Neurotransmitter systems cholinergic neurones

The two most common neurotransmitters released by neurons of the ANS are acetylcholine (Ach) and norepinephrine (NE). Several distinguishing features of these neurotransmitters are summarized in Table 9.3. Nerve fibers that release acetylcholine are referred to as cholinergic fibers and include all preganglionic fibers of the ANS — sympathetic and parasympathetic systems all postganglionic fibers of the parasympathetic system and sympathetic postganglionic... 

We will proceed with this neurotransmitter system much as we did with the cholinergic system. Keep in mind that the main neurotransmitter here is norepinephrine and that adrenergic neurons are found in the sympathetic (fight or flight) portion ofthe autonomic, peripheral nervous system. 

The preganglionic fibers terminating in the adrenal medulla, the autonomic ganglia (both parasympathetic and sympathetic), and the postganglionic fibers of the parasympathetic division use acetylcholine as a neurotransmitter (Figure 4.2). Cholinergic neurons innervate voluntary muscles of the somatic system and are also found in the CNS. 

Aldridge and Reiner 1972). The A esterases have a serine catalytic site. The tertiary structure and amino acid sequences of several AChEs and BuChEs have been established (Taylor 1994). AChEs regulate excitation at cholinergic synapses, destroying the neurotransmitter ACh. AChE is one of the most active enzymes known, cycling within a few milliseconds (Taylor 1996). AChEs are found at synapses and neuromuscular junctions, and in central-nervous-system (CNS) neuron cell bodies, axons, muscles, red blood cells (RBCs), and platelets of ovine and rodent species (Silver 1974 Traina and Serpietri 1984 Hoffmann et al. 1989). 

In the peripheral nervous system, ACh is found as the neurotransmitter in the autonomic ganglia, the parasympathetic postganglionic synapse, and the neuromuscular endplate. Cholinergic neurons in the central nervous system are either wide ranging projection neurons or short ranging interneurons in (1) the basal forebrain (septum, diagonal band, nucleus basalis of Meynert) projects to the entire cortex, the hippocampus,... 

In Chapter 8, peripheral aspects of the cholinergic system were considered. The basics of the neuron (Fig. 8-1), specifically the cholinergic neuron (Fig. 8-5), the synapse (Fig. 8-2), and depolarization (Fig. 8-3), were also presented. The significance and chemistry of acetylcholine (ACh) was discussed. Chapter 9 continued with the remainder of the peripheral autonomic nerve plan (i.e., the sympathetic, or adrenergic, system). The biosynthesis of the catecholamines DA, NE, and EP were discussed and illustrated (Fig. 9-1), and the metabolism schemes for NE and EP (Fig. 9-3) and DA (Fig. 9-4) were outlined. Much of the early (before 1960) neurochemistry elucidated, and neurotransmitters identified, were central to the functioning of the peripheral nervous system. 

---