cardiovascular system Flashcards
aorta
main artery from heart to body carrying oxygenated blood
pulmonary artery
from heart to lungs carrying de-oxygenated blood
pulmonary vein
from lungs to heart carrying oxygenated blood
vena cava
major vein from body to heart which brings de-oxygenated blood
coronary artery
artery which supplies cardiac muscle with oxygen rich blood
sinoatrial node (SAN)
heart’s pacemaker responsible for the regular contraction of the heart muscle
why is the heart myogenic?
contracts spontaneously without being stimulated by nerve cells
Bundle of His
collection of cells that transmit electrical signals from the AV node to ventricles
Purkinje fibres
branched fibres that carry electrical signals into the ventricles to allow contraction
bicuspid valve
prevents backflow of blood from left ventricle to left atrium
function of semi-lunar valve
prevents backflow from arteries into ventricles
septum
cardiac muscle that divides the left & right side of the heart
function of P wave
atria systole - atria contracts
blood is squeezed into the ventricles
function of T wave
repolarisation of ventricles as they relax and recover
ventricular diastole
QRS complex
excitation of ventricles - ventricles contract
corresponds to the spread of the impulse through ventricles when contracting
bradycardia
slow heart rate
tachycardia
fast heart rate
arrhythmia
indicated by abnormal heart beat & heart is beating irregularly
define cardiac output
the volume of blood out of the heart in one minute
how is cardiac output calculated?
stroke volume x heart beat per minute
stroke volume
volume of blood pumped out the heart by ventricles with each heartbeat
define cardiac cycle
coordinated sequence of contractions and relaxations of the heart muscle which causes the blood to flow from the atria, into the ventricles and then the arteries
atria systole
when atria is contracting
define diastole
when the cardiac muscle is in a relaxed state
define ventricular systole
atria relax and ventricles contract
define ventricular diastole
ventricles relax - complete stage of relaxation
explain what occurs in diastole of the cardiac cycle
- Walls of atria and ventricles are relaxed causing a reduction in pressure
- Pressure is lower in the ventricles than in the major arteries so the semi lunar valve closes.
- Blood returns to atria of the heart through the major veins
4.Pressure rises in the atria which forces the atrioventricular valves to open
explain what occurs in atria systole
atria contracts simultaneously
pressure is greater in atria than ventricles & volume in atria is reduced in atria
tricuspid and bicuspid valves are forced fully open
blood is pushed into the ventricles down a pressure gradient (high to low)
explain what occurs in ventricular systole
ventricles contract simultaneously which increases the pressure
blood is forced out of semi lunar valves into pulmonary artery and aorta
pressure in ventricles greater than in artieries which forces
AV valves to close to prevent backflow
define fibrillation
when the contractions of the chamber are not synchronised
the heart muscles flutters rather than contracting the muscle
how would you detect fibrillation on electrocardiogram?
a small, unclear p wave
how is the structure of an artery related to its function?
transport blood under high pressure from the heart to the tissues
thick muscle layer compared to veins thick elastic layer
large overall thickness
no valves present
how is the structure of arteriole related to its function?
carries blood under lower pressure than arteries, arteries to capillaries (blood flow between A to C is controlled)
thicker muscle layer than arteries
thinner elastic layer
how is the structure of the capillaries related to its function?
walls consists only of thin endothelium layer
numerous and highly branched
narrow diameter and narrow lumen
spaces between lining endothelial cells
why do the arteries need to have a thick muscle layer and elastic layer?
to withstand the high pressure of blood pumped by the ventricles - thick outer layer
why are the veins much thinner than arteries in terms of elastic and muscle layer
veins transport blood towards the heart and they have a much thinner layer of muscle and elastin layer as blood is at low pressure
valves to prevent backflow of blood
what occurs in the capillaries
where exchange of materials takes place
endothelium is only 1 cell thick and there may be gaps in the basal lamina that allows diffusion to take place
give three functions of capillaries
- carry oxygenated blood to tissues
- absorb nutrients in the gut
- link arteries and veins
which blood vessel has the least elastic tissue
capillaries
which blood vessel has the most smooth muscle?
arteries
what does it suggest if intervals between p waves are different?
sinus arrhythmia
why do valves open and close
to ensure no backflow of blood
high pressures in chambers forces valves to open
valves close when pressure drops
(applies the same to AV valves and semi-lunar valves)
define heart rate
number of beats per minute
what is the role of sinoatrial node (SAN)?
acts a pacemaker and generates a wave of excitation impulse over both atrial walls, travelling along the membranes of muscle tissue, causing the atria in cardiac muscle to contract muscle - atria systole
what is the role of AVN node?
as the wave of excitation cannot spread directly to the ventricle walls, due to non-conducting tissue, septum,
instead it is picked up by AVN node and the impulse is delayed
why is the delay caused by AVN node important?
this allows the atria to fully contract, allowing more time for all the blood to move from atria to ventricles and prevents the ventricles from contracting too early.
delay separates the contraction of atria and contraction of ventricles
coronary heart disease
the coronary arteries are unable to supply the cardiac muscle with sufficient oxygen and glucose for respiration
caused by build up of fatty deposits known as atheroma
what does atheroma increase the risk of?
myocardial infarction (heart attack)
what is an atheroma?
presence of fatty deposit material eg cholesterol within the wall of artery
how is an atheroma formed?
- cholesterol builds up inside the lining of artery
- a plaque forms that bulges out into the lumen cavity.
- Blood pressure in artery increases
- blood flow is reduced and
amount of glucose and oxygen transported to heart is reduced - tissues may die and can cause heart attack or death
what is thrombosis?
formation of thrombus ( blood clot) inside a blood vessels
narrows coronary arteries and can prevent/reduce supply of blood to heart tissues
tissues can die as they are deprived of oxygen and glucose
aneurysm
atheroma can lead to the formation of a blood clot that can weaken the artery walls
weakened points swell to form a balloon like, blood filled structure called aneurysm
can burst which can lead to a haemorrhage and loss of blood to body part
risk factors that increase risk of cardiovascular diseases
high cholesterol
excessive levels of stress
excessive levels of salts
lack of exercise
smoking
aging
antihypertensives
lowers high blood pressure
diuretics
helps the body get rid of excess sodium and water and help control blood pressure
cons of diuretics
can decrease potassium, weakness, leg cramps and fatigue
diabetic people - can increase blood sugar level
beta blockers
reduce the heart rate, the heart’s workload and output of blood, which lowers blood pressure
cons of beta blockers
insomnia, cold hands & feet, tiredness, slow heart rate, not suitable for pregnant women
ACE inhibitors
(angiotensin-converting enzyme) angiotensin is a chemical that causes the arteries to become narrow
ACE inhibitors can produce less angiotensin which helps blood vessels to relax and open, lowering blood pressure
cons of ACE inhibitors
skin rash, chronic dry cough, kidney damage in some cases
statins
lowers cholesterol levels in the blood
reduces formation of fatty plaques
reduces risks of blood clots, heart strokes
pros of statins
inexpensive, easy to take and prevents artery disease from worsening
risks of statins
headaches, nosebleeds, memory issues, nausea and muscle weakness
have to continue taking them & increases risk of diabetes
complications of heart transplant
immune system rejecting transplanted organ and attacking it
graft failure - donated heart fails to work
side effects of immunosuppressants such as increased vulnerability to infections, weight gain and kidney problems
