control of heart rate and ecg's

Question 1

how is a heart beat initiated?

Answer 1

depolarisation takes place at the SAN
SAN generates an electrical impluse which spreads across the left and right artia causing the atria to contract
electrial impluse travels to the AVN
after a delay of 0.13 seconds the impluse travels to the ventricles
the impluse travels to the ventricles through the purkyne fibres
the arrival of the electrical impluse causes depolarisation and the ventricle walls to contract

Question 2

what is meant by myogenic

Answer 2

the heart can contract without external nervous stimulation

Question 3

describe the purpose of ecg’s

Answer 3

used to investigate heart rhytms
the spread of depolarisation through the heart muscles causes tiny electrical changes on the surface of the skin

Question 4

describe what happens during the P-WAVE

Answer 4

depolarisation of the atria
atria contract - p wave shows atrial systole
delay at the AVN causes a delay bewteen P and Q

Question 5

describe what happens during the QRS complex

Answer 5

waves of depolarisation spreads from AVN through bundle of HIS
into the walls of ventricles causing ventricular systole

Question 6

describe what happens at the ST segment

Answer 6

no eletrical activity can pass through the heart at this time

Question 7

describe what happens at the T WAVE

Answer 7

ventricles are repolarising and returning to resting state
ventricles are relaxed - VDL