Cholinergic and Adrenergic Neurons

Cholinergic Neurons

• Excitotory (N& M1) & Inhibitory M2• Motor neurons• All autonomic preganglionic neurons• Postganglionic parasympathetic

Cholinergic II

• Basal forebrain complex: ventral to basal ganglia. Includes medial septal nuclei & bed nucleus of the stria terminalis which provide the cholinergic innervation of the hippocampus, and basal nucleus of myenrt, which provides most of the cholinergic innervation of the neocortex. Collectively, first to die in Alzehmeir’s diseas. They play a role In regulating general brain excitability during arousal and sleep-wake cycles. Play a role in learning and memory formation. Difffuse modulatory system.

Basal forebrain complex

Cholinergic III

• Pontomescensphalotegmental complex: pons & midbrain tegmentum. Act mainly on dorsla thalamus, where together with noreadrengic and sertonergic systems, regulate the excitability of sensory relay nuclei. Also project to telencephalon providing cholinergic link between brainstem & basal forebrain complexes. A diffuse modulatory system.

Diffuse Modulatory System

• Axonal system with highly divergent projections to multiple areas of the CNS providing extensive spatial control. Each system prolongs its actions by using G-proteins coupling receptors. Further coverage by the release of neurotransmitter molecules into the extracellular fluid so that they can diffuse to many neurons rather than being restricted to the immediate vicinity of synaptic cleft.

Its parts:

• Cholinergic pontomesencephalo-tegmental system

• Noradrengic system (LC)• Serotonergic (Raphe Nuclei)

Noradrenergic – Locus Coeruleus

• The locus Coeruleus means blue spot because of the colour of its pigmentation. There are two of them, one on each side in the pons just lateral to the fourth ventricle. It is a member of diffuse modulatory system. Surprisingly, it is very small with about 12, 000 neurons in each nucleus. Axons leave the nucleus, fan out, and branch to mytliple times to supply most regions of the central nervous system, including all of the cerebral cortex, the amygdala, the hippocampus, basal ganglia, thalamus, hypothalamus, olfactory bulb, midbrain, cerebellum and spinal cord.

Locus Coeruleus II

• It is involved in the regulation of attention, arousal, sleep-wake cycles, learning & memory, anxiety, pain, mood, and brain metabolism. It is a vital link to chronic stress as it sends sensory input to the amygdala & hippocampus. Along with the serotonergic raphe nuclei, it is part of the reticular activating system.

Locus Coeruleus III