Neural conduction and synaptic transmission

Question 1

What is the resting membrane potential of a neuron

Answer 1

• 70 mv

Question 2

What are the two processes that establish the resting membrane potential?

Answer 2

An active process and passive process

Question 3

Describe the cell membrane at rest in the passive process

Answer 3

Largely impermeable to many ions except from K+. Other ions can cross the membrane via specialised channels that open under some circumstances

Question 4

How is a membrane potential established in the passive process?

Answer 4

Through the selective diffusion of K+

Question 5

What is the initial first stage of the passive process?

Answer 5

K+ flows down the chemical gradients from high concentration to a low concentration (comp 1 to comp 2)

Question 6

What is the result of K+ leaving compartment 1? PP

Answer 6

Produces an electrical current

Question 7

What does the production of the electrical current result in? PP

Answer 7

A separation of charge - solutions are no longer neutral. +ve charge in comp 2 and -ve charge in comp 1

Question 8

What does the separation of charge lead to? PP

Answer 8

A potential difference/membrane potential

Question 9

How does the system reach equilibrium? PP

Answer 9

Eventually, the number of K+ ions moving down the chemical gradient balances the number of ions moving down the electrical gradient

Question 10

What is the mechanism used inn the active process?

Answer 10

Sodium potassium pump

Question 11

What is the role of the active process to establish the resting potential?

Answer 11

To transport Na+ out of the neuron and K+ in

Question 12

What is the ratio of Na+:K?

Answer 12

Three Na for every two K

Question 13

What is the energy supplied by for the active process?

Answer 13

ATP

Question 14

What is depolarisation?

Answer 14

When the membrane potential is made less negative

Question 15

What is hyperpolarisation?

Answer 15

When the membrane potential is made more negative

Question 16

What do the channels in the neurons do and when do they open?

Answer 16

They allow the passage of certain ions across the membrane and open when the cell is depolarised

Question 17

What is the potential when the cell is depolarised to threshold?

Answer 17

-60mV

Question 18

What happens when the cell membrane is depolarised to the threshold?

Answer 18

The Na+ channels open and polarity reverses to +30 inside. At this point voltage gated Na+channel closes and K+ opens, which restores the membrane potential.

Question 19

How do action potentials travel down the axon?

Answer 19

The influx of sodium ions creates enough positivity for an action potential on the next part of the membrane

Question 20

How is this process sped up by myelin?

Answer 20

The myelin allows the action potential to jump from node to node, rather than travelling the entire length of the nerve fibre.

Question 21

What is a synapse

Answer 21

A point of specialised contact between two neurons

Question 22

What is the structure of a synapse?

Answer 22

1)presynaptic element
2) synaptic cleft
3) Postsynaptic element

Question 23

What is the most important feature of the presynaptic element?

Answer 23

The vesicles which contain neurotransmitters.

Question 24

What could the postsynaptic element be?

Answer 24

A dendrite, a cell body, a terminal bouton

Question 25

What is an action potential

Answer 25

Wave of depolarisation

Question 26

What happens when the action potential reaches the presynaptic element?

Answer 26

The calcium channels are opened

Question 27

What happens when the calcium channels are opened?

Answer 27

This allows for the binding of the vesicles to the presynaptic membrane, allowing them to open and neurotransmitters diffuse into the synaptic cleft.

Question 28

What is the most important feature of the post synaptic element?

Answer 28

Receptors for the neurotransmitters. Once unlocked, the neurotransmitters open channels inside the cell

Question 29

What happens when these channels are opened inside the cell?

Answer 29

Allows certain ions to flow through them. The flow of the charged ions through channels opened by these NTa produce the effects of these substances on the post-synaptic cell.

Question 30

What are ionotropic receptors

Answer 30

Receptors made of usually 5 subunits

Question 31

What are metabotropic receptors

Answer 31

Receptors indirectly associated with an ion channel

Question 32

What happens when the neurotransmitters bind on the post synaptic element?

Answer 32

The opening of ion channels

Question 33

What is produced when NTs bind to receptors?

Answer 33

Excitatory or inhibitory post synaptic potentials

Question 34

What is an excitatory postsynaptic potential?

Answer 34

Makes the cell more likely to fire an action potential

Question 35

What is an inhibitory postsynaptic potential?

Answer 35

Makes the cell less likely to fire an action potential