What is transport
the movement of oxygen, nutrients, hormones, waste and heat around the body.
Why do animals need a transport system?
High Metabolic demand, ie need lots of oxygen and food, produce lots of waste, diffusion over long distances is not enough
SA:Vol ratio gets smaller as multicellular organisms get bigger (diffusion distances get bigger and the SA available to absorb/remove substances is small)
Movement of hormones/enzymes
Food digested in one organ, needs to be transported to all cells
Waste products of metabolism need to be removed from cells and excreted
what makes a good transport system?
what is a mass transport system
when substances are transported in a mass of fluid with a mechanism for moving the fluid around
what is a closed circulatory system
In a closed circulatory system, blood is fully enclosed within blood vessels at all times.
From the heart, blood is pumped through a series of progressively smaller vessels. In the smallest vessels, capillaries, substances diffuse in and out of the blood and into cells.
Blood then returns to the heart via a series of progressively larger vessels.
what is an open circulatory system
An open circulatory system consists of a heart that pumps a fluid called haemolymph through short vessels and into a large cavity called the haemocoel.
In the haemocoel, the haemolymph directly bathes organs and tissues, enabling the diffusion of substances.
The transport medium is under low pressure.
Haemolymph moves around the haemocoel due to the movement of the organism.
what are the similarities between the open and closed circularity systems?
Liquid transport medium
Vessels to transport the medium
Pumping mechanism to move the fluid
what are the differences between the open and closed circulatory systems?
Open has few vessels, closed has a transport medium enclosed in vessels
Open transport medium is pumped into body cavity (haemocoel) under low pressure, in closed heart pumps blood around under high pressure
In open, transport medium directly contacts the body cells, in closed no direct contact between medium and cells
In open transport medium returns to heart through open ended vessels in closed blood flows relatively fast and returns to heart all within vessels
what are examples of organisms that have an open circulatory system and organisms with a closed circulatory system
All vertebrates (fish and mammals)
what is a single circulatory system
The blood flows through the heart and is pumped out to travel all around the body before returning to the heart
Ie. Blood goes once through the heart for each complete circuit of the body
For example fish – the heart pumps blood to the gills to pick up oxygen and then on through the body to deliver oxygen.
what is a double circulatory system
The blood travels twice through the heart for each circuit of the body
For example in mammals – the heart is divided down the middle
what is the advantage with a double circulatory system
The main advantage is that the heart can give an extra push between the lungs and the rest of the body, making the blood travel faster, so oxygen is delivered quicker to the cells
what are arteries
transport blood away from the heart
blood is pumped out of the heart at high pressure so arteries are structured to withstand and maintain high pressure
what are the 4 layers in arteries and in veins
connective tissue, smooth muscle, endothelium and lumen
veins are the same but have valves
what is the connective layer in arteries
(aka tunica externa)
tissue consists mainly of tough collagen fibres which provide strength and durability
what is the smooth muscle layer in arteries
elastic tissue and smooth muslce forms the thickest layer in the artery
(aka tunica media)
enables the artery to flex and withstand and maintain high blood pressure
what is the lumen layer in the artery
narrow to maintain high blood pressure
what is the connective layer and smooth muscle in veins
thinner than arteries because don’t need to withstand high blood pressure
what is the lumen layer in veins
relatively large compared to artery because they don’t need to maintain high blood pressure
why do veins need valves
to prevent the backflow of blood away from the heart
also help prevent blood from pooling in the lower parts of the body due to gravity
what are capillaries
branch off from arterioles and are the smallest blood vessels
form capillary beds which function to bring the blood as close to cells as possible to enable the efficient exchange of substances
thin lumen - slows blood flow for diffusion
one cell thick endothelium
basement membrane anchors capillaries in position within tissues
what are arterioles
branch off from arteries
similar in structure to arteries but have less elastic tissue and more smooth muscle. this enables them to constrict and reduce blood flow through capillaries
what are venules
they drain blood from capillary beds and feed it back into veins. they contain smooth muscle and can constrict like arterioles to control blood flow through capillaries
how does blood flow through veins
as skeletal muscles relax, blood pushes back against the valves, causing them to close and prevent the blood from being forced away from the heart again. as skeletal muscles contract, blood beyond the site of contraction is forced towards the heart, opening the valves. valves behind the site of contraction prevent blood from being forced away from the heart.
