Module 3 - Transport in animals

Why do multicellular organisms need transport systems?

are larger so diffusion distance across their surface would be too large so diffusion is too slow + outer layer uses all the cells
have higher metabolic rate as need energy so can move around and good supply of oxygen for respiration
need to supply nutrients and oxygen rapidly to a larger number of active cells so diffusion alone would be too slow
larger animals have a smaller surface area to volume ratio meaning each gram of tissue has a smaller area for exchange

What circulatory system do fishes have?

single circulatory system - means blood passes through the heart only once per circuit
occurs as the heart pumps blood to the gills to pick up oxygen and blood flows directly from the gills to the rest of the body to deliver oxygen

What circulatory system do mammals have?

double circulatory system - means blood flows through the heart twice per circuit
occurs as right side of the heart pumps deoxygenated blood to lungs to pick up oxygen and the left side of heart pumps oxygenated blood to the rest of the body which gives an extra push to deliver this blood more quickly to distant body tissues or those that require high pressure like the kidneys

What is and what type of animals have a closed circulatory system?

vertebrates - their blood is enclosed in vessels + arteries generally distribute oxygenated blood and veins generally return deoxygenated blood to heart - where separate fluid called tissue fluid bathes tissues and cells
pros - higher blood pressure so blood flow more quickly - more rapid delivery of oxygen and nutrients - more rapid removal of carbon dioxide and urea - transport is independent of body movements - allows flow to be diverted

What is and what type of animals have a open circulatory system?

invertebrates - their blood flows freely through the body cavity and blood is not held in the vessels + blood returns to heart through valves and blood doesn’t just transport oxygen - in some animals movements of the body help circulate the body + in insects muscular pumping organ acts as a heart which is a long muscular tube with blood entering through pores called ostia
cons - blood pressure is low and blood flow is slow - circulation of blood may be affected by body movements or lack of body movements

What are the two system types mammals have?

have closed + double circulatory system with two main divisions
systemic circulatory system - oxygenated blood is pumped out of the heart via the aorta to most body tissues
deoxygenated blood is returned to the heart via the vena cava from the body tissues
pulmonary circulatory system - deoxygenated blood is pumped out of the heart via the pulmonary artery to the lungs
oxygenated blood is returned to the heart via the pulmonary vein from the lungs

What are the five main type of blood vessels and what is in the inner lining?

arteries - vessels that carry blood away from the heart
arterioles - small blood vessels that carry blood from arteries into capillaries
capillaries - very small vessels which is site of diffusion between blood and body tissues
venules - small blood vessels that carry blood from capillaries into veins
veins - vessels that return blood to the heart
all vessels have inner layer made of single layer of cells called endothelium which is thin layer that is smooth to reduce friction with flowing blood

How are arteries and arterioles adapted?

adapted to carry blood at high pressure away from the heart
lumen - relatively small to maintain high pressure
thicker layer of collagen - provides strength to prevent the vessel from bursting and maintains vessel shape + endothelium is also folded so it can stretch
elastic fibres - contains elastin that lets them strech and recoil to minimise changes in pressure
thick smooth muscle layer - contracts/relaxes to constrict/dilate the lumen and control blood flow
arterioles are smaller than arteries but with larger lumen - walls have more smooth muscle where contraction will constrict diameter of arteriole which increases resistance + reduces rate of flow of blood which can be used to divert flow of blood to regions demanding more oxygen and less elastin as they do not need to withstand such high pressures
arteries near heart have more elastic tissue in wall to allow stretch and recoil which helps even out fluctuations in blood pressure so further from the heart walls contain more muscle tissue

How do blood vessels control the blood flow?

through vasoconstriction and vasodilation
vasoconstriction - smooth muscle contracts,constricting the blood vessel and decreasing blood flow
vasodilation - smooth muscle relaxes,dilating the blood vessel and increasing blood flow

What are capillaries and the adaptations?

form extensive networks between arterioles and venules providing an area between blood and tissue where exchange of substance like gases and nutrients can occur between blood and tissue fluid
lumen is very narrow - allows red blood cells to be close to body cells as squeezes against walls which reduces diffusion path and increases resistance and reduces rate of flow
walls are thin - substances can be exchanged across a short distance by diffusion
highly branched - provides a large surface area for diffusion
oxygen not released by erythrocytes until they reach the capillaries as arteries have a thick wall whereas the  capillary wall is only one cell thick so the diffusion distance too large for the artery but short enough diffusion distance to occur through the capillary wall

