3:1:2 Transport in Animals Flashcards
Why do animals need to exchange substances
They need to exchange substances with their external environment (take oxygen and nutrients in, and waste products generated need to be released) and this happens at the exchange site of the organism
Why do large organisms need transport systems
Substances are said to not have entered or left an organism until it crosses the cell surface membrane, but they need transport systems due to the large transport distances, small SA:V, and high levels of activity
Why do large organisms have large transport distances
- Large and complex organisms tend to have exchange systems that are further away from each other
- This makes simple diffusion too slow to meet metabolic requirements, so a system is needed
Why do large organisms have small SA:V
- As the size of the organism increases, the volume increases
- This also means the surface area decreases, and there is less surface area for the absorption of substances
- Additionally the large volume means a larger diffusion distance
Why do large organisms have increased metabolic activity
- They are more physically active and also contain more cells than smaller organisms
- A larger number of cells means a higher level of metabolic activity
- The demand for substances like O2 and nutrients is higher
What are mass transport systems and why are they important
- Mass flow (bulk movement of materials moved by force) transport systems enable animals to transport substances to exchange sites which are the areas where diffusion can occur (e.g. circulatory system)
- Bring substances from one exchange site to the other quickly
- Maintain diffusion gradients at exchange sites
- Ensure effective cell activity by upholding the metabolic rate
Why do organisms need circulatory systems
- Cells of organisms need a constant supply of metabolic reactants (e.g. oxygen and glucose)
- Large organisms gain these from specialised exchange surfaces
- These surfaces have long diffusion distances, so are instead attached to mass transport systems
What are single circulatory systems
A circulatory system where the blood passes through the heart once during a complete circuit of the body (e.g. fish)
What is a double circulatory system
A circulatory system where the blood passes through the heart twice during a complete circuit of the body (e.g. mammals)
How does a single circulatory system work
- Deoxygenated blood is pumped to the gills from the heart (one article, one ventricle)
- The gills are the exchange site where O2 and CO2 are exchanged
- The oxygenated blood flows from the gills to the rest of the body to exchange substances
- The blood returns to the heart
How does a double circulatory system work
- As the blood passes through the heart twice, there is a right (deoxygenated) and left (oxygenated) side
- Blood in the right side of the heart leaves and travels to the lungs
- The blood that has gained oxygen from the lungs returns to the left side of the heart to be pumped around the rest of the body
- When the blood has passed through the body it returns to the right side of the heart
- When blood passes through an organ it goes straight back to the heart, apart from blood flow from the gut to the liver through the hepatic vein (to give the waste products)
What are the advantages of a double circulatory system
- When blood enters the capillary network the pressure and speed decreases
- Blood only has to pass through one capillary system before returning to the heart (unlike the two in single circulatory systems)
- Maintains a higher blood pressure and average speed flow
- High pressure allows a maintenance of a steep concentration gradient which allows for efficient exchange
What is an open circulatory system
A circulatory system where blood isn’t contained within blood vessels but it is pumped directly into body cavities (e.g. molluscs)
What is a closed circulatory system
A circulatory system where blood is pumped around the body and is always contained within a network of blood vessels
What is the human pulmonary circulatory system
The right side of the heart pumps deoxygenated blood to the lungs for gas exchange
What is the systemic circulatory system
Oxygenated blood from the lungs returns to the left side of the heart so it can be pumped efficiently (high pressure) around the body
Describe the circulatory system in insects and label a diagram
- Oxygen is delivered into the Haemolymph through trachea (system of tubes connecting to outside)
- Tubular heart in abdomen pumps haemolymph (blood) into the dorsal vessel (main blood vessel)
- Haemolymph delivered to the haemocoel (body cavity)
- Haemolymph surrounds organs and delivers oxygen directly into the tissue
- Haemolymph renters the heart via Ostia (one way valves
What are arteries
Blood vessels that transport blood away from the heart at high pressure to tissues
What are arterioles
Narrow blood vessels that branch from arteries, which transport blood to capillaries
