control of heart rate

Question 1

Role of SAN,AVN and purkyne tissue in bundle of his

Answer 1

Cardiac muscles myogenic meaning it can contract without recieving electrical impulse from nerves
sinoatrial node acts as a pacemaker and sends out regular waves across both atria-causing left and right atria to contract simultaneously
layer of non conductive tissue prevents this from crossing itno ventricles
waves of electrical activity reach AVN which delays impyulse allowing atria to fully contract and empty
AVN passes wave of electriacl activity to bundle of his which conducts wave between ventricles to the apex of the heart where the bundle branches into small fibres of purkyne tissue
ventricles contract simulatanously from bottom up

Question 2

chemoreceptors

Answer 2

located in aorta and cartoid arteries
stimulated by blood ph/co2 conc
low ph more frequent impulses to medulla-more frequent impulses sent to SAN along symmpatyhetic nuerones
cardiac muslces contract more frequntly so heart rate increases
high ph-more frequent impulses to medulla-more frequent impulses sent to SAN along parasymmpatyhetic nuerones-less frequent impulses from SAN

Question 3

barroreceptors

Answer 3

located in aorta and cartoid arteries
stimulated by high/low bp
low bp-more frequent impulses to medulla-more frequent impulses sent to SAN along symmpatyhetic nuerones
cardiac muslces contract more frequntly so heart rate increases
high bp–more frequent impulses to medulla-more frequent impulses sent to SAN along parasymmpatyhetic nuerones-less frequent impulses from SAN-hr decreases