1.2 The cellular basis of neural function

Question 1

What were 3 old ideas about how neurons work?

Answer 1

1. spirits running through hollow nerve fibres
2. mini explosions caused by fermentation when mixing fluid droplets from nerve ends and blood
3. vibrations, light of different energies transferred vibrations to nerves

Question 2

What were 3 problems from the 3 old ideas?

Answer 2

1. limbs don’t increase in volume when muscles are activated
2. nerves cut in water did not cause ferment
3. nerves are taut and

Question 3

What did Luigi Galvani discover?

Answer 3

touching a metal blade activated frogs legs, this, nerves convey animal electricity

Question 4

What did Aldini discover?

Answer 4

by stimulating the brains of executed criminals.

Question 5

What causes changes to resting membrane potential (RMP?)

Answer 5

graded potentials, can be positive or negative

Question 6

What does a large enough positive increase of RMP produce?

Answer 6

stimulates an action potential to be generated of constant magnitude

Question 7

What happens if you increase the amount of electrical stimulation to an already stimulated AP of constant magnitude?

Answer 7

only FREQUENCY of action potential changes, NOT magnitude

Question 8

What is an electrochemical equilibrium?

Answer 8

where movement of ions is determined by both concentration and electrical gradients

Question 9

Explain how electrochemical equilibrium works with potassium?

Answer 9

even if there is a concentration gradient for potassium to leave the cell, the negative change in the cell draws potassium in, causing the equilibrium

Question 10

What are ion transporters?

Answer 10

move ions against the concentration gradient to be able to maintain the membrane potential, which is electrogenic

Question 11

What are ion channels?

Answer 11

allow ions to diffuse passively along the electrochemical gradient

Question 12

What are the 2 ways of managing ion movement?

Answer 12

1. voltage gated - for action potential
2. passive leak channels - for resting membrane potential

Question 13

Which important ion channel is voltage gated and why?

Answer 13

Na+ and K+ ion channels are voltage gated and are key to creating nerve impulse

Question 14

Compare Na+ and K+ channels

Answer 14

Na+ channels open faster and have larger conductance
K+ channels open slower, lower conductance but are open for longer

Question 15

What happens when threshold potential is released?

Answer 15

input of Na+ = local depolarisation = opening of Na+ channel for Na+ to enter

Question 16

What happens when there is an increase of Na+

Answer 16

increases membrane potential - rising phase of action potential

Question 17

What happens after depolarisation?

Answer 17

depolarisation spreads for the action potential (AP) to occur where only a small amount of Na+ needs to enter for there to be a change to membrane potential (MP)

Question 18

What is the process of depolarisation?

Answer 18

Na+ channels close and K+ channels open, allowing K+ to leave axon

Question 19

What is the myelin sheath and how does it contribute to depolarisation?

Answer 19

myelin sheath made of glial cells called oligodendrocytes and ensures that depolarisation happens at the nodes to lead to a greater current density –> increases speed of conduction down the axon

Question 20

What is the silver stain and who invented it?

Answer 20

Cajal
Silver stain is still used today. It stains around 1% of the neuron, meaning that it can be differentiated from the others around it

Question 21

What is the reticular theory?

Answer 21

all neural tissue acts together in compartments

Question 22

What is the neuron doctrine?

Answer 22

neurons act as discrete cells, and this is evident by the fact that bc other neurons around an injured one and work fine and the innervated area would still be fine