2 - Synaptic transmission

Question 1

Dendrites receives stimuli using ligand gated ions channel(natural stimuli /
neurotransmitter).
In sensory neurons, they give _____________.

In motor neurons, they give ____________.

Answer 1

generator potential / receptor potential;

EPSP / IPSP

Question 2

Integration EPSP or IPSP / sensory neuron potential by spatial / temporal summation
> gives AP when above threshold.
What does the trigger zone contains?

Answer 2

High density of Voltage -gated Na+
channels

(Axon hillock = Anatomical name, function as trigger zone, for generation of AP)

Question 3

Chemical synapses only allow a ________ flow of information, and the diffusion of neurotransmitters across
the synaptic cleft gives rise to the __________ (~0.5 to several ms).

Answer 3

unidirectional;

synaptic delay

*Electric synapses = Unlike chemical synapses, electrical synapses are in most cases bidirectional;

Question 4

Docking of synaptic vesicles involves interaction between ____________ and the _______.

Answer 4

proteins in the synaptic vesicle membrane (vesicle-SNARE);

active zone
target-SNARE

Question 5

In the presence of high ______, these proteins alter their conformation such that the ____________ and ________ fuse, releasing neurotransmitter into the synaptic cleft.

Answer 5

[Ca2+]

membrane of the vesicle and the presynaptic terminal membrane

Question 6

The SNARE protein are cleaved by the botulinum toxins, which are selectively taken up at ___________.

Answer 6

peripheral cholinergic

nerve terminals

Question 7

What are the 2 types of axonal transport?
What is involved and what are the directions of transport respectively?

What substances are transported respectively?

Answer 7

Anterograde transport (kinesin) = away from cell body (NT, organelles, enzymes)

Retrograde transport (dynein) = toward cell body (growth factor, recycled vesicles)

Question 8

Uptake and degradation of NE
I. 50~80% reabsorbed and reused

II. Reabsorbed and degraded by ____________ in presynaptic terminalis

III. Diffused out into general circulation

IV. Uptake by ________

V. Degraded by the _________ at postsynaptic cell membrane

VI. Act on _________ at presynaptic membrane

Answer 8

II: monoamine oxidases

IV: astrocytes

V. Catechol-O-methyltransferases

VI. a2-adrenergic receptor

Question 9

What is convergence and divergence?

Answer 9

Convergence: allows input of signals from multiple
sources;

divergence: allows signals from one neuron to be
distributed

Question 10

Which of the followings about graded potential is correct?
A. Graded potentials are decremental

B. They are graded according to the strength of the stimulus

C. They can cause both depolarization and hyperpolarization (EPSP vs IPSP)

Answer 10

All

A: can be summative

Question 11

What are the 2 types of summative graded potential?

Briefly describe them.

Answer 11

Temporal = increasing frequency of AP arrival from 1 presynaptic fibre and added together

Spatial = Several AP received from different sources are added together

Question 12

What are the 2 types of synaptic modulation?

Give examples of each synaptic modulation and state the effect of them.

Answer 12

1. Presynaptic modulation
   - e.g. inhibitory neuron on the presynaptic neuron terminal
   - affects the AP formation and thus exocytosis of NT

• more selective effect as the control is over one axon terminal only

2. Postsynaptic modulation
   - e.g inhibitory neuron modulates the signal (EPSP/IPSP)
   - affects the graded potential and the ability to cause an AP
   - Modulated signal below threshold > no AP initiated at trigger zone
   - All targets will be inhibited equally