3.2 - Transport in Animals Flashcards
Def of double circulatory system
System in which the blood flows through the heart twice for each circuit of the body
Def of single circulatory system
System in which blood flows through the heart once for each circuit of the body
Def of transport
Movement of substances such as oxygen, nutrients, hormones, waste and heat around the body
What three factors influence need for a transport system?
Size
SA:V ratio
Level of metabolic activity
Influence of size on requiring transport system
Cells inside a large organism are further from its surface - diffusion pathway/distance is increased
So diffusion rate is reduced
So simple diffusion is too slow to supply all requirements
(Outer layer of cells will use up supplies, less will reach cells deeper inside body)
Influence of SA:V ratio on requiring transport system
Larger animals have a smaller SA:V ratio
Each gram of tissue has smaller area of body surface for exchange
So simple diffusion will not transport required amount of substances into body
Influence of metabolic activity on requiring transport system
Animals need energy from food
Releasing energy from food by aerobic respiration requires energy
The more active an animal is, the better supply of nutrients and oxygen is needed to supply energy for movement
(Animals that keep themselves warm, such as mammals, need even more energy)
Two features of a good transport system
Effective
Efficient
Features of an effective transport system
A fluid or medium to carry nutrients, oxygen and waste around the body - blood in humans
Pump to create pressure to push fluid around body - heart in humans
Exchange surfaces - enable substances to enter blood and leave it again where they are needed - capillaries in humans
Example of single circulatory system
Fish
Blood flows through one circuit of heart once for each circuit of the body
Heart - gills - body - heart
Example of a double circulatory system
Mammals
Two separate circuits - blood flows through heart twice for each circuit of body
One circuit carries blood to lungs to pick up oxygen - pulmonary circulation
Other circuit carries oxygen and nutrients around body to tissues - systemic circulation
Heart - body - heart - lungs - heart
Comparison of a double to single circulatory system - single system
Blood pressure drops as blood passes through tiny capillaries of gills
Blood has a low pressure as it flows towards the body, and doesn’t flow very quickly
Rate at which oxygen and nutrients delivered to respiring tissues, and CO2 and urea are removed, is limited.
Comparison of a double to single circulatory system - double system
Blood pressure must not be too high in pulmonary circulation, otherwise may damage capillaries in lungs
Heart can increase pressure of blood after has passed through lungs, so blood is under higher pressure as flows to body and flows quicker
Systemic circulation carries blood at higher pressure than pulmonary circulation
Why do fish have a single circulatory system?
Not as metabolically active as mammals
Don’t maintain their body temperature
Therefore need less energy
So single circulatory system delivers sufficient oxygen and nutrients for their needs
Why do mammals have double circulatory systems?
Mammals are quite active
Mammals maintain their body temp.
Energy for activity and supplying heat needed to keep body warm supplied from food
Energy released form food in respiration
To release a lot of energy, cells need a food supply of nutrients and oxygen
Cells need good removal of waste products
Features of an efficient transport system
Tubes or vessels to carry blood by mass flow
Two circuits - one to pick up oxygen and another to deliver oxygen to the tissues
Def of arteries
Vessels that carry blood away from the heart
Def of arterioles
Small blood vessels that distribute blood from an artery to the capillaries
Def of capillaries
Very small vessels with very thin walls found mainly in lungs
Def of closed circulatory system
System where blood is held in vessels
Def of open circulatory system
System where blood is not held in vessels
Def of veins
Vessels that carry blood back to the heart
Def of venules
Small blood vessels that collect blood from capillaries and lead into veins
Example of open circulatory system
In insects
Open circulatory system structure and process
Blood enters via a body cavity
Tissues and cells are bathed directly in blood
Open circulatory system process in insects
Blood from heart enters body through pores called Ostia
Heart then pumps blood towards head by peristalsis
At forward need of heart blood pours out into body cavity
(Circulation can continue when insect is at rest
Body movements may still affect circulation)
Disadvantage of open circulatory systems
Blood pressure is low, blood flow is slow
Circulation of blood may be affected by body movements or lack of body movements
Where are closed circulatory systems found?
