Lecture 3 - The Action Potential

Question 1

Golgi Stain

Answer 1

Mixture of silver nitrate & potassium chromate
-> 2% of brain cells darken cuz silver chromate crystallizes everywhere inside

Question 2

Dendrites

Answer 2

Branched, treelike extensions from soma
->Sense external environ., collect info

Question 3

Soma (cell body)

Answer 3

Nucleus located

Question 4

Processes

Answer 4

Protrusions extend out of soma (many dendrites + 1 axon)

Question 5

Axon

Answer 5

1 protrusion from soma
-> transmits info to downstream cells (via action potential)

Question 6

Myelin sheaths (rest on slide)

Answer 6

Fatty substance that insulates axon
-> improves speed & fidelity of action potential

Question 7

Axon terminal (terminal bouton)

Answer 7

Branches that extend out of the end of every axon (axon collateral)
-> release NT when action potential onto downstream cells contact with
->into synapse

Question 8

Synapse

Answer 8

Junction between axon terminal & membrane of downstream neuron

Question 9

Measuring Resting Membrane Potential

Answer 9

1) Glass micropipet (filled solution that conduct charge) -> inserted through membrane into cell
2) Voltmeter measures potential difference (mV)
3) Reference electrode into extra cellular fluid (Ground-> 0mV)
Reality: Not neutral (excess of + charge-> balances excess - charge inside cell)
4) Resting membrane potential
-> relative scale (between -40 to -90 mV in nerve & muscle)

Question 10

Potential Difference

Answer 10

Difference in electrical charge between 2 points -> millivolts (mV)

Question 11

Ion

Answer 11

Charged atom or molecule
Cation: + charge
Anion: - charge

Question 12

Electrostatic pressure

Answer 12

Attractive force (molecules oppositely charged)

Repulsive force (molecules similarly charged)

Question 13

Ion channels

Answer 13

Specialized protein molecules that sit in cell membrane
-> Pore (hole): specific ions can enter or leave cells

Question 14

Leak channel

Answer 14

Ion channel protein in membrane
-> Pore always open
(Eg: potassium leak channel)

Question 15

Atomic Composition of cells

Answer 15

Hydrogen (H) - 59%
Oxygen (O) - 24%
Carbon (C) - 11%
Nitrogen (N) - 4%
Others (P, S,…) - 2%

Question 16

Monovalent cations

Answer 16

-Sodium (Na+) -> more outside cell
-Potassium (K+) -> more abundant inside of cell (intracellular space)

Question 17

Divalent cations

Answer 17

-Calcium (Ca2+)
-Magnesium (Mg2+)
-> more outside of cell

Question 18

Monovalent anions

Answer 18

Chloride (Cl-) -> more outside of cell

Question 19

Intracellular fluid

Answer 19

Fluid within cell

Question 20

Extracellular fluid

Answer 20

Fluid outside cell

Question 21

Setting up & maintaining testing membrane potential

Answer 21

1) Sodium-Potassium pump (ATP, concentration gradients or K in & Na out of cell)
-> membrane potential=0

2) Leak potassium channels (always open, K leaves - # determines resting membrane potential)
-> Diffusion & Electro. Energy opposite & equal when membrane potential=
-90mV

Question 22

Diffusion

Answer 22

Concentration gradient + No forces or barriers preventing movement
-> molecules move high C to low C

Question 23

Receptor (proteins)

Answer 23

Detect stimuli in external environment:
1) Presence of molecules (NT)
2) Physical Pressure
3) Electrical Pressure (voltage)
4) Temperature
5) pH
6) Electromagnetic radiation (light)
Also Nutrients: proteins, fats, sugars, vitamins, minerals

Question 24

Action potential

Answer 24

1) voltage-gated sodium channel (initiate & propagate action potential)
2) voltage-gated potassium channel (restore resting membrane potential)
3) voltage-gated calcium channel (axon terminal, triggers release of NT from vesicles)

Question 25

Action potential

Answer 25

Brief electrical Impulse, conduction of info along axon -> rapid change in membrane potential by opening & closing of voltage-gated ion channels

Question 26

Measuring electrical potentials of axons

Question 27

Conduction of Action Potential