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BMA1901-Module 6 > Mod6-Obj4: Neurotransmitters > Flashcards

Mod6-Obj4: Neurotransmitters Flashcards

1
Q

Signal transmission across a synapse: Step 1

A

Action potential arrives at the presynaptic axon terminal and depolarises the membrane

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2
Q

Signal transmission across a synapse: Step 2

A

Voltage-gated Ca2+ channels open and Ca2+ enters the axon terminal

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3
Q

Signal transmission across a synapse: Step 3

A

Ca2+ surge triggers synaptic vesicles to release their stored neurotransmitters (ACh) into the synaptic cleft

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4
Q

Signal transmission across a synapse: Step 4

A

NT diffuse across synaptic cleft and binds receptors (chemically-gated ion channels) on the postsynaptic membrane

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5
Q

Signal transmission across a synapse: Step 5

A

Binding of NT opens chemically-gated ion channels, producing a graded potential

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6
Q

Signal transmission across a synapse: Step 6

A

If graded potential reaches threshold, action potential is generated and signal is transmitted

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7
Q

Signal transmission across a synapse: Step 7

A

Transmission of signal terminated if

  • Degraded by enzymes
  • Re-enters the axon terminal
  • Diffuses away from synapse
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8
Q

Postsynaptic potentials

A

Are either excitatory or inhibitory

  • Depends on membrane potential generated at postsynaptic neuron
  • Postsynaptic potential=a graded potential
  • EPSP and IPSP result from opening different gated ion channels
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9
Q

Excitatory postsynaptic potential (EPSP)

A

Depolarisation of postsynaptic membrane towards threshold

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10
Q

Inhibitory postsynaptic potential (IPSP)

A

Hyperpolarisation of postynaptic membrane away from threshold

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11
Q

EPSP

A
  1. NT binds receptors on the postsynaptic membrane
  2. Opens gated ion channels
  3. Na+ ions flow in > K+ out
  4. Graded potential = depolarisation
  5. Postsynaptic membrane is closer to threshold (facilitated)
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12
Q

IPSP

A
  1. NT binds receptors on the postsynaptic membrane
  2. Opens gated ion channels
  3. Cl- (chloride) ions flow in, K+
    flow out
  4. Graded potential = hyperpolarisation
  5. Postsynaptic membrane is further to threshold (inhibited)
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13
Q

The postsynaptic cell

A

Excitatory synapse
◦ Na+ K+ gated channels ◦ Towards threshold
Inhibitory synapse
◦ Cl- and K+ gated channels ◦ Away from threshold

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14
Q

The postsynaptic cell

A

Excitatory synapse
◦ Na+ K+ gated channels ◦ Towards threshold
Inhibitory synapse
◦ Cl- and K+ gated channels ◦ Away from threshold

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15
Q

ANS neurotransmitters: ACh

A

Any axon that releases acetylcholine is known as a cholinergic fibre

  • All preganglionic axons
  • Parasympathetic postganglionic axons
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16
Q

ANS neurotransmitters: NA

A

Any axon that releases noradrenalin (NA) is known as an adrenergic fibre
-Sympathetic postganglionic axon

17
Q

Cholinergic receptors

A

Receptors that bind ACh
Two types:
1.) Nicotinic: always excitatory
2.) Muscuarinic: Excitatory or inhibitory

18
Q

Cholinergic receptors: Nicotinic

A 
Location:
-All postganglionic neurons
-Adrenal medullary cells 
-Skeletal muscles 
Effect of NT binding:
-Excitation
19
Q

Cholinergic receptors: Muscuarinic

A 
Location:
-All parasympathetic target organs
Effect of NT binding:
-Excitation of most targets 
-Inhibition of cardiac muscle
20
Q

Adrenergic receptors

A

Receptors that bind NA and A
Two major types:
-Alpha (a1, a2)
-Beta (B1, B2, B3)

21
Q

Adrenergic receptors: B1

A

Location:
-Heart
Effect of binding:
-Increases heart rate and force of contraction

22
Q

Adrenergic receptors: B2

A

Location:
-Lungs, most sympathetic targets, blood vessels in heart, liver and skeletal muscle
Effect of binding:
-Most inhibitory: dilates blood vessels and bronchioles, relaxes smooth muscles in digestive and urinary organs

23
Q

Adrenergic receptors: a1

A

Location:
-Blood vessels (except in heart, liver and skeletal muscles), and all sympathetic targets except the heart
Effect of binding:
-Mostly stimulatory: constricts blood vessels and visceral organ sphincters, dilates pupils

24
Q

Effect of drugs

A

Drugs that bind NT receptors

  • Agonist (mimic the action)
  • Antagonist (block the action)
25
Q

Sympathetic (adrenergic): α

Receptor location and normal response to NT binding

A 
Smooth muscle of:
•  Most arterioles
•  Sphincters of bladder
and GI tract
•  Iris dilator
Effect: contraction
26
Q

Sympathetic (adrenergic): α

Typical agonist drugs

A
  • Noradrenalin

- Adrenalin

27
Q

Sympathetic (adrenergic): α

Typical antagonist drugs

A
  • Phenoxybenz- amine

- Phentolamine Prazosin

28
Q

Sympathetic (adrenergic): B1

Receptor location and normal response to NT binding

A

Cardiac muscle
Kidneys
Effect: increased rate and force of contraction. Increased renin release from kidneys

29
Q

Sympathetic (adrenergic): B1

Typical agonist drugs

A

-Noradrenalin
-Adrenalin
-Isoproteronol
0Dobutamine

30
Q

Sympathetic (adrenergic): B1

Typical antagonist drugs

A

“Beta blockers” Propranolol (used to lower blood pressure)

31
Q

Sympathetic (adrenergic): B2

Receptor location and normal response to NT binding

A 
Smooth muscle of:
•  Bronchioles of lung 
•  Arterioles of skeletal muscles, brain and lungs 
•  Uterus
Effect: relaxation
32
Q

Sympathetic (adrenergic): B2

Typical agonist drugs

A
  • Adrenalin (used for anaphylaxis)

- Albuterol (used in asthma puffers)

33
Q

Sympathetic (adrenergic): B2

Typical antagonist drugs

A

“Beta blockers” Propranolol

34
Q

Parasympathetic (cholinergic): Muscuarinic

Receptor location and normal response to NT binding

A

All parasympathetic effectors

35
Q

Parasympathetic (cholinergic): Muscuarinic

Typical agonist drugs

A
  • Acetylcholine
  • Muscarine
  • Carbachol
36
Q

Parasympathetic (cholinergic): Muscuarinic

Typical antagonist drugs

A
  • Atropine (pupil dilaiton)

- Scopolamine

BMA1901-Module 6 (5 decks)

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