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NEUROPHYSIOLOGY > NS 1 - PT 2 > Flashcards

NS 1 - PT 2 Flashcards

1
Q

Name the 2 types of synapses

A

Chemical and electrical synapses

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2
Q

Explain electrical synapses

A

Characterised by gap junction with ion channels that connect the cytoplasm of adjacent cells

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3
Q

Function of gap junctions

A

Allow free movement of ions from the cytoplasm of one cell to the next

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3
Q

Function of electrical sunapses

A

Allow bidirectional transmission of impulses

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4
Q

Explain chemical synapses

A

Characterised by the secretion of a neurotransmitter

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5
Q

Which type of synapse is abundant in the CNS

A

Chemical neurotransmitter

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6
Q

How many known neurotransmitters are there?

A

More than 50

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7
Q

Membrane of the presynaptic terminal is called the_______________

A

Presynaptic membrane

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8
Q

Which ion channel is abundant in the presynaptic membrane?

A

Voltage-gated calcium channels

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9
Q

Explain synaptic transmission

A

AP depolarises the presynaptic membrane open the calcium channels and allow influx of calcium ions into the terminal.

Calcium influx cause transmitter vesicles in the presynaptic terminal to release their neurotransmitter into the synaptic cleft

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10
Q

What guides and promotes vesicle fusion with the cell membrane?

A

SNARE proteins
Synaptobrevin
*SNAP-25
*Syntaxin
*Synaptotagmin – Ca2+ sensing
Target for neurotoxins: Botulinum toxins

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11
Q

Chemical synapses transmit signals bidirectionally - true or false

A

f. they transmit in one direction from presynaptic neuron to postsynaptic neuron

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11
Q

What is the target site of neurotransmitters?

A

Receptors in the postsynaptic membrane

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12
Q

What is the action of neurotransmitter in the postsynaptic neuron?

A

Excitation, inhibition, or modify sensitivity

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13
Q

Types of postsynaptic membrane receptors

A

Ionotropic receptors and metabotropic receptors

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14
Q

Explain the mechanisms of postsynaptic excitation

A

Opening of sodium channels allows influx of positive electrical charges to flow to the interior of the postsynaptic cell

Decrease of chloride or potassium channels or both. Increased expression of excitatory membrane receptors or decreased expression of inhibitory membrane receptors

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15
Q

What membrane mechanisms receptors cause inhibition? (3)

A

Opening of chloride channels on the postsynaptic membrane
Increased efflux of potassium ions out of the neuron
Increased expression of inhibitory synaptic receptors, or decreased expression of excitatory receptors

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16
Q

What are neurotransmitters?

A

Endogenous chemicals in the brain that enable signalling across a chemical synapse

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17
Q

3 functions of neurotransmitters

A

Carry and modulate signals between neurons or other cell types

Act on a variety of targets to elicit biological functions

Cause electrophysiological changes in the postsynaptic cell (Excitation by depolarization or inhibition by hyperpolarization)

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18
Q

Explain synthesis and transport of neuropeptides

A

Neuropeptides are
synthesized in the cell
body and pre-loaded
into vesicles which are
delivered to the axon
terminal by axonal
transport.

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19
Q

Which types of receptors does glutamate act on?

A

Glutamate acts on both ionotropic and metabotropic receptors

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20
Q

How are glutamate receptors named? give examples

A

Glutamate receptors named after synthetic agonists that activate them.
* AMPA (amino-methylisoxazole propionic acid)
* Kainite
* NMDA (N-methyl-D-aspartate)

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21
Q

Repetitive activation of the NMDA receptor leads to what?

A

Long term potentiation

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21
Q

Influx of calcium ions leads to activation of ____________________ enzymes

A

Ca2+ dependent enzymes

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22
Q

Action of calcium dependent enzymes once activated

A

They modify the structure and number of synaptic contacts in the target cell

23
Q

Action of anaesthetic drug ketamine on NMDA channel

A

▪ Anaesthetic drug ketamine blocks the NMDA channel, also blocks memory
formation

24
Q

Which glial cell is responsible for taking up glutamate?

A

Astrocye

25
Q

_______________ converts glutamate to glutamine

A

Glutamine synthase

26
Q

Where is glutamine transported?

A

Into the nerve terminal

27
Q

What happens to the glutamine once in the nerve terminal?

