Neurons and glia

Question 1

Which are excitable cells, neurons or glia?

Answer 1

Neurons.

Question 2

Which cells send signals over long distances, neurons or glia?

Answer 2

Neurons.

Question 3

Which cells are slower in sending signals, neurons or glia?

Answer 3

Glia.

Question 4

Which cells use Ca2+, neurons or glia?

Answer 4

Glia.

Question 5

What kind of communication do glial cells have?

Answer 5

Localised.

Question 6

Glial cells have syncytial networks. What does this mean?

Answer 6

A multi-nucleate mass of cytoplasm that is not organised into distinct cells.

Question 7

Neurons communicate via gap junctions and glial cells communicate over synapses. True or false?

Answer 7

False - neurons have synapses and glial cells have gap junctions.

Question 8

Which type of nerve cell composes 90% of the CNS, neurons or glia?

Answer 8

Glial cells.

Question 9

Astroglia are a type of glial cell. What do they do?

Answer 9

They are attached to the vasculature and help to regulate homeostasis, e.g. regulate diameter of blood vessels.

Question 10

Oligodendrocytes are a type of glial cell. What do they do?

Answer 10

Produce myelin for more rapid conduction.

Question 11

Microglia are types of glial cell. What do they do?

Answer 11

They are phagocytic and converge at sites of injury.

Question 12

Ependymal cells are types of glial cell. What do they do?

Answer 12

They are epithelial cells that produce CSF.

Question 13

Neuroglia are types of glial cell. What do they do?

Answer 13

The provide ‘glue’ for physical support.

Question 14

Define an EEG.

Answer 14

Electroencephalogram: picks up electrical impulses on the scalp, usually performed on the forehead.

Question 15

Define an ECoG.

Answer 15

Electrocorticogram: electrodes are placed on an exposed area of brain and records impulses in the cerebral cortex. This is usually done through the top of the skull.

Question 16

Define LFP.

Answer 16

Local field potential: looks at the summed electrical potential of multiple neurons in a section of tissue.

Question 17

How is LFP measured?

Answer 17

Sheets covered in small spikes are inserted into the back of the brain.

Question 18

LFP is a technique that is said to ‘listen to the brain’. What does this mean?

Answer 18

Electrical impulses detected are represented as spikes on a graph, and these can be transformed into sounds.

Question 19

What is neuroprosthetics?

Answer 19

Whereby living nerves are used to operate prosthetic limbs.

Question 20

What do neuroprosthetics work?

Answer 20

The severed nerves of the patient and nerves in the motor cortex are attached to the limb. The patient thinks about using their limb as they normally would.

Question 21

What is ‘intended limb function’?

Answer 21

Electrical impulses recorded in the brain when the subject imagines an action are decoded into signals the NMP (neuromotor prosthesis) can interpret and thus execute the desired movement.

Question 22

What are the 3 major components a neuroprosthesis requires?

Answer 22

1. A sensor to detect neuronal activity
2. A decoder
3. A computer in order to engage effectors

Question 23

What is an action potential (AP)?

Answer 23

A self-propagating wave of electrical activity

Question 24

Give the 4 main stages of an action potential.

Answer 24

1. Rest: the membrane is negative
2. Depolarisation: the Na+ channels open and an influx of Na+ makes the inner axon positive
3. Repolarisation: Na+ channels close, K+ channels open, axon becomes negative again
4. Hyperpolarisation: axon has lost too much K+ and become too negative, Na+/K+ pump actively pumps 2K in and 3Na out to re-establish resting potential.

Question 25

What is a threshold value?

Answer 25

Action potentials are only ever generated when stimulation is above a certain threshold level, i.e. the minimum amount of energy required to open the Na+ channels.

Question 26

APs follow an ‘all or nothing’ law. True or false?

Answer 26

True.

Question 27

APs vary in size depending on the size of the stimulus. True or false?

Answer 27

False - APs are always the same size regardless of stimulus size.

Question 28

What conveys information about the size of a stimulus?

Answer 28

The frequency of the APs. More frequent = a larger stimulus.

Question 29

How do local anaesthetics work?

Answer 29

They block Na+ channels so no APs can be generated.

Question 30

What is salutatory conduction?

Answer 30

Whereby electrical impulses jump between Nodes of Ranvier along neurons that are insulated with myelin, making conduction faster.