PHYLL 2066 - module 3 cardiovascular system

How do cardiac muscle cells interconnec

Through intercollated discs.

Why is it important to have the cardiac cells interconnecting?

To allow for the flow of ions to pass on action potentials quickly, it allows the cells of the heart to contract as one.

How does the auto-rhythimicitiy of the heart cells work?

There is spontaneous depolarisation, known as a pacemaker potential, which will cause a slow drift towards the threshold of an action potential. There is no input from the nervous system.

What are funny gates?

They are Na+ gated channels in the heart, which open during polarisation which will open during hyper-polarisation, which will allow for the influx of Na+.

How do action potentials travel through the heart?

The process involves the autorhythmic cells. They are in the sinoatrial node, the atrioventricular node and bundle of his. When the APs are generated, they travel through this conduction system.

Where the SA fibres?

In the right atrium.

Where are the AV fibres found?

In the right atrium.

Where are the bundle of his fibres found?

After dividing into left and right branches, the purkinje fibres spread through out the ventricle walls.

What is the cardiac cycle?

The systole-diastole cycle.

What is diastole?

it is the relaxation of the heart muscles.

What is systole?

The contraction of the heart muscles

What is the first heart sound?

It is the closing of the atrioventricular value, it occurs during ventricular systole.

What is the second heart sound?

The closing of the semilunar valve, during ventricular diastole.

What is the relationship between pressure and container size?

Inversely proportional

What is cardiac output?

It is the volume of blood pumped out of the heart every minute.

What is the formula for cardiac output?

CO= heart rate (BPM) x stroke volume (Litres/minute)

What sets the pace of the heart rate?

The sinoartirial node, as it depolarises the quickest.

What affect does the sympathetic system have on heart rate?

It increases the heart rate.

What affect does the parasympathetic nervous system have on heart rate?

It decreases the heart rate.

When would the sympathetic nervous system affect the heart rate?

When experiencing stress.

Where does the sympathetic system affect the heart?

Its fibres lead into the atria and the ventricles.

Where do the parasympathetic fibres end up in the heart?

They only go to the atria and not the ventricles.

What is stroke volume?

The volume of blood pumped out of the ventricle during contraction.

How do you calculate stroke volume?

End diastolic volume - end systolic volume.

What is venous return?

The volume of blood returning to the heart each mintue.

What does an increase in venous return do?

Increases EDV, causes the cardiac muscle to stretch, as the muscle stretches, it makes the next contraction stronger.

What is the purpose of the veins?

it completes the circuit of the heart, and they also act as a reservoir of blood.

what is the mean arterial pressure?

Average blood pressure in arteries. It is closer to diastolic pressure, because he heart spends longer in diastole.

What is the calculation to find the ideal mean arterial pressure?

Diastolic pressure plus 1/3 of pulse pressure.

What affects blood flow through the body?

The activity of the heart, and resistance to blood flow (vessel diameter)

How does the blood vessel’s radius affect the flow?

The larger the radius, the higher the blood flow.

How do you find the mean arterial pressure

By adding the pressure in the right arterioles arteries, capillaries, venules and veins.

How does the body control bloodpressure?

The total peripheral resistance is controlled by the radius of arterioles.

How is blood supply to tissues controlled?

It is controlled by the pre-capillary sphincters in the capillary bed. but the blood will still flow through the metarteriole is complete the circuit so to speak.

Why are capillaries good for diffusion?

Small diffusion distance, large surface area and slow blood flow, allowing for high rates of exchange.

How do solutes exchange in capillary beds?

they exchange via concentration gradients

what is bulk flow?

The continuous flow of fluid and solutes between capillaries and interstitial fluids.

What are the two forces driving bulk flow?

Capillary hydrostatic pressure and blood colloud osmotic pressure.

What is the capillary hydrostatic pressure?

Capillary hydrostatic pressure is the pressure of the blood coming into the arteriole.

What is the blood colloid osmotic pressure?

The pressure caused by osmosis in the veinule

What does a net positive filtration pressure cause?

it favours filtration (the nutrients or whatever into the tissues)

what does negative net filtration pressure favour?

it favours reabsorption. (fluid/ waste products entering back into the blood stream).