Neural Communication

Question 1

how do we measure neural communication? what exactly are we measuring?

Answer 1

• needle on the inside of the cell (intracellular electrode), and another on the outside (extracellular electrode)
  
  • inside is negative compared to the outside
• voltage is a measure of potential chemical energy

Question 2

what is the resting membrane potential? why is it important?

Answer 2

• resting membrane potential between -60 and -80 mV
  
  • failure to maintain resting membrane potential = cannot have neural connection

Question 3

in what way is neuronal communication chemical?

Answer 3

1. results of two ions, sodium (Na+), and potassium (K+)
2. ions move into or out of the cell, but not freely (plasma membrane prevents)
   
   • neurotransmission is also chemical

Question 4

in what way is neuronal communication electrical?

Answer 4

2. as they move into or out of cell, they change the potential (voltage) at the membrane
   
   1. ex. absence of potassium is negative
   2. remove a potassium, leave a negative

Question 5

what is the chemical gradient?

Answer 5

• ions want to flow from high concentration to low concentration
• ions want to disperse evenly
• there are different/separate chemical forces for Na and K

Question 6

what is the electrical gradient?

Answer 6

• charge/potential wants to flow from high concentration to low concentration
• charges want to disperse evenly, positive wants to move in, negative wants to move out
• there are the same electrical forces for Na and K but sometimes electrical and chemical gradients are at odds
  
  • potassium may have a chemical and electrical force pushing in opposite directions
• two forces find equilibrium at around 70mV instead of 0mV

Question 7

what is the cell membrane?

Answer 7

• lipid bilayer is tightly packed, keeping out all dangerous entities
• hydrophobic - lipid tail interacts with fat, rejects water
• hydrophilic - phosphate head interacts with water, rejects fat
• we require specialized proteins in order to get content inside and outside the cell

Question 8

what are channels?

Answer 8

• channels - allows passive diffusion through the cell membrane, usually specific to an ion
  
  • cell has no control over the direction of flow
  • moves according to electrical and chemical gradient

Question 9

what are pumps?

Answer 9

• pumps - actively push ions through cell membrane using ATP as it requires energy
  
  • moves from lower concentration area to higher concentration (against gradient)

Question 10

what are the proteins responsible for maintaining the resting membrane potential?

Answer 10

• sodium-potassium pump
• potassium leak channels

Question 11

how does the sodium-potassium pump work?

Answer 11

1. Sodium-potassium pumps - sodium out, potassium in, using 2/3 of all brain energy
   
   • 3 binding sites for sodium (in→out)
   • 2 binding sites for potassium (out→in)
   • ATP binds and causes protein to change shape and switch sodium out and potassium in
   • 3 positives out, 2 positives in → inside of cell becomes negative

Question 12

how does the sodium-potassium pump affect the chemical and electrical gradients?

Answer 12

• creates a chemical gradient for sodium that pushes it in
  
  • there is more sodium on the outside
• creates a chemical gradient for potassium that pushes it out
  
  • there is more potassium on the inside
• electric gradient - creates a greater negative charge inside the cell, pushing potassium back in

Question 13

how do potassium leak channels work?

Answer 13

Potassium “leak” channels - require no energy and allow potassium in and out
- as potassium leaves, makes neuron more negative and increases electrical force trying to push it back in
- electrical force pushes potassium in
- chemical force pushes potassium out
- these forces equal out, resulting in our resting membrane potential