What is in blood?
consists of plasma containing: dissolved glucose amino acids mineral ions hormones proteins (including albumin, globulins and fibrinogen) red blood cells white blood cells platelets
what are platelets
fragments of large cells called megakaryocytes found in red bone marrow
involved in blood clotting mechanism - prevents blood loss after injury
what is are the 7 functions of blood?
- oxygen to, carbon dioxide from, the respiring cells
- digested food from the small intestine
- nitrogenous waste products from the cells to the excretory organs
- chemical messages (hormones)
- food molecules from storage compounds to the cells that need them
- platelets to damaged areas
- cells and antibodies involved in the immune response
what else does blood contribute to
maintenance of a steady body temperature and acts as a buffer, minimising pH changes
what is osmosis
is the diffusion of water. It is the net movement of water molecules from a region of high water potential to a region of low water potential, through a partially-permeable membrane.
what is tissue fluid
The fluid that surrounds cells in tissues
Made from substances that leave the blood plasma (oxygen, glucose, nutrients)
But NO red blood cells or big proteins, they are too big to get through the small holes (fenestrations) in the capillary wall
what is lymph
Excess tissue fluid gets returned to the blood through the lymphatic system (10%)
Fluid is transported by squeezing of muscles and valves stop lymph going backwards
Similar composition to plasma and tissue fluid, but less oxygen and fewer nutrients.
what are the three components of lymph
what are lymph nodes
found along the lymph vessels, sac-like organs, contain lymphocytes, which produce antibodies to intercept bacteria.
compare blood, tissue fluid and lymph
only blood has red blood cells
all have white blood cells but tissue fluid has very few
only blood has platelets
blood has proteins, tissue fluid has very few and lymph has it antibodies
all have water and all have dissolved solutes
explain tissue fluid in capillaries
At the arterial end there is a high hydrostatic pressure because of heart action. Hydrostatic pressure is higher than osmotic effect. Capillary wall is leaky/ has pores so lets fluid through and dissolved substances. Red blood cells/proteins are too large so can’t get through. Pressure is lower at venule end so osmotic effect due to plasma proteins so fluid returns to capillaries. Valves in the lymph vessels allows fluid to go in lymph vessel forming lymph - allows protein out of tissue fluid
overall how does blood plasma go to tissue fluid then to lymph and back to the blood plasma?
blood plasma to tissue fluid by ultrafilteration
tissue fluid to blood plasma by reabsorbtion
tissue fluid to lymph by drainage
lymph to blood plasma by lymph vessels
how are erythrocytes adapted for carrying lots of oxygen
no nucleus or other organelles to carry as much hemoglobin as possible
biconcave to increase surface area
almost same width as capillary - can fit through narrow capillaries
contains haemoglobin to react with 4 oxygen molecules making oxyhaemoglobin
what’s the structure of haemoglobin
It is a globular protein
It contains 4 iron heam groups
Each heam group joins to one oxygen molecule
So in total, 4 oxygen molecules can join to a haemoglobin molecule to form: oxyhaemoglobin
what does an oxygen dissociation curve show
shows how much oxygen the haemoglobin has compared to the oxygen available
0% saturation means none of the Hb molecules are carrying any oxygen
when the percentage of oxygen is low Hb has low affinity (hard to get) oxygen. It will release oxygen to the tissues
when the percentage of oxygen is high Hb has a high affinity for the oxygen
It will join to oxygen and become more saturated
100% saturation means all Hb molecules are carrying the max of 4 oxygen molecules
why is the oxygen dissociation curve S shaped?
Slow incline on graph - it’s difficult for the first oxygen molecule to bind as the haem groups are arrange near the middle of the Hb molecule.
Conformational change - once the first oxygen has joined, the shape of the hb molecule changes slightly
Rapid incline - this makes it easier for the 2nd and 3rd oxygen molecules to join positive cooperativity
Gradual incline at the end - once the 3rd oxygen has joined, the concentration of oxygen within the Hb is quite high and so there is not a very large difference between inside and out, making it harder for the final oxygen to attach
how is oxygen concentration measured?