How are veins and venules adapted?

adapted to carry blood towards the heart at low pressure
collagen - provides a strength to prevent the vessel from bursting and maintain vessel shape
little smooth muscle and elastic fibre - not much is needed due to low blood pressure and thinner walls allow veins to be easily compressed aiding the flow of vlood
lumen - relatively large in order to ease the flow of blood 12
valves - pocket valves shut to prevent the backflow of bloof when veins are squeezed by surrounding skeletal muscle
pocket valves are similar in structure to valves in heart but are controlled by skeletal muscle where contraction of surrounding skeletal muscle applies pressure to blood forcing the blood to move along in direction determined by valves
venules are smaller than veins - they have very thin walls and very little smooth muscle - collect blood from capillary bed and lead into veins

What is the composition and functions of blood?

plasma - mostly water transports substances in solution - red blood cells - carry oxygen - white blood cells (leucocytes) - immune cells - platelets - involved in clotting - minerals,amino acids + plasma proteins
functions - transports oxygen + carbon dioxide - transports nutrients from digestion - transports waste for excretion - transports hormones - transports food from storage - transports clotting factors

What is the composition of tissue fluid?

fluid that surrounds cells in tissue + site of diffusion between blood and body cell providing cells with nutrients and oxygen while removing waste products + helps fight infection as forms part of immune response
has same composition as plasma except has no red blood cells has fewer plasma proteins and fewer white blood cells
substances dissolved in blood plasma able to enter the tissue fluid via diffusion from high concentration to low concentration down the concentration gradient as hydrostatic pressure in the capillary is higher than in the tissue fluid + the capillary walls are leaky so fluid is forced out of the capillary down the pressure gradient as the fluid moves out the glucose, oxygen + other small molecules leave with it
erythrocytes aren’t found in tissue fluid because the gaps between endothelial cells are too small for them to fit through + the erythrocytes can’t change shape much so can’t bend to fit through the fenestrations between the endothelial cells

How does tissue fluid form?

formed from the blood flowing through capillaries
at arteriole end of capillaries: high hydrostatic pressure generated by contraction of the ventricle muscle wall in the heart forces fluid out of capillaries through tiny gaps down pressure gradient (mass movement) - fluid consists of plasma with dissolved nutrients + oxygen leaving rbc,platelets, most wbc + plasma proteins as too large to be pushed out - tissue fluid surrounds body cells so exchange of gases and nutrients can occur across plasma membranes via diffusion with oxygen entering cells and carbon dioxide leaving cells
at venule end of capillaries: hydrostatic pressure is lower as drops as blood moves away from the heart as more vessels the further you get from the heart so the vessels have a larger total lumen/cross-sectional area + there is reduced resistance to blood flow, the arteries stretch/expand + fluid is lost as plasma from the capillaries - proteins in blood exert a high oncotic pressure in capillaries - water potential lower in capillaries than tissue fluid due to fluid loss - some tissue fluid moves back into capillaries by osmosis carrying carbon dioxide and waste substances into blood

What are the features of good transport system and efficient transport system?

effective if:has a fluid to carry nutrients,oxygen and waste around the body - a pump to create pressure to push fluid around the body - exchange surfaces that enable substances enter and leave the blood where needed
efficient will also include:tubes or vessels to carry blood by mass flow - two circuits with one to pick up oxygen and another to deliver oxygen to the tissues

What are the advantages of double circulation?

efficient circulatory system will deliver oxygen quickly to parts of the body that need it where blood can flow more quickly if blood pressure is increased
in single circulatory system of fish:blood pressure drops as blood passes through capillaries of gills - blood has low pressure as it flows towards the body so will not flow very quickly - rate oxygen delivered to respiring tissues + carbon dioxide removed is limited but as fish not as metabolically active and don’t need to maintain body temperature so need less energy + single system is sufficient

How do the frog and mammalian circulation compare?

