8. Blood pressure and electrical activity Flashcards
what does diastolic pressure mean
minimum pressure
what does systolic pressure mean
maximum pressure
how do you work out pulse pressure
Systolic pressure- diastolic pressure
how do u measure blood pressure
sphygmomanometer
or electrical device
how does a blood pressure device work
pressure in the cuff exceeds SP and cuts off blood flow, as u release pressure you can hear blood entering the lower part of the arm, this makes noise called Korotkoff sounds (can be heard via stethoscope). when sounds disappear diastolic pressure can be measured
what is a normal blood pressure reading
120/80 mm Hg
what is a hypertensive blood pressure reading
~150/ 95 mm Hg
what is atherosclerosis
build up of fatty deposits in the artery walls, narrowing lumen
what term describes an atherosclerotic plaque which dislodged and moved around the body
embolism
heart muscle is myogenic, what does this mean
the heart is able to produce its own electronic signals to stimulate its contraction
the heart is made up of two types of cells, what are these
myocardial cells and pacemaker cells
where are pacemaker cells most concentrated in the heart
the sinoatrial node and the atrioventricular node
describe the process of signal transduction in the heart
- SA node passes signal to both atria which contract simultaneously
- signal reaches AV node and there is a delay.
- AV node passes signal down bundle of His to purkinje fibres at heart apex
- signal at apex of the heart facilitates complete ventricular contraction
what happens when the impulse reaches papillary muscles
trigger chordae tendinae to ensure closure of AV valves preventing prolapse into atrium
why is there a delay at the AV node
allows both atria to contract fully and push remaining blood into the ventricles
how long is the AV nodal delay
0.1 seconds
how does a pacemaker potential graph differ from a normal action potential graph
no steady resting potential
slowly depolarises until threshold is met
what channel is responsible for the slow depolarisation in pacemaker potentials
funny channels
describe ion influx/ efflux in a pacemaker potential
- slow depolarisation- k+ channels close, funny channels open
- before threshold- calcium channels open, slow influx of calcium
- threshold- rapid calcium influx
- repolarisation- calcium influx decreases, potassium efflux increases
define cardiac output
the volume of blood pumped out of each ventricle in one minute
what is the formula for cardiac output
heart rate x stroke volume
what is the effect of sympathetic input on the heart
increase in heart rate and cardiac output
AV nodal delay is decreased and ventricles contract more forcibly
what is the effect of parasympathetic input of the heart
AV nodal delay increases reducing activity of the heart
what is starlings law
when blood flow rate into the heart changes, the heart automatically adjusts its output to match the input
