3.4.1 Mass Transport In Animals

The left side of the heart pumps blood to the rest of the body and the right side of the heart pumps blood to the lungs. Blood passes through the heart twice for each circuit of the body

It increases blood pressure so increases rate of blood flow

The coronary arteries supply blood containing oxygen to the heart muscles A blockage in this artery would restrict the flow of blood and oxygen to the heart muscle If the clot completely blocks the coronary artery, then no oxygen will reach the muscle of the heart The heart muscle can no longer respire so some heart muscle cells begin to die

Blood flows from a high to low pressure, down a pressure gradient There are valves present which prevent the backflow of blood

The heart muscle is relaxed There is a low pressure in the ventricles but pressure increases in the atria The AV valves are slightly open So blood starts to enter ventricles

MPVD The atrial muscle contracts So the pressure increases the atria increases This increase in pressure forces the AV valves open So blood flows from the atria to the ventricles because pressure is lower in the ventricles than the atria

MPVD The ventricular muscle contracts Pressure in the ventricles increases So pressure in the ventricle is higher than the artery So blood flows from the ventricle to the arteries, Forcing the semi lunar valve open But the AV valves are forced closed because the pressure in the ventricles is higher than in the atria Av valves prevent blood flowing back into the atria

The muscle relaxes Pressure in all chambers decreases Pressure in arteries is now greater than in ventricles SL valves forced closed Blood enters atria from veins

Number of heart beats per minute

The volume of blood pumped during each heart beat

The volume of blood pumped by the heart per minute

HR= 60/time taken for one beat

Cardiac output= stroke volume x heart rate

Size of the heart increases Muscle size in the wall increases Strength of contraction increases Stroke volume increases Cardiac output stays the same

Elastic tissue allows stretch and recoil to maintain blood pressure Elastic tissue stretches when ventricles contract Muscle allows contraction and vasoconstriction Thick walls stop bursting Smooth endothelium reduces friction SL valves prevent backflow

There is a high hydrostatic pressure in the capillaries due to contraction of ventricles This is greater than the hydrostatic pressure of tissue fluid outside of capillaries Therefore water moves out of the capillaries by osmosis forming tissue fluid Small molecules are forced out and plasma proteins and RBC remain in the blood since they are too large to cross the membrane

The loss of water from capillaries reduces the hydrostatic pressure inside So now the hydrostatic pressure is lower inside the capillaries than the tissue fluid outside The water potential is lower inside the capillary than outside in the tissue fluid since water has been lost from capillaries and rbc and plasma proteins make water potential more negative So water/ tissue fluid re enters the capillaries by osmosis down a water potential gradient

There is more time for exchange of substances

They contract to make the lumen more narrow

More efficient since there is more time for exchange

Has a quaternary structure Each polypeptide is associated with a haem group which contains an Fe 2+ ion Each haem group combines temporarily with an oxygen molecule, so four oxygen molecules can be carried by one haemoglobin molecule

Bigger increase in pO2 causes small increase in % saturation of oxygen because it is difficult to bind the first oxygen molecule to the haemoglobin due to the shape of it Smaller increase in pO2 causes a larger increase in % saturation of oxygen because the binding of the first oxygen changes the tertiary/quaternary structure of the haemoglobin molecule so opens more binding sites for O2 so makes it much easier for other O2 molecules to bind Bigger increase in pO2 causes a smaller increase in % saturation because binding of 4th oxygen molecule is harder since it is less likely that the 4th oxygen molecule will find an empty binding site

In the tissues, CO2 is released by respiring cells This forms carbonic acid (when the CO2 reacts with the blood) which dissociates into H+ ions lowering the pH of the blood The acidity changes the shape of the Hb so now it has a lower affinity for oxygen O2 is now more readily released to respiring tissues

The pO2 is lower in these environments, So the Hb has a higher affinity for oxygen This means that it is able to load more oxygen at lower pO2 So it is saturated with oxygen at lower pO2 And dissociation curve is shifted to the left