to compare state how they are similar, how they are different, and then comment on which is more effective and why
both have  double circulations though blood from mammalian heart transported separately to lungs and body and  oxygenated and deoxygenated blood never mix, whereas blood from frog heart transported to lungs and body together so the blood going to the body in the frog is partially oxygenated and oxygenated blood only separate when returning from lungs + in frogs the spiral valve partly separates oxygenated and deoxygenated blood
in terms of effectiveness both can be considered to be effective frog could be considered to be less effective as frog has less oxygen available for the body cells but the circulation is effective enough for the frog’s needs as the frog has lower metabolic rate and as the frog maintains body temperature by other means + as the frog heart may beat faster to compensate
however frog circulation may limit its size - mammalian system more effective as mammalian body cells get maximum available O2 though this is necessary as the mammal has a higher metabolic rate and uses metabolism to maintain body temperature

What is pressure like in double circulatory system of mammals?

blood pressure must not be too high in pulmonary circulation as may damage capillaries in lungs - heart can increase pressure of blood after passed through lungs so blood under high pressure as flows to the body and flows more quickly - systemic circulation can carry blood at even higher pressure as active animals and maintain body temperature - supplying energy for activity where to release a lot of energy need good supply of oxygen and nutrients and removal of waste products

What happens to excess tissue fluid?

drained into another tubular system called lymphatic system where excess tissue fluid returns to blood system in subclavian vein
fluid known as lymph and is similar in composition to tissue fluid but has more lymphocytes as are produced in lymph nodes swellings along system which help immune support (if tissue infected and more leaky the extra fluid directed into lymph system but also has less oxygen and nutrients ans has more fatty acids
some tissue fluid doesn’t re-enter capillaries - fluid drains into lymph vessels forming lymph - lymph transported through lymph vessels by muscle contractions - lymph passed through lymph nodes to filter pathogens - lymph is eventually returned to the blood

What causes the movement of fluids?

blood,tissue fluid and have hydrostatic pressure + solutes oncotic pressure has influence
hp of blood tends to push fluid out into tissue as has high hp more negative op than tissue fluid
tissue fluid has low hp and less negative op than blood plasma
lymph has low hp and a less negative op than blood plasma + contains more fats than tissue fluid
hydrostatic plasma - pressure fluid exerts when pushing against side of vessels
oncotic pressure - pressure created by osmotic effects of solute
net results of these forces creates a pressure gradient to push fluid out of capillary at arterial end and into capillary at venule end

How does haemglobin transport oxygen?

oxygen enters lungs from atmospheric air + needs to be transported to body cells
transported to body cells via the blood: red blood cells contain haemoglobin (red pigment used to transport O2 in blood) which has 4 haem groups + high affinity for oxygen - in capillaries in lungs where pO2 is high oxygen binds to iron in haem group forming oxyhaemglobin where oxygen enters red blood celss by diffusion - each haemglobin molecule can carry 4 oxygen molecules one per haem group - oxyhaemoglobin can be transported via blood to respiring body tissues - at body cells oxygen dissociates from haemoglobin as needed + pO2 is low

How does oxygen pressure affect haemoglobin/oxygen saturation?

higher po2 means haemglobin has high affinity for oxgen and association of oxygen and haemoglobin occurs (eg in the lungs)
lower po2 means haemoglobin has low affinity for oxygen and dissociation of oxygen and haemoglobin occurs (eg at respiring body cells)

How is oxygen binding cooperative?

when haemglobin binds with one oxygen it changes shape so becomes easier to bind another oxygen
when haemoglobin is mostly saturated with oxygen is harder for more oxygen to bind

What is the difference between fetal and adult haemoglobin?

fetal haemoglobin are in the red blood cells of unborn fetus
fetus needs to obtain oxygen from mothers’ blood therefore has higher oxygen affinity than adult haemoglobin therefore curve is to the left of curve of adult haemoglobin as fetal haemoglobin must be able to associate with oxygen in an environment where oxygen tension is low enough to make adult haemoglobin unload more oxygen - in placenta pO2 is low so fetal haemoglobin will absorb oxygen from surrounding fluid reducing oxygen tension further so oxygen loads more readily from maternal haemoglobin which dissociates oxygen - ensures fetus gets enough oxygen to survive while it develops
fetal haemoglobin contains gamma subunits to give it a higher affinity for oxygen than adult haemoglobin

How can sickle cell anaemia be treated?

benefit from drugs that cause them to produce fetal haemoglobin as fetal haemoglobin may not crystallise much at low pO2 so these red blood cells do not change shape + so cause symptoms of sickle cell anaemia
also fetal haemoglobin can pick up more oxygen at lower pO2 than sickle haemoglobin so more oxygen is transported around the body

What causes the pressure and saturation graph to shift right?

