherent rate in specialized cardiomyocytes

What can change rate of spontaneous depolarization?

autonomic influences

What is phase 2 of the action potential in heart?

plateau