Heart Flashcards
Rbc and hb role in oxygen transport
● Red blood cells contain lots of Hb
○ No nucleus & biconcave → more space for Hb, high SA:V & short diffusion distance
● Hb associates with / binds / loads oxygen at gas exchange surfaces (lungs) where partial pressure of oxygen (pO2) is high
● This forms oxyhaemoglobin which transports oxygen
○ Each can carry four oxygen molecule, one at each Haem group
● Hb dissociates from / unloads oxygen near cells / tissues where pO2 is low
Hb structure
● Protein with a quaternary structure
● Made of 4 polypeptide chains
● Each chain contains a Haem group containing an iron ion (Fe2+)
Explain how the cooperative nature of oxygen binding results in an S-shaped (sigmoid) oxyhaemoglobin dissociation curve
- Binding of first oxygen changes tertiary / quaternary structure of haemoglobin
- This uncovers Haem group binding sites, making further binding of oxygens easier
Bohr effect
Effect of CO2 concentration on dissociation of oxyhaemoglobin → curve shifts to right
Explain effect of CO2 concentration on the dissociation of oxyhaemoglobin
- Increasing blood CO2 eg. due to increased rate of respiration
- Lowers blood pH (more acidic)
- Reducing Hb’s affinity for oxygen as shape / tertiary / quaternary structure changes slightly
- So more / faster unloading of oxygen to respiring cells at a given pO2
Areas with low po2
Respiring tissue
Hb has a low affinity for oxygen
● So oxygen readily unloads / dissociates with Hb
● So % saturation is low
AreaswithhighpO2
Gas exchange surfaces
has a high affinity for oxygen
● So oxygen readily loads / associates with Hb
● So % saturation is high
Advantage of Bohr effect during exercise
More dissociation of oxygen → faster aerobic respiration / less anaerobic respiration → more ATP produced
Explain why different types of haemoglobin can have different oxygen transport properties
Different types of Hb are made of polypeptide chains with slightly different amino acid sequences
● Resulting in different tertiary / quaternary structures / shape
● So they have different affinities for oxyge
Curve shifts left
Hb higher affinity for o2
● More O2 associates with Hb more readily
● At gas exchange surfaces where pO2 is lower
● Eg. organisms in low O2 environments - high
altitudes, underground, or foetuses
Curve shifts right
Hb lower affinity for o2
● More O2 dissociates from Hb more readily
● At respiring tissues where more O2 is needed
● Eg. organisms with high rates of respiration /
metabolic rate (may be small or active)
Describe the general pattern of blood circulation in a mammal
Closed double circulatory system - blood passes through heart twice for every circuit around body:
- Deoxygenated blood in right side of heart pumped to lungs; oxygenated returns to left side
- Oxygenated blood in left side of heart pumped to rest of body; deoxygenated returns to right
Importance of double circulatory system
● Prevents mixing of oxygenated / deoxygenated blood
○ So blood pumped to body is fully saturated with oxygen for aerobic respiration
● Blood can be pumped to body at a higher pressure (after being lower from lungs) ○ Substances taken to / removed from body cells quicker / more efficiently
Vena cava
transports deoxygenated blood from respiring body tissues → heart
Pulmonary artery
Deoxygenated blood heart 2 lungs
Pulmonary vein
– transports oxygenated blood from lungs → heart
Aorta
transports oxygenated blood from heart → respiring body tissues
Atrial systole
● Atria contract
● So their volume decreases,
pressure increases
● Atrioventricular valves open
when pressure in atria
exceeds pressure in ventricles
● Semilunar valves remain shut
as pressure in arteries
exceeds pressure in ventricles
● So blood pushed into
ventricles
Ventricular systole
● Ventricles contract
● So their volume decreases,
pressure increases
● Atrioventricular valves shut
when pressure in ventricles
exceeds pressure in atria
● Semilunar valves open when
pressure in ventricles exceeds
pressure in arteries
● So blood pushed out of heart
through arteries
Diastole
Atria & ventricles relax
● So their volume increases,
pressure decreases
● Semilunar valves shut when
pressure in arteries exceeds
pressure in ventricles
● Atrioventricular valves open
when pressure in atria
exceeds pressure in ventricles
● So blood fills atria via veins &
flows passively to ventricles
Slv closed
Semilunar valves closed
● Pressure in [named] artery higher than in ventricle
● To prevent backflow of blood from artery to ventricles
Slv open
● When pressure in ventricle is higher than in [named] artery
● So blood flows from ventricle to artery
Av valve closed
Pressure in ventricle higher than atrium
● To prevent backflow of blood from ventricles to atrium
Av valve open
● When pressure in atrium is higher than in ventricle
● So blood flows from atrium to ventricle
Arteries S2F
Carry blood away from heart at high pressure
Thick smooth muscle tissue - contract and control pressure
Thick elastic tissue
Can stretch as ventricles contract and recoil as ventricles relax, to reduce pressure surges
Thick wall Withstands high pressure
Smooth endothelium reduces friction h
Narrow lumen maintains high pressure
Arterioles s2f
Direct blood to different capillaries and tissues
Thicker smooth muscle layer than arteries
○ Contracts → narrows lumen reduces blood flow to capillaries
○ Relaxes → widens lumen, increases blood flow to capillaries
Thinner elastic layer → pressure surges are lower
Vein s2f
blood back to heart
at low pressure
Valve - prevent back flow of blood
Little muscle and elastic tissue as bp low
Wider lumen than arteries so less resistance to blood flow
Capillary s2f
allow efficient exchange of substances between blood and tissue fluid
Wall is a thin layer of endothelial cells reducing diffusion distance
Capillary bed - large network of branched capillaries incr SA 4 diff
narrow lumen reduces blood flow rate so more time for diffusion
Pores in walls between cells Allow larger substances through
