Microstructures of the nervous system

Question 1

What are the main cell types of the PNS?

Answer 1

Schwann cells - form myelin sheath
Satellite cells - provide structural support, regulate exchange of material between neural body and interstitial fluid

Question 2

What are the main cell types of the CNS?

Answer 2

Astrocytes - contains microfilaments to strengthen neurons
Oligodendrocytes - form + maintain myelin sheath
Microglial- phagocytic properties
Ependymal - produce + assist in circulation of cerebrospinal fluid

Question 3

How is the resting membrane potential maintained?

Answer 3

Na enters the cell via voltage gated channels
K leaves via voltage gated channels
The Na-K pump sends 3NA+ out for 2K+ in

Question 4

What are the phases of an action potential?

Answer 4

1. Na+ channels open, Na+ enters the cell
2. K+ channels open, K+ leaves the cell
3. Na+ channels become refractory, no more Na+ can enter
4. K+ continues to leave the cell, causing the return of resting potential
5. K+ channels close and extra K+ diffuse away

Question 5

What are the two refractory periods?

Answer 5

Absolute - From when Na+ gates open until just after they close, neuron won’t respond to additional stimuli

Relative - Until K+ gates close and membrane returns to threshold, neuron will respond to additional stimuli if strong enough

Question 6

What are the two types of summation?

Answer 6

Spatial - input from multiple cells
Temporal - series of synaptic potentials occurring within ms of each other