Lecture 7&8 Cardiac Output, resistance and flow blood pressure Part 1 Flashcards
What is Heart Rate?
(HR) The number of contractions per minute
What is Stroke volume?
Stroke volume or SV is the volume of blood ejected per contraction
What is Cardiac output
Cardiac Output (CO) is the volume of blood pumped out of the left ventricle (right ventricle) per minute
What is Venous Return?
The volume of blood returning to the heart right or left ventricle per minute
What does this equation mean? CO = HR x SV
Cardiac output(l/min) = Heart Rate(Beats/min) times Stroke Volume (ml/beat). The answer will be in ml (1000ml) and will need to be converted to Litres (1L)
True or false? Sympathetic activation increases HR
True
True or false? Sympathetic activation decreases HR
False
True or false? parasympathetic activation increases HR
False
True or false? parasympathetic activation decreases HR
True
Hormones such as adrenaline or noradrenaline act on adrenergic receptors (Beta receptors) from the parasympathetic or sympathetic?
sympathetic
What is the difference between alpha and beta receptors?
Beta receptors are on the heart, alpha receptors are in the arteries or veins
What are the three ways we can increase stroke volume?
Increase pre-load (end diastolic volume) decrease after-load (aortic blood pressure) Increasing contractility
Pre-load is defined as what?
The degree of stretch of the ventricular wall prior to contraction.
For practical purposes, what is measured as a ventricular end-diastolic volume?
Pre-load
After-load is defined as what?
the pressure that the ventricles must overcome to eject blood.
The aortic pressure (diastolic) at the time the aortic valve opens is defined as Pre-load or After-load?
After-load
Is this pre-load or After-load?
After-Load
Is this Pre-load or After-load?
Preload
An increase in venous return will result in what?
An increase in end-diastolic ventricular volume
An increase in end-diastolic ventricular volume results in what?
An increasd force of ventricular contraction
An increasd force of ventricular contraction results in what?
An increase stroke volume
An increase stroke volume results in what?
an increase cardiac output
An increase in after-load results in what?
Reduced stroke volume
Reduced stroke volume results in what?
increase end-systolic ventricular volume
increase end-systolic ventricular volume results in what?
increased end-diastolic ventricular volume
increased end-diastolic ventricular volume results in what?
increased force of contraction
increased force of contraction results in what?
stroke volume incrases, back towards original value.
Cardiac contractility is defined as what?
the ability of the heart to contract, at any given end-diastolic ventricular volume.
Increases in cardiac contractility are caused by what?
activation of cardiac sympathetic nerves or an increase in circulating adrenaline
Decreases in cardiac contractility are caused by what?
activation of cardiac parasympathetic nerves that produces a decrease in myocardial intracellular
What are the three factors that control the venous return?
Skeletal muscle pump (increases VP Peripheral)
Respiratory pump (decreases VP Central)
Sympathetic venoconstriction (increases VP Peripheral)
What is Venoconstriction?
Venoconstriction is the contraction of skeletal muscle to push blood back up to the heart
How do you find out the mean arterial pressure
Find out the diastolic pressure, add a third of the Pulse pressure.
Pulse pressure is systolic pressure minus diastolic pressure,
Divide the PP by 3 to get a third.
DBP + 1/3PP
MAP = 80 (120-80)/3=93.33
