3.2 TRANSPORT IN ANIMALS Flashcards
State the need for transport systems in multicellular animals
- Multicellular animals cells have a long diffusion distance, so diffusion is not efficient
- Multicellular animals have small SA:V ratio
- Multicellular animals have a higher level of metabolic activity
Define and describe single circulatory systems
- Where the blood flows through heart just once per circulation of the body
- (heart - gills - body)
Blood flows through two sets of capillaries before going back to heart - Blood returns to heart slowly,low pressure
- For animals with low metabolic activity
Define and describe double circulatory systems
- Where the blood flows through heart twice per circulation of the body
- (heart - lungs - heart - body)
- Blood flows through one set of capillaries before going back to heart
- Blood returns to heart quicker/ higher pressure
- For animals with high metabolic activity
Define closed circulatory system
- Where blood is maintained inside vessels
Define open circulatory system
- Where blood is not maintained in vessels
State three similarities between open and closed circulatory systems
- Both have liquid transport medium
- Both have vessels to transport the medium
- Both have pumping mechanism to move medium around the system
State three differences between open and closed circulatory systems
- In open : transport medium in direct contact with cells, transport medium pumped into body cavity at low pressure/slowly , has only a few vessels
- In closed : transport medium has no direct contact with cells, transport medium pumped around body at high pressure/quickly , has many vessels with transport medium exclusively enclosed in them
State three features of a good transport system
1) A pump to create efficient pressure to push transport medium around
2) Exchange surfaces that enable waste/nutrient exchange
3) Vessels to carry transport medium by mass flow
Draw the structure of arteries, veins and capillaries
Describe veins/venules
- Blood travels towards the heart
- Blood is at low pressure so thin walls
- Lumen is large to ease the flow of blood
- Valves prevent the backflow of blood
- Thin elastic tissue/thin smooth muscle as NO constriction/recoil
Describe arteries/atrioles
- Blood travels away from the heart
- Blood is at high pressure so thick walls to withstand it
- Lumen is small to maintain high pressure
- Elastic tissue allows for stretch/recoil for flunctuations neart the heart
- Smooth muscle can contrict to resist flow and reduce rate when needed
Describe capillaries
- Very thin (one cell thick)
- Lumen very narrow
- Walls are leaky to allow blood plasma and dissolved substances to leave
- Endothelium is flattened to reduce diffusion distance
Define plasma
- The fluid portion of the blood conatining dissolved substances (e.g CO2,O2,glucose,amino acids,mineral ions,hormones,proteins)
Define tissue fluid
- The plamsa fluid surrounding cells
Define lymph
- The plasma fluid held in the lymphatic system
Define lymphatic system
- System of tubes that return excess tissue fluid to the blood system
Define hydrostatic pressure
- Pressure that a fluid exerts when pushing on vessel walls
Define oncotic pressure
- pressure created by the osmotic effect of solutes
Describe the movement of fluids
1) Blood has relatively high hydrostatic pressure at the arteriol end of the capilaries
2) Thus, blood plasma fluid is pushed out the capilaries tiny gaps into the surrounding cells
3) Plamsa proteins however are too large to be forced out, so are not present in the tissue fluid
4) Exchange occurs across plasma cell surface membrane of cells with the surrounding tissue fluid
5) O2 and nutrients enter the cells, CO2 and waste leaves the cell
6) At the venous end of the capilaries, the hydrostatic pressure is much lower which allows SOME of the tissue fluid to return with the CO2 and waste
7) The rest of the excess fluid goes into the lymphatic system which is returned to the blood
Compare the composition of blood plasma,tissue fluid and lymph
State the effect of hydrostatic pressure of the blood
- Pushes plasma fluid out into the tissues
State the effect of hydrostatic pressure on tissue fluid
- Pushes fluid back into the capilaries
State the effect of oncotic pressure on the blood
- Pulls water back into the blood (negative value)
State the effect of oncotic pressure on tissue fluid
- Pulls water into the tissue fluid
Compare the relative hydrostatic and oncotic pressures in the venule and atriole end of the capillaries
- Arteriole end has higher hydrostatic pressure than oncotic pressure, so fluid moves out
- Venule end has a lower hydrostatic oressure than oncotic pressure, so fluid moves in
- (Remaining fluid returns to circulation via the lymphatic system)
Compare the sides of the heart
- Right side pumps deoxygenated blood from the body to the lungs to become oxygenated
- Left side pumps oxygenated blood to the rest of the body
State the pathway of blood in the heart
Body → Vena cava → Right atrium → Tricuspid atrio-ventricular valve → Right ventricle → Semi-lunar valve → Pulmonary artery → Lungs → Pulmonary vein → Left atrium → Bicuspid semi-lunar valve → Left ventricle → Semi-lunar valve → Aorta → Body