Bohr effect where haemoglobin has lower affinity for oxygen and higher partial pressure of carbon dioxide (pCO2)
higher pCO2 at respiring tissues causes haemoglobin to release oxygen as Bohr effect decreases affinity for oxygen in haemoglobin when carbon dioxide is present meaning oxygen saturation of haemoglobin is lower for a given pO2 when pCO2 is higher
needed as active tissues that produce carbon dioxide require a lot of oxygen from blood so Bohr effect shifts oxygen dissociation curve to right
blood offloads more oxygen to actively respiring tissues than resting tissues as in actively respiring tissues has higher levels of carbon dioxide which lower the affinity of haemoglobin for oxygen resulting in dissociation of carbonic acid and increase of H+ leading to the release of oxygen so more oxygen released at same pO2 

How is carbon dioxide transported in bloodstream?

beneficial for CO2 to be converted into another form in blood to maintain steep diffusion gradient between respiring tissues which need to get rid of CO2 and blood which removes CO2 to lungs
multiple ways CO2 transported via the blood: 5% dissolved directly in plasma (amino acids) - 10% CO2 enters red blood cells + is transported bound to haemoglobin as carbaminohaemoglobin - 85% CO2 enters red blood cells + undergoes reaction in cytoplasm to form hydrogen carbonate ions

How does the transport of carbon dioxide as hydrogen carbonate ions occur?

once CO2 from respiration enters red blood cells it undergoes changes so can be transported as hydrogen carbonate ions which explains why Bohr effect occurs
at respiring tissues which has high pCO2 the following occurs:CO2 reacts with water to form carbonic acid (H2CO3) and is catalysed by enzyme carbonic anhydrase - this dissociates to hydrogen ions and hydrogen carbonate ions (HCO3-) - hydrogen ions bind to haemoglobin forming haemoglobinic acid (HHb) causing haemoglobin to release oxygen which prevents blood from becoming too acidic so haemoglobin acts as a buffer - also causes Bohr effect at high pCO2 haemoglobin releases oxygen so can diffuse into respiring tissues - hydrogen carbonate ions leave red blood cells + transported via plasma while chloride ions enter red blood cells called chloride shift which maintains charge balance by preventing excessive positive charge in red blood cells
at lungs which have low pCO2 the following occurs:low pCO2 causes hydrogen carbonate ions and hydrogen ions to reform carbon dioxide - carbon dioxide diffuses out of the body during expiration

What is haemoglobin?

complex protein with four subunits with each subunit consisting of polypeptide chain and haem group which contains single iron ion in form of Fe - ion can attract and hold oxygen molecule with haem group having a high affinity for oxygen

How is oxygen transported around the body?

oxygen is absorbed into blood as passes alveoli in lungs - oxygen molecule diffusing into blood plasma enter red blood cells and here oxygen associates with haemoglobin which means oxygen binds reversibly to haemoglobin which takes oxygen out of solution maintaining steep concentration gradient so more oxygen can enter blood from lungs and diffuse into cells
blood carries oxygen from lungs back to heart before travelling around body to supply tissues where in body tissues cells need oxygen for aerobic respiration therfore the oxyhaemoglobin must be able to release the oxygen called dissociation

What is the haemoglobin dissociation curve?

ability of haemoglobin to associate and dissociate depends on oxygen concentration in surrounding tissues which is measured by relative pressure it contributes to mixture of gases called partial pressure of oxygen (pO2) and measured in (kPA) - haemoglobin associates with oxygen in way that produces S-shaped curve
at low oxygen pO2 haemoglobin doesn’t readily associate with oxygen molecules as haem group which attracts oxygen in centre of haemoglobin molecule which makes it difficult for oxygen molecule to reach haem group and associate with it - this difficulty in combining with first oxygen molecule accounts for low saturation level of haemoglobin at low pO2
as oxygen tension rises diffusion gradient into haemoglobin molecule increases + eventually one oxygen molecule enters haemoglobin molecule and associates with one of the haem groups which causes a slight change of shape of molecule known as conformational change and it allows more oxygen molecules to enter haemoglobin molecule and associate with other haem groups easier which accounts for steepness of curve as pO2 rises
as haemoglobin approaches 100% saturation curve levels off where mammalian haemoglobin well adapted to transporting oxygen to tissues and oxygen tension found in lungs is sufficient to produce close to 100% saturation where oxygen tension is sufficiently low to cause oxygen to dissociate readily from oxyhaemoglobin