A

n the nerve terminal glutamine converted to glutamate
by glutaminase.
5. Glutamate returned to a synaptic vesicle

28
Q

Explain the process of glutamate reuptake and resynthesis

A
  1. Glutamate is taken up by an astrocyte.
  2. Glutamate is converted to glutamine by glutamine
    synthetase.
  3. Glutamine is transported back into the nerve terminal.
  4. In the nerve terminal glutamine converted to glutamate
    by glutaminase.
  5. Glutamate returned to a synaptic vesicle.
29
Q

Full name of GABA

A

Gamma-aminobutyric acid

30
Q

Name the 2 major types of GABA receptors

A

ionotropic and metabotropic.

31
Q

what happens when GABA receptors are activated?

A

▪ Activation of GABA receptors - channel pores opens and Cl− ions influx from the
synaptic cleft to the cytosol – Hyperpolarisation

32
Q

What receptors are activated when sedative hypnotic agents are administered?

A

Activation of GABA receptors

33
Q

Examples of sedative hypnotic agents

A

barbiturates, benzodiazepines and alcohol

34
Q

What is useful for the Rx of seizures? Why?

A

Barbiturates and benzodiazepines.
They are Anticonvulsant

35
Q

What drugs are GABA receptor antagonist?

A

Bicuculline. It is therefore a convulsant

Picrotoxin

36
Q

Which glial cell takes up GABA?

A

Astrocyte

37
Q

Explain GABA reuptake and resynthesis (5)

A
  1. GABA is converted to glutamate by GABA transaminase.
  2. Glutamate is converted to glutamine by glutamine synthetase.
  3. Glutamine is transported back into the nerve terminal and converted to glutamate by glutaminase.
  4. Glutamate is converted to GABA by glutamate decarboxylase.
  5. GABA returned to a synaptic vesicle
38
Q

What neurotransmitter plays a role in learning and memory?

A

Acetylcholine

39
Q

What causes onset of Alzheimer’s disease?

A

Degeneration of cholinergic neurons is associated with the onset of Alzheimer disease

40
Q

_________ is the main neurotransmitter in the NMJ

A

ACh

41
Q

▪ Ionotropic ACh receptors are called ______________.
▪ Metabotropic ACh receptors are called __________.

A

nicotinic.
muscarinic

42
Q

Explain ACh synthesis (4)

A

▪ Choline from the extracellular fluid is sent to the nerve ending.
▪ Choline is acetylated by acetyl coenzyme A (acetyl CoA) released by mitochondria
and the reaction catalysed by choline acetyltransferase (ChAT).
▪ Synthesized ACh molecules are taken up by synaptic vesicles.
▪ Released ACh binds with its receptor

43
Q

Explain ACh degradation (2)

A

Acetylcholinesterase (AChE) hydrolyses the transmitter.
▪ The choline is transported back into the cytosol

44
Q

Explain recycling of ACh (3)

A

Formation of a fresh molecule of ACh is mediated by the transferase, en route to a
synaptic vesicle.
▪ Acetate is transported into the cytosol.
▪ Mitochondria use the acetic acid to produce fresh acetyl CoA

45
Q

Examples of catecholamines

A

dopamine, norepinephrine, and epinephrine

46
Q

Catecholamines are derived from which amino acid?

A

Tyrosine

47
Q

Which catecholamine is associated with Parkinsons disease, drug addiction and schizophrenia?

A

Dopamine

48
Q

What is the classic feature of Parkinson disease?

A

Degeneration of neurons in the substantia nigra

49
Q

Explain catecholamine degradation

A

▪ Catecholamines molecules within the synaptic cleft are broken down by catechol Omethyltransferase (COMT).
▪ Surplus catecholamines molecules in the cytosol are degraded by mitochondriaderived monoamine oxidase (MAO) enzyme

50
Q

Another name for serotonin

A

5-HT (5-hydroxytryptamine)

51
Q

Serotonin is implicated in which conditions?

A

Serotonin is implicated in depression, insomnia, anxiety disorders.

52
Q

Serotonin is derived from which amino acid?

A

Tryptophan

53
Q

Tryptophan is converted to_________________ by the __________________ enzyme

A

5-hydroxytryptophan

tryptophan
hydroxylase.

54
Q

5-hydroxytryptophan is converted to _____________________ by the _________________ enzyme

A

serotonin

5-hydroxytrytophan
decarboxylase.

55
Q

What returns serotonin to the cytosol?

A

Serotonin reuptake transporter

56
Q

What degrades serotonin?

A

monoamine oxidase (MAO).

57
Q

Name 2 antidepressants

A

SSRI:
Selective Serotonin Reuptake Inhibitor
▪ MOA:
Monoamine oxidase A inhibitors

NEUROPHYSIOLOGY (2 decks)

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