3.2 Flashcards
Double circulatory system
One in which the blood flows through heart twice for each circuit of body
Single circulatory system
Heart pumps blood into a haemocel and tissue surrounded by blood takes requirements and removes waste
Transport
The movement of substances such as oxygen, nutrients, hormones, waste and heat around body
Arteries
Vessels that carry blood away from heart
Arterioles
Small blood vessels that distribute blood from artery to capillaries
Capillaries
Very small vessels with very small walls
Closed circulatory system
One in which blood is held in vessels
Open circulatory system
One in which blood isn’t held in vessels
Veins
Vessels that carry blood back to heart
Venules
Small blood vessels that collect blood from capillaries and lead into veins
Blood
Fluid used to transport materials round body
Hydrostatic pressure
Pressure that fluid exerts when pushing against sides of vessel or container
Lymph
The fluid held in lymphatic system, which is a system of tubes that returns excess tissue fluid into blood system
Oncotic pressure
Pressure created by osmotic effects of solutes
Plasma
Fluid portion of blood
Tissue fluid
Fluid surrounding cells and tissues
Atrio-ventricular values
Valves between atria and ventricles which ensure blood flows in correct direction
Cardiac muscle
Specialised muscle found in walls of heart chambers
Semilunar valves
Valves that prevent blood re-entering heart from arteries
Cardiac cycle
The sequence of events in one full beat of the heart
Bradycardia
A slow heart rhythm
Ectopic heartbeat
An extra beat or an early beat if the ventricles
Electrocardiogram
A trace that records electrical activity of heart
Fibrillation
Uncoordinated contraction of atria and ventricles
Myogenic muscle
Muscle that can imitate it own contractions
Purkyne tissue
Consists of specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum to the ventricles
Sino atrial node
Hearts pacemaker, it’s small patch of tissue that sends out waves of electrical excitation at regular intervals in order to initiate contractions
Tachycardia
A rapid heart rhythm
Affinity
A strong attraction
Dissociation
Means releasing the oxygen from the Oct haemoglobin
Fetal haemoglobin
Type of haemoglobin usually found only in the fetus
Haemoglobin
Red pigment used to transport oxygen in the blood
Carbonic anhydrase
The enzyme that catalysed the combination of carbon dioxide and water
Chloride shift
Movement of chloride ions into erythrocytes to balance the charge as hydrogencarbonate ions leave the cell
Bohr effect
Effect that extra carbon dioxide has on haemoglobin, explains release of more oxygen
Haemoglobinic acid
Compound formed by the buffering action of haemoglobin as it combines with excess hydrogen ions
Where are open circulatory systems found
In Molluscs and arthropods
How does blood move back into circulatory system in open circuit
Via cells
How does insects circulatory system work
Heart composed of series of pumps towards head, blood drains from vessel wall directly to areas in need like head and legs, blood flows in a posterior direction and returns to dorsal vessel through holes called Ostia
What animals are closed circulatory systems found in
Vertebrates, annelips and cephalopods
How does closed circulatory system work
Blood stays in vessels and pumped through them by heart, exchange of nutrients and respiratory gases via diffusion between blood vessels and tissue fluid
What are 3 main factors that influence the need for a transport system
Size, sa:v ratio, level of metabolic activity
What is sa:v ratio
For each gram of tissue if their body, they have sufficient area of bodies surface through which exchange can occur, so in larger animals each gram of tissue has smaller area of body surface for exchange
Why do animals need food energy and what does it need along as food
So they can move, releasing food energy via aerobic respiration requires oxygen
Why do animals need other energy’s as well as food
Mammals need to keep warm so they need energy so more active animals also respire faster so need more oxygen
What is the function of valves
Keep blood flowing in one direction
Features of good transport system(fluid or medium)
Fluid or medium to carry nutrients, oxygen and waste around body, blood in mammals
Feature of good transport system (pump)
Pump to create pressure that will push fluid round body (heart)
Feature of good transport system (exchange surface)
Exchange surface to allow substances in o enter and leave blood (capillaries)
Feature of good transport system (tubes/vessels)
Include tubes and vessels to carry blood by mass flow and 2 circuits, one to pick up oxygen and one to deliver oxygen to tissue
What type of animals have single circulatory system and what does this mean
Fish have single circulatory system where blood flows through heart once for each circuit of the body (heart-gills-body-heart)
What animals have double circulatory system
Mammals
What does a double circulatory system mean
Have 2 separate circuits, one for carrying blood to lungs and one carry’s oxygen and nutrients around the body to tissues known as systemic circulation