How does the Bohr effect impact hydrogen ions?

hydrogen ions are formed from carbonic acid - these ions make cytoplasm more acidic which affects tertiary structure of haemoglobin which reduces the affinity of haemoglobin for oxygen - haemoglobin unable to hold as much oxygen and oxygen is released from oxyhaemoglobin to tissues where tissues are respiring more there will be more carbon dioxide - as a resuly will be more hydrogen ions produced in red blood cells making oxyhaemoglobin releases more oxygen
so when carbon dioxide present haemoglobin becomes less saturated with oygen which reflects the Bohr shift which results in more oxygen being released where more carbon dioxide produced during respiration which is what muscles need for aerobic respiration

What is the effect of increasing carbon dioxide?

blood entering respiring tissues carries oxygen as oxyhaemoglobin - partial pressure of oxygen in respiring tissues is lower than lunds as oxygen been used in respiration - meaning oxyhaemoglobin begins to dissociate and releases oxygen to tissues - means haemoglobin available to take up hydrogen ions forming haemoglobinic acid where tissues are very active there is more carbon dioxide released

What is a summary of the Bohr effect?

occurs as carbon dioxide reduces the affinity of haemoglobin for oxygen - protons from the dissociation of carbonic acid interact with haemoglobin to form haemoglobinic acid as this prevents the fall of pH in the cells in the surroundings so provides a buffering effect
H+ ions alter the structure of haemoglobin such that more oxygen released where it is needed more (i.e: respiring tissues) as carbon dioxide concentration is high in these areas
CO2 then binds to haemoglobin forming carbaminohaemoglobin

What are the internal features of the mammalian heart?

heart divided into four chambers - left + right atria and left + right ventricles
atria - top chambers in heart that collect blood from blood vessels (veins) where deoxygenated blood from body flows through vena cava into right atrium + oxygenated blood from the lungs flows through pulmonary vein into left atrium
from atria blood flows down atrioventricular (attached to the valves are tendious cords which prevent the valves turning inside out when ventricles contract) into ventricles which are bottom chambers in heart that pump blood into blood vessels (arteries) - deoxygenated blood leaves the right ventricle flows into pulmonary artery leading to lung where its oxygenated + oxygenated blood leaves the left ventricle flows into the aorta which carries blood to a number of arteries which supply all parts of the body + at base of major arteries where they exit the heart are the semilunar valves which prevent blood returning to heart when ventricles relax
left side of heart contains oxygenated blood and the right side contains deoxygenated blood where septum separates two sides of heart preventing oxygenated and deoxygenated blood from mixing
in a dissection it is better to use the heart that has blood vessel present

Why does the heart have two separate pumping mechanisms?

blood pressure drops in lungs as it flows through capillaries
single pump would slow blood flow to body cells so two pumps increase pressure before blood circulates
muscular pump where on both sides of the heart squeezes the blood putting it under pressure where the pressure forces blood along arteries and through circulatory system

What are the valves between the two heart chambers?

atrioventricular vales: tricuspid valve located between right atrium and ventricle - bicuspid valve located between left atrium and ventricle
both valves prevent backflow of blood into atria when ventricles contract + ensures blood flows in right direction

What is another valve in the heart?

semi-lunar valves - located between ventricles and pulmonary artery and aorta
prevent backflow of blood into ventricles when they relax
prevents blood re-entering heart from the arteries

What are the blood vessels associated with the heart?

pulmonary vein - moves oxygenated blood into left atrium from the lungs
aorta - moves oxygenated blood from left ventricle to body
vena cava - moves deoxygenated blood into right atrium from the body
pulmonary artery - moves deoxygenated blood from right ventricle to lungs
right side on diagrams is always on left and vice versa

What walls are thicker in the heart?

