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NAS > NMJ And Synapses > Flashcards

NMJ And Synapses Flashcards

1
Q

What are special senses

A

sight
Smell
hearing
Taste

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2
Q

Electrical synapse?

A

Gap junctions
Fastest and most primitive
Allows synchronous activity
Common between glial cells and neurones/ glial-glial and cardiomyocytes
Direct transfer of ions
Bi directional

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3
Q

Chemical synapse?

A

Release of NT from presynaptic terminal
Diffuses
Interacts with receptor on post synaptic

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4
Q

What is presynaptic area with vesicles known as

A

Active zone

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5
Q

How is signal terminated

A

Enzymatic breakdown

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6
Q

Features of NT receptors

A

Transmembrane spanning proteins
Binding causes conformational change
Specific
One NT - several receptor subtypes

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7
Q

Ionotropic receptor signalling mechanism?

A

(Receptor operated/ ligand gated channel)
Transmitter binds
Conformational change
Channel opening
Ion movement

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8
Q

Metabotropic receptor signalling mechanism?

A

(G protein coupled)

Transmitter binding
conformational change
activates G-protein
activates ‘effector systems’
indirect effects: e.g. open or close ion channels; stimulate or inhibit enzymes/ secondary messenger systems

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9
Q

Indirect effects of G coupled protein receptors

A

Open or close ion channels
Stimulate or inhibit enzymes/ secondary messenger systems

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10
Q

Spatial summation

A

Summing of post synaptic potentials generated at separate synapses to reach threshold value

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11
Q

Temporal summation

A

Summing of post synaptic potentials generated at same synapse, if they occur in rapid succession
Single synapse repeatedly stimulating the cell

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12
Q

Axon hillock?

A

Region where an action potential is generated and then propagated along the axon
Between soma and axon
An input closer to axon hilllock will have a much larger effect on excitability of cell compared to input at dendritic tree

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13
Q

What is gap junction?

A

An electrical synapse
Gap junction is a physical point of contact between adjacent cells via their cell membrane

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14
Q

Which type of myocytes are connected via gap junctions?

A

Cardiac myocytes
Allows cardiac muscle to depolarise to cause contraction

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15
Q

Two ways of termination of signal

A
  1. Enzymatic breakdown and Reuptake of NT
    Specific re-uptake sites. NT hydrolysed by enzymes in presynaptic membrane/ repackaged into vesicles
  2. Enzymatic breakdown in extracellular fluid
    Without uptake. Mitochondria in extracellular fluid. e.g. acetylcholine
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16
Q

Types of monoamine NT

A

Noradrenaline (adrenal medulla)
Dopamine
Serotonin

17
Q

Mixed synapse?

A

Both inhibitory and excitatory synaptic inputs

18
Q

GABA?

A

Inhibitory NT
Promotes anti-stress and calmness

19
Q

What is in white matter?

A

Axons of neurones

20
Q

How is muscle contraction guaranteed ?

A
  • Many NMJ along the length of the muscle to ensure muscle fibres contract simultaneously
  • Many vesicles in pre synaptic membrane
  • Many post synaptic receptors
21
Q

Description of ligand gated ion channel for ACh?

A

5 protein subunits
Two binding sites for ACh. Two need to bind for conformational change.

22
Q

Junctional folds on post synaptic neurone

A

Invaginations in the Sarcolemma (cell membrane of muscle fibre) at NMJ
Increases surface area

High density of ACh receptors and voltage gated Na channels

23
Q

What is EPP?

A

End plate potential
Separate event to AP and occurs first
Voltage produced solely by ACh binding to nAChR on motor end plate
Generated by ligand gated channels

24
Q

How is AP generated?

A

Generated by voltage gated Na channels

25
Q

EPP is very large in NMJ compared to most synapses?

A

Yes
Because
- many ACh vesicles released
- high density of nAChRs

26
Q

Where are Ca ions released from in the muscle fibres?

A

Depolarisation of sarcolemma
Causes Ca to release from terminal cisternae

27
Q

Synaptotagmin?

A

Family of proteins
Facilitate synaptic vesicles exocytosis

28
Q

Em of muscle cells?

A

-90mv

29
Q

Value of EPP

A

-20mV

30
Q

Two electrical events of upon NT binding to receptors on post synaptic membrane

A
  • EPP initiates AP in muscles
    1. EPP (prod by ligand acted channels) decays as it moves away from end late as nAChRs absent away from NMJ
    2. AP travels through muscle
31
Q

Why is the threshold of AP generation easily passed at NMJ?

A
  • high density of voltage gated Na channels at end plate
  • many NT vesicles
32
Q

How to achieve sustained muscle contraction

A

One single AP causes a twitch
Summation of twitches into a sustained contraction
Tetanus

33
Q

What enzyme breaks down ACh and how

A
  • Acetylcholinesterase
  • hydrolysed into acetate and choline
  • choline taken back up and ACh resynthesised
34
Q

Myesthenia Gravis

A

Muscle weakness during sustained activity
Autoimmune disease of nAChR - so reduced receptors at NMJ

35
Q

Treatment of myesthenia Gravis

A

AChE inhibitors
Prolongs signal

NAS (17 decks)

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