Introduction to Neurons

Question 1

What are neurons

Answer 1

The principle building blocks and instruments of communication of the CNS and PNS.

Question 2

Communication in PNS and CNS

Answer 2

Both components of the nervous system form complex communication networks that allow an organism to interact in appropriate ways with its internal (contents of the body) and external (world outside the body) environments.

Question 3

Label 1-4 (going down)

Answer 3

• dendrites
• cell body
• axon
• axon terminal

Question 4

Function of dendrites

Answer 4

Receives electrical input

Question 5

Function of the cell body

Answer 5

Passively conducts electrical input

Question 6

Function of the axon

Answer 6

Propagates action potentials

Question 7

Function of the axon terminal

Answer 7

Releases chemical signals

Question 8

What is the resting membrane potential (RMP)

Answer 8

The voltage across the cell membrane which can exhibit relatively large changes during various states of cell activity in neurons (and muscle fibres).

Question 9

What is the range of voltage within the cell

Answer 9

Voltage can range between -100 and +50mV.

Question 10

What is the RMP voltage

Answer 10

Refers to voltage at rest (i.e in the absence of synaptic potentials and action potentials) and its value is usually between -50 and -70mV.

Question 11

How can the RMP be measured

Answer 11

With intracellular microelectrodes and with patch-clamping pipettes (the patch-clamp technique).

Question 12

What generates the RMP

Answer 12

Electrical potential difference (50-70mV) across cell membrane which results from a separation of charge. There is more negative charge inside the cell in comparison to the extracellular fluid.

Answer 13

1. Unequal concentrations of Na+ and K+ inside and outside the cell - electrochemical gradients during the movement of these ions.
2. Unequal permeability of cell membrane to these ions

Question 14

Why are there more negative charges inside the cell in comparison to the extracellular fluid

Answer 14

1. Unequal concentrations of Na+ and K+ inside and outside the cell - electrochemical gradients during the movement of these ions.
2. Unequal permeability of cell membrane to these ions

Question 15

What are the relative concentrations of K+ and Na+ inside and outisde the cell

Answer 15

K+ concentration always higher inside then outosde.
Na+ concentration always higher outside.

Question 16

How are the concentration gradients of K+ and Na+ maintained

Answer 16

By the Na+/K+ pump. At a ratio of 3 Na+ out and 2 K+ in.

Question 17

What are the two main types of ion channels in neurons

Answer 17

Non-gated (leak) channels and gated cannels

Question 18

Type of ion channel in neuron

What are non-gated (leak) channels

Answer 18

Channels which are open ar rest (on-off state) which allows for the diffusion of ions.

Question 19

Type of ion channel in neuron

What are gated channels

Answer 19

Can be voltage gated, ligand gated or mechanically gated which are closed at rest.

Question 20

What is the concept of the ‘equilibrium potential’ for one ion type is

Answer 20

An intracellular potential at which the net flow is zero according to its electrochemical gradient.

Question 21

eq

How can the equilibrium potential be calculated

Answer 21

Nernst equation

Question 22

When only can the Nernst equation apply to a situation

Answer 22

Where a cell membrane is permeable only to one ion.

Question 23

The higher the permeability of the cell membrane…

Answer 23

The more this ion shifts the RMP toawards its own equlibrium position.

Question 24

Are neurons is the RMP less negative than Ek and why

Answer 24

Smal contribution of Na+ leak channels