Lecture 2 - cells of the nervous system

Question 1

What are the 2 types of cells in the nervous system?

Answer 1

• Neurons
• Glia

Question 2

What are neurons?

Answer 2

excitable cells that conduct impulses

Question 3

What are the purpose of neurons?

Answer 3

integrate & relay information within a neural circuit

Question 4

What are glia cells?

Answer 4

supporting cells - the ‘glue’

Question 5

What is the purpose of glia cells?

Answer 5

maintain homeostasis, protection, assist neural function - assist in rapid transmission

Question 6

How many neurons and glia cells are there?

Answer 6

85 billion of each cell type

Question 7

What are neurons & glia cells both?

Answer 7

part of the neural circuits that make up the neural system

Question 8

What does Nissl staining do?

Answer 8

• allows us to distinguish between neurons & glia
• nucleolus of all cells stained - this is because staining binds to negatively-charged molecules (RNA in the nucleolus)

Question 9

Do neurons have Nissl bodies?

Answer 9

Yes, as well as a stained nucleolus

Question 10

Do glia have Nissl bodies?

Answer 10

No, but they do have a stained nucleolus

Question 11

How large are cell bodies?

Answer 11

Up to 50um

Question 12

What is the purpose of Nissl staining?

Answer 12

allows visualisation of variation in size, density & distribution of neurons

Question 13

What is the soma?

Answer 13

cell body (perikaryon)

Question 14

What organelles are used for protein synthesis & processing?

Answer 14

• ribosomes
• rough ER
• Golgi apparatus

Question 14

What is the function of mitochondria in neurons?

Answer 14

found in high quantity used by neurons to affect membrane potential

Question 15

What are the 4 compartments of the neurons?

Answer 15

1. Cell body, soma, perikaryon
2. Dendrites
3. Axons
4. Presynaptic terminal

Question 16

What are the neurites?

Answer 16

term for any process coming off neuronal body:
- dendrites
- axons

Question 17

What is the Golgi (Camillo) stain?

Answer 17

this stain showed that neurones are more than just cell bodies, however doesn’t pick up all neurones

• silver chromate
• small%

Question 18

Who used the golgi stain?

Answer 18

Santiago Ramon y Cajal - used Golgi stain and did drawings of the brain of different neurons.

Question 19

What doesn’t the Golgi stain show?

Answer 19

synaptic terminal

Question 20

Describe the cytoskeleton of a neuron

Answer 20

Microtubules - longitudinally down neurites & a hollow tube composed of polymers of tubulin

Question 21

What is the axon hillock?

Answer 21

where the cell body transitions into the axon

Question 22

What is the axon initial segment?

Answer 22

important for generation of action potentials (specialised area for action potentials)

Question 23

What are axon collaterals?

Answer 23

(branches - often at right angles) - each collateral ends with a terminal

Question 24

Describe the features of an axon

Answer 24

• no rough ER or free ribosomes (which is why it doesn’t appear when stained)
• membrane composition is different - important in transmission of action potentials, as well as ensuring unidirectional flow of action potential
• 1<mm>1m</mm>
• 1um - 25um diameter (width)
• inter neurons - small neurons

Question 25

Why are there a lot of voltage-gated sodium channels in the AIS - axon initial segment?

Answer 25

as they are needed for action potential generation

Question 26

How can we use immunohistochemistry to observe the axon initial segment?

Answer 26

primary antibodies can be used to locate sodium channels, by attaching to them. Fluorescent secondary antibodies can then be used to show where sodium channels are located

Question 27

What is immunohistochemistry?

Answer 27

specific primary antibodies & fluorescent secondary antibodies

Question 28

What do axons look like?

Answer 28

• may be myelinated
• axons may have many collateral = high levels of divergence

Question 29

What are uses of collaterals?

Answer 29

the spreading of signals further and wider

Question 30

How is the terminal cytoplasm specialised?

Answer 30

• no microtubules
• synaptic vesicles
• specialised proteins
• mitochondria - high levels of energy-requiring processes

Question 31

What do presynaptic terminals look like?

Answer 31

• collaterals can have their own terminals
• axons may have a terminal along their axon (boutons en passent)

Question 32

Describe axoplasmic transport

Answer 32

• fast axoplasmic transport
• radioactive amino acids
• 1000mm per day
• microtubules, kinesin & ATP
• anterograde by dynein

Question 33

What does Kinesin do?

Answer 33

carries vesicles down to the presynaptic terminal (ATP-requiring)

Question 34

What is anterograde?

Answer 34

forward movement from the cell body to the terminal

Question 35

What type of movement does dyenin use?

Answer 35

retrograde (opposite of anterograde)

Question 36

How can you manipulate axoplasmic transport to visualise cells?

Answer 36

anterograde or retrograde labelling

Question 37

What do dendritic branches together form?

Answer 37

dendritic trees (dendritic arbors)

Question 38

Why is it useful that one cell body can have many dendrites?

Answer 38

integration of information from thousands of synapses into 1 cell body (can have thousands of synapses)

Question 39

What can abnormalities in dendritic spines lead to?

Answer 39

cognitive impairment

Question 40

Why is it useful that dendritic spines are plastic (dynamic)?

Answer 40

may be lost due to lack of activity or grow due to high levels of activity