Cardiac output as the product of heart rate and stroke volume.

Cardiac output is a measurement of how much blood is being pumped by the heart, it is calculated by multiplying the speed at which it is pumping by how much it pumps each stroke.

Cardiac output= heart rate x stroke volume.

Myogenic stimulation of the heart and transmission of a subsequent wave of electrical activity. Roles of the sinoatrial node (SAN), atrioventricular node (AVN) and bundle of His.

Myogenic stimulation means that the heart is caused to move because of signals that originate inside of it. In normal muscles movement is caused by signals from the CNS.

The signals come from the sinoartrial node (SNA) which is sometimes refered to as the pace maker. Although the signals for the cardiac cycle are generated in the heart, the pace is controlled by signals from the brain.

• SNA sends electrical activity accross the top of the atria (they contract)
• The atrioventricular septum is non-conductive tissue which stops the signal going down the sides.
• The signal that travelled down between the atria reaches the atrioventricular node (AVN).
• The AVN delays the signal (so that the atria fully contract) before transmitting it again.
• The electrical activity now travels down the bundle of His.
• The signal reaches the bottom of the ventricles where it causes them to contract.

Its important that the ventricles contract upwards so that the blood is being pushed towards the semi-lunar valves.

It is also of importance that the AVN delays the signal long enough for the atria to finish their contraction- so that the most blood possible goes into the ventricle before it starts contracting and closes the atrio-ventricluar valves.

Pressure and volume changes and associated valve movements during the cardiac cycle. Candidates should be able to analyse and interpret data relating to pressure and volume changes during the cardiac cycle.

Diastole

The ventricle relaxes, decreasing its pressure. This causes the blood which it just pushed into the aorta/pulmonary (left/right) flow back towards the heart trying to get to the low pressure area: the blood pushes the semi-lunar valve shut (making the second noise of a heart beat 'dub')

Blood flows from the atrium into the ventrical. This happens because there is a lower pressure in it: 1. because it has no blood in and 2. because it has just relaxed.
The blood going through pushes the atrio-ventricular valves open.

Atrial systole

The atrium contracts: so there is more pressure on the blood. It does this to push the remaining blood into the ventricle that didn't flow in during diastole.

Ventricular systole

Ventricles contract- more pressure- pushing blood through the semi-lunar valves, out of the heart.
When they contract the blood pushes against the atrio-ventricular valve, which pushes it shut (this makes the first sound of a heart beat 'lub')

http://library.med.utah.edu/kw/pharm/hyper_heart1.html

Atrium (left):
Bump- atrium contracts.
Drop- blood is pushed into ventricle.
Gradual rise- blood fills the atrium.
Drop- blood flows into ventricle.
Gradual rise- blood continues to flow in and through into the ventricle.

Ventricle (left) pressure:
First small bump- blood is pushed in by atrium.
Massive bump- the ventricle contracts.
Fall with aorta line- blood has been pushed out.
Fall after the aorta line- ventricle relaxes.
Gradual rise- pressure is below that in the atrium so blood rushes in.

When the ventricle pressure rises above that in the atrium, the atrio-ventricular valve is pushed shut.
When the ventricle pressure falls below that of the atrium, the atrio-ventricular valve opens.

Ventricle (left) volume:
Initial rise- blood is pushed in from the atrium.
Fall- blood is pushed out into the aorta.
Plateau- both valves are closed so no blood is moving in or out (volume can't change.)
Increase- blood flows in from the atrium.


Aorta:
When the pressure of the ventricle meets that of the aorta the semi-lunar valve opens.
Big bump- blood is pushed in from the ventricle.
The ventricle pressure drops below that of the atrium, back flow shuts the semi-lunar valve.
Small bump- the elasticity of the walls brings them in before...
Gradual fall- the walls of the aorta relax.

Valves are pushed open because the pressure has been made grater in one chamber than it is on the other side of the valve, so blood tries to go through it into a lower pressure area, pushing it open.

The gross structure of the human heart and its associated blood vessels in relation to function.

The heart has four main areas: two atriums and two ventricles.

• Blood first enters the heart into the right atrium from the vena cava;
• passes through the right atrio-ventricular valve into the right ventricle;
• leaves through a semi-lunar valve into the pulmonary artery;
• goes past the lungs in capillaries where it is oxygenated;
• then re-enters the heart through the pulmonary vein into the left atrium;
• passes through the left atrio-ventricular valve into the left ventricle;
• then out through the left semi-lunar valve into the aorta (which takes it to the body.)

wikibooks

Veins always going into the heart and arteries away from it.
Atrium means entrance hall in latin.
Pulmonary means to do with the lungs.

The mechanism of breathing.

When volume is increased pressure is decreased.
Air rushes into areas of lower pressure.
So increasing volume in the lungs brings air in:

Breathing in (inspiration)
Diaphragm contracts: flattens- increasing volume.
Intercostal  muscles contract: pulling up and out- increasing volume.

When volume is decreased it increases pressure.
Air rushes to areas of lower pressure.
So if volume is decreased in the lungs air will rush out:

Breathing out (Expiration)
Diaphragm relaxes: becoming a dome shape and pushing up- decreasing volume.
Intercostal muscles relax: pushing the ribcage down and in- decreasing volume.

Pulmonary ventilation as the product of tidal volume and ventilation rate.

Tidal volume is the amount of air breathed in. Measured in decemeters cubed.

Ventilation rate is the number of breaths taken in one minute. Measured in minutes to the power of -1.

If you times these two things together you get a measure of pulmonary ventilation in dm3min-1.

The exchange of gases in the lungs.

Oxygen diffuses from the alveoli- where it is in high concentration- into the capillaries- where it is in low concentration.

Carbon dioxide diffuses from the capillaries- high conc.- into the alveoli- low conc..