cardiovascular system Flashcards
Pathway of blood
Body - vena cava - RA - tricuspid valve - RV - pulmonary semi-lunar valve - pulmonary artery - lungs - pulmonary vein - LA - bicuspid valve - LV - aortic semi-lunar valve - aorta
Define myogenic
heart generates its own impulses
Pathway of the cardiac conduction system
SAN - AVN - bundle of His - branches - purjinkie fibres
Define systole
contract
Define diastole
relax
Role of AVN
- impulse moves from SAN - AVN
- delays transmission
- allows atria systole and ventricles to fill up
- sends signals to bundle of His
Define sympathetic nervous system
stimulates the heart to beat faster
Define parasympathetic nervous system
returns heart to resting heart rate
Define medulla oblongata
regulates process that keeps us alive such as breathing/ HR
What do chemoreceptors do
- sense chemical changes
- increased CO2 levels stimualtes sympathetic nervous system
- increased HR
What do baroreceptors do
- responds to increased arterial pressure = increased stretch of atria = decreased HR
- decreased arterial pressure = decreased stretch of atria = increased HR
What do proprioreceptors do
- detect muscle movement and increases HR
Define stroke volume
volume of blood pumped out by the heart ventricles in each contraction
Define venous return
volume of blood returning to the heart via the veins
Define ejection fraction
percentage of blood pumped out by the left ventricle per beat
Starling’s Law
increased venous return
greater diastolic filling of heart
cardiac muscle stretched
more force of contraction
increased ejection fraction
Equation for ejection fraction
stroke volume/ end diastolic volume
Define HR
number of times the heart beats in a minute
Define cardiac output
volume of blood pumped out by the heart ventricles per minute
Equation of cardiac output
Q= SV x HR
Define cardiac hypertrophy
thickening of the muscular wall of the heart so it becomes bigger and stronger = larger ventricle cavity
Define bradycardia
decrease in resting heart rate to below 60 bpm
What are the 4 main mechanisms for venous return
1) pocket valves
2) respiratory pump
3) muscle pump
4) smooth muscle
Describe how muscle pump works
during exercise working muscles will compress the veins during contraction and push blood back into the heart
Describe how respiratory pump works
increased respiration during exercise will increase/ change pressure in the thorax which pushes blood back into the heart
Describe how smooth muscle works
layer of muscle in the veins that contracts and pushes blood back up into the heart
Describe how pocket valves work
one way valves that stop the back flow of blood, thus maximising the volume of blood returning to the heart
Coronary heart disease
occurs when coronary arteries that supply the heart musle with oxygenated blood become blocked/ narrow
cause a gradual build up of fatty deposists called ATHEROMA - process called ATHEROSCLEROSIS
as they narrow they cannot deliver enough oxygen to the heart causing pain called AGINA
Process of build up of fatty deposists
atherosclerosis
What is a pain in the heart
Angina
Define high blood pressure
the force exerted by blood against the blood vessels
What does high blood pressure do
puts extra strain on the heart
regular exercise decreases blood pressure - reduces systolic/ diastolic pressure
LDL
low density lipoproteins
transport cholesterol in blood tissues and are classified as ‘bad’ cholesterol
HDL
high density lipoproteins
transports excess cholesterol away from the heart back to the liver where it’s broken down
classified as ‘good’ cholesterol
Define stroke
occurs when the blood supply to part of the brain is cut off casuing a brain injury so brain cells start to die
Define ischaemic stroke
blood clot stops the blood supply to the brain
Define haemorrhagic stroke
weakened blood vessel supplying the brain bursts
Cardiovascular drift process
- in warm environment during exercise heart rate will increase to pump more blood to working muscles
- this is compencated by less venous return = less ejection fraction = less cardiac stretch = less SV
- plasma lost in sweat (vasodialition) so blood volume decreases
- cardiac outuput maintained
What are the two types of circulation
- pulmonary
- systemic
Define pulmonary circulation
deoxygenated blood from the heart to the lungs and oxygenated blood back to the heart
Define systemic circulation
oxygenated blood to the body from the heart and then deoxygenated blood from the body to the heart
Equation of blood pressure
blood flow x resistance
Why is it important for venous return
- ensure oxygen is supplied to skeletal muscles
at rest valves and smooth muscle is enough - demand for oxygen increases - skeletal pump + respiratory pump ensured VR is maintained
- after exercise, cool down keeps them working/prevents blood pooling
What does the skeletal muscle pump do in venous return
muscles contract/ relax they change shape so they press on nearby veins squeezing the blood back to the heart
What does the respiratory pump do in venous return
during inspiration/ expiration the muslces contract = the changes of pressure occur in the thoraic (chest) and abdominal cavities
this compresses nearby veins and assists blood return
What do pocket valves do in venous return
stops the back flow of blood so it travels directly back to the heart
once blood has passed through they contract and squeeze the blood up
What happens to venous return with increased systolic pressure
increased venous return
Equation for pressure gradient
venous pressure (Pv) - right atrial pressure (Pra) / venous vascular resistance (Rv)
Definition for vascular resistance
the resistanec that must be overcome to push through the circulatory system
What happens if there is increased venous resistance
decreased venous return and constricition of veins
What is the pressure gradient like in peripheral veins and right atrium
very low as pressure gradient driving venous return to the heart is low
How many oxygen molecules does haemoglobin carry
4 - when fully saturated
Definition of myoglobin
iron containing muscle pigment in slow twitch fibres
stores oxygen in muscle fibres which can be used quickly (high affinity for O2)
Definition of oxyhaemoglobin dissociation
release of oxygen from oxyhaemoglobin to the muscles and tissues
What direction does the curve during exercise move in the oxyhaemoglobin dissociation graph
RIGHT
Definition of the Bohr shift
an increase of blood carbon dioxide levels and a decrease in pH resulting in a reduction of the affinity of haemoglobin for oxygen
What are the three factors that increase dissocation of oxygen
- increased blood temperature = increased temp O2 dissociates more readily
- increased partial pressure of carbon dioxide = level of CO2 rises so does O2 level
- pH = more CO2 will lower blood pH a drop in pH will cause it to dissociate quicker
Defintion of vascular shunt mechanism
the redistribution of cardiac output ( to the areas that need it )
Why should performers not eat less than an hour before their race
a full gut results in more blood being directed to the stomach to break dwon the food isntead of the working muscles so less O2 is readily available
What is blood pressure and blood flow controlled by
vasomotor centre (located in the medualla oblongta)
What happens in the vasomotor centre during exercise
chemical changes occur (increase in CO2 and lactic acid) this is detected by the chemoreceptors
these stimualte the vasomotor centre so it redistributes blood flow through vasodilation and vasoconstriction
Definition of A-VO2 diff
difference between the O2 content of the arterial blood arriving athe the muscles and the venous blood leaving the muscles
What are pre-capillary sphincters
tiny rings of muscles located at the opening of capillaries
What is A-VO2 diff like at rest
it is low
What is A-VO2 diff during exercise
it is high
Where does vasoconstriction and vasodiliation occur
arterioles
