Acetylcholine Flashcards
ACh plays a crucial role in both
sympathetic
and parasympathetic branches of the autonomic
nervous system.
ACh is responsible for muscle contractions, as it is released at
neuromuscular junctions.
Many drugs, cosmetics and toxins act on the …. system
cholinergic
what is Botulin Toxin produced by
the bacteria Clostridium botulinum.
Botox interferes with Ach release at nerve terminals, thereby blocking
neurotransmission
what was the first neurotransmitter discovered
acetylcholine
Sympathetic and
parasympathetic preganglionic
neurons
are cells in the CNS
that send axons to the
autonomic ganglia and various
target organs.
ACh is the neurotransmitter used
for
communication
-Mediates parasympathetic
functions (e.g. inhibits heart);
- Released onto muscles leading to
muscle contraction (activates)
characteristics of sympathetic division
- energy mobilization
- origin in thoracic and lumbar spina cord
- relatively short preganglionic fibres, long post ganglionics
- releases acetylcholine in ganglia and norepinephrine at target
characteristics of parasympathetic division
- energy conservation and storage
- origin in cranial nerves and sacral spinal cord
- long preganglionic fibres ending near organs, short postganglionic
- releases ACH t both ganglia and target
ACh is formed from
choline and acetyl coenzyme A
(Acetyl CoA)
The reaction of Ach is catalyzed by
choline acetyltransferase
Choline
an essential nutrient found in
many foods, principally in the form of
phosphatidylcholine and as free choline.
- Phosphatidylcholine: beef liver, egg yolks, soya;
- Free choline: beef liver, iceberg lettuce, peanut
butter, peanuts, cauliflowe
Acetyl CoA is produced during the 2nd step of
aerobic cellular respiration
ChAT is synthesized within the.. and transported to .. it is also used as a marker for…
ChAT is synthesized within the cell body and
transported to the nerve terminal.
marker for motor neurons
ACh is stored in
very small
synaptic vesicles
Vesicular ACh Transporter
(VAChT) is responsible for
loading ACh into vesicles
Cholinergic cell bodies are primarily located in
the:
- Caudate putamen;
- Nucleus Accumbens;
- Nucleus basalis;
- Pedunculopontine Nuclei (PPN);
i. Laterodorsal tegmental nucleus
ii. Pedunculopontine tegmental nucleus - Medial Septum
two families of cholinergic receptors
distributed throughout the brain
- Nicotinic acetylcholine receptors
- Muscarinic acetylcholine receptors
Nicotinic acetylcholine receptor
Respond to nicotine
- Localized at neuromuscular junctions;
- Ionotropic receptors;
Each nicotinic receptor consists of how many subunits
5
When nicotinic receptors are
subjected to continuous agonist
exposure, they become
desensitized – the channel will not
open even when agonist binds;
- Desensitized receptors will
naturally, and spontaneously, re-
sensitize and are able to respond
again
Muscarinic acetylcholine receptors
Responds to muscarin
- Unlike nicotinic receptors, muscarinic receptors are
metabotropic operate via 2nd messenger system
how many subunits muscarinic receptor are they and where are they found
5
- M1 are common in secretory glands;
- M2 are found in cardiac tissue;
- M3 are found in smooth muscles and in secretory glands
M1,M3 & M5 receptors cause the activation of
phospholipase C, leading to an intracellular increase of
Ca2+
M2 & M4 inhibit
adenylyl cyclase, which decreases the
production of cAMP
M5 receptors in the brain are primarily in the
hippocampus,
hypothalamus, and midbrain dopamine areas
They contribute to the excitatory effect on dopamine neurons
mediated by nicotinic receptors;
- They appear to be involved in the rewarding and dependence-
producing effects of some illicit drugs.
Cellular acetylcholine levels are
regulated by an enzyme called
acetylcholinesterase (AChE)
AChE breaks down ACh into
choline
and acetic acid
AChE is located in multiple places:
- Presynaptic cells so they can metabolize
excess ACh; - Postsynaptic membrane so they can
break down ACh after its release into
synaptic cleft
Some compounds cause irreversible
inhibition of AChE, what does this result in
- This would prevent acetylcholine from being
metabolized; - Acetylcholine would therefore remain in the cleft to
continue binding and activating receptors.
ACh accumulation and overstimulation of
cholinergic synapses throughout both CNS and PNS lead to
muscle paralysis and death by
asphyxiation
Alzheimer’s Disease (AD) is associated with a loss of.. that project from the … to the ….
loss of cholinergic neurons that
project from the basal forebrain to the cerebral cortex and hippocampus
Pyruvate decarboxylation
conversion of
pyruvate, the end product of glycolysis, into
acetyl CoA
