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Physiology and Neuroscience > Principles of Synaptic Transmission > Flashcards

Principles of Synaptic Transmission Flashcards

1
Q

What are the two specialised junctions signals can be transferred at?

A 
Neuron-neuron= synapse
Neuron-muscle= neuromucular junction
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2
Q

What are the two types of synapses?

A

Chemical

Electrical

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3
Q

What is a chemical synapse?

A

Chemical neurotransmitters

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4
Q

What is electrical synapses?

A

Flow of current

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5
Q

Who first found evidence for chemical transmission?

A

Otto Lowei during a dream

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6
Q

What is Lowei’s experiment?

A

2 isolated frog hearts (still beating)
Reservoir of physiological solution
Perfused the first heart and went into the second heart
Stimulated a nerve on first heart connected to various pointers
When stimulated the vagus nerve, the first heart slowed down
After time the heartbeat of the second heart also slowed down
Conclusion: chemical slowed the heart beat

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7
Q

Who discovered acetylcholine?

A

Henry Dale

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8
Q

How is pharmacological evidence used as evidence for chemical transmission?

A

Drugs used to study neuromuscular junction (NMJ)

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9
Q

What does NMJ release?

A

Acetylcholine

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10
Q

What are agonists?

A

Drugs that mimic the actions of the natural transmitter

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11
Q

Give an example of an agonist?

A

Nicotine- nicotinic acetylcholine receptors

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12
Q

What are antagonists?

A

Drugs that block the actions of the neurotransmitter, bind to receptor (high affinity, low efficacy)

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13
Q

What is curare?

A

Antagonist at nicotinic receptors, paralyse at neuromuscular

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14
Q

What was the experiment at NMJ with curare?

A

Competitive antagonist
Clock with curare
Inactivate acetylcholine with serine
More acetylcholine is available- overcomes the action of curare

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15
Q

What can be used to show the morphological evidence of chemical transmission?

A

Electron microscopes

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16
Q

What can electron microscopes show about chemical transmission?

A

Presynpatic element- axon terminal

Postsynaptic element- dendrite

17
Q

What are the key features of the synapse?

A 
Synaptic cleft- space between the element (20-30nm in width)
In pre-synaptic element there is the axon terminals which contain vesicles- transmitter diffuses across the synaptic cleft- synaptic delay (.5 of millisecond)
Postsynaptic density (Psd)- collection of proteins- scaffold proteins etc.
18
Q

What are the two actions of synapses?

A

Excitation

Inhibition

19
Q

What is excitation?

A

Depolarisation of the postsynaptic membrane, i.e. less negative
Excitatory postsynaptic potentials (EPSPs)

20
Q

How are action potentials generated?

A

Summation

21
Q

What are the two types of summation?

A

Spatial summation

Temporal summation

22
Q

What is spatial summation?

A

Several synapses generate EPSPs simultaneously

23
Q

What is temporal summation?

A

Same synapse generates EPSPs rapidly

24
Q

What is inhibition?

A

Hyperpolarisation of the postsynaptic membrane, i.e. more negative
Inhibitory postsynaptic potentials

25
Q

What are the locations of inhibitory and excitatory synapses?

A

Inhibitory synapses on the cell body and axon hillock

Excitatory synapses on the dendritic tree

26
Q

Where is presynaptic inhibition?

A

Spinal cord and brainstem

27
Q

Where are the inhibitory synapses on the axon terminals?

A

Axo-axonic synapses

28
Q

What effects Ca channels?

A

Reduce the amount of transmitter released from axon terminals

29
Q

What is electrical synapses?

A

Direct flow of current across a low resistance junction

30
Q

What is shown when you inject current into presynaptic neuron and record from target neuron?

A

Small voltages with same signs

Very short latencies- no synaptic delay

31
Q

How is electrical transmission shown by gap junctions?

A

Gap junctions do not have vesicles associated with them
Membranes are closely apposed but are separated by a small gap of 2-3nm
An array of tubes or connexons are responsible for communication

32
Q

What is the basis of the low resistance junction?

A

Connexons- responsible for communication

Large enough to allow charge power ions i.e. K+ ions

33
Q

What are the functions of electrical synapses?

A

No synaptic delay
Escape mechanisms
Synchronising neuronal activity

Physiology and Neuroscience (40 decks)

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