How does double circulatory system work
Blood flows through heart twice for each circuit of the body (heart-body-heart-lungs-heart)
What are are disadvantages of single circulatory system
In single circulatory system blood pressure drops as blood passes through gills capillaries and means it moves slowly as it travels around body, so rate at which oxygen, nutrients delivered to respiring tissue and CO2 and urea are removed is limited
Why does it not matter that fish only have single circulatory system
Fish not as metabolically active as mammals as they don’t have to maintain their body temp so less energy is needed as single circulatory system is sufficient
What are advantages of double circulatory system
Blood pressure cannot be too high in pulmonary circulation as may damage delicate capillaries in lungs, but after this heart can increase blood pressure so it flows round body faster as system circulation can carry blood at higher pressure than at pulmonary circulation
Why do mammals need double circulatory system
As mammals are active and must maintain body temp, they need food energy for this (energy released from food in respiration) to release lots of energy cells need good blood supply of oxygen and nutrients and removal of waste products
Why is a pump needed for transport medium to be effective
Blood I closed in vessels and contraction of muscle causes directional flow for blood to circulate which is what happens in insects and similar animals
What happens in open circulatory system
Blood circulated in large open spaces and cells are in direct contact with blood so materials are exchanged by direct diffusion, in open system Herat is weak muscle pumping blood around large area
What do insects have instead of blood
Haemocel
Evaluate open circulatory system
Inefficient and low pressure
Function of open circulatory system
Important in removing nitrogenous gases and supplying nutrients but not oxygen as the tracheal system does that
What happens in closed circulatory system
Blood entirely closed in tubular vessels and gas exchange happens across capillary walls, in this system heart is strong and blood pressure high
Evaluate closed circulatory system
More efficient that open one, and animals with closed system are larger and more active
Disadvantage of closed system but why does this not matter
Diffusion must happen to get air and nutrients to cells and waste to blood, but capillaries near so short diffusion distance
How is blood held in open circulatory system
Blood is not always held in vessels but blood fluid circulated through body cavity so that tissues and cells are in direct contact with the blood
What do some animals do to help circulate their blood
Some animals move their body
What would happen without movement of blood
Transport of o2 and nutrients would stop
What is the structure of an insects circulatory system
Long muscular tube that lies under dorsal surface of body, blood enters heart through pores called Ostia, then heart pumps blood to Peristalsis, at front end of heart near head blood pours into cavity and continues when insect is resting but body movements may still effect circulation
What is different about larger insects circulatory system compared to smaller ones
Locus have open ended tubes attached to their heart which direct a blow towards active part of body
Disadvantage of open circulatory system
Blood pressure low and flow is slow, circulation of blood affected by body movements or lack of body movements
What animals blood stays inside vessels separate from tissue fluid and cells
Larger animals as they have double circulatory system
What is tissue fluid
Fluid which bathes tissue
Advantages of double circulatory system
High pressure, blood flow quick, rapid delivery of oxygen and nutrients and rapid removal of CO2 and waste, transport independent from body movements
What does blood travel in
Series of vessels each adapted to a role in relation to distance from heart
Structure of blood vessels
All have an in layer/lining made of single layer of cells called endothelium which is a smooth thin layer in order to reduce friction with flowing blood
What is arteries function
To carry blood away from heart
When is blood like when in the arteries and why does this effect it’s structure
At high pressure so walls must be thick to withstand pressure
Structure of lumen of artery
Relatively small to maintain high pressure, inner wall folded to allow lumen to expand as blood flow increase
How many layer does artery wall have
3
Structure of inner layer of artery
Consists of thin layer of elastic tissue which allows wall to stretch and recoil to help maintain blood pressure
Structure of middle layer of artery
Consists of thick layer of smooth muscle
Structure of outer layer of artery
Relatively thick layer of collagen and elastic tissue to provide strength to withstand high pressure and recoil to maintain pressure
What are arterioles
Small blood vessels that distribute blood from arteries to capillaries
Structure of arterioles
Contain layer of smooth muscle
Function of smooth muscle and how it works
