Synaptic signalling Flashcards Preview

Foundations of Neuroscience > Synaptic signalling > Flashcards

Flashcards in Synaptic signalling Deck (28):
1

What is the postsynaptic density?

Where the membrane appears thicker and receptors are located

2

What is the presynaptic active zone?

Where vesicles fuse, can be seen down a microscope

3

What is a Grays type I synapse

Asymmetrical
Has thicker postsynaptic density
Usually excitatory
e.g. glutamate

4

What is a Grays type II synapse

Symmetrical
Thickness is equal
Usually inhibitory
e.g. glycine or GABA

5

What is an axodendritic synapse?

Synapse onto dendrite of neurone

6

What is an axosomatic synapse?

Synapse onto soma of neurone

7

What is an axoaxonic synapse?

Synapse onto an axon of the neurone

8

Why is the point of synaptic contact important?

Closer to axon hillock = greater influence on action potential generation
Inhibitory synapses are often on soma or axon hillock
This is the best position to control neuron activity

9

Are axodendritic synapses effective?

No
Input may not spread down dendrite to reach soma or axon hillock
Yes
Could amplify excitatory input
Increasing likelihood of action potential at axon hillock

10

What happens if the dendrite has no channels?

Passive spread of depolarisation
Large input required

11

How many synapses does a typical neuron have?

1000-10,000

12

What is synaptic integration of information?

The integration of multiple synaptic inputs

13

What does SEPSP stand for?

A small excitatory post synaptic potential

14

What is an SEPSP?

A small excitatory post synaptic potential is a small change in Em, smaller than threshold value

15

Why will multiple synaptic inputs trigger an action potential?

Combined size of SEPSP will be greater than threshold

16

What is spatial summation?

Summing of post synaptic potentials generated at separate synapses

17

What is an SIPSP?

A small inhibitory post synaptic potential

18

When are EPSPs most effective?

When they coincide

19

How can one EPSP trigger an action potential in the post synaptic neurone?

Synaptic input at a high frequency

20

What is temporal summation?

Summing of post synaptic potentials generated at same synapse, if they occur in rapid succession

21

Outline neuronal communication

Receive messages from connected neurones
Integrate all inputs
Send a frequency-encoded message

22

What is the purpose of frequency coding?

Action potentials are all-or-nothing
Can't differ in amplitude
Communication therefor via frequency

23

Frequency of action potential firing is directly related to...

...the intensity of the stimulus

24

Signalling is described as being...

...frequency-modulated

25

What happens when a stimulus is at threshold?

Just strong enough to trigger an action potential

26

What happens when a stimulus is at sustained threshold level?

A 2nd action potential fires
This is delayed
Time taken = sum of absolute refractory period and relative refractory period

27

What happens with a supra-threshold stimulus?

Multiple action potentials fire
An action potential fires in relative refractory period
Only absolute refractory period limits action potentials firing

28

How frequently can action potentials fire?

200-300 times a second