Oxygen binds to haemoglobin when oxygen is at a high concentration, and dissociates from haemoglobin when oxygen is at a low concentration.
The concentration of a gas in a mixture of gases can be quantified in terms of its partial pressure. (pO2)
This is also called the oxygen tension.
Partial pressure is measured in kilopascals (kPa) and is written as P(O2), P(CO2), etc
what is fetal haemoglobin? how is it different to normal haemoglobin?
Fetus gets O2 from its mother’s blood across the placenta
By the time the mother’s blood reaches the placenta, its O2 saturation has decreased
The fetal hb must be able to pick up O2 from an environment that makes adult hb release O2, in order to get enough O2 to survive and it does this by having a higher affinity for O2
The curve is higher than adult hb because it has a higher affinity
what is the Bohr effect?
As PCO2 increases:
Hb gives up oxygen more easily.
The oxygen dissociation curve moves to the right
what are the three ways carbon dioxide is transported around the body?
5% Dissolved in blood plasma
10-20% Combined with the amino group in the polypeptide chains of haemoglobin to form carbaminohaemoglobin
75-85% Transported in the form of hydrogencarbonate ions
how do hydrogen carbonate ions form
As CO2 diffuses into the blood, some of it enters the RBC’s.
It combines with water to form a weak acid = carbonic acid
This is catalysed by carbonic anhydrase (an enzyme)
CO2 + H2O → H2CO3
This carbonic acid dissociates to release hydrogen ions (H+) and hydrogen carbonate ions (HCO3-)
The hydrogencarbonate ions diffuse out of the RBC’s into the plasma.
what is chloride shift
the negatively charged hydrogen carbonate ions move out of the erythrocytes into the plasma by diffusion down a concentration gradient. Negatively charged chloride ions move into the erythrocytes which maintains an electric balance of the cell
how does haemoglobin pay an important role in the transport of CO2
it acts as a buffer and prevents changes in the pH by accepting free hydrogen ions in a reversible reaction to form haemoglobinic acid
what happens when blood reaches the lung tissue
there is a relatively low co2 concentration
carbonic anhydrase catalyses the reverse reaction - breaking down carbonic acid into co2 and water
hydrogen carbonate ions diffuse back into the red blood cells and react with hydrogen ions to form more carbonic acid. this releases free carbon dioxide which diffuses from the blood to the lungs.
chloride ions diffuse out of the red blood cells back into the plasma down an electrochemical gradient.
what is the mammalian heart made of and how does it move
contracts and relaxes in a regular rhythm
what has happened if you have a cardiac arrest
the muscle tissue in your heart is supplied with oxygenated blood by the coronary arteries.
if these arteries are blocked then you have a cardiac arrest.
what are all the features in the heart
aorta pulmonary vein left atrium heart valve left ventricle septum right ventricle right atrium vena cava pulmonary artery
what is the order of blood flow in the body
left ventricle aorta body vena cava right atrium right ventricle pulmonary artery lungs pulmonary vein left atrium left ventricle
what is the septum
where the two sides of the heart are divided by a layer of muscle
what is the right atrium and the left atrium
the two small chambers at the top of the heart
what is the right ventricle and the left ventricle
two larger chambers at the bottom of the heart
what are the pulmonary veins
blood vessels that bring oxygenated blood from the lungs into the left atrium
what is the aorta
very large blood vessel that carries oxygenated blood from the left ventricle to the rest of the body
what is the pulmonary artery
blood vessel that takes deoxygenated blood from the right ventricle and delivers it to the lungs
what is the vena cava
blood vessel that brings deoxygenated blood from the body and empties it into the right atrium
what is diastole
the whole heart is relaxed and the atria fill with blood
what is atrial systole
the atria contract squeezing blood into the ventricles
what is the ventricular systole
the ventricles contract squeezing blood out of the heart
what is the first main stage of a heartbeat
The atria contract, which decreases their volume and increases their pressure
This pushes blood into ventricles through AV valves
There’s a slight increase in ventricular pressure and volume as the ventricles receive blood from atria
what is the second main stage of a heartbeat
Ventricles contract (decreasing their volume), increasing pressure
Pressure becomes higher in ventricles than atria, causes AV valves to shut preventing backflow
High pressure in ventricles opens semi-lunar valves
Blood is forces into the pulmonary artery and aorta
what is the third main stage of a heartbeat
Ventricles and atria both relaxed
Higher pressure in pulmonary artery and aorta causes semi-lunar valves to close, preventing backflow
Atria fill with blood (increasing their pressure), due to higher pressure in vena cava and pulmonary vein
Ventricles continue to relax, pressure falls below the pressure in the atria, causing AV valves to open and blood flows passively (70%) into ventricles from atria
The atria contracts, cycle starts again
when will the tricuspid and bicuspid valves open and why
During atrial systole. The atrial contraction causes the blood pressure to be higher in the atria than the ventricles forcing them open
when will the semilunar valves open and why
When the pressure in the ventricles is higher than the aorta/pulmonary artery, so that the blood is forced out into the arteries
what is happening at each point on a heart pressure graph
look at the graph to help
at the bottom left of the curve the AV valves close
at the top left of the curve the semilunar valves open
at the top right of the curve the semilunar valves close
at the bottom right of the curve the AV valves open
what causes the sounds in the heart
the sounds are from the blood pressure closing the heart valves.
