Chemical Neural Signalling

Question 1

What is the cause of the maximum for the firing rate of a neuron?

Answer 1

Duration of the refractory period

Question 2

Ion associate with hyperpolarization at the dendrite (IPSP)

Answer 2

Cl- and K+ (also a way of polarizing a cell)

Question 3

What is an example of endogenous ligand?

Answer 3

Acetyl choline

Question 4

Is acetyl choline an excitatory or inhibitory neurotransmitter?

Answer 4

Depends on the receiver

Question 5

Characteristics of electrical synapses

Answer 5

• Flows between cells (an action potential will continue)
• Faster than chemical one (no delay) -> electrical speed (instant)
• Used for synchronisation
• Bi-directional -> 2 direction of flow

Question 6

Characteristics of chemical synapses

Answer 6

• Active (new potential is created)
• One direction -> from a cell to the other
• Slow (1 ms delay)
• Used for integration and computation

Question 7

Which element flow into the cell at the end of the axon?

Answer 7

Ca 2+ (calcium) flow into the cells (because outside concentration is bigger) and release the content of vesicles, neurotransmitters.

Question 8

Different types of neurotransmitters

Answer 8

• Serotonin
• Glutamate
• Gaba
• Acetyl choline
• Dopamine

Question 9

Postsynaptic receptors

Answer 9

channel that open when a particular neurotransmitter binds the receptor -> Na+ can enter the cell and, if sodium enter the cell, we add positivity and the cell get depolarised. This channels are located in the postsynaptic membrane.

Question 10

2 type of receptors

Answer 10

• metabotropic receptor
• ionotropic receptor

Question 11

Metabotropic receptor

Answer 11

somewhere else in the cells an axion channel opens up (g protein-coupled receptors). They are slower and used slow process that larger one

Question 12

Ionotropic receptor

Answer 12

ligand-gated ion channel. They are faster (change immediately).

Question 13

Type of channels

Answer 13

1) Non gated -> always open (resting potential of the cell)
2) Voltage-gated -> they can open
3) Mechanosensitive -> sensitive to movement

Question 14

EPSP (excitatory postsynaptic potential)

Answer 14

increase likelihood of action potential. It pushes the postsynaptic cell a little closer to the threshold for an action potential.

Question 15

IPSP (inhibitory postsynaptic potential)

Answer 15

decrease the likelihood of action potential. It results from the opening of channels that permit chloride ions (Cl-) to enter the cell. These ions are much more concentrated outside the cell than inside -> they make the cell more negative.

Question 16

Spatial summation

Answer 16

sums input from different synapses that overlaps in time. Sums the inputs from different places at the same time

Question 17

Temporal summation

Answer 17

sums input from one synapse that overlaps in time. In this case post-synaptic potential is being sum -> they last longer and they can create action potential (too fast)

Question 18

The prompt cessation of transmitter effects is achieved in one of two ways

Answer 18

• Degradation: transmitter can be rapidly broken down and thus inactivated by a special enzyme, a process known as degradation
• Reuptake: transmitter molecules may be rapidly cleared from the synaptic cleft by being taken up into the presynaptic terminal. In this case special receptors for the transmitter called transporters are located on the presynaptic axon terminal and bring the transmitter back inside.

Question 19

Convergence

Answer 19

information flow from a lot of sources come to one cell -> different sources of information together

Question 20

Divergence

Answer 20

information flow into different outputs