cardiac function & dysfunction Flashcards
what does systole means
contract
what does diastole mean?
relax
when does the relaxation period occur?
after the T wave
how does the relaxation period work?
ventricular pressure drops below atrial & AV valves open
ventricular filling occurs
what happens after the P wave
atrial systole/contraction and ventricular diastole
what happens QRS
ventricular systole and atria diastole
how many heart sounds can be heard from one heart beat?
2 sounds from 4
which out of the 4 sounds can you heat
sound 1/2
what happens during sound 1
‘lub’
louder longer closure of AVvalves soon after ventricular systole
what happens during sound 2
‘dub’
quieter shorter closure of semilunar valves at beginning of ventricular diastole
what happens during sound 3
rapid ventricular filling
what happens during sound 4
atrial contraction
what is a heart murmur
abnormal sounds
rushing/ gurgling
how do you measure cardiac output
CO= stroke volume (SV) x heart rate
(ml/min) (ml/beat) (beats/min)
what happens during exercise
CO rises to supply working tissue with more O2 & nutrients
what happens if stroke volume may fail
ventricular myocardium damaged or blood volume reduced by bleeding
what happens during homeostatic mechanisms
act to maintain adequate CO by increasing heart rate & contractility
autonomic regulation of heart rate
originates in the cardiovascular centre in the medulla oblongata
input to CV centre
From higher brain centres (e.g., hypothalamus)
From sensory receptors
Proprioceptors
Chemoreceptors
Baroreceptors
output to heart
Increased depolarisation in SA node: increases heart rate
Increased contractility of A & V: increases stroke volume
Decreased depolarisation in SA node: decreases heart rate
what are 2 chemical regulations of heart rate
hormones and ions
how do hormones regulate heart rate
released with exercise, stress & excitement
epinephrine & norepinephrine
increase both heart rate & contractility
thyroid hormones (do same as above)
how does ions regulate heart rate
increase in K+ or Na+ decreases heart contraction & rate
high conc of Na+ blocks Ca2+ influx during cardiac AP, so contraction decreased
high conc K+ blocks generation of AP
increase Ca2+ speeds heart rate & strengthens heart
what are 4 other factors that can regulate heart rate
age
gender
physical fitness
body temperture
what is arrhythmia
Irregular heart rhythm due to defect in the conduction system of the heart
Causes:
drugs (caffeine, nicotine, alcohol etc.,)
anxiety
Hyperthyroidism
K+ deficiency
certain heart diseases.
examples of arrhythmia
heart blockers
atrial flutter
atrial fibrillation
ventricular fibrillation
