Mass Transport & The Heart

Mass Transport in Animals

Red blood cells transport oxygen using the protein haemoglobin
- oxygen + haemoglobin = oxyhaemoglobin
Haemoglobin is made up of 4 polypeptide chains, each containing a prosthetic haem group. Each haem group binds one oxygen molecule
Haemoglobin saturation depends on the partial pressure of oxygen (pO2). Binding the first oxygen creates a conformational change, making the haem group more accessible
Fetal haemoglobin has a oxygen affinity higher than adult haemoglobin because fetal haemoglobin must be able to bind oxygen from adult haemoglobin in the placenta
Carbon dioxide is transported in the blood for release from the lungs
- 5% in blood plasma
- 10% is combined with haemoglobin to make carbaminohaemoglobin
- 85% Hydrogencarbonate ions dissolved in blood plasma
Bohr Effect- Haemoglobin's oxygen binding affinity is inversely related to the concentration of carbon dioxide, causing the oxygen dissociation curve to shift
A good transport system has
- A fluid medium to transport substances
- A pump to create pressure for the circulation of the transport fluid
- Exchange surfaces

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An open circulatory system is one in which the blood is not held in vessels
A closed circulatory system is one in which the blood is conatined within vessels
A single circulatory system the blood flows through the heart once for every circuit
A double circulatory system the blood flows through the heart twice for every circuit
Tissue fluid formation
- Arteriole: hydrostatic pressure > oncotic pressure, so fluid moves out
- Venule: Hydrostatic pressure < oncotic pressure, so fluid moves in
  - Remaining fluid returns to circulation via the lymphatics system

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The cardiac cycle is the sequence of events that occur within one full beat of the heart
Systole is the contraction stage
Diastole is the relaxation stage
Cardiac msucle is myogenic, meaning it can contract and relax without recieving signals from the nervous system
The sinoatrial node (SAN) sends out regular waves of electrical activity to the left and right atrial wall causing contraction
- The electrical waves are then passed onto the atrioventricular node (AVN), then to the bundle of his
  - with a slight delay, the bundle of his splits into the purkynge tissue, causing contraction of the left & right ventricles from the bottom up
The rate at which the SAN fires is controlled inconsciously by the medulla oblongata in the autonomic nervous system

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High blood pressure
- Baroreceptors in the aorta & carotid arteries
  - Medulla sends impulses along parasympathetic neurones, using acetylcholine to reduce the heart rate
Low blood pressure
- Baroreceptor in the aorta & carotid arteries
  - Medulla sends impluses along sympathetic neurones, using noradreniline to increase the heart rate
High blood O2, pH or low CO2
- chemoreceptors in the aorta carotid arteries & medulla
  - Medulla sends impulses along parasympathetic neurones, using acetylcholine to reduce the heart rate
Low blood O2, pH or high CO2
- chemoreceptors in the aorta carotid arteries & medulla
  - Medulla sends impluses along sympathetic neurones, using noradreniline to increase the heart rate

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ECGs can detect the electrical signals through the skin
- P wave shows atrial systole
- QRS complex shows ventricular contraction
- T wave shows diastole

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The phloem transports assimilates from sources to sinks via translocation
Sucrose is actively transported into the companion cells and moves via diffusion into the sieve tube followed by water. Assimilates move from area of high to low pressure (mass flow). At the sink the solutes are removed, water leaving by osmosis.

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Water moves through plant tissue via 3 pathways
The xylem transports water and mineral ions up the plant against gravity. It is made of dead cells and lignified
Water evapourates from the leaves creating tension (transpiration), and the cohesion nature of water moves the whole column of water up the xylem (cohesion-tension theory)
Water moves up the xylem due to capillary action, root pressure and transpiration pull
The rate of transpiration is affected by: light, temperature, humidity & wind
Xerophytes are plants adapted to living in dry conditions. They can reduce water loss by having: hairs, waxy cuticle, small leaves, sunken stomata, rolled leaves
Hydrophytes are plants adapted to living in water. their adaptations include: stomata on the upper epidermis, using hydathodes, large air spaces for buoyancy and oxygen diffusion

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