Introduction to neurophysiology

Question 1

What are the 3 types of neurons?

Answer 1

Sensory neurons
Motor neurons
Interneurons

Question 2

What are the 4 types of glial cells of the CNS?

Answer 2

Astrocytes
Ependymal cells
Oligodendrocytes
Microglia

Question 3

What are the 2 types of glial cells of the PNS?

Answer 3

Schwann cells
Satellite cells

Question 4

What is a key difference between glial cells and neurons in terms of electrical excitability?

Answer 4

Glial cells, unlike neurons, are not electrically excitable and do not fire action potentials

Question 5

List 3 key functions of astrocytes.

Answer 5

Maintain the blood brain barrier

Regulate extracellular potassium [K+] levels

Re-uptake of neurotransmitters e.g. glutamate

Question 6

By which 2 main mechanisms do astrocytes regulate extracellular potassium levels?

Answer 6

Uptake
Spatial buffering

Question 7

Astrocytes regulate extracellular K+ levels via spatial buffering. What is this?

Answer 7

Astrocytes redistribute K+ via gap junctions to areas with lower K+ concentration

This prevents local K+ buildup and maintains neuronal excitability

Question 8

Which cell is responsible for myelination in the CNS? …PNS?

Answer 8

CNS - Oligodendrocytes

PNS - Schwann cells

Question 9

What is the function of the myelin sheath?

Answer 9

Insulates the axon to allow for rapid conduction of electrical signal along the axon

Question 10

What kind of epithelium are ependymal cells?

Answer 10

Ciliated cuboidal

Question 11

Ependymal cells line which 2 areas of the brain?

Answer 11

Ventricles
Choroid plexus

Question 12

What are the functions of ependymal cells in the ventricles and choroid plexus?

Answer 12

Ventricles - circulate CSF

Choroid plexus - CSF production

Question 13

How and where is CSF produced?

Answer 13

Ependymal cells in the choroid plexus filter blood plasma to produce an ultrafiltrate

Question 14

Where do microglia originate from, and how do they enter the brain during development?

Answer 14

Microglia originate from bone marrow-derived yolk sac progenitors

These progenitors cross the blood brain barrier early in development (before it is fully formed) and then populate the brain and spinal cord

Question 15

Local interneurons are important for which processes?

Answer 15

Spinal reflexes

Question 16

Which type of interneurons connect different brain regions?

Answer 16

Relay interneurons

Question 17

Are interneurons mostly excitatory or inhibitory?

Answer 17

Inhibitory

Question 18

What 4 ways can neurons be classified based on their morphology?

Answer 18

Unipolar
Bipolar
Multipolar
Pseudo-unipolar

Question 19

What are the 4 common functional domains in typical neurons?

Answer 19

Dendrites
Soma (cell body)
Axon
Pre-synaptic terminals

Question 20

Which specialised feature is seen on dendrites?

Answer 20

Dendritic spines

Question 21

Where in the post-synaptic neuron is the action potential first generated?

Answer 21

Initial segment of the axon

Question 22

By what process does an AP travel from the soma to the pre-synaptic terminal along the axon?

Answer 22

Fast axonal transport

Question 23

Through which structures do substances travel during fast axonal transport?

Answer 23

Microtubules

Question 24

Microtubules in axons are stabilised by what?

Answer 24

Tau proteins

Question 25

The cytoskeleton in an axon contains which 3 key structures?

Answer 25

Microtubules Microfilaments Neurofilaments

Question 26

Abnormalities in tau proteins are implicated in which disease?

Answer 26

Alzheimer's disease

Question 27

Which type of motor protein is involved in anterograde transport?

Answer 27

Kinesins

Question 28

Which type of motor protein is involved in retrograde transport?

Answer 28

Dyneins

Question 29

What is meant by the hyperpolarization phase of an AP and what causes it?

Answer 29

When the membrane potential undershoots the resting potential and becomes more negative than the resting potential K+ channels are slow to close, allowing excess K+ to leave the cell

Question 30

What are the 2 types of AP refractory periods?

Answer 30

Absolute refractory period Relative refractory period

Question 31

A new AP cannot be generated in the absolute refractory period due to what?

Answer 31

Na+ channel inactivation

Question 32

Describe the generation of an AP during the relative refractory period.

Answer 32

A new AP is possible, but only with a stronger stimulus

Question 33

Dendrites have slower electrical conduction than axons due to what?

Answer 33

Less VG Na+ channels

Question 34

What is the conduction velocity of a myelinated neuron?

Answer 34

120 m/s

Question 35

What is the conduction velocity of an unmyelinated neuron?

Answer 35

25 m/s

Question 36

What is saltatory conduction?

Answer 36

The process by which an AP jumps from one node of Ranvier to the next, skipping over the myelinated sections of the axon

Question 37

What are 3 things that influence conduction velocity in an axon?

Answer 37

Density of voltage-gated Na+ channels Diameter of axon Myelination

Question 38

In what way does axon diameter affect conduction velocity? Why is this?

Answer 38

The larger the axon diameter, the faster the conduction velocity This is because large diameter reduces internal resistance, allowing ions to move more freely through the axon

Question 39

In what ways does myelination affect membrane resistance and membrane capacitance?

Answer 39

Increases membrane resistance (prevents ion leak) Reduces membrane capacitance (prevents charge loss to membrane)