Cardiovascular system - part 1
- Created by: Kelsey Mcmanmon
- Created on: 03-03-17 23:31
The heart
The left atrium recives oxgenated blood via the pulmonary viens from the lungs and pumps it thought he left ventricle and out to the body and its muscles via the bicuspid valve and out the pulmonary artery, the only artery in the body to carry deoxygenated blood.
The right atrium recieves deoxygenated blood via the vena cava and pumps it through the right ventricle and through the tricuspid valve out of the aorta to the lungs for gaseous exchange.
the left ventricle is larger due to maore cardiac muscle for a greater force of contraction as the blood needs to be pumped around the body so this requires lots of blood pressure.
Cardiac system
Cardiac Diastole
- The tricuspid and bicuspid valves close
- the atria fill with blood
- semilunar valves are open once the atria are full with blood the pressure forces open the tricuspid and bicuspid valves, the semilunar valves are then closed, and the ventricles begin to fill, at rest this lasts on average 0.5 seconds.
Cardiac Systole
- The atria contract pushing blood to the ventricles
- the blood is forced through the bicuspid and tricuspid valves
- the ventricles fill with blood and the semilunar valves stay shut once the ventricles are full with blood, they contract forcing blood through the semilunar valves. the tricuspid and bicuspid valves are closed. blood flows to the pulmonary artery or aorta next, at rest this lasts on average about 0.3 seconds.
Conductive system
The heart beat is caused by an electrical impulse being sent to the cardiac musclecasuing it to contract.This is the simplified journey of the electrical impule across the heart:
1) SA node - sino atrial node fires waves of depolorisation which reaches the AV node- atrio ventricular node.
2) The AV node then carries the signal to the bundle of his
3) the bundle of his tranfers it to each bundle branch which contract the heart via purkinji fibres.
Control of HR
Heart rate increses along with the intensity of exercise, this is required to provide the body and muscles with suffiecient oxygen. The SA Node controls heart rate by increasing or decreasing the frequency of the elctrical impulse being fired. The CCC- cardiac control centre controls the increases of the frequency via the sympathetic nervous system, the vagus nerve slows SA node firing via the pararsympathetic nervous system. Neural Control
CCC in the medulla oblongata of the brain increases HR after being stimulated by :
- chemoreceptors - detecting chnage in co2 levels in the blood
- barorecpetors - detect changes in blood pressure
- proprioreceptors - detect changes in muscle and joint movement Hormonal control
- stress hormones are released - adrenaline/noradrenaline via the adrenal glands, This stimulates the SA node and increases the speed and strength of the contraction, increasing blood pressure and glucose levels in the blood. Acetycholine is released after exercise decreasing HR back to resting levels.
Key terms
Anticipatory rise - the HR increases prior to exercise caused by adrenaline release due to stress or exitement/ arousal.
Heart rate - the number of beats per minutem usually around 72 bpm, if trained bradycardia can occur, maxmum heart ate in 220- age.
Bradycardia - a heart rate below 60 bpm,known as athletes heart.
Cardiac output - the amount o blood pumped out of the left ventricle every minute, the average resting = 5L the calculation is Q= SV x HR were Q is cardiac output SV is stroke volume and HR is heart rate.
Stroke volume - amount of blood pumped out of the left ventricle in 1 beat, this is determined by venous return, elasticiity of fibres and contractibility of tissue. Ejectio fraction average = 60% and can increase to 85% is trained.
Ejection Fraction - the percentage of blood levaing the heart at each contraction/beat.
HR, SV &Q values
Heart rate at rest
trained = 40-60 bpm
untrained = 60-80 bpm
Stroke volume at rest
trained = 80-110 bpm
untrained = 60-80 bpm
Cardac output at rest
trained = 5 L
untrained = 5L
HR in response to exercise
During submaximal exercise a plateau will occur, this is steady state exercise until the oxygen demand can no longer be met. HR will not reach its maximum during this type of exercise.
During maximal exercise heartrate will increase to the maximum due to stressing of anaerobic systems, it the drops suddenly as exercise stops.
submaximal/trained = 110 bpm submaximal/untrained = 140 bpm
maximal/trained/untrained = 220-age
SV response to exercise
Maximal Exercise
During maximal exercise Stroke Volume increases linearly to intensity but only to about 40%- 60% of maxmal effort after which it plataeus, this is because there is a shorter diastolic phase where the ventricles fill as hearet rate increases with maximal effort. stroke volume is determined by: venous return - This is the volume of blood returning from the body to the right atrium.
