Lecture 3

Question 1

Histology

Answer 1

Staining of the nerve tissue

Question 2

Membrane proteins

Answer 2

1. Channel: diffusion, permeability depends on number of channels
2. Gate: conformation, change depends on voltage or chemical stimulus
3. Pump: active transport, requires energy (ATP)

Question 3

Neuronal metabolism

Answer 3

• Glucose as fuel (through blood-brain barrier)
• Brain consumes a lot of oxygen due to glucose consumption
• Glucose can be synthesized by the liver
• Vitamin B1 enables glucose use

Question 4

Types of glial cells

Answer 4

• Schwann cell (myelin sheath)
• Astrocyte
• Oligodendrocyte
• Microglia (Phagocytotic)
• Ependymal cells

Question 5

Types of neurons

Answer 5

• Primary sensory neurons
• Motor neurons
• Interneurons

Question 6

Astrocyte

Answer 6

Type of glial cell.
Regulate the chemical content of extracellular space.
Actively remove neurotransmitters from synaptic cleft.
Influence neurite growth.
Structural integrity.
Maintain blood brain barrier

Question 7

Oligodendrocyte and Schwann cells

Answer 7

Oligodendrocytes are found in the CNS and Schwann cells in the PNS
Both provide myelin sheaths to the axons of neurons

Question 8

Microglia

Answer 8

Remove debris left by dead or degenerating neurons or glia.
Involved in remodeling synaptic connections by gobbling them up

Question 9

Blood-brain barrier

Answer 9

Selectively permeable. Passive: small molecules (O2, CO2), Active: glucose, amino acids

Function: maintains composition of brain fluid by preventing toxic substances from entering the brain

Astrocytes maintain tight junctions

Question 10

Sodium-potassium pump

Answer 10

Pushes sodium outside and potassium inside
3:2 sodium:potassium

Question 11

Electrochemical potential

Answer 11

Ions encounter 2 forces: electrical and chemical gradient
Sum determines whether the ion will diffuse in or out

Question 12

Concentration gradient

Answer 12

Pushes potassium out of the cell
Pushes sodium and chloride into the cell

Question 13

Electrical gradient

Answer 13

Pushes chloride out of the cell
Pushed potassium and sodium into the cell

Question 14

Excitatory post-synaptic potentials (EPSP)

Answer 14

• Chemical stimulus in synapse -> Sodium channels open
• Positive charge ions (sodium) flow into cells and diffuse along membrane
• Cell membrane depolarises locally

Question 15

Inhibitory post-synaptic potential (IPSP)

Answer 15

• Chloride channels open
• Negative charge flows in
• Membrane hyperpolarizes locally

Question 16

Conduction of graded potentials

Answer 16

The current fades aways over a distance due to diffusion of charge over an increasingly large surface area.
Also due to outward leakage of potassium ions (+) through constitutively open potassium channels.

Question 17

Molecular basis of action potential

Answer 17

• Voltage dependent sodium channels in axon hillock
• When threshold is reached these sodium channels open
• Massive influx of sodium so the membrane potential shoots up and then action potential.

Question 18

Termination of action potential

Answer 18

• Opening of voltage dependent potassium channels, with a delay
• Slow inactivation of voltage dependent sodium channels

Question 19

Active propagation of action potential

Answer 19

Repeating depolarization at neighbouring parts of the axon (Nodes of Ranvier).

Question 20

Events at the electrochemical synapse

Answer 20

1. Action potential reaches presynaptic terminal
2. Depolarization causes opening of Ca2 (+) channels and calcium moves in
3. Calcium causes vesicles to fuse with presynaptic membrane
4. Transmitter is released into cleft by exocytosis
5. Transmitter binds to receptor in postsynaptic membrane which opens or closes channels
6. Opening/closing of channels causes excitatory or inhibitory potential

Question 21

Types of CNS synapses by function

Answer 21

1. Type 1: assymmetrical, excitatory, influx Na and Ca
2. Type 2: symmetrical, inhibitory, influx Cl

Question 22

Types of CNS synapses by connection

Answer 22

1. Axodendritic
2. Axosomatic
3. Axoaxonic