Exam 2: Acetylcholine

Question 1

neurons that use Ach are called

Answer 1

cholinergic

Question 2

where are acetylcholine neuron cell bodies located

Answer 2

• basal forebrain
• striatum
• dorsal lateral pons (PPN, LTD)

Question 3

involved in attention, memory, learning
- provides Ach to cerebral cortex (lobes of brain) and hippocampus
- made of many regions (nucleus basalis is main region)
cell bodies in basal forebrain but axons extend out

Answer 3

basal forebrain

Question 4

striatum

Answer 4

cell bodies AND axons in striatum
movement
balance between dopamine and acetylcholine

Question 5

dorsal lateral pons (PPN and LTD)

Answer 5

pons - part of brainstem
-cell bodies project to spinal nerves for movement, cerebellum, basal ganglia
balance and coordination, gait (walking)

Question 6

what is acetylcholine important in

Answer 6

CNS (learning, memory, attention, motor movements)
neuromuscular junctions (contract muscles, maintain posture)
autonomic nervous system

Question 7

branches of autonomic nervous system and how they relate to Ach

Answer 7

sympathetic - only preganglionic Ach

parasympathetic-pre and postganglionic Ach

Ach monitors if the body is in a state of arousal or stress

Question 8

What is Acetylcholine formed from and what is it catalyzed/synthesized by?

Answer 8

formed from: choline and acetyl CoA

synthesized by: choline acetyltransferase (ChAT)

Question 9

acetylcholine storage and release - how is it moved into vesicles

Answer 9

stored in vesicles at axon terminals

moved into vesicles by vesicular Ach transports (VAChT) embedded in vesicle memrbane

Question 10

what are the VAChT blocked by

Answer 10

vesamicol
this reduces the amount of Ach released when the neurons fire
- if Ach cannot get packaged there s a decrease in Acetylcholine released in response to an action potental

Question 11

what toxin inhibits Ach releas

Answer 11

botulism toxin

• prevents fusion of synaptic vesicles to the presynaptic membrane
• cannot release its contents - paralyzes the face

Question 12

acetylcholine inactivation

Answer 12

• ALL Ach BROKEN DOWN

enzyme: acetylcholinesterase (AchE) breaks it down into choline and acetate

Question 13

where is acetylcholinesterase found?

Answer 13

• in presynaptic cell (metabolizes excess Ach)

- on the membrane of postsynaptic cell (breaks Ach down after release after bound to receptor)

Question 14

after acetylcholine inactivation what is transported back into the cell for reuse

Answer 14

choline

Question 15

is there a reuptake transporter for Ach?

Answer 15

NO

Question 16

drugs that block AChE prevent _____

Answer 16

inactivation of ACh which increases postsynaptic effects of the transmitter

Question 17

how can drugs that block AChE be harmful

Answer 17

• can cause muscle paralysis or death (asphyxiation)
• depends on BBB permeability and whether it blocks AChE reversibly or irreversibly
• insecticides, sarin gas (SLUDGE)
• cardiac muscle has M2 receptors, stimulate parasympathetic system, dec HR, dec contraction strength and can kill someone (excess Ach, excess slwoing of heart and breathing)

Question 18

SLUDGE

Answer 18

S: salivation/drooling
L: lacrimation
U: urination
D: diarrhea
G: GI distress
E: vomiting, emesis

Question 19

acetylcholine receptors

Answer 19

nicotinic and muscarinic

Question 20

nicotinic receptors

Answer 20

ionotropic

• Ach binds, channel opens and Na or Ca enter cell, depolarizing it
• mediate fast excitatory responses in both CNS and PNS

Question 21

nicotinic subunits

Answer 21

each receptor has 5 protein subunits (alpha, beta, gamma, delta, epsilon)

10 types of alpha, 4 types of beta

receptor in muscle cells have diff composition than ones in neurons

• muscles have lots of variety (2a1, B1, y, and delta or epsilon
• neurons have a7 - al a7 or a4b2(2a4, 3b2)

Question 22

what are the two types of neuronal nicotinic receptors ((a4)2 and (b2)3)involved in … and where in brain?

Answer 22

learning, memory, cognition - targets of medications under development

• basal forebrain, caudate putamen, cerebellum, temporal lobe

Question 23

distribution of nicotinic receptors in PNS vs CNS

Answer 23

PNS: neuromuscular junctions and ganglia of ANS

CNS: hippocampus and cerebral cortex, basal ganglia, ventral tegmental area and nucleus accumbens

Question 24

3 states of nicotinic ionotropic receptors

Answer 24

closed-neurotransmitter not bound, channel closed
open-agonist is bound and pore opens
desensitized - pore is closed and cannot be opened by agonist binding while in this state (related to tolerance and reduced responding)

Question 25

prolonged exposure to an agonist on a nicotinic receptor…

Answer 25

enhances the rate of conversion to the desensitized state

Question 26

when is a desensitized receptor able to respond to an agonist again?

Answer 26

afte re-sensitization

Question 27

what is a depolarization block

Answer 27

the resting potential of a membrane is lost

cell cannot be excited until agonist removed and membrane repolarized

Question 28

example of a depolarization block

Answer 28

succinylcholine 
- muscle relaxer
-resistant to breakdown by AChE
- continually activates receptor and induces depolarization block of the muscle cell
membrane potential never resets

Question 29

muscarinic receptors

Answer 29

metabotropic
M1-M5
M1,3,5 - excitatory
M2,4 - inhibitory

Question 30

which muscarinic receptor is highly implicated in addiction and pleasure

Answer 30

M5
- found on dopamine neurons in VTA
implicated in reward