Transport in Animals - Control of the Cardiac Cycle Flashcards
describe cardiac muscle grown in culture
- cardiac muscle is myogenic, therefore cells grown in culture will contract and relax rhythmically
- cardiac cells joined together contract in unison
why do contractions of the cardiac muscle need to be coordinated
to prevent fibrillation and ensure the efficient pumping of blood
what is the sino-atrial node
a small patch of tissue in the wall of the right atrium that initiates an electrical wave of excitation
what does the initial wave of excitation do
passes over the walls of both atria, causing them to contract
what prevents the electrical wave passing to the ventricles
a band of non-conducting collagen fibres between the atria and the ventricles
what is the atrio-ventricular node
a small gap in the non-conductive collagen fibres at the top of the septum which allows the wave of depolarisation through with a small delay
after passing the atrio-ventricular node, what does the electrical wave then do
travels down conductive Purkyne tissue which runs down the septum
what is the function of Purkyne tissue
- transmits the excitation very rapidly to the apex of the ventricles
- it then conducts the wave upwards and outwards through the ventricle walls
- this causes muscles to contract from bottom up
why should the ventricles contract from bottom up
to ensure all the blood is pumped out of the ventricles
what could cause changes in heart rate to be initiated
- drugs
- exercise
- smoking
- alcohol
what are the two nerves that carry impulses from the brain to the SAN
- vagus nerve
- sympathetic nerve
what does the vagus nerve release
a substance that makes the heart beat more slowly
what does the sympathetic nerve release
a substance that makes the heart beat faster
what are the drugs that could be used to help a person with heart problems
- digoxin
- propranolol
what does digoxin do
increases force of muscle contraction
what is propranolol and what does it do
a beta-blocker
decreases heart rate
