Functional Aspects of the Autonomic Nervous System Flashcards
What is the major pathway for information transmission from the CNS to the involuntary effector tissues (smooth muscle, cardiac muscle, and exocrine glands)?
The motor efferent portion of the ANS
What is the meaning of Adrenergic?
A nerve ending that releases norepi as the primary transmitter
What is meant by adrenergic receptor?
A receptor that binds and is activated by one of the catecholamine transmitters or hormones such as; epi, norepi, dopamine and related drugs
What is meant by cholinergic?
Nerve ending that releases acetylcholine; also a synapse where the primary transmitter is acetylcholine
What is meant by homeostatic reflex?
A compensatory mechanism for maintaining a body function at a predetermined level
What is the primary transmitter in all autonomic ganglia and at the synapses between parasympathetic postganglionc neurons and their effector cells
Acetylcholine
What is the rate limiting step in the synthesis and storage of Acetylcholine?
The transport of into the nerve terminal
What drug can inhibit the transport of Acetylcholine into its nerve terminals after synthesis?
Hemicholinium
What is the transporter responsible for transporting acetylcholine into its vesicles for storage?
Vesicle associated transporter VAT
What drug inhibits VAT?
Vesamicol
What ion mediates the release of acetylcholine from its vesicles in nerve endings?
Calcium entry through channels and triggering of an interaction between SNARE proteins and t-SNARE
How does Botulinum toxin work?
Enzymatically alters synapto-brevin or one of the other docking or fusion proteins to prevent the release process of acetylcholine
How is the Acetylcholine action terminated?
ACh is metabolized to acetate and choline by Acetylcholinesterase in synaptic cleft
What is the primary transmitter at sympathetic postganglionic neuron effector cell synapses in most tissues?
Norepi
What function does serve in Renal blood vessels?
Vasodilator transmitter
What is the rate limiting step and enzyme in the synthesis of Norepi and Dopamine?
The hydroxylation of Tyrosine to DOPA by Tyrosine Hydroxylase
How can tyrosine hydroxylase be inhibited?
By Metyrosine
What molecule transports Norepi and Dopamine into their vesicles?
VMAT
What is (MOA) Monoamine Oxidase?
A molecule which is present on mitochondria in the adrenergic nerve ending that inactivates a portion of the dopamine and norepi in the cytoplasm
What effect does MOA inhibitors have?
Inhipits the breakdown of Norepi and Dopamine and othe monoamines in nerve endings
What drug inhibits VMAT?
Reserpine
What mechanism is responsible for the release of Norepi and Dopamine?
Same as ACh, calcium dependent
What mechanisms are responsible for the termination of action of Norepi and Dopamine.
Diffusion and reuptake (especially uptake 1) by transporters NET and DAT
What does Guanethidine do?
Blocks norepinephrine release blocking sympathetic but not parasypathetic functions
What are Muscarine receptors?
These receptors respond to Muscarine as well as acetylcholine, the effect of these receptors resemble those of postganglionic parasympathetic nerve stimulation.
Where are muscarinic receptors mostly located?
Primarily on autonomic effector cells incuding heart vascular endothelium smooth muscle and presynaptic nerve terminals
What do all muscarinic receptors have in common?
Are G-coupled receptors
What are the nicotinic receptors?
These receptors are located on Na-K ion channels and respond to acetylcholine and nicotine but not Muscarine by opening the channel
Where are the Nicotinic receptors located?
In ganglia and in Skeletal muscle
What are the Adrenoceptors?
- Alpha
2. Beta
Where are Alpha receptors located?
On vascular smooth muscle, presynaptic nerve terminals, blood platelets, fat cells and neurons in the brain
Where are Beta receptors located?
Mostly on smooth muscle, cardiac muscle some presynaptic nerve terminals and lipocytes
What do all the subtypes of Beta receptors have in common?
All us the same G-coupling protein
Where are Dopamine receptors most found/important?
Renal and Splanchnic vessels and the Brain
Which is the most important subtype of Dopamine receptors?
D1
What is the purpose of the release of ATP and substance P with ACh?
Modulation
What is an presynaptic AUTORECEPTOR?
is a receptor for the Ligand that is being released from the presynaptic nerve ending at a cholinergic synapse it would be a Muscarinic receptor and it essentially turns off action
What is a presynaptic Heteroreceptor?
Regulatory receptor that responds to substance other than the transmitter itself
Drugs which are not impacted by Acetylcholinesterase inhibitor
Carbachol Chloride
Bethanecol chloride
How do Cocaine, and Tricyclic antidepressants work?
Inhibit uptake of Norepi from synaptic cleft by blocking NET
How does Bretylium guanethidine work?
Inhibiting fusion of transmitter containing vesicles with the end plate by blocking VAMPs in Adrenergic fibres
Where are Beta-2 Adrenergic receptors mostly found?
Lung
Vasculature of Skeletal Muscle
What is the specificity of the transmitter Epi?
A-a=A-2;B-1=B-2
Which drug causes a widening of the pulse pressure?
Epinephrine
Why does Pulse pressure widen when Epi is given?
Due to stimulation of Beta-2 which causes vasodilation and pressure is falling
What is the difference in Calcium dependency for Myocyte contraction vs Smooth muscle of vasculature?
In Cardiac cells its the release of Ca2+ from SR where as in smooth muscle its the influx of Calcium from outside the ell that triggers the action
What is the effect of activation of the B-2 receptors in Bronchio Smooth muscle?
Relaxation of the smooth muscle
What is Tachyphylaxis?
Loss of activity of a drug
Which receptors are stimulated in response to Hypoglycemia?
Alpha-1 and Beta-2
In which type Diabetes would you expect non-selective Beta Blockers to delay recovery from hypoglycemia?
Type -1
Is there Cholinergic innervation of the Blood vessels?
No
What is the effect of Mucarinic agents on the vasculature then?
Promote release of NO which causes Vasodilation