Contraction of muscle constricts arteriole lumen and increase resistance to flow so reducing rate of flow of blood, the contraction of arteriole wall is used to divert blood flow to body regions demanding more oxygen
Structure and function of capillaries
Have thin walls and allow gas exchange of materials between blood and tissue fluid
How wide is capillaries lumen
Very narrow (same as red blood cell)
What happens in the capillaries
Red blood cells squeezed against their walls reducing diffusion distance which increases resistance and reduces rate of flow
Detail structure of capillaries
Walls are single layer of flattened endothelial cells which reduce diffusion distance of exchanging materials and walls are leaky to allow blood plasma and dissolved substances to leave blood
What are venules
Small vessels that blood from capillaries flows into, they collect blood from capillary bed and lead into veins
Structure of venule
Wall consists of thin layer of muscle and elastic tissue outside endothelium and thin outer layer of collagen
Veins function
To carry blood back to heart
What is the blood like in the veins
At low pressure so walls don’t need to be too thick
Structure and function of veins
Relatively large lumen to ease blood flow, walls have thinner layer of smooth muscle, elastic fibres and collagen than arteries as don’t need to stretch and recoil and don’t actively constrict to reduce blood flow
Why do veins have valves
To help blood flow back to heart and prevent it flowing in opposite direction
What does veins relatively thin walls mean
They can be flattened by action of surrounding skeletal muscle and contraction of surrounding skeletal muscle applies pressure to blood forcing blood to move along in direction determined by valves
What is blood
Fluid held in our vessels which contains a liquid called plasma and many blood cells
What does plasma contain
Many dissolved substances such as oxygen, CO2, minerals, glucose, amino acids, hormones and plasma proteins
What are the various components in blood plasma
Erythrocytes, different types of leukocytes and fragments called platlets
What is the difference between tissue fluid and blood plasma
Doesn’t contain most cells that are found in blood plasma and doesn’t contain plasma proteins
How is tissue fluid formed
Plasma leaking from capillaries to surrounding cells and tissue and supply them with the oxygen and nutrients they need
What happens as blood plasma leaks from capillaries
Carries dissolved substances into tissue fluid called mass flow, not diffusion
What happens to cells waste products from metabolism
Carried back into capillaries as some tissue fluid is returned to capillaries
What happens when arteries reach tissue
They branch into smaller articles and then into a capillary network to eventually link with venules to carry blood to veins so blood flowing into organ/tissue is contained in capillaries
What is the pressure at the arterial end of the capillaries
Quite high known as hydrostatic
What does high pressure at arterial end of capillaries mean
High pressure pushed blood fluid out of capillaries through their walls, fluid leaves between tiny gaps between cells in capillary walls
What does fluid that leaves blood at capillaries contain
Plasma with dissolved nutrients and oxygen
What remains in the blood when plasma leaves the capillaries and why
All red blood cells, platelets, most white blood cells and plasma proteins all stay in capillaries as they are too large to be pushed out of gaps in capillary walls
Why does tissue fluid surround cells
So exchange of gas and nutrients can occur across their plasma membrane
How does exchange from tissue fluid to cell occur
By diffusion, facilitated diffusion or active uptake
What is the blood pressure at venous end of capillaries and what does this mean
Low pressure as allows some tissue fluid to return to capillaries carrying CO2 and other waste substances into blood
Does all tissue fluid return to the blood
No
What happens to tissue fluid that doesn’t return to the blood
Some directed to another tubular system called lymphatic system which drains excess tissue fluid out of tissues and returns it to blood system in subclavian vein in the chest
What is fluid in lymphatic system called
Lymph
What is lymph
Similar composition to tissue fluid but contains more lymphocytes produced at lymph nodes
What are lymph nodes
Swellings found at intervals along lymphatic system which are important in immune response
What is blood plasma hydrostatic and oncotic pressure
High hydrostatic pressure and oncotic is more negative than tissue fluid
Are there fats in blood plasma
Yes transported as lipoproteins
What is tissue fluid hydrostatic and oncotic pressure
Hs is low and oncotic is less negative than blood plasma
What is lymph hydrostatic and oncotic pressure
Low hydrostatic pressure and less negative oncotic pressure than blood plasma
Is hydrostatic pressure the only influence on movement of fluid in and out of capillary
No
Tissue fluid has its own hydrostatic pressure of solutes which also has an influence and is called….
