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Flashcards in Board 6 Deck (21)
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1
Q

What are the two broad classes of synapses?

A

chemical and electrical

2
Q

What feature clearly allows you to identify the pre-synaptic cell in an electron micrograph?

A

vesicles in the pre-synaptic cleft

3
Q

By which mechanism is neurotransmitters released from an axon terminal?

A

exocytosis

4
Q

What happens to the membrane potential of a postsynaptic cell when an excitatory neurotransmitter binds to its receptors on the postsynaptic cell?

A

excitatory post-synaptic potentials are elicited by stimuli of increasing strenght. once the critical firing level is achieved the action potential is initiated

5
Q

What happens to the membrane potential of a postsynaptic cell when an inhibitory neurotransmitter binds to its receptors on the postsynaptic cell?

A

the membrane potential is driven away from the critical firing level. the increasing stimulus strengths, and as the stimulus strength increases, so does the amplitude of the IPSP

6
Q

What type of image does the confocal laser scanning microscope allow you to produce?

A

three-dimensional structures can be re-constucted from the obtained images

7
Q

Which class of synapse is predominant in mammals?

A

chemical synapses

8
Q

how do nerve cells communicate with each other?

A

at specialised junctions known as synapses

9
Q

what forms the synapses?

A

the axon terminals of one neuron and dendrites or cell bodies of another neuron.

10
Q

what is a chemical synapse?

A

where the action potential triggers the opening of calcium-sensitive channels

11
Q

what does the binding of the neurotransmitter to receptors on the post-synaptic cell (after being released from pre-synaptic cell) cause?

A

changes in membrane potential

12
Q

what is characteristic of the chemical synapse?

A

there is a delay of 0.5 milliseconds between the arrival of the impulse at the pre-synaptic terminal and the detection of a post-synaptic potential change

13
Q

what is an electrical synapse?

A

where current flows directly from the presynaptic to the post-synaptic neuron via gap junctions

14
Q

is there a delay in electrical synapses?

A

no

15
Q

are electrical synapses common in mammals?

A

no - but there are examples in the retina of the eye and during development of the nervous system

16
Q

how can a tissue be optically sectioned?

A

using immunocytochemistry combined with confocal microscopy

17
Q

what does immunocytochemistry allow?

A

locate terminals containing particular transmitters precisely

18
Q

what should be used to confirm the presence of an active synapse?

A

Transmission Electron Microscopy (TEM) or electrical recording from the cells

19
Q

which technique is the only one that allows us to view synapses?

A

electron microscope - resolution of light microscope is not sufficient

20
Q

events at the synapse

A
  1. action potential depolarises the axon terminal
  2. the depolarisation opens voltage-gated Ca2+ channels and Ca2+ enters the cell
  3. Calcium entry triggers exocytosis of synaptic vesicle contents
  4. neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell
21
Q

what two subsequent stages can be added to the events at the synapse?

A
  1. excess transmitter is removed by enzyme action, reuptake or diffusion
  2. vesicle membrane is recycled