3.4.A Mass Transport in Animals

• When do atrioventricular valves open and close?

  They open when the pressure in the atruim is greater than the pressure in the ventricle. So they close when the pressure in the atrium is less than the pressure in the ventricle.
• When do semi lunar valves open and close?

  They open when the pressure in the ventricle is greater than the pressure in the aorta. So they close when the pressure in the ventricle is less than the pressure in the aorta.
• Is the beating of two sides synchronised in the cardiac cycle?

  Yes.
• What are the three main stages of the cardiac cycle?

  Atrial systone, Ventricular systone and Diastole.
• What happens during the atrial systole stage of the cardiac cycle? [6]

  ○Walls of the atria contract.

  ○Blood passes through atrio-ventricular valves into ventricles.

  ○Atrial walls are thin so don't produce much pressure but produce enough to open the valve.

  ○This takes approximately 0.1 seconds.

  ○During this stage the ventricular walls remain relaxed.

  ○When the pressure of the blood in the ventricles is higher than the pressure in the atria, the flaps of the atrioventricular valve are pushed shut. Preventing blood from flowing back into the atria.
• What happens during the ventricular systole stage of the cardiac cycle? [6]

  ○Thick muscle walls of ventricles contract.

  ○Blood in ventricles is squeezed and pressure rises.

  ○Pressure of blood in ventricles is higher than that in the arteries leaving the heart.

  ○The semi-lunar valves open.

  ○Blood flows out of the right ventricle into the pulmonary artery and out of the left ventricle into the aorta.

  ○This lasts approximately 0.3 seconds.
• What happens during the diastole stage of the cardiac cycle? [6]

  ○Walls of the atria and ventricles relax.

  ○Dropping the pressure rapidy.

  ○Aterial blood pressure is now higher, forcing semi-lunar valves shut.

  ○Blood can't flow back into the ventricles.

  ○Blood flows from the veins into the atria and the cycle starts again.
• What can we do to calculate the length of one cardiac cycle when looking at a graph? [3]

  Look for repeating patterns. Time is on the X-axis, read between the two repeating peaks and record the time in seconds.
• How can the beats per minute (bpm) of the heart be calculated?

  Divide 60s by the length of one cycle in seconds
• What is cardiac output?

  The volume of blood pumped by the left ventricle of the heart in one minute.
• What is the formula for cardiac output?

  cardiac output = heart rate x stroke volume
• Why do we need transport systems? [2]

  We're active organisms with a low SA:Vol ratio and we need to transport enough oxygen from our lungs to respiring tissues to generate ATP.
• What key features does a transport system need?

  ○A medium to carry materials (plasma).

  ○Mass transport (move in bulk over large distances).

  ○A closed system of branching vessels to distribute oxygen to all tissues.

  ○A mechanism of moving the medium (heart generates a pressure gradient and other structures control the direction of flow).
• What is the structure of the circulatory system? [4]

  It's a closed system, blood is in a vessel making it more efficient as it's easier to maintain pressure this way. It has double circulation, oxygenated blood returns to the heart to ensure enough pressure to pump the blood around the rest of the body which is important for high rates of metabolism.
• Compare the types of circulation between animals, insects and fish.

  Animals have double circulation, insects have open circulation and fish have single circulation.
• What is the purpose of blood flow?

  To carry glucose and oxygen to cells for respiration to produce ATP and to carry carbon dioxide away from cells.
• Why is less muscle needed in the right ventricle compared to the left ventricle? [2]

  The right ventricle only needs to pump blood a short distance to the lungs so requires little muscle to do so compared to the left ventricle which has to pump blood to the rest of the body requiring more muscle to do so.
• What is the corinary artery?

  The heart muscles own blood vessel.
• When the left side of the heart contracts what does the other side do?

  It also contracts and they're synchronised.
• Which side of the heart transports blood to the lungs?

  The right side.
• Describe and explain how capillaries are adapted for the exchange of substances between the blood and the surrounding tissue.

  ○ Fenestrations allow large molecules through singly, slowing blood flow rate and shortening diffusion distance providing more time for difusion.

  ○ Narrow lumen provides a large surface area.

  ○ Due to there being a large number of them and being highly branched a large surface area is provided for diffusion.
• What is hydrostatic pressure?

  The pressure that a fluid exerts on its container.
• What is the direction that fluid moves in a capillary bed due to?

  A balance of hydrostatic pressure and osmosis.
• What is ultrafiltration?

  Ultrafiltration is a type of membrane filtration process that separates particles and solutes of different sizes from a liquid solution.
• !Tissue fluid notes!
• What is haeomoglobin? [3]

  Haemoglobin is a protein with a quatinary structure, it's composed of four subunits each containing a haem group. The haem group contains an iron ion which can associate with one oxygen molecule .
• Oxyhemoglobin is oxygenated haemoglobin. What is deoxygenated haemoglobin called?

  Deoxyhaemoglobin
• How are red blood cells suited for oxygen uptake? [1]

  They have haemoglobin
• What does the partial pressure of oxygen reprrosent?

  The level of oxygen dissolved in plasma
• How does partial pressure allow oxygen to move out of the capillaries and eventually into cells? [2]

  As oxygen is released and carried in a solution the partial pressure of oxygen in the capillaries becomes greater than the partial pressure of oxygen in the surrounding tissues. This causes oxygen to diffuse out of the capillaries and into tissue then finally into cells.
• For haemoglobin to be efficient at transporting what two things must it be? [2]

  Ready to associate with (load) oxygen at gas exchange surfaces and ready to dissociate (unload) oxygen at respiring tissue.
• Why can haemoglobin be ready to associate and dissociate from oxygen when needed? [4]

  It changes its affinity for oxygen under different conditions. Haemoglobin has a lower affinity for oxygen in the presense of CO2 as CO2 reduces the pH and this will affect the shape of haemoglobin so it can't bind to oxygen as easily. This is useful as oxygen needs to be released where there is CO2 as this is where respiration is occuring.