2 - Cells of the nervous system

Question 1

What is a neurone?

Answer 1

• Basic structural and functional unit of the nervous system.
• Information processing unit.
• Responsible for the generation and conduction of electrical signals.
• Communicate with one another via chemicals released at the synapse.

Question 2

What are neurones supported by?

Answer 2

Supported by neuroglia, comprising several different cell types.
Neuroglia outnumber neurons by approx 9:1.

Question 3

What is the basic neuronal structure?

Answer 3

Cell body (soma)
Dendrites
Axon
Terminals
Neuronal cytoskeleton

Question 4

What is the cell body (soma)?

What organelles does it contain?

Answer 4

• Metabolic centre of the cell
• Large nucleus with prominent nucleolus
• Big rough ER
• Lots of mitochondria and lysosomes
• Highly organised cytoskeleton
• Highly organised metabolically active cell.

Question 5

What are dendrites and what is their function?

Answer 5

• Major area of reception of incoming information
• Spread from the cell body and branch frequently
• Increase the surface area of the neurone
• Dendritic spines receive majority of synapses
• Large pyramidal neurons may have as many as 30,000/40,000 spines

Question 6

What is the axon and what is it’s function?

Answer 6

• Conducts impulses away from the cell body
• Emerges as the axon hillock
• Action potential generated at hillock
• Usually only 1 axon per cell but can branch extensively
• Microtubules and neurofilaments are prominent
  myelinated or unmyelinated – axon membrane exposed only at nodes of Ranvier.

Question 7

What are axon terminals?

Answer 7

• Close to the target the axon forms a number of terminal branches (terminal arbor).
• Specialised structures called synaptic terminals.
• Boutons or varicosities

Question 8

What is the function of the neuronal cytoskeleton?

Answer 8

• Highly organised cytoskeleton is required
• Neurofilaments play a critical role in determining axon caliber
• Microtubules are very abundant in the nervous system

Question 9

What is the difference between a bouton and varicosities?

Answer 9

Boutons are the end of the axon terminal that is a big bulge which synapses.
A varicosity is an axon terminal that spreads across something (smooth muscle) with lots of bulges.