Both the SNS and PNS employ different forms of neurotransmitters to facilitate their signals. Preganglionic parasympathetic and sympathetic fibres utilise acetylcholine (ACh) as their neurotransmitter molecule, which are termed ''cholinergic'' neurones. Postganglionic PNS fibres also release ACh whilst nearly all postganglionic SNS fibres release norepinephrine as their neurotransmitter (there are exceptions to this rule but in general these are the expected neurotransmitters). Neurones releasing norepinephrine are called ''adrenergic''.