Noradrenaline (norepinephrine) is the sympathetic neurotransmitter in the effector organs. It is released from postganglionic fibres and activates both α and ß receptors.
Adrenaline (epinephrine) also activates the sympathetic receptors. It is synthesised in the adrenal glands and reaches the sympathetic receptors via the circulation, figure 1.
Figure 1. Summary of effects of sympathetic nervous system on the cardiovascular system.
Drugs that activate the sympathetic receptors, hence mimicking the activity of the sympathetic nervous system, are called sympathomimetics.
The neurotransmitter for the parasympathetic system is acetylcholine. This activates two types of acetylcholine receptors, nicotinic and muscarinic receptors. The receptors on effector organs are of the muscarinic type.
The neurotransmitter in sympathetic and parasympathetic ganglia is acetylcholine and the receptors are of the nicotinic variety.