3.1.2 Transport in animals Flashcards
Why do multicellular organisms require transport systems
- Large size (small SA:V) so need high metabolic rates
- Demand for oxygen is high so need a specialised system to ensure a strong supply to all respiring tissues
Summarise the different types of circulatory systems
- Open = blood can diffuse out of vessels e.g. insects
- Closed = blood confined to vessels e.g. fish and mammals
- Single = blood passes through pump once per circuit of the body
- Double = blood passes through heart twice per circuit of the body
Relate the structure of arteries to their function
- Thick muscular walls to handle high pressure without tearing
- Elastic tissue allows recoil to prevent pressure surges
- Narrow lumen to maintain high pressure
Relate the structure of veins to their function
- Thin walls due to lower pressure
- Require valves to ensure blood doesnt flow backwards
- Have less muscle and elastic tissue as they dont control blood flow
Relate the structure of capillaries to their function
- Walls only 1 cell thick for a short diffusion pathway
- Very narrow so can permeate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues
- Numerous and highly branched providing a large surface area
Relate the structure of arterioles and venules to their functions
- Branch off arteries and veins so that the change in pressure is more gradual as blood passes through increasingly small vessels
What is tissue fluid
- A watery substance containing glucose, amino acids, oxygen and other activities
- Supplies these to the cells while removing waste materials
What types of pressure influence formation of tissue fluid
- Hydrostatic pressure: higher at arterial end of capillary than venous end
- Oncotic pressure: changing water potential of the capillaries as water moves out induced by proteins in the plasma
How is tissue fluid formed
- As blood is pumped through increasingly small vessels hydrostatic pressure is greater than oncotic pressure so fluid moves out of the capillaries
- It then exchanges substances with cells
How does tissue fluid differ from blood and lymph
- Tissue fluid is formed from blood but doesnt contain red blood cells, platelets and various other solutes usually present in blood
- After tissue fluid has bathed cells it becomes lymph and therefore this contains less oxygen and nutrients and more waste products
Describe what is happening during cardiac diastole
- The heart is relaxed
- Blood enters the atria increasing pressure and pushing open the atrioventricular valves
- This allows blood to flow into the ventricles
- Pressure in the heart is lower than in the arteries so semilunar valves remain closed
Describe what is happening during atrial systole
The atria contract pushing any remaining blood into the ventricles
Describe what happens during ventricular systole
- The ventricles contract
- The pressure increases, closing the atrioventricular valves to prevent backflow and opening semilunar valves
- Blood flows into the arteries
How do you calculate cardiac output
cardiac output = heart rate x stroke volume
what does myogenic mean
The hearts contraction is initiated from withing the muscle itself rather than nerve impulses
Explain how the heart contracts
- SAN initiates and spreads impulse across the atria so they contract
- AVN receives, delays and then conveys the impulse down the bundle of his
- Impulse travels into the purkinje fibres which branch across the ventricles so they contract from the bottom up
What is an ECG
A graph showing the amount of electrical activity in the heart during the cardiac cycle
Describe types of abnormal activity that can be seen on an ECG
- Tachycardia: fast heart beat
- Bradycardia: slow heart beat
- Fibrillation: irregular, fast heart beat
- Ectopic: early or extra heartbeat
Describe the role of haemoglobin
- Present in red blood cells
- Oxygen molecules bind to haem groups and are carried around the body, then released where they are needed in respiring tissues
How does partial pressure of oxygen affect oxygen haemoglobin binding
- As partial pressure of oxygen increases the affinity of haemoglobin for oxygen also increases so oxygen binds tightly to haemoglobin
- When partial pressure is low oxygen is released from haemoglobin
What do oxyhaemoglobin dissociation curves show
- Saturation of haemoglobin with oxygen (%) plotted against partial pressure of oxygen (kPa)
- Curves further to the left show the haemoglobin has a higher affinity for oxygen
Describe the Bohr effect
- As partial pressure of carbon dioxide increases, the conditions become acidic causing haemoglobin to change shape
- The affinity of haemoglobin for oxygen therefore decreases so oxygen is released from haemoglobin
Explain the role of carbonic anhydrase in the Bohr effect
- Carbonic anhydrase is present in red blood cells
- Converts carbon dioxide to carbonic acid which dissociates to produce H+ ions
- These combine with the haemoglobin to form haemoglobinic acid
- Encourages oxygen to dissociate from haemoglobin
Explain the role of bicarbonate ions (HCO3-) in gas exchange
- Produced alongside carbonic acid
- 70% of carbon dioxide is carried in this form
- In the lungs bicarbonate ions are converted back into carbon dioxide which we breathe out
