PHA 303- NEUROTRANSMITTERS PDF

## Neurotransmitters and Neuroreceptors * Acetylcholine and Norepinephrine * All preganglionic neurons are cholinergic * Parasympathetic post ganglionic neurons are cholinergic * Sympathetic post ganglionic neurons are adrenergic except * Sympathetics innervating sweat glands, blood vessels in skel...

## Neurotransmitters and Neuroreceptors * Acetylcholine and Norepinephrine * All preganglionic neurons are cholinergic * Parasympathetic post ganglionic neurons are cholinergic * Sympathetic post ganglionic neurons are adrenergic except * Sympathetics innervating sweat glands, blood vessels in skeletal muscle, and piloerection muscles are cholinergic ## Neurotransmitters The image depicts schematic representation of the location of various neurotransmitters and their receptors in the somatic and autonomic nervous system. **Somatic Nervous System** * Acetylcholine - Striated muscle **Autonomic Nervous System** * **Sympathetic** * Acetylcholine - Heart, Smooth Muscles, Glands * Acetylcholine - Sweat glands * Acetylcholine - Adrenal Medulla, E, NE - Striated muscle * **Parasympathetic** * Acetylcholine - Heart, Smooth Muscles, Glands ## Acetylcholine * **Nicotinic receptors** * Nm (muscular-type or N2): skeletal muscle * Nn (neuron-type, or N1): autonomic ganglia, CNS * **Muscarinic receptors** * Postganglionic parasympathetic and a few sympathetic sites, CNS (also autonomic gang.) * Receptor subtypes: M1-5 ## Catecholamines * **Norepinephrine** * Postganglionic sympathetic, CNS, adrenal medulla * Receptors: α1, α2, β1 * **Epinephrine** * Adrenal medulla, CNS * Receptors: α1, α2, β1, β2 * **Dopamine** * Autonomic ganglia, CNS * Receptors: D(1-5), α1, β1 ## Location of ANS Receptors The image depicts schematic representation of the location of receptors in the sympathetic and parasympathetic nervous systems. It shows how the sympathetic and parasympathetic nervous systems interact and how different types of receptors are involved in each. **Sympathetic division** * Most target tissues innervated by the sympathetic division have adrenergic receptors. When norepinephrine (NE) binds to adrenergic receptors, some target tissues are stimulated, and others are inhibited. For example, smooth muscle cells in blood vessels are stimulated to constrict, and stomach glands are inhibited. * Some sympathetic target tissues, such as sweat glands, have muscarinic receptors, which respond to acetylcholine (ACh). Stimulation of sweat glands results in increased sweat production. **Parasympathetic division** * All parasympathetic target tissues have muscarinic receptors. The general response to ACh is excitatory, but some target tissues, such as the heart, are inhibited. ## Function of the Sympathetic and Parasympathetic Nerve **SNS** * Sympathetic nervous system prototypically “fight” or “flight”. * Associated with increased * energy expenditure, * cardiopulmonary adjustments for intense activity, * blood flow adjustments for maximum energy expenditure. **SNS - Fight & Flight Reaction** * You’re walking alone at night and all the sudden you hear an unfamiliar noise nearby... In a matter of seconds, * your heart rate increases dramatically, * blood vessels in your skeletal muscles dilate, * blood vessels in the visceral muscles constrict, * digestion is ceased, * your liver ramps up glucose release, * your pupils dilate, * salivary production decreases, * sweat increases. **Parasympathetic Nervous System** * If that noise turns out to be the result of wind, then the body is returned to “pre-noise” state. * This is the job of the parasympathetic nervous system ## Autonomic Nervous System * **Parasympathicus** * Wind down, relaxation, digestion * Dominated by Acetylcholine * **Sympathicus** * Fight & Flight Reaction * Dominated by Noradrenaline (Adrenaline) * Fear, exercise, rage