6.2a: The Transport System

15/10/2013 § 1 Comment

Hahahahaha, okay, I’m glad we’re out of the digestive system because that stuff makes me feel queasy. The heart is so much more welcoming. You could say this topic is more… heartwarming.

Oh my god that doesn’t even work.

Anyway, the heart. The heart is composed of cardiac muscle (hence we call the heart and vein system the cardiovascular system) and is a double pump. The right side pumps blood to the lungs and is called the pulmonary circulation. The left side pumps blood to all of the other organs in the body and is called the systemic circulation. In the pulmonary circulation, blood that flows through is deoxygenated. Once it gets to the heart for systemic circulation, it’s been oxygenated. These two flows of blood shouldn’t mix.

The pumping of the heart is super systematic. Structures called the atria (atrium = singular), are the collecting chambers in the heart and are responsible for gathering blood from the veins. Then there are ventricles, which are the main pumpers, using high pressure. Then there are valves that are there to make sure blood always flows the right way and never back or into the wrong tube (vein/artery).

Every single heartbeat happens just so:

  1. The filled atria’s walls contract and pushes blood into the respective ventricles through the atrioventricular valve (the valve that obviously connects the atrium to the ventricle). At this point, the semilunar valves are still closed so now the ventricles are bloody.
  2. Blood pressure rises in the ventricles, which closes the atrioventricular valves and opens the semilunar valves, preventing any blood from returning back into the atria. Blood is pumped out of the semilunar valves and into the arteries while at the same time the atria start to gather more blood.
  3. When the ventricles empty out of all blood, the release in pressure closes the semilunar valves, which keeps the blood from flowing back into the ventricles. The drop in pressure also opens the atrioventricular valves again, and the whole thing can start again.

The heart is myogenic, which means that the muscles stimulates itself and needs no nerves to function. Nerves that are sent to the brain concerning the heart merely tell it to quicken its beating or to slow it down. Adrenalin is a hormone that speeds up the heart rate.



Page 220, heart action and blood pressures

1. Deduce when blood is being pumped from the atrium to the ventricle. Give both the start and the end times.

It starts at around 0.1 seconds and ends at around 0.35 seconds.

2. Deduce when the ventricle starts to contract.

The ventricle starts to contract at 0.4 seconds.

3. The atrioventricular valve is the valve between the atrium and the ventricle. State when the atrioventricular valve closes.

The atrioventricular valve closes at 0.2 seconds.

4. The semilunar valve is the valve between the ventricle and the artery. State when the semilunar valve opens.

0.15 seconds.

5. Deduce when the semilunar valve closes.

At around 0.4 seconds.

6. Deduce when blood is being pumped from the ventricle to the artery. Give both the start and the end times.

It starts at 0.15 and ends at 0.4 seconds.

7. Deduce when the volume of blood in the ventricle is

a) at a maximum: 0.34 seconds

b) at a minimum: 0.52 seconds

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§ One Response to 6.2a: The Transport System

  • Dave Ferguson says:

    Grade 5 A consistent and thorough understanding of the required knowledge and skills, and the ability to apply them in a variety of situations. The student generally shows evidence of analysis, synthesis and evaluation where appropriate and occasionally demonstrates originality and insight.

    DBQ: heart action and blood pressures
    page 220
    1 Blood is pumped from atria to ventricles 0 seconds to 0.1 seconds (N.B the slight rise in atrial pressure at 0.15 seconds is probably due to the AV valve bulging back into the atria as ventricular systole starts.)
    2 Ventricles start to contract at 0.10 seconds.
    3 AV valve closes at 0.1 seconds (atrial pressure falls below ventricular pressure).
    4 SL valve opens at 0.15 seconds (ventricular pressure rises above arterial pressure).
    5 SL valve closes at 0.4 seconds (ventricular pressure falls below arterial pressure).
    6 Blood is pumped from the ventricle to the artery from 0.15 to 0.4 seconds.
    7 a Blood in the ventricle is at a maximum at 0.1 seconds (just before the SL valve opens).
    b Blood in the ventricle is at a minimum at 0.35 seconds (at the peak of ventricular systole).

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