Lecture 3: Electrophysiology (Online Lecture)

Question 1

Neurons communicate in two ways:
1. ________
2. ________

Answer 1

1. Electrical: within a neuron
2. Chemical: between neurons

Question 2

Within a neuron, communication occurs through an ________ ________ (electrical impulse that carries information along the axon of a neuron).

Answer 2

action potential

Question 3

What is the outer layer of the neuron?

Answer 3

lipid bilayer known as the cell membrane

Question 4

Cells surrounded by and filled with fluid:
- Intracellular vs Extracellular

Answer 4

• inside the cell
• outside the cell

several different ions dissolved in this fluid

Question 5

All living cells have an electrical charge — more negative ________ the cell than ________ the cell.

Answer 5

inside; outside

Question 6

What are ions?

Answer 6

electrically charged molecules

Question 7

Anions vs Cations

Answer 7

• negatively charged; onions make you cry, negative thing
• positively charged; paws-itive charge or cutest ion ever

Question 8

Why does an action potential occur?

Answer 8

membrane potential

Question 9

Membrane potential

Answer 9

different in electrical charge (ion composition) between the inside and outside of a cell; cell membrane polarized at rest
- membrane potential exists because of differences in ionic co position of intra- & extra- cellular fluid

Question 10

What is resting potential?

Answer 10

• 70 mV; when not receiving or sending messages

Question 11

Electrical charge of an axon is a balance between two forces. Name and define the forces.

Answer 11

• diffusion: molecules will distribute themselves evenly throughout a liquid where they are dissolved; a substance simply diffuses across lipid bilayer
  
  • concentration gradient: ions move from areas of high concentration to areas of low concentration
• electrostatic pressure: force exerted in repelling/attracting ions
  
  • opposites attract
  • like charges repel

Question 12

How do molecules enter or leave the cell?

Answer 12

semipermeable cell membrane
- gases (such as oxygen and carbon dioxide), small nonpolar molecules, and water cross a bilayer freely
- other solutes (molecules and ions) cannot cross a lipid bilayer on their own

Question 13

Passive vs. Active Transport

Answer 13

• passive transport (facilitated diffusion): a solute moves across bilayer through interior of passive transporter; movement is driven by concentration gradient (no energy)
  
  • a passive transport protein allows a specific solute (such as glucose) to follow its concentration gradient across a membrane
    
    • gated passive transporter: changes shape when a specific molecule binds to it
    • open-channel transporter: does not change shape
• active transport: uses energy (often, ATP) to pump a solute through bilayer against its concentration gradient, to the more concentrated side of the membrane
  
  • calcium pump

Question 14

Passive transport: gated vs open-channel transporter

Answer 14

• changed shape when a specific molecule bind to it; think as toll booth
• does not change shape

Question 15

Typical Ionic Distribution at Rest: Which ions are inside the cell? outside the cell?
- Potassium (K+)
- Chloride (Cl -)
- Sodium (Na+)
- Calcium (Ca++)
- negatively charged ions

Answer 15

Inside cell
- Calcium (Ca++)
- negatively charged ions

Outside cell
- Potassium (K+)
- Chloride (Cl -)
- Sodium (Na+)

Question 16

Potassium movement

Answer 16

• higher concentration INSIDE the cell at rest
• at rest, K+ ions move into the negative interior because of electrostatic pressure
• as K+ ions build up inside the cell, they also diffuse out, along the concentration gradient
• K+ reaches equilibrium when the movement out is balanced by the movement in, corresponding to the resting membrane potential of about -70 mV

Question 17

What keeps Na+ out of the cell?

Answer 17

• Na+/K+ pump
  
  • uses ATP to push out 3 Na+ and pull in 2 K+
  • active transport mechanism