parasympathetic nervous system

what are the two types of indirect agonist muscarinic receptors?

1. irreversible inhibitors

2. reversible inhibitors

esteric site

catalytic center of enzyme AChE

what is the mechanism of edrophonium?

temporarily inhibits activity of AChE leading to an increased level of AcH in the synaptic cleft

what is the test called to determine if an animal has myansthenia gravis?

tensilon test

what occurs in the body of an animal with myansthenia gravis?

their nicotinic receptors are occupied by an antibody meaning the muscles will not be stimulated

what system is affected by myansthenia gravis?

somatic system

what is the mechanism of muscarinic antagonists?

1. drug interacts with muscarinic receptor of effector

2. interaction prevents ACh binding to muscarinic receptors

3. competitive antagonism

4. blockade of cholinergic effect meaning sympathetic actions will become dominantr

5. eversal of this will be required

what is another name for muscarinic antagonists?

parasympatholytics

what is the primary neurotransmitter for the parasympathetic nervous system?

acetylcholine

cholinergic

refers to nerves releasing ACh or drugs that mimic ACh

muscarinic receptors

G-protein coupled receptors found in various parasympathetic target tissues

nicotinic receptors

ionotropic receptors at neuromuscular junctions and autonomic ganglia

parasympathomimetic drugs

mimic ACh and stimulate cholinergic receptors

parasympatholytic drugs

block ACh at muscarinic receptors inhibiting parasympathetic activity

what neurotransmitter is released at the postganglionic parasympathetic nerve terminal?

acetylcholine

what G-protein receptor stimulation leads to bradycardia?

muscarinic

what is the origin of preganglionic neurons in the parasympathetic division?

cranio-sacral regions of intermediolateral gray matter in spinal cord

what is the ratio of preganglionic fibers to postganglionic fibers in organs for parasympathetic system?

3:1

what does the low ratio of pre and post ganglionic fibers in the parasympathetic division mean?

more pinpointed and specific signal

in the parasympathetic division, is the preganglionic or postganglionic neuron longer?

postganglionic neuron

what is different about the ganglion in the parasympathetic division compared to the sympathetic division?

ganglion is embedded into the organ rather than innervated

why is the postganglionic fiber short in the parasympathetic division?

directly next to target cells (glands and smooth muscle)

adregeneric

neuron releases epinephrine

parasympathetic division = __ energy

recovering

what is important to note about blood vessels in the parasympathetic division?

blood vessels do NOT have parasympathetic nerves, only sympathetic nerves; you inhibit or activate the sympathetic nerves depending on what reaction you want

explain the basic steps of mydriasis

1. dim light perceived

2. sympathetic postsynaptic neuron releases norepinephrine

3. radial muscle contracts

4. pupils dilate

explain the basic steps of miosis

1. bright light is perceived

2. parasympathetic postsynaptic neuron releases acetylcholine

3. circular iris muscles stimulated to contract

4. pupils constrict

mydriasis

pupils dilated

miosis

pupils constrict

what is important to note about mydriasis and miosis?

both cause contraction of the eye

what is the effect of parasympathetic division stimulation on the pupil diameter?

miosis

what is glycopyrrolate used for in veterinary medicine?

preanesthetic

what does the release of AcH trigger?

action potential triggers calcium influx, causing vesicle fusion and Ach exocytosis

what are the locations of nicotinic receptors?

1. autonomic ganglia

2. neuromuscular junctions

3. adrenal medulla

4. CNS

where are muscarinic receptors found?

1. neuroeffector junctions

2. blood vessels

3. pre-synaptic terminals

4. CNS

M2 receptors located

heart and SA node

what does the M2 subtype do?

decrease heart rate and impulse conduction

M3

smooth muscle and glands

M3 causes

smooth muscle contractions and glandular secretion