Module 4: Cardiovascular System Flashcards
What are the layers of the heart
pericardian (outer), myocardian (middle), endocardial (inner most)
what are the main arteries
Subclavian artery - arms. carotid artery - head, iliac artery - arms
whats the stimulus for a heart beat
the conductile network. automatic, always active and created by specialised cells which make an action potential
what are the key parts of the conductile system of the heart
sinoatrial node, atrioventricular node, atrioventricular bundle, bundle branches, endocardial conducting network,
what happens in the sinoatrial node(SA)
master controller, depolarises faster than others, depolarises atria
what happens in the atrioventricular node (AV)
slower than SA node, controlled by SA, controls ventricular rhythm, sends signals to AV bundle
what are the main veins in the body
external jugular vein, internal jugular vein, superior and inferior vena cava, common iliac vein, subclavian vein
what happens in the atrioventricular bundle
only electrical connection between atria and ventricles. auto rhythm slower than AV node
what happens when cell is at threshold
voltage gated calcium channels open, calcium enters cell and depolarisation occurs.
define pressure
total force acting over an area.
formula for pressure
pressure=force/area
how does a sphygmomanometer work
used to constrict blood flow in a vessel. when the flow returns the brachial artery is very contracted resulting in turbulent and noisy flow. this is the systolic pressure. when the flow returns to continuous, laminar and quiet it is the diastolic pressure
what is diffusion
the spontaneous movement of particles in a fluid from a high concentration to low concentration
what happens as pressure and densities increase in diffusion
diffusion rates decrease because the material is more closely packed
what does the amount of diffusion depend on
surface area and thickness of the membrane
what is osmosis
the diffusion of water through a semi-permeable membrane
what does the semi-permeable membrane allow
diffusion of water but no other substance or particles
what are the effects of osmosis
as diffusion continues, the region into which the water diffuses increases in volume creating excess pressure
what is an isotonic solution
cells retain their normal size and shape, water moves in and out
what is hypertonic solution
cells lose water by osmosis and shrink, more solute (e.g salt)
what is hypotonic solution
cells take in too much water and become bloated and burst. lower concentration of solute
what ion causes the muscle cells to start contracting
calcium
what components of the muscle cell store calcium
endoplasmic reticulum and sacroplasmic reticulum
what two protein bundles are in myofibrils
actin (and troponin) and myosin, contractile units.
how does an action potential stimulate muscle contraction
action potential travels along membrane to sarcoplasmic reticulum (SP), and releases calcium. calcium binds to troponin on actin and allows actin and myosin to interact
what is the contraction-sliding filament theory
actin can now interact with myosin, myosin pulls past actin, using ATP and the muscle shortens
what happens when the muscle shortens in the heart
this makes the muscle smaller, which makes the chamber smaller. pressure increase, blood moves out of chamber into area of lower pressure
is the pressure high or low when the atrioventricular valves open
low pressure
is the pressure high or low when the atrioventricular valves closes
high pressure
is the pressure high or low when the arterial valves open
high pressure
is the pressure high or low when the arterial valves close
low pressure
name the phases in which the atria and ventricles are filling
passive ventricular filling
what happens in atrial contraction
the atria are topping up the ventricles
what happens in isovolumetric contraction
the ventricles are in systole but not ejecting blood
what happens in ventricular ejection
the ventricles are in systole ejecting blood
what happens when the AV valves close
isovol contraction, vent ejection
what happens when the AV valves open
passive filling, atrial contraction
what happens when the Semilunar valves close
all but ventricular ejection
what happens when the semilunar valves open
ventricular ejection
summarise the contraction sequence to end of atrial contraction
the passive ventricular filling, heart muscle is relaxed. the contraction starts conductile cells in the SA node generate AP, AP travels to atrial node and AV node. Atrial pressure rises above ventricular pressure, blood passes from atria to ventricles. end of atrial contraction. AV valves close, signal goes from AV node to AV bundle. Start of ventricular contraction.
summarise the contraction sequence to end of ventricular contraction
Start of ventricular contraction. Signal goes from AV bundle to bundle branches then to endocardial network. Ventricles start to contract= isovolumetic contraction. pressure in ventricles rises above pressure in arteries to force SL valves open - causing ventricular ejection= blood goes into arteries. pressure in ventricles drops below pressure in arteries so Sl valves shut. ventricular muscle relaxes (repolarising). blood stops moving into arteries. this is isovolumetric relaxation. Finally AV valves open and passive ventricular filling begins again.
what is cardiac output
total volume pumped out of the heart in 1 minute= stroke volume * heart rate
what is the stroke volume
blood pumped out per beat
blood pumped out of heart per beat is the sum of…
end diastolic volume - end systolic volume
what to do to increase flow`
either pressure has to increase or resistance has to decrease (blood vessels dilate)
what is the pulse pressure
difference between systolic and diastolic pressures
where is pulse pressure greatest and least and why
greatest in arteries and zero in veins because pressure drops through the cycle
what happens n sympathetic stimulation
increases cardiac contraction, increases heart rate, increases cardiac output
what happens in parasympathetic stimulation
doesn’t affect cardiac contraction, decreases heart rate, decreases cardiac output
how is blood pressure regulated
blood flow to organs depends on the body’s requirements, there is a homeostatic set point for rest but gets altered depending on activity.
what receptors sense the arterial blood pressure
baroreceptors
where are the baroreceptors located
aorta and carotid arteries
if baroreceptors sense a fall in BP what will happen
the vasomotor centre will stimulate contraction of arteries (vasoconstriction)
if baroreceptors detect rise in BP what will happen
the cardio inhibitory centre will cause the heart rate to decrease
