Transport In Animals Flashcards
Why do multocellular organisms require transport systems
Large size (small SA:V) subsequently 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 system
Open = blood can diffuse out of vessels e.g. insects
Closed = blood confined to vessels e.g. fish, 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 surges.
Narrow lumen to maintain pressure
Relate the structure of veins to their functions
Thin walls due to lower pressure
Requires valves to ensure blood doesnt flow backwards. Have less muscular and elastic tissue as they dont have to control blood flow
Relate the structure of capillaries to their functions
Walls only one cell thick, 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 large surface area
Relate the structure of arterioles and venules to their function
Branch off arteries and veins in order to feed blood into capillaries
Smaller than 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 nutrients. It supplies these to the cells, while also removing any 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 capillaries. It then exchanges substances within the cells
How does tissue fluid differ from blood and lymph
Tissue fluid is formed from blood, but not contain red blood cells, platelets, and various other solutes usually present in blood
After tissue fluid has bathed cells it becomes lymph, and there this contains less oxygen and nutrients and more waste products
Describe what happens during cardiac diastole
The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the atriovetricular 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 happens 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 the 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 heart’s contraction is initiated from within the muscle itself, rather than by 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 electrocardiogram (ECG)
A graph showing the amount of electrical activity in the heart during the cardiac cycle
Describe types of abnormal activity that may be seen on an ECG
Tachycardia = fast heartbeat (>100 bpm)
Bradycardia = slow heart beat (<60 bpm)
Fibrillation = irregular, fast heartbeat
Ectopic = extra or early heartbeat
Describe the role of haemoglobin
Present in red blood cells. Oxygen molecules bind to the 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 (in %), plotted against partial pressure of Oxygen (in kPa). Curves further to the left show the haemoglobin has a higher affinity for oxygen
Describe the Bohr effet
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 RBCs
Converts CO2 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 CO2 is carried in this form. In the lungs, bicarbonate ions are converted back into CO2 which we breathe out
Describe the chloride shift
The intake of chlorine ions across a RBC membrane. This repolarises the cell after bicarbonate ions have diffused out
How does foetal haemoglobin differ from adult haemoglobin
The partial pressure of oxygen is low by the time it reaches the foetus, therefore foetal haemoglobin has a higher affinity for oxygen than adult. Allows both mothers and childs oxygen needs to be met
