Session 2-The Heart As A Pump Flashcards
What do capacitance vessels allow?
Allow the system to vary the amount of blood pumped around the body
What do resistance vessels do?
Restrict blood flow to drive supply to hard to perfume areas of the body
Give an example of resistance vessels
Arterioles
True or false:
The heart is two pumps acting in series
TRUE
True or false:
The systemic circulation has low pressure
FALSE - systemic circulation has high pressure, pulmonary circulation has low pressure
Does the output of the left and right sides of the heart over time have to be equal?
YES
What do atria act as for the ventricles?
“Priming pumps”
What happens in systole?
Contraction and ejection of blood from the ventricles
What happens in diastole?
Relaxation and filling of ventricles
At rest, how much blood does the ventricle pump per beat and what is this called?
~70ml
Stroke volume
What type of cell is a cardiac muscle cell?
Functional syncytium
How are functional syncytiums connected?
By gap junctions so that action potential can pass readily and quickly
In heart muscle cells, what does an action potential cause a rise in?
Intracellular calcium
Complete the sentence:
Cardiac action potential is relatively _____ and lasts for the duration of a single contraction of the heart (~____ms)
Long
280
Which four valves determine the pathway of blood flow through the heart?
1) tricuspid valve
2) pulmonary valve
3) mitral valve
4) aortic valve
Which of the four valves have two leaflets as opposed to three?
Mitral valve (also called the bicuspid valve)
Which are the valves on the right side of the heart?
Tricuspid valve (in) Pulmonary valve (out)
Which are the valves on the left side of the heart?
Mitral (in)
Aortic (out)
What does the opening and closing of a valve depend on?
Blood pressure on each side
Why do valve cusps close?
To prevent backflow
What are the cusps of mitral and tricuspid valves attached to and what does this prevent?
PAPILLARY muscles via CHORDAE TENDINEAE
Prevents inversion of valves on systole.
What type of cells are in the sinoatrial node?
Pacemaker cells (specialised cardiac myocytes)
What do the cells in the SAN (sinoatrial node) do?
Generate an action potential and the activity spreads over the atria, stimulating atrial systole
Why is the activity delayed at the atrioventricular node for ~120ms?
To allow the atria to finish contracting before the ventricles contract
Complete the sentences:
From the AV node, the excitation spreads down the ________ between the ventricles. Next, it spreads through the ventricular myocardium from the inner (___________) to the outer (____________) surface.
Septum
Endocardial
Epicardial
What are the seven phases of the cardiac cycle?
1) atrial contraction
2) isovolumetric contraction
3) rapid ejection
4) reduced ejection
5) isovolumetric relaxation
6) rapid filling
7) reduced filling
On the Wiggers diagram, at which point does the cycle start?
Atrial contraction
What is the difference between a Wiggers diagram for the left and right sides of the heart?
Very similar but right side would be at lower pressures