Module 3.2 - Transport In Animals Flashcards
Diastole
Atria and ventricles relax and recoil
Blood flows from veins into atria
Pressure in ventricles is lower than in atria
Blood flows through open A-V valves into ventricles
Volume in atria and ventricles increases
Pressure in atria and ventricles slowly increases
Atrial systole
Both atria contract
Causes further increase in pressure in the atria
Increase in pressure causes blood to be pumped through the open A-V valves into the ventricles (causing volume in ventricles to increase)
Ventricular systole
When ventricles are full, they begin to contract from the apex upwards
Pressure in the ventricles increases above atrial pressure
A-V valves shut to stop blood returning to atria
Pressure in ventricles increases quickly as the blood can’t escape
When ventricular pressure exceeds pressure in major arteries, semilunar valves open and blood is pumped out of heart due to pressure
Volume in ventricles drops quickly
Causes pressure to drop in ventricles below pressure of major arteries so semilunar valves pushed closed by blood in arteries and stop blood flowing back into ventricles
Order of the cardiac cycle
Diastole
Atrial systole
Ventricular systole
External features of the heart
Made out of cardiac muscle
Coronary arteries lie over surface of the heart to supply it with oxygen for aerobic respiration
At top of heart are arteries (carry blood away) and veins (carry blood towards)
Bottoms of heart is the apex
Why are the coronary arteries important?
If they become blocked they will restrict blood flow and therefore delivery of oxygen to the heart muscle
Can cause myocardial infarction
Internal features of the heart
Semilunar valves at base of arteries prevent blood flowing backwards into ventricles when they relax (lower pressure there)
Atrio-ventricular valves prevent blood flowing backwards from ventricles to atria
Ventricular septum stops oxygenated and deoxygenated blood mixing, ensures oxygenated blood gets to body, would be a possible drop in blood pressure if hole present
Atrial walls
Thinnest
Don’t need to create high pressure as blood only needs to be pushed into ventricles
Right ventricular wall
Thicker than atrial wall
Needs to create enough pressure to pump blood to lungs (pulmonary system)
Pressure must not be too high otherwise thin capillary walls in lungs could burst
Left ventricular wall
Thickest
Needs to create most pressure to pump blood through aorta to whole body (systemic system)
Define transport
The movement of oxygen, nutrients, hormones, waste and heat around the body
Factors that affect the need for a transport system
Size
SA:Vol
Level of activity
Good transport systems
Have a fluid (blood)
Have a pump to create pressure (heart)
Have exchange surfaces
Define open circulatory system
Blood is not always in vessels (e.g. insects)
Define closed circulatory system
Blood always remains inside vessels (e.g. mammals and fish)
How does an open circulatory system work?
Consists of a heart that pumps blood through short vessels into a large body cavity by peristalsis
Blood bathes the cells and tissues where substances are exchanged with cells
Blood returns to heart through pores called ostia
Structure of haemoglobin
Transports O2 as oxyhaemoglobin
Has 4 subunits (2 alpha and 2 beta chains) each made of a polypeptide chain with a prosthetic haem group (non-amino acid)
Haem groups contain 1 Fe2+ each which has a high affinity for oxygen
4 O2 molecules per haemoglobin
Define partial pressure
The amount of pressure exerted by a gas relative to the total pressure exerted by all the gases in the mixture
Measured in kPa written as pO2 (oxygen tension)
What is pO2?
Equivalent to the concentration of oxygen in an area
Proportion of the total pressure exerted by a mixture of gases produced by oxygen
Explain the shape of the oxyhaemoglobin dissociation curve
At low pO2 - low saturation of haemoglobin with oxygen - haem group at centre making it difficult to associate
As pO2 increases - faster increase in saturation - higher concentration of O2, steeper gradient for diffusion of O2 into haemoglobin - when one O2 associated conformational change makes it easier for O2 to diffuse in and associate
At high pO2 - saturation is high but levels off as unlikely to reach 100% - when 3O2 associated, difficult for 4th to diffuse in and associate to reach 100% even at highest pO2
Points about foetal haemoglobin
Found in erythrocytes of foetuses
Higher affinity for oxygen than adult haemoglobin
Why is it important that the foetal and adult haemoglobin are different?
Foetus gains O2 for respiration from mother across placenta
pO2 in placenta is low (2-4kPa)
Maternal haemoglobin releases O2
Foetal haemoglobin has higher affinity for oxygen
This maintains a diffusion gradient towards the foetus
Why do adult haemoglobin replace foetus haemoglobin after birth?
Affinity for oxygen would be too high so would not release oxygen readily enough
Pregnant mothers would need a difference between the affinity of their haemoglobin and that of their foetuses for oxygen
How is CO2 transported in the blood?
5% dissolved in plasma
10% combines with haemoglobin to form carbaminohaemoglobin
85% in the form of hydrogencarbonate ions (HCO3-) in the plasma
How is CO2 converted into HCO3- ions for transport
CO2 in plasma diffuses into erythrocytes and combines with water to form carbonic acid (catalysed by carbonic anhydrase), H2CO3
The carbonic acid dissociates to release hydrogen and hydrogencarbonate ions
The hydrogencarbonate ions diffuse out of the erythrocyte into the plasma and Cl- ions move into the erythrocyte to maintain the charge (chloride shift)
The build up of H+ ions can make the erythrocyte very acidic so they combine with haemoglobin to form haemoglobinic acid (HHb)
Haemoglobin acts as a buffer (maintains constant pH)
What is the Bohr effect?
Change in shape of the oxyhaemoglobin dissociation curve when CO2 is present as CO2 causes oxyhaemoglobin to release more readily
Points about myoglobin
Used as an oxygen reserve
Has an extremely high affinity for O2
Will only dissociate from O2 when O2 levels are low
Found in muscle cells