Oncotic pressure
What does hydrostatic pressure of blood tend to do
To push fluid out into tissues
What does hydrostatic pressure of tissue fluid tend to do
Push fluid into capillaries
What does oncotic pressure of blood tend to do
Pull water back into blood (negative figures)
What does oncotic pressure of tissue fluid do
Pulls water into tissue fluid
What does the net force of hydrostatic and oncotic pressure mean
Net result of these forces means fluid pushed out of capillaries at arterial end and drawn back at venule end
What is a mammal heart
A muscular pump divided into two sections
How is the heart divided
Right side has deoxygenated blood which goes to the lungs to be oxygenated and left side has oxygenated blood to go around the whole body
What muscle is the heart
A dark red cardiac muscle
What are the two main pumping chambers and what is bigger
Ventricle and atrium, ventricles much bigger
Where are coronary arteries located
Live over the surface of the heart
What is the function of coronary artery
Supply oxygenated blood to the heart muscle which is important as heart is a hard working muscle
Why is it dangerous if coronary arteries restricted
Restricts blood flow to the heart muscle reducing oxygen and nutrient such as fatty acids and glucose which may cause angina or myocardial infarction
What carries blood into the heart
Veins (pulmonary vein and vena cava)
What carries blood away from heart
Arteries (aorta and pulmonary artery)
Where are atria located in the heart
2 found at top of the heart
What blood flows into each atria
Deoxygenated blood from body flows into right atrium through vena cava and oxygenated blood flows in through pulmonary vein to left atrium
Where does blood go after the atria
It flows down through atrioventricular valve to ventricle
Why don’t valves turn inside out when ventricle walls contract
Valves are attached to tendinous chords to prevent this
What is the septum
Separates the ventricles from one and other to ensure oxygenated and deoxygenated blood stays separate
What happens when deoxygenated blood leaves right ventricle
Flows to pulmonary artery which leads to the lungs where it can be oxygenated
Where do blood go once it has left the left ventricle
Into aorta to be transported around the body
Why are there valves at the base of the two major arteries and what are they called
They prevent blood returning to the ventricles as heart relaxes and called semilunar valves
How is high pressure created in the heart
Cardiac muscle in wall of each chamber will contract to create high pressure in the blood
What does high blood pressure mean
The blood can travel round the body further at high speed
Structure of atria
Very thin walls as don’t need to create much pressure
Function of atria
To receive blood from veins and push it into ventricles
Structure of right ventricle and why
Thicker walls than atria as must pump blood out of heart to lungs but lungs are near the heart so it doesn’t need to travel very far and alveoli are delicate so they may be damaged if blood is at high pressure
Structure of left ventricle and why
Wall of left ventricle is 2/3 thicker than right ventricle as blood is pumped through aorta and need sufficient pressure to overcome resistance of systemic circulation and must travel round the whole body
What does the cardiac muscle consist of
Fibres that branch producing cross-bridges which help to spread stimulus around heart and ensure muscle can produce squeezing action rather than a simple reduction in length
Why are there many mitochondria between muscle fibres (myofibrils) in the heart
To supply energy for contraction
How are muscle cells separated in the heart and what does this do
Intercalated discs which facilitate synchronised contraction
What does each cell in the heart muscle have and how is each cell divided
Each has a nucleus and each cell is divided into contractile units called sarcomeres
In single circulation(fish) what blood flows into the heart
Only deoxygenated blood flows through heart
Is there a left and right side in fish hearts (single circulatory)
No
What is plasma
Mainly water containing variety of dissolved substances which transport around body like glucose, amino acid taken up from small intestines to liver and takes urea form liver to kidneys
What does plasma provide a medium for
Cells to exchange waste for needed materials
What is it called when heart contracts and then called when it relaxes
Systole, diastole
What happens when pressure in atria is higher than ventricles
Atrioventricular valve opens
Which side is the tricuspid valve on and which is the bicuspid
Tricuspid is on the right and bicuspid is on the left as it only has two flaps
What is the cardiac cycle
Systole followed by diastole where heart refills with blood again before contracting
What happens when blood pumped into aorta due to the semilunar valve
Wall of the first section of the artery becomes distended but as heart relaxes so does this section of the aorta
Why do capillaries only have a single layer of squamous endothelium
To allow rapid diffusion
