Intercellular (between) signaling

Question 1

Neurotransmitters either … or … neuronal activity of the postsynaptic neuron. (2)

Answer 1

1) Excitatory - opens channels positively charged ions onto the neuron and negatively charged ions out,increasing the potential and likelihood of firing.
2) Inhibitory - opens channels to negatively charged ions into the neuron and positively charged out, decreasing the potential and likelihood of firing.

Question 2

Fast-onset / Slow-onset signals (2)

Answer 2

1) Fast-onset - Initiate AP within Ms of occupying the receptor. Work by activating ion gates in the PS membrane (as above).
2) Slow-onset - known as neuromodulators, takes longer to produce effect, influence the effect of other neurotransmitters as well as the PS membrane directly.

Question 3

Large / small neurotransmitters (3)

Answer 3

1) The process of NT release is different between large and small.
2) Small - released through vesicles fusing with the presynaptic membrane due to calcium ions entering the neuron. ‘Pulses each time AP fires.
23 Large (neuropeptides) - no ‘pulse, gradually released in response to increased levels of intracellular calcium ions.

Question 4

Ionotropic/ metabotropic receptors

Answer 4

1) Neurotransmitter molecules binding to a postsynaptic receptor can have one of two effects:
2) Ionotropic - ion channels spring open immediately, leading to postsynaptic potential,
3) metabotropic - potential longer lasting and slower to develop. Effects PS potential through signal protein. 2 types: 1) G protein binds at ion channel (ether exciting or inhibiting) 2) a ‘second messenger’ is synthesized which effects neuron through the nucleus
4) Small molecule neurotransmitters activate either ionotropic or metabotropic receptors that act directly on ion channels.
5) large molecule neurotransmitters work via metabotropic receptors producing secondary messengers.

Question 5

What is a neurotransmitter? (5)

Answer 5

Criteria

a) chemical must be produced in the neuron;
b) when neuron stimulated chemical is released;
c) must then act on postsynaptic receptor to produce effect;
d) must then be deactivated; e) must have same effect if experimentally applied then when released by neuron.