2.6 DONT KNOW

Question 1

what does the sino-atrial node do and what does this mean?

Answer 1

it exhibits spontaneous excitation

pacemaker initiates electrical impulses making cardiac muscles contract at a certain rate

Question 2

5 steps in a heartbeat

Answer 2

originating in the SAN, a wave of excitation through the muscle cells in the wall of the 2 atria makes atria contract simultaneously (atrial systole)

wave of excitation picked up by atrio-ventricular node located centrally near the base of the atria and is passed to a bundle of conducting fibres which divides into left and right continuous branches

continuous branches contain a dense network of tiny conducting fibres in the ventricular walls

stimulation of the conducting fibres causes simultaneous contraction of the 2 ventricles (ventricular systole) starting from the heart apex and spreading upwards

this coordinated heartbeat ensures each type of systole involves the combined effect of many muscle cells contracting, and ventricular systole occurs slightly later than atrial systole which allows time for ventricles to fill completely before they contract

Question 3

P,QRS,T waves

Answer 3

P wave corresponds to the wave of electrical excitation spreading over the atria from the SAN that brings about atrial systole

QRS complex represents the wave of excitation passing through the ventricles that brings about ventricular systole

T wave corresponds to the electrical recovery of the ventricles occurring towards the end of ventricular systole

Question 4

3 steps in measuring blood pressure

Answer 4

cuff is inflated until the pressure it exerts stops blood flowing through arm artery

cuff allowed to deflate gradually until blood starts to flow at systolic pressure which is detected by a pulse

more air released from cuff until a pulse is no longer detected as blood flows freely through the artery at diastolic pressure