Larger animals like mammals
Advantages of closed circulatory systems
Higher pressure so blood flows more quickly
More rapid delivery of oxygen and nutrients
More rapid removal of CO2 and other waste products
Transport is dependent of body movements
Direction of blood flow in arteries
Away from the heart and around the body
Structure of artery walls
Thick so can withstand high pressure
Small lumen to maintain high pressure
Inner wall is folded - allows lumen to expand as blood flow increases
Three layers of artery wall
Inner layer - thin layer of elastic tissue which allows walls to stretch and recoil to maintain blood pressure
Middle layer - thick layer of smooth muscle
Outer layer - relatively thick layer of collagen and electric tissue
Provides strength to withstand high pressure
Recoil to maintain the pressure
Arterioles
Small blood vessel that distribute blood from ey to the capillaries
Contain a layer of smooth muscle
Contraction of muscle constricts diameter of arteriole
This increases resistance to blood flow and reduces rate of flow of blood
Constriction of arteriole walls can be used to divert flow of blood to regions of body that demand more oxygen
Structure of Capillaries
Very thin walls - one cell thick
Allow exchange of materials between blood and tissue fluid
Narrow lumen, same diameter of a red blood cell(they can squeeze against walls of capillaries as they pass along capillary)
Helps transfer of oxygen as reduces diffusion path to the tissues
Increases resistance and reduces rate of flow
Walls consist of a single layer of squamous epithelial cells - reduces diffusion distance for exchange of materials
Walls are leaky/permeable - allow blood plasma and dissolved substances to leave the blood
Venule structure
Blood flows into them from capillaries
Venule wall consists of thin layers of muscle and elastic tissue outside endothelium
Has a thin outer layer of collagen
Structure of veins
Relatively large lumen - ease flow of blood
Walls have a thinner layer of collagen, smooth muscle and elastic tissue than artery walls
As don’t need to stretch and recoil - and aren’t actively constructed to reduce blood flow
Contain valves - stop blood flowing on opposite direction to heart, as blood at lower pressures
Walls are thin - vein can be flattened by surrounding skeletal muscle.
This applies pressure to blood, forcing blood to move along in direction determined by valves.
Def of blood
Fluid used to transport materials around the body
Def of hydrostatic pressure
Pressure that a fluid exerts when pushing against sides of a vessel or container
Lymph def
Fluid held in lymphatic system, a system of tubes that returns excess tissue fluid to blood system
Oncotic pressure
Pressure created by osmotic effects of the solutes
Plasma def
Fluid portion of the blood
Tissue fluid def
Fluid surrounding cells and tissues
What substances does blood carry?
Plasma - fluid part of blood
Red blood cells(erythrocytes)
White blood cells(leukocytes)
Platelets
What does blood plasma carry?
Dissolved substances: Oxygen Carbon dioxide Minerals Glucose Amino acids Hormones Plasma proteins
Formation of tissue fluid mechanism
-Arteries branch into arterioles, and then into a network of capillaries
-These link up with venules to carry blood to veins
-Therefore blood flowing into an organ or tissue is contained in the capillaries
-At arterial end of a capillary, blood is at relatively high hydrostatic pressure.
This pressure tends to blood fluid out of capillaries through their walls
-The fluid can leave through tiny gaps between cells in capillary walls
-Fluid that leaves the blood consists of plasma with dissolved nutrients and oxygen.
-All RBCs, platelets and WBCs remain in the blood, as do the plasma proteins
These are too large to be pushed out through the gaps in the capillary wall
-Tissue fluid surrounds the body cells, so exchange of gases and and nutrients can occur across the plasma membrane.
-Exchange occurs by diffusion, facilitated
diffusion, and active uptake
-Oxygen and nutrients enter the cells; CO2 and other wastes leave the cells
How tissue fluid returns to blood mechanism
- The blood pressure at the venous end of the capillary is much lower.
- This allows some of the tissue fluid to return to the capillary carrying carbon dioxide and other waste substances into the blood.
