Cardiovascular Physiology Flashcards
What is ANP (atrial natriuretic peptide) released in response to?
Increased atrial pressure
How many liters of blood per minute is pumped in a 70kg man
5-6 liters
What is BNP (b-type natriuretic peptide) released in response to?
overstretched ventricles
Intercalated discs allow the heart to contract in synchrony as one unit, what is this called?
Syncytium
What is happening with the ions in the initial repolarization in cardiac muscle contraction?
Inactivation of Na+ influx
K+ efflux
What is happening in the plateau phase of the cardiac muscle contraction? (ions)
Ca++ influx through L-type Ca++ channels
What determines the force of contraction of the myocardial cell?
The amount of intracellular calcium
No action potential can be initiated regardless of the stimulus strength, what refractory period is this?
Absolute refractory period
An action potential can be elicited, however a greater stimulus is needed, what refractory period is this?
Relative refractory period
Why is cardiac muscle incapable of sustained contraction (tetany) as in skeletal muscle?
Because of the relatively long refractory period
What is the Frank-Sterling law?
Cardiac output is directly proportional to venous return
The 1st heart sound is due to what?
Closure of the tricuspid and mitral valves
The 2nd heart sound is due to what?
Closure of the pulmonary and aortic valves
3rd heart sound occurs when?
After the 2nd heart sound and is seen in congestive heart failure
The 4th heart sound is heard when?
Before the 1st heart sound and is seen in hypertrophic ventricles
Systole (contraction) occurs between which heart sounds?
1st and 2nd
Diastole (relaxation) occurs between which heart sounds?
2nd and 1st
If there is a prolonged PR interval (>200 milliseconds)
1st degree AV block
If there is progressive prolongation of the PR interval with dropped beats
2nd degree AV block (Mobitz 1- Wenckebach phenomenon)
Isovolumic contraction occurs when?
Between the closure of the AV valves and the opening of the aortic valve
Increase in pressure without change in volume is called what?
Isovolumic contraction
What is it called when only 70ml of the 120ml of blood is expelled from the ventricle?
Ejection fraction
A decrease in the ventricular pressure without a change in the volume is called?
Isovolumic relaxation
When does isovolumic relaxation occur?
Between the closing of the aortic valve and the opening of the AV valves
Sympathetic control of heart rate comes from which vertebral levels and which sympathetic ganglia?
T1-T5, middle and inferior cervical ganglia
What is it called when the sympathetic nervous system increases heart rate?
Positive chronotropism
How does the sympathetic nervous system increase the heart rate?
By increasing the rate of Phase 4
What is it called when there is an increase in conduction velocity?
Positive dromotropism
How does the sympathetic nervous system increase conduction velocity?
By decreasing the PR interval
What is it called when there is an increase in force of contraction in the heart?
Positive inotropism
How does the sympathetic nervous system increase force of contraction?
By increasing Ca++ influx in Phase 2
Which CN controls parasympathetic control to the heart?
Vagus through its cardiac branches
Cardiac Output x Peripheral Resistance = ?
Blood Pressure
Stroke Volume x Heat Rate = ?
Cardiac Ouput
Afferent high pressure sensors (baroreceptors) information in the carotid sinus are carried in which nerve?
Cranial nerve IX
Afferent high pressure sensors (baroreceptors) information in the aortic arch is carried in which nerve?
Cranial nerve X
CN IX and CN X carry afferent high pressure baroreceptor information to which area of the brain?
The Medulla
Where are the low pressure baroreceptors located?
SVC, IVC and the right atrium
What do low pressure baroreceptors monitor?
Volume
What is Poiseuille’s Law?
Peripheral resistance is directly proportional to viscosity of blood and lenth of the vessel and inversely proportional to the radius of the vessel raised to the 4th power
The greatest resistance in the vascular system is offered where?
Arterioles
Blood flow through a tubular structure is governed by which law?
La Place’s law
What is La Place’s law?
The pressure within a blood vessel is related to the tension, size and shape of the vessel
What is blood flow inversely proportional to?
The diameter of the blood vessel
How much of the total blood volume is contained within the venous system?
60%
How much of the total blood volume is contained within the pulmonary system?
15%
How much of the total blood volume is contained within the capillaries?
5%
Where is blood flow the greatest?
Within the arteries and veins
Where is the least amount of blood flow?
The capillaries
How much of the total blood volume is contained within the arteries and arterioles?
20%
Pressure which tends to force fluids out into the interstitial space (+)
Intracapillary hydrostatic
Pressure which tends to pull fluids into the capillary (-)
Intracapillary oncotic pressure
Pressure which forces fluids into the capillary
Interstitial hydrostatic pressure
Pressure which pulls fluid out of the capillary
Interstitial oncotic pressure
Prolonged exercise leads to cardiac muscle hypertrophy which leads to?
Athletic Heart Syndrome