Elasticity of cardiac fibres - (starlings law) amount of stretch in the cardiac tissue, during the ventricular diastole, the ventricles will stretch more if there is more venous return which will result in a greater contraction force pumping blood out of the heart.
Contractiliy of Cardiac Tissue (myocardium) - the grater the contractiltiy the greater the force of contraction, this effect ejection fraction, the average is 60% but it can be increased with training.
resting/trained = 80-110 ml sub-max/trained = 160-200 ml maximal/trained = 160-200 ml
resting/untrained = 60-80 ml sub-max/untained = 100-120 ml maximal/untrained = 100-120 ml
Q responses to exercise
Maximal Exercise
Cardiac Output increases linearly with exercise intensity ntill the max exercise capasity is reached, at which point it plateaus.(same as HR)
Regular traning will lead to CARDIAC HYPERTROPHY, if the heart is bigger and stronger it can pump out more blood per beat. resting heart arte remains the same meaning HR will decrese as more volume of blood is being pumped out per beat, this is called BRADYCARDIA, during exercise HR and SV will increse untill the required Cardiac Output is achieved orMAX capasity is reached.
trained/ resting = 5L/min trained/sub-max = 15-20L/min trained/maximal = 30-40L/min
untrained/resting = 5L/min untrained/sub-max = 10-15L/min untrained /maximal = 20-30L/min
Cardiovascular Drift
Cardiovascular Drift is the progressive decrease in SV while there is a rise in HR. this is due to a lost volume of blood via sweating, this results in a decrease of venous return an so stroke volume, heart rate increases to allow suffiecient blood to the body.
This occurs during prolonged exercise in a warm environment where intensity stays the same. Heart rate increases to compensate for the loss of volume and venous return, to maintain carisac output.
Heart Disease
Heart disease is caused by the process of atherosclorosis where an atheroma forms and causes the narrowng and ahrdeing of arteries that supply the heart with oxygen. Fatty deposits form a plaque which results in an atheroma which can completely block supply if it grows. it can result ina heart attack or angina. Risk factors
- age
- gender
- smoking
- stress
- high bp
- high cholesterol
- sedentary lifestyle Reducing risk
- stop smoking & 2nd hand
- exercise
- control bp and cholesterol
- reduce stress
- healthy diet
Stroke
A stroke is where the blood supply to the brain is cut off, the brain cells become oxygen starved, and get damaged there are 2 type of stroke;
- Ischaemic/blockage - the fatty deposit forms a clot &prevents blood from reaching the brain, 85% of stokes are Ischaemic.
- Haemorragic/bleed - Blood vesel bursts due to high bp, and so the blood bleeds out into the brain, 15% of strokes are Haemorragic.
F - face is drooping A- Arms cant be lifted S- speech is slurred T- time to call 999
stroke is most commonly cuased by high BP to reduce the risk:
- low sodim diet
- fruit and veg diet
- exercise
- BP medication
- reduce cholesterol levels
Cholesterol
Cholsterol is made by the body in the liver, it is also found in foodand so diet has an important role in cholesterol levels, it is needded to make vitamin D; there are 2 types of cholesterol:
- LDL(low density lipoproteins) - these are bad and are linked with atheromas.
- HDL (high density lipoproteins) - these are good and help remove LDL from the blood
Causes
- genes
- diet
- exercise
- gender
- age
- ethnicity
- medical history
Reduce risk
- loose/maintain weight
- east foods high in LDL- fish nuts beans fruit wholegrain
High Blood Pressure
Blood pressure is the pressure on the walls of blood vessels, high blood pressure cuses damage to an artery wall, which results in the inflammatory response and plaque formation (Atheroma) This can block the artery over time, resulting in stroke, heart attack, loss of vision, and kidney failure.
Normal BP = 120/80
High BP = 140/90
linked to;
- Smoking
- obesity
- lack of activity
- high sodium diet
- alcohol consumption
- genes
- stress
reduce risk:
- limit alcohol cosumption dont smoke low sodium diet healthy diet lose/ maintain weight and exercise
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