Structural Forms and Function

Question 1

Compare axons and dendrites

Answer 1

Dendrites tend to be thicker than axons in an individual neuron. Dendrites have spines. Molecular makeup is different as they express different cytoskeletal proteins. Both are electrically active but in different ways due to their structure.

Question 2

How are neurons classified?

Answer 2

Excitatory/Inhibitory, number of neurone extensions, stellate/non-stellate cells, communication distance

Question 3

Name common excitatory cells (glutamatergic)

Answer 3

Pyramidal cells and Stellate spiny neurons.

Question 4

Name common inhibitory cells (GABAergic)

Answer 4

Purkinje cell, thalamic reticular cell, medium spiny neurons

Question 5

What determines whether a neuron is excitatory or inhibitory?

Answer 5

The neurotransmitter they release

Question 6

Classification of a neuron due to its neurite extensions

Answer 6

Multipolar neuron has multiple extensions (dendrites) emerging from the cell body as its main function= integration.

Question 7

Classification of stellate/non-stellate cells

Answer 7

Stellate cells have a central body and huge numbers of dendrites emerging from all directions. Role of stellate= integration.

Question 8

Common stellate cells

Answer 8

Large reticular formation, inferior olivary nucleus neuron, cell of thalamic nucleus

Question 9

Describe pyramidal cells

Answer 9

Main excitatory drivers in the cortex. Cell bodies found in layers 3 and 5. Their apical dendrite comes out the top of the cell and stretched from layer 5 up to the cortical surface. All along the apical dendrite are synapses.

Question 10

Why is the apical dendrite of a pyramidal cell long?

Answer 10

Different regions of the dendrites can receive separate inputs from parallel fibres running through the cortex. This allows a single cell to pick up information from different regions of the brain and integrate it together.

Question 11

What do stellate cells do in relation to cortical pyramidal cells?

Answer 11

These cells are often inhibitory, they modulate the information coming in as inhibitory interneurons. E.g. it can prevent info from above it reaching the pyramidal cell body. Different sets of stellate cells in different regions of the apical dendrite can regulate how much info is coming down to soma and where it’s coming from.

Question 12

Name the 2 ways to classify a neuron due to communication distance

Answer 12

Projection neurons and local circuit neurons

Question 13

Projection neurons

Answer 13

Neurons with long axons that extend from one part of the brain to another. E.g. pyramidal cells in the cortex; other cell types in sub-cortical grey matter.

Question 14

Local circuit neurons

Answer 14

Neurons with short axons that don’t extend beyond the vicinity of the cell body. E.g. Stellate cells in the cortex and sub-cortical regions.

Question 15

What is retrograde neuronal tracing?

Answer 15

A technique that allows you to see cell bodies from where the dye has been injected, thereby showing the network of neurons in the brain.

Question 16

Steps of retrograde neuronal tracing

Answer 16

1- inject dye at axonal arbour. 2- dye is transported along axon in retrograde direction. 3- soma is stained.