lecture 3

Question 1

difference between different potentials?

Answer 1

1. receptor potentials: activation of sensory neurons by external stimuli ( this is the exception that axon is where receptors are located)
2. synaptic potentials: activation of neurons at the synapse
3. action potentials:
   * the first two are graded, AP is all-or-none

Question 2

difference between transporter and channel?

Answer 2

1. transporter actively moves ions against concentration gradient.
2. channels allow ions to diffuse down concentration gradient

Question 3

does ion concentration change much when ions reach equilibrium?

Answer 3

NO. the number of ions that needed to diffuse cross membrane to reach equilibrium is very low.

Question 4

why can squid have giant axon?

Answer 4

invertebrates don’t myelinate. to make faster conduction, they actually increase the axon diameter.

Question 5

how three ions contribute to resting potential?

Answer 5

K has the major contribution, Cl has a secondary contribution, Na has the smallest contriution

Question 6

is pumping Na+out of the cell going to increase extracellular concentration of Na+?

Answer 6

NO. because extracellular space is considered to be infinitely large, compared to the cell.

Question 7

why Na+ can hardly affect resting potential even though there is a large driving force?

Answer 7

permeability should be taken into account. even though there is a large driving force for Na at rest, there is a very low permeability to Na at rest, which means changing the concentration hardly affects the resting potential.

Question 8

how can driving force of Na+ change if decreasing K+ outside?

Answer 8

decreasing extracellular K+ can decrease equilibrium potential which increases the driving force of Na+ even though there are the same number of sodium channels.