cardiac muscle in each chamber wall contracts to create pressure with the higher pressure created the further it will push the blood
ventricles have thicker walls with more muscle than the atria as atria muscle very thin as only need enough pressure to pump blood a short distance into the ventricle + ventricle needs lots of pressure to pump blood a long distance out of heart to other organs where greater resistance than shorter distances
the left ventricle has a thicker wall with more muscle than wall of right ventricle as right ventricle only needs enough pressure to pump deoxygenated blood a short distance to lungs + left ventricles need a lot more force created for pressure to pump oxygenated blood to other more distant organs of the body so needs sufficient pressure to overcome resistance of systemic circulation

What are the external features of the heart?

heart lies just off-centre towards the left of the chest cavity where the main part of heart consists of firm,dark-red muscle called cardiac muscle - there are two main pumping chambers ventricles and above are two thin-walled chambers called the atria which are much smaller than ventricles
lying over the surface of the heart are coronary arteries that supply oxygenated blood to the heart muscle as heart hard-working organ these arteries are very important as if they become constricted it can have severe health consequences - restricted blood flow to the heart muscle reduces delivery of oxygen and nutrients such as fatty acids and glucose which may cause angina or a heart attack (myocardial infarction)

What are cardiac muscles?

specialised muscles found in walls of the heart chambers - consists of fibres that branch producing cross-bridges which help to spread the stimulus around the heart + ensures muscle can produce squeezing action - numerous mitochondria between myofibrils to supply energy for contraction - separated by intercalated discs which facilitate synchronised contraction + each cell has a nucleus

What is the cardiac cycle and three stages?

sequence of contraction and relaxation of cardiac muscle in walls of heart in one full beat of the heart
stages: atrial systole - ventricular systole - diastole where ventricular + atrial systole cause pressure inside the heart chambers

What is atrial systole?

ventricle relax + recoil and atria contract - increases the atrial pressure - atrioventricular valves open - blood flows into ventricles + pressures in atria and ventricles rises slowly as they fill with blood - both right and left atria contract together with muscle in the wall being thin so only small increase in pressure which helps push blood into ventricles - pressure in major arteries is higher than in ventricles meaning semilunar valves are closed

What is ventricular systole?

ventricle contract and atria relax - ventricular pressure increases + when rises above atria blood moves upwards where this movement fills valve pockets and keeps them closed - semi-lunar valves (tendinous cords attach to valves to prevent turning them inside out) pushed open and atrioventricular valves close as this raises ventricular pressure such that it is higher than atrial pressure + the pressure generated by ventricular contraction pushes the valves shut + chordae tendinae prevent inversion - blood flows into arteries as under high pressure so forced out of the ventricles - right and left ventricle pump together + contraction starts at apex of heart so blood pushed upward towards arteries + allows for complete emptying of the ventricles

What is diastole?

follows systole in the mammalian heart as cardiac muscle takes a short time to repolarise after being stimulated - ventricle and atria relax - semi-lunar valves close - blood flows passively into the atria - muscular wall of all four chambers relax + elastic recoil causes chambers to increase in volume allowing blood to flow in from the veins + ventricle pressure drops below majort arteries blood flows back towards ventricles - semilunar valves pushed closed by blood collecting in pockets of the valves

What is the summary of the process?

in a heartbeat the sinoatrial node initiates the excitation - wave of excitation spreads over atrial walls causing them to contract in a synchronised manner (atrial systole) - non-conducting tissue forces the wave of excitation to pass through the atrioventricular node so the excitation spreads down the septum through the Bundle of his + then through the Purkyne fibres in the walls of the ventricles causing the ventricles to contract (ventricular systole) from apex of the upwards - is a delay between the excitation of the atria and the excitation of the ventricles to allow time for the atria to fully contract and empty of blood + to allow time for the ventricles to fill with blood so they do no contract too early
where all this can occur due to cardiac muscle is found in the walls of the heart chamber

What is the pressure like in the blood vessels?

blood enters aorta + pulmonary artery in rapid spurt but tissue requires blood to be delivered in even flow where structure od artery wall helps achieve this through: artery walls close to the heart have lots of elastic tissue - when blood leaves the heart these walls strech - as blood moves on and out of the aorta the pressure starts to drop - elastic recoil of walls helps to maintain blood pressure in aorta where the further blood flows along arteries the more pressure drops + fluctuations become less obvious - important to maintain pressure gradient between aorta and arterioles as this is what keeps blood flowing towards tissues

What are some more details about pressure?

