The Heart Flashcards
what is the function of chordae tendineae?
stabilize the cusps during ventricular contractions and hold the cusps in place preventing retrograde flow of blood
what is the serous pericardium?
combination of visceral and parietal pericardium
SV = ______
EDV - ESV
what is EDV?
end diastolic volume. Volume in ventricles and atria at the end of diastole.
what does EDV represent?
maximal volume of the chambers of the heart (just before the aortic and pulmonary valves open)
what does ESV represent?
minimum amount of blood in chambers of the heart
Does the heart completely empty?
NO
define Stroke Volume (SV)
amount of blood pumped from ventricle per beat
T/F: the R/L atria are induced to contract simultaneously?
TRUE
What is the pathway for electrical activity in the heart?
- SA node
- AV node
- bundle of His
- Purkinje fibers
why is there a delay at the AV node?
allows maximal filling and contraction
what does a P wave represent on a ECG?
depolarization of atria in response to SA node triggering
what does the PR interval represent?
delay of AV nodes to allow filling of ventricles
what does the QRS complex represent?
depolarization of ventricles, triggers main pumping contractions
What does the ST segment represent?
beginning of ventricle repolarization, should be flat
What does the T wave represent?
ventricular repolarization
T/F: the heart has a refractory period?
TRUE
define CO
liters of blood pumped per minute
CO = _______
SV * HR
define preload
volume of blood coming back to heart
what occurs if preload is compromised?
- SV to R ventricle is compromised
- amt of blood going to lungs is compromised
- blood going to left side of heart is compromised
- CO to rest of body is decreased
SV is regulated by what 3 variables?
- preload (EDV)
- afterload (TPR)
- contractility
what is TPR?
total peripheral resistance
define afterload
resistance left ventricle must overcome to circulate blood (systolic BP)
what happens if afterload is compromised?
the heart has to work harder
relationship between afterload and SV, CO?
increase in afterload = decrease in SV and CO
What is the Frank Starling Law?
increased EDV stretches cardiac muscle causing an increase in contractility and thus increasing SV
what does the Frank Starling Law demonstrate?
the role that preload has in defining the SV
what is contractility?
strength of a contraction. It is a measure of pump function
how is contractility assessed?
EF (ejection fraction)
what does EF tell us?
provides insight into delivery of blood to systemic circulation, assess cardiac contractility
EF = __________
(SV/EDV) * 100
what is a normal EF?
~50-75%
what does venous return influence?
EDV
what factors influence venous return?
- blood volume
- breathing (neg. intrathoracic pressure)
- venous pressure
what is the inherent rate of the SA node (in total absence of neural or hormonal input)?
100 bpm
T/F: Cardiac muscles contract all or nothing?
False, cardiac muscle can have graded contractions dependent on the amount of Calcium being released by the SR
T/F: cardiac muscle can grade the strength of their contractions?
TRUE
difference between refractory periods in cardiac and skeletal muscle?
skeletal muscle has a shorter refractory period which means contractions can add up and result in tetanus.
The heart has a longer absolute refractory period
what is the period called between the aortic valve closing and the AV valve opening?
isovolumetric ventricular relaxation
when does isovolumetric ventricular relaxation occur?
during diastole, prior to the AV valves opening and after the aortic/pulmonary valves close
when does atrial contraction occur?
at the end of diastole, after most of the ventricular filling has taken place
at rest the SA node is more heavily influenced by ________
parasympathetic vagus input
what are the 3 factors that influence changes in SV?
- changes in EDV»_space; preload
- changes in sympathetic input
- afterload
SV is directly proportional to _____
EDV
the relationship between SV and EDV is known as ________
the Frank-Starling mechanism
how does afterload effect SV?
increases in afterload tend to reduce SV
