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Flashcards covering the introduction to autonomic pharmacology, divisions of the nervous system, cholinergic transmission, and the mechanism of action of cholinergic receptors (muscarinic and nicotinic).
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What are the two main divisions of the Peripheral Nervous System (PNS)?
The Autonomic and Somatic divisions.
What is the primary characteristic that defines the Autonomic Nervous System (ANS)?
It controls 'automatic' bodily functions and is not under direct conscious control.
What are the three main divisions of the Autonomic Nervous System disclosed in the lecture?
The Sympathetic (thoracolumbar), Parasympathetic (craniosacral), and Intrinsic divisions (Enteric and Intracardiac Nervous Systems).
What neurotransmitter is used by all preganglionic nerves leaving the Central Nervous System (CNS) in both sympathetic and parasympathetic divisions?
Acetylcholine (ACh).
What is the primary postganglionic neurotransmitter in the sympathetic nervous system, and what is its main exception?
Noradrenaline (norepinephrine) is the main postganglionic transmitter, with the exception of acetylcholine (ACh) in sympathetic nerves to sweat glands.
Where do parasympathetic preganglionic nerves emerge from, and where are most of their ganglia located?
They emerge from sacral and cranial levels of the spinal cord (e.g., Vagus nerve), and most ganglia lie within the target tissues.
What is the postganglionic neurotransmitter in the parasympathetic nervous system, and what type of receptors does it act on in target tissues?
Acetylcholine (ACh), which acts on muscarinic receptors (mAChR) in target tissues.
What are the two main plexuses that make up the Enteric Nervous System?
The Myenteric Plexus (of Auerbach) and the Submucous Plexus (of Meissner).
What enzyme is responsible for the synthesis of acetylcholine (ACh) in the cytoplasm of cholinergic nerve terminals?
Choline acetyltransferase.
How is acetylcholine (ACh) released from cholinergic nerve terminals, and what toxin can block this process?
ACh release is Ca2+-dependent, triggered by action potentials, and blocked by Botulinum Toxin (BOTOX).
How is the action of acetylcholine (ACh) at the synapse terminated?
By the enzyme Acetylcholinesterase, which is blocked by nerve gases and insecticides.
What type of receptor are Muscarinic Cholinergic Receptors (mAChR)?
They have a heptahelical structure and are G-protein coupled (metabotropic).
Name the three primary muscarinic receptor subtypes and one key function or location for each.
M1 (neurons), M2 (cardiac), M3 (smooth muscle, endothelial cells, & glands).
How do M1 and M3 muscarinic receptors typically exert their effects on cells?
They act through Gq phospholipase C, inositol trisphosphate (IP3), Ca2+, and/or diacyl glycerol, activating protein kinase C.
Describe the unique location and action of muscarinic receptors in blood vessels.
Muscarinic receptors are located on endothelial cells lining blood vessels, not directly on the smooth muscle. Activation leads to nitric oxide release, which then diffuses to smooth muscle to cause relaxation and dilation.
What type of receptor are Nicotinic Cholinergic Receptors (nAChR)?
They are ligand-gated ion channels permeable to Na+/K+.
What is the primary effect of nicotinic acetylcholine receptor (nAChR) activation in autonomic ganglia and skeletal muscle?
It causes depolarization, leading to an excitatory postsynaptic potential (e.p.s.p.) in autonomic ganglia and an excitatory junctional potential (e.j.p.) in skeletal muscle.