Outline the control of the heartbeat by the nervous and endocrine systems.

Explain the principles of synaptic transmission.

myogenic muscle contraction;
contracts without stimulation;
pacemaker/sino-atrial node/SAN in (wall of) right atrium;
pacemaker/sino-atrial node/SAN initiates contraction;
nerves (from brain) transmit messages to pacemaker;
to alter/increase/decrease the rate of the pacemaker;
medulla of the brain controls heart rate/beat;
epinephrine/adrenaline is hormone produced by adrenal gland;
epinephrine/adrenaline accelerates heart rate/beat;

Ca²⁺/calcium ions enter presynaptic neuron;
release of neurotransmitter/acetylcholine;
from pre-synaptic membrane/neuron;
diffusion/movement across cleft/gap;
to post-synaptic membrane/neuron;
binding of the neurotransmitter to receptors/binding sites;
change in membrane permeability;
sodium ions flow into post-synaptic neuron;
depolarization of post-synaptic membrane;
initiation of an action potential;
removal of the neurotransmitter;
by enzyme / cholinesterase;
inactivated neurotransmitter returns to pre-synaptic neuron;

The terms myogenic and pacemaker were clearly explained on occasion in 7(b). However, there was also confusion about the concept of being “myogenic” and the pacemaker as the structure which initiates the heartbeat. Sometimes candidates traced the pathway of the control signals through the heart in great detail rather than explaining how the nervous system and endocrine systems can control the heartbeat. When addressed, correct reference was made to adrenaline but usually not to the role of the medulla or nerves

Part 7(c) was generally answered well, sometimes with nicely annotated diagrams.  Most candidates had a good understanding of pre and post synaptic neurons, the role of Ca²⁺ ions and the concept of polarization/depolarization. Very few candidates mentioned removal of the neurotransmitter by enzyme or cholinesterase. Otherwise, accurate detail showed good knowledge and understanding.