- Some tissue fluid directed to another tubular system called lymphatic system
- This drains excess tissue fluid out of tissues and returns it to blood system in subclavian vein in chest
- Fluid in lymphatic system called “lymph” and is similar in composition to tissue fluid
- Contains more lymphocytes, as they are produced in the lymph nodes
What are lymph nodes?
Swellings found at intervals along the lymphatic system, which play an important part in immune response by producing lymphocytes and other WBCs
Movement of fluids in exchange
Hydrostatic pressure of blood tends to push fluid out into the tissues
Hydrostatic pressure of tissue fluid tends to push fluid into capillaries
Oncotic pressure of blood tends to pull water back into the blood(has negative figure)
Oncotic pressure of tissue fluid pulls water into tissue fluid
Effect of movement of fluids in exchange
Pressure is created to push fluid out of capillary at arterial end and into capillary at venule end
Def of atrio-ventricular valves
Valves between atria and ventricles, which ensure blood flows in the right direction
Def of cardiac muscle
Specialised muscle found in the walls of the heart chambers
Def of semilunar valves
Valves that prevent blood re-entering the heart from the arteries
Different chambers and direction of blood flow
Left Ventricle - pumps oxygenated to aorta towards rest of body
Right Ventricle - pumps deoxygenated blood to lungs via pulmonary artery
Left atria - pumps oxygenated blood to left ventricle from pulmonary vein
Right atria - pumps deoxygenated blood into right ventricle from Vena Cava
Def of bracycardia
A slow heart beat rhythm
Def of ectopic heartbeat
An extra beat or an early beat of the ventricles.
Def of electrocardiogram
A trace that records the electrical activities of the heart
Def of fibrillation
Uncoordinated contraction of the atria and ventricles
Def of myotonic muscle
Muscle that can initiate its own contraction
Purkyne tissue def
Consists of specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum to the ventricles.
Def of sino-atrial node(SAN)
The heart’s pacemaker.
It is a small patch of tissue that sends out waves of electrical excitation at regular intervals in order to initiate contractions
Def of tachycardia
A rapid heart rhythm
Why is coordination needed in the cardiac cycle?
- If contractions of muscle in heart are not synchronised, there could be inefficient pumping
- So coordination of all four chambers is needed
Process of controlling cardiac cycle
- SAN initiates wave of excitation which spreads over atrial wall causing the atria to contract simultaneously
- Band of fibres between atria and ventricles stops wave of excitation passing directly to ventricular walls
- Wave of excitation reaches AVN in the septum
- This delays the wave of excitation for 0.1 seconds to allow atrial systole to complete before ventricular systole
- Wave of excitation spreads down Bundle of His to Purkyne fibres
- Both ventricles contract simultaneously
- They contract from the apex upwards to completely empty the ventricles
Function of electrocardiograms
Monitors electrical activity of the heart
Sensors on skin pick up electrical signals and convert this into a trace
Different waves on electro graph and what they show
P Wave - shows atrial systole
QRS wave - shows ventricular systole
T wave - shows diastole
Def of affinity
A string attraction
Def of dissociation
Releasing oxygen from the haemoglobin
Def of fetal haemoglobin
Type of haemoglobin usually only found in the foetus
Def of haemoglobin
Red pigment used to transport oxygen in the blood
Scientific name for red blood cells
Erthyrocytes
Structure of haemoglobin
Four complex subunits of:
A polypeptide chain
A haem
Why does a haemoglobin molecule hold oxygen and how many oxygen molecules can it hold?
Haem group contains an Fe2+ ion
This can hold an oxygen molecule
So the haem group has a high ‘affinity’ for oxygen
Therefore haemoglobin can carry four oxygen molecules(four subunits)/8 oxygen atoms
What is partial pressure?
The amount of pressure exerted by a gas relative to the total pressure exerted by all the gases in the mixture
Name of graph produced by haemoglobin and its oxygen uptake
S-shaped graph
Called oxyhaemoglobin dissociation curve
What is dissociation?
