Neuronal Cells (Part 1 & 2)

Question 1

What are the two main types of cells in the brain?

Answer 1

Neurones and glial cells

Question 2

Roughly how many neurones are in the adult human brain?

Answer 2

10^11 (100 billion)

Question 3

Roughly how many glial cells are in the adult human brain?

Answer 3

10^12 (1 trillion)

Question 4

What is the simplified function of a neurone?

Answer 4

Cell signalling/communication

Question 5

What is a simple description of the function of a glial cell?

Answer 5

Maintains ideal environment for optimal neuronal signalling

Question 6

Is it true that humans are born with all their adult brain cells?

Answer 6

Yes, except for neurogenesis (which hardly produces any)

Question 7

What did Schleiden and Schwann propose in 1838?

Answer 7

That the nucleated cell is the fundamental unit of structure and function
(As animals become bigger there are more cells, rather than the cells becoming bigger)

Question 8

1mm^3 of cortex contains 100,000 neurones, 100,000,000 synapses and 4km of axon. Why is this significant in regards to the function of a brain?

Answer 8

Neurones are very small so you can pack many of them into a small area.

This results in transmission of lots of information, which is important for the function of a brain.

Question 9

What are the four regions of a neurone?

Answer 9

Dendritic field
Cell body (soma)
Axon
Pre-synaptic region/terminal

Question 10

What is the general direction of travel of information in a neurone?

Answer 10

Dendritic field receives synaptic info
Feeds into Soma
Axon emanates from soma and terminates in Pre-Synaptic region
Pre-Synaptic region impinges on dendritic field of another neurone and cycle continues

Question 11

What is back propagation

Answer 11

Where the direction of travel in a neurone is backwards, from the cell body up to the dendrites

Question 12

What is the approximate length of the diameter of a dendrite?

Answer 12

< 1 micron

Question 13

Briefly describe the structure and function of a dendrite

Answer 13

Function
Neurotransmitters bind from previous neurone to receptors and signal is transformed to electrical energy that is transmitted to cell body for integration and processing

Structure
A number of receptors on the surface of the membrane which are specific according to the neurotransmitter released from pre-synaptic region of previous neurone
Ion channels in its membrane

Question 14

Briefly describe the structure and function of a soma

Answer 14

Portion of cell which surroundings nucleus (containing mRNA).
Contains most of the endoplasmic reticulum (calcium storage) and Golgi apparatus (translation / transcription)

Ensures healthy environment 
Synthesises proteins (eg ion channels)
Integrated synaptic function

Question 15

How do ion channels made in the soma end up in the right place in the membrane?

Answer 15

They are transported along axon via molecular motors in the cytoskeleton

Question 16

How is the cytoskeleton in a neurone different to other cells?

Answer 16

Contains neuro filament which is exclusive to neurones.

This may be used to identify neuronal structures.

Question 17

Briefly describe the structure and function of an axon

Answer 17

Transmits neurone signals in the form of an action potential

Can be over a meter long depending on location and location.
Only 1-20 microns in diameter
Can contain 1000x more cytoplasm than the soma
May be myelinated

Question 18

Briefly describe the structure and function the the pre-synaptic terminal

Answer 18

Rapid conversion of electrical to chemical signals (synaptic transmission)

A single neurone may have thousands of pre-synaptic terminals, meaning it can communicate with many other neurones

Question 19

Define synaptic transmission

Answer 19

The rapid conversion of an electrical signal (action potential) to a chemical signal (neurotransmitter)

Question 20

Why is it easier to trace a neuronal signal in an organism such as C. elegans than it is in a human?

Answer 20

C elegans only have 308 neurones in total, humans have millions
Neurones in humans therefore produce much more complex patterns of connections and are much more difficult to trace as a result

Question 21

Define divergence

Answer 21

where one neurone can impinge a signal upon thousands of other neurones

Question 22

Define convergence

Answer 22

Where each neurone can receive inputs from thousands of other neurones