What are veins
Blood vessels which transport blood to the heart at low presssure
What are venules
Narrow blood vessels that transport blood from the capillaries to the veins
What is the structure of arteries
- Narrow lumen and pulse to maintain high blood pressure
- Tunica intima: endothelium lumen lining, connective tissue, elastic fibres
- Tunica media: smooth muscle cells, thick elastic tissue layer
- Tunica adventitia: collagen
Why do endothelium cells line blood vessel lumens
Once cell thick for short diffusion distance, and it’s smooth to reduce friction of blood flow
Why do arteries/arterioles have a muscle cell layer
To allow the vessel to contract the lumen to regulate blood flow, as well as to withstand high pressure
What do arteries/arterioles/veins have elastic fibres
To stretch and recoil to maintain blood pressure
What is the structure of arterioles
- Muscle layer to contract and partially restrict blood flow
- Low proportion of elastic fibres
- Endothelium lines lumen
Why is collagen included in veins/arteries
It helps with strength and keeping the shape of the blood vessel
What is the structure of veins
- Veins have a wide lumen and no pulse, as well as valves
- Tunica intima: endothelium lined lumen
- Tunica media: only elastic fibres
- Tunica adventica: lots of collagen
Why do veins have valves
To prevent back flow of low pressure blood to the heart
What is the structure of venules
- Endothelium lined wide lumen
- No muscle or elastic fibres
- Collagen exterior
What are capillaries
- Form networks (capillary beds) which branch between cells
- Part of exchange surfaces, allow substance to diffuse in and out
What is the structure of capillaries
- Small lumen allowing blood to move slowly for maximum diffusion
- Wall made from single celled layer of endothelial cells to reduce diffusion distance
- Pores in cell to allow blood plasma to leak out and form tissue fluid
What is blood plasma
Straw coloured liquid that makes up 55% of blood, and is composed mainly of of water so many substances are soluble and can be transported
What is tissue fluid
Blood plasma which leaks through capillary pores (contains less proteins as they are too big for the pores), allowing the exchange of substances between cells and blood
What is hydrostatic pressure and its usual value in humans
- Pressure exerted by fluid (e.g. blood)
- 4.6kPa
What is oncotic pressure and its values in humans
- Osmotic pressure exerted by plasma proteins within a blood vessel
- The tendency of water to move into the blood via osmosis
- -3.3kPa
How is tissue fluid formed at the arterial end of capillary
- Hydrostatic pressure is great enough to force fluid out of the capillary
- Proteins remain in blood as too large for capillary pores
- Increased blood protein content creates a water potential gradient between capillary and tissue fluid
- Hydrostatic pressure is greater than osmotic pressure so net movement of water is out of the capillaries and into tissue fluid against the water potential gradient
How is tissue fluid formed at the venous end of the capillary
- Hydrostatic pressure reduced due to increased distance from heart
- Water potential gradient between tissue fluid and capillary is the same as at arterial end
- Osmotic pressure is greater than hydrostatic pressure so water moves into capillary from tissue fluid down the water potential gradient
What percentage of tissue fluid is collected by lymph vessels
90% of fluid lost at the arterial end is collected at the venous end, and 10% remains as tissue fluid and is returned by the lymph vessels
What happens to the formation of tissue fluid if blood pressure is high
When hypertension occurs the pressure at the arterial end is higher and more fluid is forced out of the capillary, causing it to accumulate around the tissues (oedema)
Labelled heart diagram
What are coronary arteries
Arteries which supply blood to the heart, if they get blocked it can lead to angina or heart attack
What is atrial systole
- Atria walls contract (volume decrease, pressure increase)
- Pressure increases above ventricle pressure causing bicuspid and tricuspid valves to open
- Blood forced into ventricles causing slight increase in ventricular pressure and volume
- Ventricles are relaxed (ventricular diastole coincides with atrial systole)
What is ventricular systole
- Walls of ventricles contract (volume decreases, pressure increases)
- Pressure in ventricles rise above the atria, forcing the bicuspid and tricuspid valves to close
- Pressure in ventricles rises above that in aorta and pulmonary artery forcing semilunar valves to open and blood is forced into arteries and out of heart
- Atrial diastole coincides with ventricular systole
What happens during cardiac diastole
- The ventricles and atria are both relaxed
- Pressure in ventricles drops below that of aorta and pulmonary artery and semilunar valves close
- Atria fill with blood and pressure rises above that of the ventricles forcing the bicuspid and tricuspid valves to open