The breakdown of a molecule into 2 molecules
Oxyhaemoglobin into oxygen and haemoglobin
Oxygen partial pressure def
pO2(oxygen tension) - equivalent to conc. of oxygen in an area e.g. tissues
It is the proportion of the total pressure exerted by a mixture of gases produced by oxygen
Explanation of oxygen dissociation curve at low pO2
At low pO2 there is a low saturation of haemoglobin with oxygen
- haem group is at centre, so it is more difficult to associate
Explanation of oxygen dissociation curve as pO2 increases
There is a faster increase in saturation
- there is a higher conc. of oxygen, so a steeper gradient for diffusion of oxygen into haemoglobin
- when one O2 is associated - conformational change in shape of haemoglobin makes it easier for O2 to diffuse in and associate
Explanation of oxygen dissociation curve at high pO2
Saturation is high but levels off as it is unlikely association will reach 100%
- When 3O2 are associated, it is difficult for 4th molecule to diffuse in and associate to reach 100% even at highest pO2
Where does oxygen dissociate from haemoglobin at low pO2?
Happens in respiring tissues
Steepest part of curve is between 2-5kPa - this drop in pO2 gives a large drop in stair action and releases a lot of O2
This corresponds to the pO2 in the respiring tissue as they need a lot of oxygen for aerobic respiration
Diff between adult and fetal haemoglobin
Foetus gains O2 for respiration, form mother across placenta
pO2 in placenta is low(2-4kPa)
maternal haemoglobin releases O2
Foetal haemoglobin has higher affinity for O2
This maintains a diffusion gradient towards foetus
After birth, the adult haemoglobin replaces the foetal haemoglobin
Why does this happen?
Affinity of foetal haemoglobin 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
Result of Bohr effect
- Lowers haemoglobin’s affinity for oxygen
- Haemoglobin dissociation curve shifts to the right
- so more oxygen is being released where more CO2 is produced in respiration
- good for muscles as aerobic respiration can continue during exercise
What can CO2 be transported by and what percentage is it transported as?
- 5% is dissolved directly in the plasma
- 10% is combined directly with haemoglobin to form a compound called carbaminohaemoglobin
- 85% transported in the form of hydrogencarbonate ions
Formation of hydrogencarbonate ions mechanism
- CO2 in the blood plasma diffuses into the red blood cells
- It combines with water to form carbonic acid
- This reaction is catalysed by carbonic anhydrase
- CO2 + H2O —> H2CO3
- The carbonic acid dissociates to release hydrogen ions(H+) and hydrogencarbonate ions(HCO3-)
- H2CO3 —> HCO3- + H+
- The hydrogencarbonate ions diffuse out of the red blood cell into the plasma
- The charge of the red blood cell is maintained by the movement of chloride ions(Cl-) from the plasma into the red blood cell.
- This is called chloride shift
- The hydrogen ions building up in the red blood cell could cause the contents of the red blood cell to become acidic
- To prevent this, the hydrogen ions are taken out of solution by associating with haemoglobin to produce haemoglobinic acid(HHb).
- The haemoglobin is acting as a buffer(a compound that maintains a constant pH)
Both effect mechanism
- Carbon dioxide enters the red blood cells forming carbonic acid, which dissociates to release hydrogen ions(H+)
- H+ makes pH of the cytoplasm more acidic
- Increased acidity alters the tertiary structure of haemoglobin
- So reduces the affinity of haemoglobin for oxygen
- The haemoglobin is unable to hold as much oxygen and oxygen is released from the oxyhaemoglobin to the tissues
- So when more CO2 is present, haemoglobin has a lower affinity for oxygen
Suggest why reduced heart rate is sometimes seen in people who are very aerobically fit.
(2 Marks)
- increased stroke volume
- increased volume of ventricle
- increased thickness/strength of heart muscle
March mocks - compare pressure changes in the left atrium and ventricle.
(4 Marks)
In the left atrium (give pressure values - kPa)
- pressure rises to max of 1.7 kPa
- starts to drop at 0.055 seconds
- steep increase
- gradual increase in pressure during atrial diastole - blood from pulmonary vein
