Paul Felts

Question 1

Define the components of the central nervous system

Answer 1

1. Brain
2. Spinal cord

Question 2

What makes up the brainstem?

Answer 2

1. Midbrain
2. Pons
3. Medulla oblongata

Question 3

What are the principal cells of the CNS?

Answer 3

1. Neurons
   
   • multipolar (motor)
   • unipolar (sensory)
2. Glial cells
   
   • astrocytes
   • oligodendrocytes
   • microglia
   • ependymal cells

Question 4

Describe neurons

Answer 4

“communicators”

• they receive information mostly from synapses, integrate the information, and then transmit electrical impulses to another neuron or effector cell
• most are multipolar meaning they have 2/> dendrites and one cell body

Question 5

Can you list some “atypical” neurons found in the body?

Answer 5

• amacrine cell of retina
• tract cell of spinal gray matter
• motor neuron in spine
• primary sensory neurone of spinal ganglia
• principal neurone of sympathetic ganglia
• golgi type II interneuron

Question 6

Discuss glial cells

Answer 6

“glial” means “glue” in Greek

There’s no connective tissue in the brain (except for a small amount coming in with larger blood vessels) so a major role of glial cells is structural integrity

However, our understanding of them has developed since first discovering them and there are 4 different types of glial cells each with their own important role:

1. Astrocytes
2. Oligodendrocytes
3. Microglia
4. Ependymal cells

Question 7

What are astrocytes?

Answer 7

*type of glial cell*

• numerous processes
  
  • (often star shaped hence the name)
• maintenance of blood-brain barrier
• environmental homeostasis

Question 8

What cell type is this and which of its functions can it be seen doing?

Answer 8

Astrocyte

• the white circle is a capillary lumen
• a process can be seen coming from the astrocyte which surrounds the capillary
• it is maintaining the blood-brain barrier

Question 9

What is the role of oligodendrocytes?

Answer 9

Produce myelin in the CNS

_(_not the PNS)

• they have numerous branches that extend to produce internodes of myelin around different axons
  
  • they wrap layer upon layer of cell membrane around the axon
• AP can jump from one node of ranvier to the next
  
  • think of myelination as electrical insulation

Question 10

What important feature of which important cell is shown here?

Answer 10

A myelinated neuron

Node of Ranvier is pointed out

Question 11

What is the role played by microglia?

Answer 11

Immune monitoring and antigen presentation

• cells of similar lineage to macrophages
  
  • i.e. haemopoietic origin
• they move to CNS during development and stay there; they don’t traffic in and out
  
  • in a resting state they have an elongated nucleus and a number of spiny short cell processes
  • when activated (for example by a bacterial infection) the processes withdraw and the microglia take on an appearance more similar to macrophages

(photo shows them in resting state)

Question 12

What are the ependymal cells?

Answer 12

Ciliated columnar/cuboidal epithelial cells that line the ventricles

NB: these cells do not normally form a blood brain barrier in the CNS

Question 13

What cell types are labelled here?

What is the lighter blue bit in the top half of the image?

Answer 13

Question 14

Which is there more of in the CNS?

Glial cells

or

neurons?

Answer 14

Different parts of the CNS will have different ratios of these cells types

but

overall, there are more glial cells than neurons