Spread of the Nerve Impulse

Question 1

What are the functions of the vertebrate nervous system?

Answer 1

Detect, relay, integrate and respond appropriately to conditions in the outside world

Question 2

What are the two functions of the glia?

Answer 2

1- Structural support

2- Shock absorption

Question 3

Where does information arrive at the cell body of the neuron?

Answer 3

Dendrites

Question 4

Where is information passed on to the target?

Answer 4

Boutons

Question 5

What are the three neuronal phenotypes?

Answer 5

1- Multipolar
2- Bipolar
3- Pseudounipolar

Question 6

What is the most abundant neuronal phenotype in the CNS?

Answer 6

Multipolar neurons

Question 7

What factors influence the speed of nerve impulses?

Answer 7

1- Diameter of axon

2- If axon is myelinated or not

Question 8

What is the relation between resistance and axon diameter?

Answer 8

1- The larger the diamter, the lower the resistance

2- Inversely proportionate

Question 9

What is capacitance?

Answer 9

1- Amount of charge accumulated at the membrane
2- The higher the capacitance, the harder it is for charge to cross over the membrane or for charge to overcome the repellent force of charge which has been accumulated

Question 10

What is the relation between capacitance and axon surface area?

Answer 10

1- The more surface area there is, the larger the capacitance
2- Direct proportion

Question 11

Describe the steps of depolarisation.

Answer 11

1- At resting potential, Na+ channels are closed.
2- Depolarization opens the activation gate and Na+ flows into the cell along its electrochemical gradient.
3- Channel is blocked by the inactivation gate after ~0.5ms
4- Repolarisation occurs and gates are reset to their equilibrium positions

Question 12

What are the two refractory periods?

Answer 12

1- Absolute refractory period

2- Relative refractory period

Question 13

What is the absolute refractory period?

Answer 13

1- During repolarisation
2- Cell cannot be stimulated to its threshold potential
3- All Na channels closed

Question 14

What is the relative refractory period?

Answer 14

1- After action potential
2- Immediately after absolute refractory period
3- Cell is hyperpolarised
4- Some Na channels are open but many K channels are open
5- Stronger stimulus than normal could induce action potential

Question 15

What are the 4 different types of glial cells?

Answer 15

Oligodendrocytes
Microglial
Astrocytes
Ependymal

Question 16

What is the function of astrocytes?

Answer 16

Layering of the blood vessels which pass around the CNS

Creates the blood-brain barrier

Question 17

What is the function of oligodendrocyte?

Answer 17

Myelination

Question 18

What is the function of ependymal cells?

Answer 18

Cuboidal-columnar ciliated cells that line the ventricles and central canal of the spinal cord

Question 19

What is the function of a microglial cell?

Answer 19

Immune system and homeostasis in the CNS

Question 20

What does myelination cause?

Answer 20

Stops leakage of current, so the nerve transmission is faster