736 Exam 3 Flashcards
What neurotransmitter is recognized at nerve terminals within the Parasympathetic Nervous System?
Acetylcholine
What are SLUDS?
Muscarinic receptor agonist effects, AKA Parasympathomimetics
SLUDS
Salivation Lacrimation Urination Defecation Sweating
What are the effects of Muscarinic Receptor Agonists at the Eye?
Miosis by contracting the iris sphincter
(May help dislodge an adherent iris in acute (closed angle) Glaucoma)
Near-sighted-ness by contraction of ciliary muscles
(may improve aq humor flow in chronic open angle glaucoma)
What are the effects of muscarinic receptor agonists at the GI tract?
Contraction of longitudinal muscles and relaxation of sphincters for increased motility.
What are the effects of muscarinic receptor agonists at the Urinary tract?
Contraction of the detrusor muscle and relaxation of sphincter for increased urinary output
What are the effects of muscarinic receptor agonists on the heart?
decreases heart rate at sino-atrial node, and conductivity through AV node.
What are the effects of muscarinic receptor agonists on the Lungs?
Bronchoconstriction
What are the effects of muscarinic receptor agonists on glands?
Increase Salivation, Lacrimation and sweating
How does Choline Acetyltransferase synthesize ACh?
From Choline and Acetate
Where does choline uptake and acetylcholine synthesis occur?
Neuronal Cytoplasm
What is required at VAT prior to Acetylcholine release?
Vesicular reuptake
What ion is required to release Acetylcholine into the synaptic cleft?
Calcium 2+
What is the stepwise process of Cholinergic signaling/recycling at the synaptic cleft?
- Choline uptake into neuronal cytoplastm
- Acetycholine synthesis
- Vesicular uptake of Acetylcholine
- Ca++ dependent release of ACh into synaptic cleft
- Activation of post-synaptic receptors
- Catabolism of ACh by acteycholinesterase
- Choline re-uptake
- Inhibition of ACh release by M2 muscarinic receptors on presynaptic neurons.
What are the function of SNAPs?
Synaptosome proteins, what the vesicles from presynaptic nerve must fuse with in order to release ACh in the synaptic cleft.
What are the functions of VAMPs?
Ca++ sensitive vesicle associated membrane protein, they bind to neuronal membrane to facilitate release of ACh to synaptic cleft.
What is the difference between CHT, ChAT, and VAT?
CHT - Choline Uptake Transporter, uptakes extracellular choline into neuron.
ChAT - Choline acetyl transferase, forms acetycholine from Acetyl Coa and Choline
VAT - Vesicular acetycholine transporter, fills acetycholine into vesicles.
What happens to Ach at Cholinoreceptors on Postsynaptic cells?
It is transferred to acetycholinesterase where it is broken down into choline and acetate, Choline is then taken up by CHT.
What is the difference between M2 Autoreceptors and Heteroreceptors?
Heteroreceptors work by inhibiting a Neurotransmitter when acted upon by a different neurotransmitter
Autoreceptors on presynaptic neurons cause inhibition by reuptaking ACh as soon as its released
Describe general characteristics of Muscarinic Receptors
Located on parasympathetically-innervated target organs
G-protein coupled receptors (M1 and M2 subclasses (m1-m5 subtypes))
- only few agonists distinguish among 5 receptor subtypes
What subtypes does the M1 subclass contain?
m1, m3, m5
What subtypes does the m2 subclass contain?
m2, m4
What is the family of g-protein that M1 type receptors couple to?
Gq/11 which activates phospholipase C-Beta enzymes to increase IP3, DAG, Intracellular Ca++ levels, leading to protein kinase C activation
What parasympathetically innervated organs would you find M1 type receptors in?
Glands (pulmonary, GI, sweat, lacrimal, Naso) Longitudinal GI Bladder Smooth muscle Bronchiol Smooth muscle Iris Sphincter Ciliary Muscle
Where outside parasympathetic nervous system would you see M1 type receptors?
Brain Blood vessels (m3 to stimulate release of NO)
What would an exogenous source of muscarinic agonist circulating within the blood cause? (Stepwise)
Activation of PLC-Beta to increase IP3/DAG to increase Ca++ to increase NO which leads to a relaxation in vessel smooth muscle
why are the m3 receptors on endothelium never naturally activated?
There are no PNS nerves or ACh at vascular endothelium so only exogenous substances activated them?
