3.4 - Mass transport in animals Flashcards
What is haemoglobin?
- water soluble globular protein (quaternary structure)
- each molecule can carry 4 O2 molecules
What is the role of haemoglobin and red blood cells in oxygen transport?
bind to O2 and carry molecules
Describe the loading, transport and unloading of oxygen by haemoglobin relative to the oxyhaemoglobin dissociation curve
Left:
- haemoglobin has a higher affinity for O2
- so associates with O2 molecules easily
- forming oxyhaemoglobin
Right: (Bohr effect) - haemoglobin has a lower affinity for O2
- so dissociates from O2 molecules more readily
Describe the cooperative nature of oxygen binding to haemoglobin
- haemoglobin molecule undergoes conformational change to tertiary structure after binding of 1st O2
- breaks H bonds
- becomes easier for subsequent molecules to bind
- creates another binding site
Describe the effect of CO2 concentration on the dissociation of oxyhaemoglobin
- Bohr effect
- decreases pH
- O2 dissociates from haemoglobin more readily as has a lower affinity for O2
Name the blood vessel which supplies oxygen and glucose to the heart muscle
coronary artery
Describe precautions to take during/after a dissection
- carry sharp instruments pointed away from body
- disinfect instruments and surfaces
- wash hands with soap and water before and after
- dispose of organ in separate bag
- use sharp scalpel
- wear gloves
- cover any cuts
Explain how an artery can reduce blood flow into capillaries
- muscle contracts
- narrows lumen
Explain how an atrioventricular valve maintains a unidirectional flow of blood
- pressure in atrium is higher than in ventricle
- so valve opens
- pressure in ventricle is higher than in atrium
- so valve shuts
Describe the structure and function of arteries
- thick muscle: constriction and dilation to control volume of blood
- thick elastic fibres: stretch and recoil in response to heartbeat
- thick wall: prevent bursting due to high pressure
- smooth endothelial lining: reduces friction of blood flow
- smaller lumen than veins
Describe the structure and function of arterioles
- thicker muscular layer than artery: restrict blood flow into capillaries
- thinner elastic layer and wall thickness: low pressure
Describe the structure and function of veins
- relatively thin muscular layer: cannot control blood flow
- relatively thin elastic layer: low pressure
- thin walls: lower pressure so low risk of bursting + easily flattened helping blood flow to heart
- valves: prevent backflow of blood
- wider lumen than arteries: blood flows at lower pressures
Describe the structure of capillaries and the importance of capillary beds as exchange surfaces
- narrow diameter: slows blood flow + maximises diffusion
- no muscle or elastic layer
- 1 cell thick: short diffusion distance
- highly branched capillary network: large SA
Describe how tissue fluid forms and how it is returned to the circulatory system
- contraction of ventricle produces high hydrostatic pressure
- forces H2O out of capillaries
- proteins remain in blood vessel
- creates WP gradient
- H2O moves into blood by osmosis
- returns by lymphatic system
What are the common features of a circulatory system?
- suitable medium
- means of moving medium
- mechanism to control flow around body
- closed system of vessels
Describe the stages of the cardiac cycle
cardiac diastole:
- atria and ventricles relax
- elastic recoil lowers pressure inside heart chambers
- AV valves open
- blood flows into atria
(NB: aorta pressure > ventricle pressure)
atrial systole:
- atria contract forcing blood into ventricles
ventricular systole:
- ventricles contract
- AV valves shut
- semi-lunar valves open
- blood leaves (LV via aorta, RV via pulmonary artery)
Explain the importance of a small increase in pressure at the same time as a small increase in rate of blood flow in aorta
- maintains high pressure
- elastic recoil
What causes a heart attack?
- coronary arteries clogged
- thickens blood
What is an atheroma and describe how it can block blood flow in artery
fatty deposit buildup made from cholesterol
- clogs artery
- artery walls damaged and burst open
- platelets transported to damaged part and accumulate there, causing formation of thrombus
- prevents blood flow in artery as lumen narrows
What do arterioles connect?
arteries to capillaries
Describe how the structure of the aorta is related to its function
- thick muscular layer: contraction
- thick elastic layer: stretch and recoil
- thick wall: withstand high pressures
- smooth endothelial lining: reduces friction so smooth blood flow
Equation for cardiac output
stroke volume x heart rate
