the final learning objective for the autonomic nervous system is to compare the neurotransmitters secreted by the different divisions of the autonomic nervous system based on the neurotransmitter that a neuron in the autonomic nervous system producers and releases they classified as either colonic or adrenergic neurons The receptors for these neurotransmitters are integral proteins which are located in the plasma membrane of the poptic neuron or the affector cell so colonic neurons release the neurotransmitter aceto Coline in the autonomic nervous system coleric neurons include all of our sympathetic and parasympathetic preganglionic neurons so the first neuron in all of those chains they include sympathetic postganglionic neurons that innovate our sweat glands as well as all parasympathetic Pro ganglionic neurons in these neurons aceto choline is stored in synaptic vesicles and released by exocytosis it then diffuses across a synaptic Clift and binds with specific coleric receptors in the plasma membrane of the post synaptic neuron so the two types of colonic receptors both of which bind to acetylcholine are nicotinic receptors and muscarinic receptors nicotinic receptors are found in the plasma membrane of dendrites and cell bodies of both our sympathetic and our parasympathetic poang onic neurons the plasma membranes of the chromaffin cells in the adrenal Medela and in the motor n plate at the neuromuscular Junction now neuromuscular Junction is just that syapse between a neuron and a muscle activation of The nicotinic nicotinic receptors which just means when the acetal choline actually binds to these nicotinic receptors causes depolarization and THX excitation of the prooptic cell this can either be a post synaptic neuron or an autonomic affector or a sceletal muscle fire our muscarinic receptors are found in the plasma membranes of all autonomic effectors so our cardiac muscle our smooth muscle and our glands which are innovated by our parasympathetic postganglionic axons in addition most sweat glands are innovated by colonic sympathetic postganglionic neurons and possess these muscarinic receptors activation of the muscarinic receptors so when acetylcholine binds to these receptors sometimes causes depolarization or excitation and sometimes causes hyperpolarization or inhibition depending on the cell that actually contains those receptors so as an example binding of acetylcholine to music receptors inhibits or relaxes our smooth muscle sphincters in the gastrointestinal tract so the food can move through that pathway whereas acetal Coline excites or depolarizes music receptors in smooth muscle fibers in the circular muscles of the RS so this is what causes your pupil to contract or constrict adrenergic neurons in the autonomic nervous system release nor epinephrine which you may also see termed nor adrenaline so they're the same thing most of the pre uh post ganglionic neurons in the sympathetic division of the autonomic nervous system are classified as adrenergic receptors H sorry neurons and like acetal choline nor epinephrine is stored in synaptic vesicles and released by exocytosis those molecules of norepinephrine diffuse across the synaptic Clift and they bind to specific adrenergic receptors on the prooptic membrane causing either excitation or in ition of that effective cell adrenergic receptors bind both nor epinephrine and epinephrine or nor adrenal adrenaline and adrenaline and that nor epinephrine can be released either as a neurotransmitter so by the sympathetic postganglionic neurons or it can actually be released as a hormone into the blood by those chromaffin cells of the adrenal Medela so we can release it in two different ways but will bind in the same manner to those receptors so the two main types of adrenergic receptors are alpha receptors and beta receptors these are found on all of our visceral affectors which are innovated by sympathetic postganglionic axons and these receptors are actually further classified into subtypes so we have type one and two alpha receptors and types one 1 two and three beta receptors now although there are some ex uh exceptions activation of our alpha 1 and beta 1 receptors generally produces depolarization or excitation and activation of our Alpha 2 and beta 2 receptors causes inhibition of our affector cells our beta 3 receptors are only present on the cells of brown adipose tissue which when they are activated causes thermogenesis or heat production now again I know that that was a lot it's lots of words it's even hard to get out but summarizing that information for you with a bit of an image and in the autonomic nervous system neurons are named based on the neurotransmitter that they release so colonic neurons release acetal choline ad ergic neurons release norepinephrine all pre ganglionic neurons are coleric neurons because they release acetyl choline and you can see that here so each of these pre ganglionic neurons is releasing acety choline most sympathetic postganglionic neurons are adrenergic neurons because they release norepinephrine so this is an adrenergic neuron because it releases norepinephrine the sympathetic postganglionic neurons that innovate sweat glands are colonic neurons because they release acetycholine so this is our sweat gland here so this is a colonic neuron because it's releasing acetal choline as well as all of our parasympathetic postganglionic neurons so that's what we've got here our parasympathetic postganglionic neuron is colonic because it's releasing acetal choline lastly acetal choline combined to either nicotinic receptors or muscarinic receptors nicotinic receptors which we can see here here and here produce depolarization or excitation that's good we want this action potential to pass all the way along our motor pathway so produces depolarization of that gangion binding of aceto choline to our muscus muscarinic receptors can produce either depolarization or hyperpolarization now nor adrenaline binds to adrenergic receptors so we have our adrenergic receptors up here these can either be our alpha or our beta receptors and remember we have a number of different subtypes Alpha and beta 1 receptors cause depolarization and Alpha and beta two receptors typically cause hyperpolarization