They are described as lub-dub.
The 1st sound comes from the blood forced against the AV valves as the ventricles contract.
The 2nd sound comes as a backflow of blood closes the semi lunar valves in the aorta and pulmonary artery as the ventricles relax.
What does it mean when you say the cardiac muscles is myogenic?
it doesn’t need to be told to beat
sets its own rhythm
what is the order of the wave of excitation?
- SAN (sinoatrial node) is located in the right atrium - it starts the wave of excitation
- The wave passes over the walls of the atria causing it to contract
- Non-conductive tissue prevents the wave from passing straight down to the ventricles.
- The wave is picked up by the AVN (atrioventricular node)
- This delays the wave slightly before passing it down the bundle of His in the septum.
- Bundle of His splits up both sides of the ventricles and passes the wave from the apex up the sides of the ventricles.
- This causes the ventricles to contract from apex to top.
why is the bundle of His important in a heartbeat
It splits into 2 branches and conducts the wave of excitation to the apex.
The purkyne fibres spread out through the wall of the ventricles.
This triggers contraction of ventricles starting at the apex.
Contraction starting at the apex allows more efficient emptying of the ventricles.
what is an ECG?
What are the stages?
Electrocardiograms measures electrical activity of the heart 1) contraction of atria 2) (the point) contraction of ventricles 3) relaxation of ventricles
what is tachycardia?
a fast resting (above 100bpm) heartbeat caused for no reason
the heart produces rapid electrical signals
pumps less efficiently so blood flow is reduced
the muscles are using more oxygen because they are pumping quicker so if it carries on then you could have a cardiac arrest because the muscles aren’t receiving enough oxygen
treatment includes relaxation therapy or beta blocker
what is an increased heartbeat due to?
what is VF
the ventricles contract but it’s not coordinated so fluttering occurs and little blood is pumped
what is happening in defibrillation
Heart is shocked
Heart restarts with the hope that it restarts with a normal rhythm
what is bradycardia
when the heart rate slows down below 60bpm
what is an ectopic heartbeat
extra heartbeats that are out of normal rhythm
happens to everyone once a day but if it regular then it can be dangerous
What happens to the pressure of the left atria in a heartbeat
- The pressure is lower than ventricles and aorta as thin walls so doesn’t give much force
- when contracting the atria is at its highest pressure as there’s a lot of blood
- pressure then drops as no blood in atria and AV valve is closed so now in relax phase
- pressure increases again as atria fills with blood
What happens to the pressure of the left ventricle through a heartbeat
- When ventricles are relaxing, pressure is low
- when AV valves close, all blood in ventricles so pressure goes up as ventricles contract
- when pressure of ventricles goes above the aortic pressure, that’s when the SL valves open and blood goes into the aorta
- then pressure goes down as the blood leaving the ventricles and relaxing again
What happens to the aortic pressure in a heartbeat
Pressure rises when ventricles contract as blood is going into the aorta
Pressure falls once all the blood has gone through
Semilunar valve closing and recoiling phase produces a temporary pressure rise