- The cycle begins again with atrial systole
What happens at point A
- Both left atrium and left ventricle are relaxed
- Pressure at 0kPa
What happens between point A and B
- Atrial systole occurs
- Left atria contracts and blood enters left ventricle
What happens at point B
- Ventricular systole begins
- Ventricular pressure increases
- AV closes and causes LUB heart sound
- Pressure in atria decreases
What happens at point C
- Pressure in ventricle exceeds aorta
- Ventricle contracts
- Aortic valve opens
- Blood enters aorta causing increase aortic pressure
What happens at point E
- AV valves open as atria pressure increases higher than ventricle pressure
- Atria pressure normally lower due to thinner walls
- Blood enters atria and cycle begins again
How to calculate cardiac output
- Heart rate: number of beats per minute
- Stroke volume: volume of blood pumped from the left ventricle during one cardiac cycle
- Cardiac output = heart rate x stroke volume
How is the heart beat controlled
- Myogenic (no external stimulus)
- Intrinsic rhythm around 60 beats/minute
- Sinoatrial node initiates wave of depolarisation causing atria to contract (70 impulses/minute)
- Annulus fibrosus is non-conducting tissue that prevents depolarisation spreading to ventricles
- Depolarisation carried to atrioventricular node, and after a slight delay of 0.1 secs (so atria can contract before ventricles) it is stimulated (50 impulses/minute) and stimulation (action potential) is passed to bundle of His
- Bundle of His is collecting tissue in septum which divides into two conducting fibres (Purkyne tissue) and carries excitation with it
- Purkyne fibres spread around ventricles and initiate depolarisation of ventricles from apex of heart
- Causes ventricles to contract and blood forced out of the heart
What causes the P wave
The depolarisation of the atria, resulting in atrial contraction (atrial systole)
What causes the QRS complex
- Depolarisation of the ventricles resulting in ventricular contraction (ventricular systole)
- Largest wave as ventricles have largest muscle mass
What causes the T wave
Re-polarisation of the ventricles resulting in ventricular relaxation (ventricular diastole)
What causes the U wave
Uncertain, potentially caused by the re-polarisation of Purkyne fibres
How do ECG machines diagnose tachycardia
- Heat beating too fast
- Resting heart rate over 100 bpm
- Peaks are close together
How do ECG machines diagnose bradycardia
- Heart beating too slow
- Resting heart beat below 60 bpm
- Peaks are far apart
How do ECG machines diagnose ectopic heartbeat
- Early heartbeat followed by a pause
- Heart beat come too early
How do ECG machines diagnose fibrillation
Irregular heartbeat disrupts rhythm of heart
How are hydrogen carbonate ions formed
- Carbon dioxide diffuses from plasma into RBC’s
- CO2 combines with water to form H2CO3 in a reaction catalysed by carbonic anhydride (found in RBC, so H2CO3 is formed slower in plasma)
- Carbonic acid dissociated into H+ and HCO3- ions
- H+ combined with haemoglobin (buffer) forming haemoglobinic acid preventing the ions from lowering the RBC pH
- HCO3- ions diffuse into plasma
Explain the oxygen dissociation curve shape
- Binding of first oxygen to haemoglobin happens slowly due to shape of haemoglobin molecule (shallow curve)
- Haemoglobin protein undergoes conformational change, so second oxygen can bind easier (cooperative binding) (steep middle curve)
- Haemoglobin molecule approaches saturation and 4th O2 molecule binds slower due to lack of binding sites (shallow curve at top)
How is the oxygen dissociation graph interpreted when read left to right
- Rate of haemoglobin binding to oxygen
- At low pO2 oxygen binds slowly, as haemoglobin has a low affinity for O2 at low pO2, so haemoglobin isn’t saturated
- At medium pO2 oxygen binds faster, as haemoglobin has high affinity for O2 at medium pO2, and haemoglobin is saturated at high rates
- At high pO2 bonds fast, as haemoglobin has high affinity for O2 at high pO2, but there are less binding sites for O2 so saturation increases slowly
How is the oxygen dissociation graph interpreted when read right to left
- Rate of haemoglobin dissociating with oxygen
- High pO2 (lungs) there is low dissociation
- Medium pO2 allows for ready dissociation (steep graph) (correlates with pO2 in respiring tissue as it needs O2) (decrease in pO2 = large decrease in haemoglobin saturation)
- Low pO2 there is slow dissociation as release of last O2 in binding site is difficult
How is foetal haemoglobin different than adult haemoglobin
- Higher affinity for oxygen, allowing it to get oxygen from its mothers blood at the placenta
- Can bind to O2 at low pO2, as that is when mothers haemoglobin is dissociating with O2
- The foetal haemoglobin curve on the oxygen dissociation graph is shifted to the left
- At any given pO2 foetal haemoglobin has a higher % saturation than adult haemoglobin
- Baby produces adult haemoglobin at birth gradually