How can the pressure in the capillaries be changed
Muscle at arteriole end can contract or relax
How are lymphatic vessels different to veins
More valves and no red blood cells but otherwise the same
What does the lymph system do
Return tissue fluid to blood as lymph
Role of heart
To create pressure that pushes blood round heart
What must the wall of all four chambers do and what is this process Called
Contract in synchronised sequence to allow heart to fill will blood before pumping it out, known as cardiac cycle
What is ventricular systole
Left and right ventricle contact to pump blood into aorta/ pulmonary artery
What is diastole
All muscles in each chamber relaxes, elastic recoil causes chamber volume to increase so blood flows in from veins
What is atrial systole
Left and right atrium contract, thin wall so only small pressure increase to push blood into ventricle to ensure they’re full of blood
What do valves insure
Blood flows in correct direction
What causes valves to open and close
Different pressures in the heart chambers
What happens after ventricular systole
Ventricular walls relax and recoil causing pressure in ventricles to rapidly drop lower than atria pressure causing blood in atria to push open atrioventricular valve open
What happens in diastole when blood enters atria
Flows directly through atria into ventricle causing the pressure in atria and ventricle to both slowly rise as they fill with blood
At what stage in the cardiac cycle does the atrioventricular valve close
Valve is open when atria contracts but closes when atria starts to relax
What causes the closing of the atrioventricular valve
Swirling action in blood around valves when ventricle is full
What happens in cardiac cycle as ventricle begins to contract
Ventricular systole, pressure of blood in ventricles rises and when it becomes higher than atria pressure it begins to move upwards
What prevents blood flowing back into the atria
The rising of the blood in the ventricles fills the valve pockets keeping them shut and tendinous chords stop them turning inside out so blood doesn’t flow back into atria
Why are the semi lunar valves closed before ventricular contraction
Pressure in arteries is higher than in ventricles
What happens in ventricular systole
Ventricular systole causes blood pressure to rise quickly in ventricles, and when pressure in ventricles is higher than in arteries the semilunar valves are pushed open, blood under high pressure is forced out of ventricle in powerful spurt
What happens once the ventricles Finnish contracting
Semilunar valve closes and all heart muscles relax (diastole)
What happens in diastole
Elastic tissue in wall of ventricles recoiled which stretches muscle so it turns back to its original size causing pressure in ventricles to drop rapidly
What happens when ventricular pressure drops below arterial pressure
Blood starts to back flow into ventricle but semilunar valves are closed by this blood collecting in the valve pockets to prevent blood returning to ventricles
When is a pressure wave created
When left semilunar valve closes it is the pulse felt on neck or wrist
The graph of pressure change of the heart usually shows what side of the heart and why
Left side as it contracts at more pressure than right side so more visible on a graph
What is on y axis of graph of pressure change in heat
Pressure (kPa)
Revise graph
How does blood enter the arteries
In a rapid spurt
What is the issue with blood being rapidly spurted from heart into arteries and how is it resolved
Tissue requires blood delivery in even flow but artery wall has lots of elastic tissue and wall stretches when blood spurted in which helps even flow
What happens as blood moves on and out of aorta
Pressure in aorta drops so elastic recoil in artery wall helps maintain a higher pressure but the further along the arteries the blood flows the further the pressure drops and fluctuations are less obvious
Why is it important to maintain pressure gradient between aorta and arterioles
Helps keep blood flowing in the right direction towards the tissue
When do you see the largest and then smallest blood pressure fluctuations on a graph
Most at aorta as high pressure and least at capillaries, venules and veins as low blood pressure
What does it mean when you say the heart is a myogenic muscle
Can initiate its own contractions
What will the heart muscle do in terms of its rhythm
Contract and relax rhythmically even when not connected to the body due to it being myogenic
What does the muscle from the atria and ventricle both have
Their own natural frequency of contraction
Does atria or ventricle contract at higher frequency
Atria contracts at higher frequency
What happens if heart chambers contractions aren’t in sync and how is this solved
Problem known as fibrillation often solved with addition of a pace maker
What is found at the top of right atrium where superior vena cava puts blood into atria
Sino-atrial node (SAN)
What is the sino-atrial node
Small patch of tissue that initiates electrical activity, SAN initiates wave of excitation at regular intervals
