control of CVS Flashcards
what are the functions of the CVS?
. transport of nutrients, oxygen and waste products round the body . transfer of heat . buffer body pH . transport of hormones . assist in response to infection . assist in formation of urine
describe the flow of blood through the heart
. blood enters via superior and inferior vena cava
. flows from right atrium through AV valve to right ventricle
. travels through pulmonary valve into pulmonary artery and out to lungs
. back in through pulmonary vein into left atria
. through AV valve into left ventricle
. through aortic valve into aorta to be pumped round body
which ventricular muscular wall is larger and why?
left as it pumps blood at higher pressure
name the 4 valves of the heart
left AV, right AV, aortic (semilunar) and pulmonary (semilunar)
what controls the valves of the heart?
pressure
what is the function of valves?
prevent back flow of blood
which two muscles orientate valve flaps?
chord tendinae and papillary muscles
what is the clinical name for a hole in the wall dividing the right and left ventricles?
ventricular septal defect
what is a calcified valve?
calcium deposits form on an aortic valve, narrowing the opening of the aortic valve ad reducing blood flow
what is the clinical term for an enlargement of the walls of the left ventricle, causing it to work harder?
left ventricular hypertrophy
what is the first heart sound?
AV valves closing
what is the 2nd heart sound?
pulmonary and aortic valves closing
what are korotkoff sounds?
turbulent blood flow
why is a 3rd heart sound abnormal?
maybe be due to heart failure, or valve defect, represents 2 way flow of blood
the cardiac cycle consists of which 2 phases?
systole (contraction) and diastole (relaxation)
does pressure increase or decrease as blood flows round the body?
decreases
what term describes the volume of blood left in the ventricles after systole?
end diastolic volume
what is stroke volume?
amount of blood ejected per beat
which law states that SV can be increased under certain conditions?
starlings law
what equation is used to calculate cardiac output?
CO = SV x HR
what is a normal CO?
5 l/min on each side
describe the series of events that follow an impulse being generated in the SA node
. impulse generated by pacemaker spreads over the heart muscle causing both atria to contact
. impulses from SA node reach AV node, here this is a small delay which allows atria to empty
. impulse sent down AV bundle to left and right ventricles
. AV bundle divides into purkinje fibres which trigger muscle fibres (myocytes) in ventricles to contact
What is the function of the AV node?
slows conduction, act as secondary pacemaker if required
describe excitation contaction coupling
millions of purkinje fibres interdigitate with myocytes to spread impulse across ventricles
name the 4 types of heart arrhythmias
ectopic beat, tachycardia, bradycardia, fibrillation
what is an ectopic beat?
premature heart beat
what is tachycardia?
increased heart rate
what is bradycardia?
slower heart rate
what is fibrillation?
trembling or shaky heart rate
what does ECG stand for?
electrocardiogram
what does an ECG detect?
phasic changes in potential difference between 2 electrodes
what can an ECG be used to diagnose?
arrhythmias
what is the P wave on an ECG?
atrial depolarisation
what is the QRS complex on an ECG?
ventricular depolarisation
what is the T wave on an ECG?
ventricular repolarisation
what is the P-R interval on an ECG?
delay through AV node
what is the S-T wave on an ECG?
plateau phase of AP
SA nodal action is split into 3 phases: phase 4, phase 0 and phase 3, describe what occurs at each of these phases
phase 4 - spontaneous depolarisation that triggers AP
phase 0 - depolarisation of AP (calcium in)
phase 3 - repolarisation (potassium out)
what happens if potassium permeability in SA node increase?
longer time to threshold = fewer bpm = HR decreased (Ach from vagus nerve)
what happens if calcium permeability in SA node increase?
shorter time to threshold = more bmp = increased HR (noradrenaline)
how does entry of calcium ions into a cardiac muscle cell stimulate contraction?
. calcium enters myocyte cells triggering more calcium ions to be released into cell from sarcoplasmic reticulum
. plateau phase occurs where cell remains depolarised briefly before it becomes polarised by entry of potassium ions
under what circumstances does the force of of contraction of cardiac muscle cells increase?
in response to increased filling of heart chambers
why is it essential that cardiac muscle cells are able to increase force of contraction?
ensure blood circulation does not fail
which 2 forms do adrenoreceptors exist in?
alpha and beta
which adrenal receptor is found predominantly on nodal tissue, conducting system and myocardium?
beta 1
which neurotransmitters bind to adrenoreceptors?
noradrenaline (produced by sympathetic nerves) and adrenaline (produced by adrenal medulla)
what are the effects of noradrenaline and adrenaline binding to adrenoreceptors?
positive intropy, positive chronotropy, positive lustropy, positive dromotropy
what is positive intropy?
increase contraction strength
what is positive chronotrpy?
increased heart rate
what is positive lusitropy?
relax more rapidly
what is positive dromotrpy?
increased conduction speed in AV node
which nodal tissue does the right vagus terminate on?
SA node
which nodal tissue does the left vagus terminate on?
AV node
release of acetylcholine through vagal nerve has what effect on the heart?
deceased HR
which vagolytic drug increases HR in bardylytic patients?
atropine
which nervous system can alter stroke volume?
sympathetic
which NS controls BP during sleep and emotions?
CNS
which branch of the PNS has more effect on the heart?
ANS