pressure fluctuates in the aorta due to systole increasing pressure via contraction of the left ventricle wall and diastole decreasing pressurewhere the number of pressure fluctuations per minute is the pulse/heart rate
important that blood pressure changes as blood flows from the aorta to the capillaries as the capillary wall is thin so high pressure would damage the capillary wall so lower pressure reduces the risk of tissue fluid build up

How is the heart beat controlled?

cardiac muscle is myogenic which means contraction of cardiac muscle initiates within the heart itself (initiates its own contraction) - basic rhythm of heart maintained by wave of electrical excitation - muscle with contract and relax rhythmically even if not connected to the body
muscles from the atria and the ventricle each have own natural frequency of contraction where atrial muscle contracts at higher frequency which can cause muscle to inefficiently pump if contractions of chambers not synchronised - known as fibrillation so heart needs mechanism that can coordinate contractions of all four chambers

What structures does the wave travel through?

1.sinoatrial node (SAN) - initiates heart beat by stimulating artria to contract - at top right atrium near vena cava which is small patch of tissue that generates electrical activity + initiates a wave of excitation at regular intervals arround 55-80 times a minute
2.layer of collagen fibre - prevents direct electrical flow from atria to ventricles
3.atrioventricular node (AVN) - picks up electrical activity from SAN and imposes slight delay
4.bundle of his - recieves electrical activity from AVN and conducts the waves of excitation to the apex (base) of the heart
5.purkyne fibres - these branch off the bundle of his causing the right and left ventricle to contract from the bottom upwards

What happens during the contraction of the atria?

wave of excitation quickly spreads over walls of both atria - travels along membrane of muscle tissues - as wave of excitation passes it causes cardiac muscle cells to contract this is an atrial systole - tissue at base of atria unable to conduct wave so cannot spread directly down to ventricle walls so top of interventricular septum is the AVN which is the only route that can conduct wave through to ventricles - wave is delayed in this node allowing time for atria to finish contracting + for blood to flow down into ventricle before they begin to contract (maximises bloodflow)

What happens during the contraction of the ventricle?

after short delay wave of excitation is carried away from AVN and down specalised conducting tissue called purkyne tissue which run down the interventricular septum - at base of septum wave spreads out over walls of ventricles as excitation spreads upwards from base of ventricles it causes muscle to contract from base upwards which pushes blood up towards major arteries at top of heart -  controlled by a wave of depolarisation from the AVN moving along the Purkyne fibres to cause the contraction of the ventricles

What is purkyne tissue?

consists of specially adapted muscle fibres that conduct the wave of excitation from AVN down the septum to the ventricles
a toxin that reduces speed of conduction down the purkyne fibres slows down heart rate as slows transmission of impulse from AVN to ventricles slows ventricular systole - longer delay before ventricular systole/contraction begins + increases time the heart is in diastole/relaxation

How electrocardiograms monitor heart function?

ECGs trace that records the heart’s electrical activity using electrodes - we can monitor this which inolves number of sensors on skin which pick up electrical excitation created by the heart and convert this into a trace
shows various stages of caridiac cycle: P wave - atrial systole QRS - ventricular systole T wave - diastole

What abnormalities can ECG help diagnose?

tachycardia - this is an abnormally rapid heart rate
bradycardia - this is an abnormallu slow heart rate
ectopic heartbeats - this is extra heartbeats out of the normal rhythm (of the ventricles)
atrial fibrillation - abnormally rapid and ineffective contraction of the atria + uncoordinated contraction of atria or ventricles

What are some other issues with the cardiac system?

high blood pressure causes cell death as increased blood pressure causes small blood vessels such as capillaries to burst/break causing a localised build up of pressure leading to cell death + in this place blood cannot circulate to supply oxygen so cells cannot respire leading to cell death
if the ventricles contract twice for every atrial contraction in the heart then less blood leaves heart for each ventricular contraction as the ventricles do not have time to fill before contracting
hole in the septum between heart chambers is open in a fetus before birth as the lungs are not functioning as they are not filled with air so blood is not oxygenated in the lungs + instead is oxygenated in the  placenta therefore pulmonary circuit/lungs are bypassed
a weak irregular heartbeat may result in fatigue as it results in slow blood flow and lower blood pressure so less oxygen reaches the cells for oxidative phosphorylation in aerobic respiration so less glucose reaches the cells for respiration so less ATP produced + is then also increased acidity as CO2/lactate builds up which affects the enzymes involved in respiratory metabolism