How often does the SAN initiate wave of excitation in human
55-80 times a minutes
What is the SAN also described as
Pacemaker
What happens when SAN initiates wave of excitation
Wave quickly spreads across walls of both atria travelling across membranes of the muscle tissue and as wave of excitation passes, it causes cardiac (atria) muscles to contract known as atrial systole
Why can’t wave of excitation spread directly down to ventricle walls
Tissue at base of atria cannot conduct the wave of excitation
What is located at the top of the inter ventricular septum
Atrioventricular node (AVN)
Why is the atrioventricular node necessary
As it is the only route to get the wave of excitation through to the ventricles
What happens at AVN
Wave of excitation is delayed to allow atria to stop contacting and ventricle to fill with blood
What happens after wave of excitation is delayed at AVN
Wave carried away from AVN down specialised conducting tissue called purkyne fibres
What is located just before the purkyne fibres
The bundle of His
Where does the bundle of his run down to
Runs down inter-ventricular septum
Where does bundle of His turn into purkyne fibres
At apex of heat where tissue rises around the ventricles
What happens to wave of excitation at bottom of septum
Wave spreads out over ventricle walls, wave spreads from apex upwards and causes the muscle to contract from base upwards which pushes blood up towards major arteries at top of the heart
What is an ECG used to measure
Hearts electrical activity
How do you work an ECG
Attach sensors to skin, picked up on ECG as some electrical activity generated by heart spreads through tissue close to the heart and out to the skin, the sensors on the skin pick up this electrical excitation from the heart and convert it into a trace
On an ECG what does the P wave show
Excitation of atria (atria systole)
What does the QRS complex on ECG represent
Indicates excitation of ventricle (ventricular systole)
What does T wave show in ECG
Diastole
Why are ECG used
To show if heart is healthy or not and can diagnose heart issues
What does bundle of his separate into
Purkyne fibres
How much blood does heart pump into the arteries compared to what it receives from veins
Pumps out same amount as it receives
When is the greatest systolic contraction
The more the heart muscle stretches in diastole the greater the contraction will be
How is oxygen transported round body
In erythrocytes which contain the protein haemoglobin
What is oxygen + haemoglobin
Oxyhemoglobin
What is haemoglobin structure
It is a complex protein with 4 subunits, each subunit has a polypeptide chain and a haem (non-protein group) and each charm has an iron ion Fe2+
What can the iron ion on haemoglobin attract and hold and what does this mean
One oxygen molecule meaning iron ion has high affinity for oxygen
How many oxygen molecules can each haem group hold
One oxygen molecule
How many haemoglobins are there in a Red blood cell
About 280million
How many oxygen molecules can an erythrocytes carry
Over a billion
Where is oxygen absorbed into the blood
At alveoli
What happens to oxygen molecules diffusing into blood plasma
Enter red blood cells and become associated with haemoglobin
What does it mean when oxygen molecule associated with haemoglobin
Oxygen binds reversibly to the haemoglobin
How is a steep contraction gradient maintained between oxygen in blood and alveoli
Oxygen associates with haemoglobin to make oxyhemoglobin so oxygen molecule taken out of blood plasma and therefore low concentration of oxygen in blood plasma
Where does blood go after lungs
Back to the heart before travelling around body to supply tissue with oxygen and nutrients
In the tissue what do cells need oxygen for
Aerobic respiration
What happens at cells to oxyhemoglobin
It dissociates so cell just gets the oxygen not the haemoglobin molecule
What does haemoglobins ability to associate with and release oxygen depend on
Oxygen concentration in surrounding tissue
How is concentration of oxygen measured and in what units
Relative pressure (which is contributed to by a mixture of gases) called partial pressure of oxygen (pO2) or oxygen tension and measured in units of pressure (kPa)
What would you expect concentration of oxygen absorbed by the liquid to be in a normal liquid
It would be directly proportional to oxygen tension in surrounding air so a graph showing this would be linear (not the case with haemoglobin)
How does haemoglobin associate with oxygen in terms of a graph
Associates in a way that produces an s-shaped curve
What is haemoglobins s-shaped curve called
Haemoglobin dissociation curve
What happens to haemoglobin association to oxygen at low oxygen tension
Haemoglobin doesn’t readily associate with oxygen molecules as haem groups that attract oxygen are at centre of haemoglobin molecule making it hard for oxygen molecules to reach haem group to associate with it
What accounts for low saturation levels of haemoglobin molecule and low oxygen tensions