Define cardiac muscle
- Muscle found in the walls of the heart chamber that automatically contracts and relaxes without ever tiring (myogenic)
Explain why the left ventricle has thicker cardiac muscle
- So it can contract with more force to push/pump blood at a higher pressure so it flow around the whole body
State how valves are opened/closed
- By changes in pressure of the heart chambers
State the formula for cardiac output
Define stroke volume
- The volume of blood pumped by the heart in one minute
Define heart rate
- A measure of heart beats per minute
Define cardiac cycle
- The contractions and relaxations of cardiac muscle that result in pressure and volume changes that enable the valves to maintain a unidirectional flow of blood
Draw the cardiac cycle
Explain what causes valves to OPEN
- When pressure is higher behind them
Explain diastole
- Atrium and ventricle walls relax but pressure in the ventricles drop lower than pressure in the atrium (due to previous blood loss)
- Atrioventricular valves thus open to allow blood to flood in
- Semilunar valves are closed to prevent blood escaping out
- Elastic recoil allows chamber volume increase
Explain atrial systole
- Both atria contract together creating a SMALL pressure increase
- Thus, the atrioventricular valves open and blood is forced into the ventricles
Explain ventricular systole
- Both ventricles contract from the apex/base while the atria relax
- The increased pressure in ventricles result in closure of the atrioventricular valves and opening of the semilunar valves
- Thus, blood is forced out of the pulmonary artery and aorta
Draw a pressure graph of the cardiac cycle
State what the rate of contraction is determined by
-Waves of electrical activity
Define sino-atrial node (SAN)
- The pacemaker in the top right atrium, sends out waves of electrical excitation at regular intervals to initiate contractions
Define atrio-ventricular node (AVN)
- The node between atria and ventricles that delay the wave of excitation to ensure the atria has finished contracting, so ventricles can fill up with blood
Define purkyne tissue
- Tissue that contains mucle fibres that conduct the wave of excitation from the AVN down to the septum between ventricles
Describe the steps of electrical excitation in the heart
1) SAN generates a wave of electrical impulse over the atria, causing them to contract (P)
2) A layer of non-conducting tissue in the atrio-ventricular septum prevents the wave from crossing to ventricles
3) Instead, the wave of excitation passes through the AVN between both atria
4) After a short delay form the AVN, the AVN conducts a wave of excitation through the ventricles, along the purkyne tissue, down the septum to the base/apex
5) Here, it spreads upwards, over ventricle walls
6) Cardiac muscles now contract from the base/apex upwards, causing blood to be ofrced out of the major arteries (QRS)
Define bradycardia
- Slow heart rate
Define tachycardia
- Fast heart rate
Define ectopic
- Early ventricular beat
Define fibrillation
- Atria beats more frequently than ventricles
- No clear P-waves
Draw a wave of excitation
(Normal heart rate)
What is an electrocardiodiagram (ecg) used for
- To measure heart rate rythms
State how oxygen is transported
- Via the conjucated globular protein haemoglobin in erythrocytes
State the three ways carbon dioxide is transported
1) Dissolved in plasma
2) As haemoglobinic acid (when carbon dioxide reversibly binds to haemoglobin)
3) As hydrogen carbonate ions HCO3- (when it joins with water in red blood cells cytoplasm via the catalyst carbonic anhydrase)
Define haemoglobinic acid
- The compound formed by the buffering action of haemoglobin as it combines with excess hydrogen ions in red blood cells
Define chloride shift
- The movement of chloride ions into red blood cells to balance the charge as hydrogen carbonate ions leave the red blood cells
Define carbonic anhydrase
- The enzyme that catalyses combination of CO2 and H2O in the cytoplasm of red blood cells to form hydrogen carbonate ions HCO3-
Define bohr effect
- When partial pressure (concentration) of CO2 results in haemoglobin having a reduced affinity for oxgyen resulting in dissociation of oxygen
Explain the bohr effect
(Effect of increasing CO2 concentration on haemaglobin)
- CO2 enters red blood cells and forms carbonic acid HCO3- which releases a H+ ion when it dissociates so increases acidity of pH of red blood cell
- The acidity now effects the tertiary structure of haemoglobin and reduces haemoglobins affinity for oxygen, so less is taken up
(Causes the curved line to shift to the right)
Draw the formation of hydrogen carbonate ions HCO3- in red blood cells
Compare and explain fetal and adult haemoglobin
- Fetal haemoglobin has a higher affinity for oxygen because the placenta has a low oxygen partial pressure (concentration) so must be able to take up oxygen at low partial pressures when adult haemoglobin dissociates/releases oxygen in the placentas low oxygen partial pressure
State where haemoglobins affinity for oxygen comes from
- The Fe2+ ion
How many oxygen molecules can one RBC hold
- Four
