Ch. 4 - Electrical Activity

Question 1

water tank analogy

Answer 1

charge: water
voltage: water pressure
flow: current
hose width: resistance

Question 2

measuring electricity in the brain (who)

Answer 2

Hodgkin/Huxley 1963 Nobel Prize
used the giant squid axon (1mm neuron)
most neurons: 1-20 micrometres

Question 3

cell membrane (molecules and types)

Answer 3

polar: needs help with diffusion
non-polar: effortless, no ATP required for diffusion
impermeable membrane: will not let any ions/molecules pass
semipermeable membrane: will allow specific ions/molecules through
EQUILIBRIUM: when all diffusion is complete and resting

Question 4

membrane gradients

Answer 4

voltage or concentration (same thing)
voltage gradients: ions diffuse DOWN (high to low)
concentration gradients: molecules diffuse DOWN (high to low)

Question 5

membrane potential

Answer 5

charge difference inside vs. outside the cell in mV.
inside: MORE NEGATIVE
outside: MORE POSITIVE

Question 6

resting membrane potential (+ what is needed to maintain it)

Answer 6

inside: -70mV (high K+ and A-)
outside: 0mV (high Na+ and Cl-)

** requires Na+/K+ pump, anions within cell, and K+ leakage.

Question 7

sodium potassium pump

Answer 7

maintains resting potential and keeps inner-cell more negative.
3+ Na OUT for every 2 K+ IN.

Question 8

graded potentials (and which way they fluctuate)

Answer 8

SMALL fluctuations in charge that send signals. can either:
- hyperpolarize: dip more negative
- depolarize: rise more positive

Question 9

action potentials

Answer 9

ALL OR NONE (requires threshold to be met by stimulus)`

Question 10

stages of the action potential

Answer 10

1. rest @ -70mV
2. threshold met @ -50mV
3. depolarization (spike in positive ions - Na+ INFLUX; K+ closed)
4. peak @ ~30mV (Na+ gates inactivate)
5. re-polarization (spike in negative ions - K+ EFFLUX, Na+ inactivated)
6. hyper-polarization (continued K+ efflux as gates are very slow to close)
7. rest @ -70mV (all gates closed)

Question 11

role of myelin

Answer 11

oligodendrites (CNS) and Schwann (PNS) cells produce
- conduct action potentials at 120m/s
- saltatory conduction: signal jumps from node to node (of Ranvier)

Question 12

multiple sclerosis

Answer 12

degeneration of myelin in the CNS, slows down action potentials

Question 13

summation of action potentials

Answer 13

1. temporal (same spine, different signals in succession)
2. spatial (different spines, simultaneously conducting same signal)

Question 14

inhibitory vs. excitatory potentials

Answer 14

inhibitory: IPSP (hyperpolarization - more negative)
excitatory: EPSP (depolarization - more positive)