the cardiovascular system Flashcards
functions of cv system
-transportation of oxygen, nutrients and metabolites
-removal of metabolic waste products
-distribution of hormones
-involvement in controlling body tempurature
how is the systemic system connected?
in parallel
there is a choice of which parts of the body receives more or less blood volume
how is the pulmonary system connected
in series
entire blood volume has to pass through pulmonary system every time blood circulates the body
what is Darcy’s law?
regulates where in the body blood goes
flow= pressure difference/ resistance
how to work out velocity of blood
velocity= flow rate/ cross-sectional area
the narrower the vessel the faster the flow
role of pericardium
protects heart by providing lubrication during constant movement
helps anchor heart against diaphragm and spine
which node conducts the heart
sino atrial node initiates action potential that spreads throughout the heart
describe systole
-occurs as soon as ventricles have stopped filling
-bicuspid and tricuspid valves close so no movement of blood
-as ventricular contraction continues, pulmonary and aortic valves open so blood flows out
describe diastole
-isovolumetric ventricular relaxation
-all 4 valves closed
-when pressure in ventricles drop, bicuspid and tricuspid valves open so ventricles start to fill due to gravity
-atria contract
what is driving pressure
flow created by the pressure difference between two points
flow requires a pressure difference and for resistance to be overcome
what is poiseuille’s law
resistance is inversely proportionate to radius of a blood vessel
doubling vessel radius reduces resistance by a factor of 16
what is the intrinsic rate of the SA node
100bpm without the influence of the ANS
how does SA node initiate action potential
due to unstable membrane potential that is continuously drifting towards the threshold
action potential is generated when threshold is reached
what does rate of firing depend on
-initial value of the membrane potential
-the gradient of the slope drifting towards the threshold
what effect does sympathetic stimulation have on rate of firing
leads to an increase in gradient the drift sue to increased permeability of Na+ current
what effect does parasympathetic stimulation have on rate of firing
leads to decrease in slope gradient
how does conduction travel through the heart
-stimulation of atria by SA node spreads from fibre to fibre through gap junctions
-stimulus spreads through atria almost simultaneously
-ventricular stimulation spreads initially via a network of conduits beginning at AV node and terminates via purkinje fibres
-AV node and bundle of His are only pathway for electrical stimulus to travel from atria to ventricles
-signal delayed at AV node to allow atria to empty
-ventricle contract upwards, depolarising muscle fibres via purkinje fibres
when does the tricuspid valve open
when right atrium pressure is greater than right ventricle pressure
when does bicuspid valve open
when left atrium pressure is greater than left ventricle pressure
when does pulmonary valve open
when right ventricle pressure is greater than pulmonary artery pressure
when does aortic valve open
when left ventricle pressure is greater than aortic pressure
what is cardiac output
volume of blood pumped out by the heart every minute
how is heart rate controlled
-regulated by ANS
-under sympathetic control, heart rate slows down as membranes become depolarised
-under parasympathetic control heart rate increases due as membranes become hyperpolarised
sympathetic nervous system innervation
thoracic spinal nerves (by noradrenaline)
parasympathetic nervous system innervation
vagus nerve (by acetylcholine)
how can sympathetic nervous system control heart rate
-slow heart rate by depolarising membranes
-shorten av node delay
-shorten myoctye action potential
-increase speed of relaxation
how is stroke volume regulated
-by force of heart contraction
-by atrial pressure against which the ventricles eject blood
what is starlings law of the heart
the more the heart stretches, the stronger it will contract
which hormones increase contractility of the heart
adrenaline and noradrenaline
what is blood pressure
the driving force for flow in the cv system
must be maintained at all times
how does blood pressure work in arteries
pulsatile, reflects oscillations from heart
how does blood pressure work in veins
continuous, reflecting loss of forward energy due to friction
what factors affect blood pressure
-gender. women have lower blood pressure than men
-age. arteries become stuffer due to loss of elasticity
-location in body. pressure higher in foot and lower in head due to hydrostatic pressure
how does dynamic exercise affect blood pressure
mean blood pressure remains relatively steady
how does static exercise affect blood pressure
mean blood pressure rises dramatically
how can mean arterial blood pressure be calculated?
cardiac output x total peripheral distance