Difficulty in combining haemoglobin with the 1st oxygen molecule which is why starts of with low partial pressure and percentage saturation
What happens to haemoglobin as oxygen tension rises
Diffusion gradient into haemoglobin molecule increases
What is conformational change
Eventually one oxygen molecule enter haemoglobin and associates with one of the haem groups causing a slight change in shape of haemoglobin molecule know as conformational change
What happen after one oxygen molecule associates
Allows more oxygen molecules to enter haemoglobin molecule and associate with other haem groups relatively easily which is why curve gets steeper as oxygen tension increases
Why does the curve level of at the end
Haemoglobin molecule has reached 100% saturation of oxygen
Why is it good that mammalian haemoglobin is well adapted to transport oxygen to tissues of a mammal
As oxygen tension found in lungs is sufficiently high to produce close to 100% saturation and oxygen tension in respiring body tissue is sufficiently low to cause oxygen to dissociate from oxyhemoglobin
Why is fetal haemoglobin different to adult haemoglobin and how does this affect dissociation curve
Has higher affinity for oxygen so haemoglobin dissociation curve for fetal haemoglobin it to the left of adult haemoglobin
Why is it necessary that fetal haemoglobin has higher affinity for oxygen
As it must be able to associate with oxygen in an environment where the oxygen tension is low enough to make adult haemoglobin release oxygen
What happens in placenta where oxygen tension is low
Fetal haemoglobin will absorb oxygen from surrounding fluids which reduces oxygen tension in mothers blood which in turn makes maternal haemoglobin release more oxygen (dissociation)
What must happen to CO2 released from respiring tissue
Must be removed from tissue and transported by blood to lungs for excretion
What are the three ways CO2 is transported and what it its percentages
5% dissolved directly in blood plasma, 10% combined with haemoglobin to form carbaminohaemoglobin, 85% transported in form of hydrocarbonate ions (HCO3-)
What is the first step in formation of hydrocarbonate ions
CO2 in blood plasma diffuses into red blood cells where it combines with water to form a weak acid called carbonic acid (CO2 + h2o -> H2CO3)
What enzyme catalysed the reaction between CO2 and water to form carbonic acid
Carbonic anhydrase
What happens after CO2 combined with water into carbonic acid
Carbonic acid then dissociates to release hydrogen ions (H+) and hydrocarbonate ions (HCO3-),,,, (H2CO3 -> HCO3- + H+)
What happen after formation of hydrocarbonate ions and hydrogen ions in formation of hydrocarbonate ions
Hydrocarbonate ions diffuse out of red blood cell into blood plasma which causes pH in red blood cell to change but is maintain by movement of chloride ion (Cl-) from plasma in erythrocyte known as the chloride shift
What happens after the chloride shit in red blood cell
Hydrogen ions building up in erythrocyte could cause content of red blood cell to become very acidic and to prevent this hydrogen ions are taken out of solution by associating with haemoglobin to produce haemoglobinic acid (HHb)
When the haemoglobin and hydrogen associate what is the haemoglobin acting as
Haemoglobin acting as a buffer (compound which maintains a constant pH)
What does blood entering respiring tissue carry blood as
Oxyhaemoglobin
Is partial pressure of oxygen at respiring tissue lower or higher than at the lungs and why
Lower as used in respiration
What does low partial pressure of oxygen at respiring tissues cause
Oxyhaemoglobin to dissociate so oxygen is released into the tissue meaning that haemoglobin is available to take up a hydrogen ion forming haemoglobinic acid
What happens where tissue is more active
More CO2 released causing dramatic effect on the haemoglobin
What does the Bohr effect describe
Describes effect than an increasing concentration of CO2 has on haemoglobin
What is Bohr effect
CO2 entering erythrocyte forms carbonic acid which dissociates to release hydrogen ions which have affect on pH of RBC cytoplasm, change in pH can affect tertiary structure of haemoglobin, for example more acidic alters haemoglobin structure and reduces its affinity for oxygen, so haemoglobin is unable to hold as much oxygen and o2 released from oxyhaemoglobin to the respiring tissue
Is there more or less CO2 at respiring tissues
More
What does more CO2 at respiring tissues result in
There will be more hydrogen ions produced in the red blood cells causing oxyhaemoglobin to release more oxygen as it has a higher affinity for hydrogen than oxygen
What happen to oxygen saturation in haemoglobin when more CO2 is present
Haemoglobin becomes less saturated with o2
What happens to dissociation curve when there is more CO2
Shifts down and to the right known as the Bohr shift
What does Bohr effect mean overall and why is this good
Bohr effect results in more Oxygen being released when more CO2 is produced in respiration and this is exactly what muscles need in order for aerobic respiration to continue
