circulation + the heart Flashcards
(25 cards)
what does an open circulatory system do?
heart pumps blood into space in body cavity
tissues bathe in blood directly
blood flows slow back to heart (assistance from muscles and valves)
what does a closed circulatory system do?
blood is transported in blood vessels
blood is pumped by muscular heart at high pressure
tissues are not in direct contact with blood
blood contains haemoglobin
what are the advantages of closed circulatory system?
blood flow is more rapid and efficient
blood can be directed to where it is needed
more efficient delivery of oxygen and nutrients
what is single circulation?
blood from anywhere in the body may pass only once through the heart
what is double circulation?
blood must pass at least twice through the heart before returning to the same location in the body
why do mammals need a double circulatory system?
high metabolic rate so cells require large amounts of oxygen and glucose
what are the advantages of a double circulatory system?
blood flows more quickly to tissues as heart
increases pressure after it has passed through lungs
more efficient delivery of oxygen and nutrients
higher blood pressure
what are the disadvantages of a single circulatory system?
blood pressure is reduced as blood passes through the capillaries of the gills
blood flow to the body is not very quick
what does the heart do?
double pump helps keep oxygenated and deoxygenated blood separate
myogenic contractions
what are myogenic contractions?
heart beat is initiated by muscle cells and not dependant on nervous or hormonal stimulations
when do valves open?
when pressure above valve is greater than below
when do semilunar valves open?
when the pressure in the ventricle is greater than the artery
why do valves close?
to prevent back-flow of blood
lub-dub sound due to closing of valves
what is the cardiac cycle (simple)?
atria contract (atrial systole)
ventricles contract (ventricular systole)
heart relaxes and fills (diastole)
what is the cardiac cycle (complex)?
blood enters atria from vena cava and pulmonary vein
atria contract
volume decreases
pressure increases
blood enters ventricles down pressure gradient through atrioventricular valves
ventricles contract
volume decreases
pressure increases
blood is forced through semilunar valves into the aorta and pulmonary artery
what is the blood pressure like in the atria?
thin muscle wall exert small pressure to push blood to ventricles (gradient)
what is the blood pressure like in the right ventricle?
higher pressure than atria
has to push blood to lungs so thicker muscle wall than atria
what is the blood pressure like in the left ventricle?
highest pressure as has to pump blood through the aorta to the rest of the body
what is the septum?
separates two sides of the heart
stops deoxygenated and oxygenated blood from mixing
allows different pressures to be maintained each side
what are the stages of a heart beat (simple)?
SAN initiates wave of excitation
atria walls contract
excitation delayed at AVN
passes excitation to bundle of His
base of ventricles contract
excitation transmitted to purkyne fibres in ventricle walls
blood pushed up arteries
heart goes into period of relaxation
what are the stage of a heart beat (complex)?
sinoatrial node initiates wave of excitation
causes atria walls to contract
wave of excitation reaches atrioventricular node where it is delayed to allow full contraction of atria
excitation passes down highly conductive nerve tissue (bundle of His)
excitation transmitted to purkyne fibres causing ventricle to contract from apex upwards
pushes blood up arteries and empties ventricles
heart goes into period of relaxation as electrical impulse is terminated
what does ECG stand for?
electrocardiogram
what does the P wave show?
wave of excitation/signals from SAN spread through atria
what does the QRS complex wave show?
depolarisation and excitation (contraction) of ventricles
