Neurophysiology

Question 1

Phospholipid bilayer

Answer 1

Diffusion barrier
Capacitor action
Separation of positive and negative charges
Ion flow via channels

Question 2

Channel characteristics

Answer 2

Different states (open, closed)
Selectivity (charge-selection via AA polarity or size-selection via pore size)
Gating: voltage, ligand, thermal, mechanical

Question 3

Ion concentration

Answer 3

Na: 140/15
K: 4/130
Ca: 2.5/1E-4
Cl: 120/5

Question 4

Nernst equation

Answer 4

Seriously? Like seriously?

E = RT/zFln([X_out]/[X_in]) = 58/zlog([X_out]/[X_in])

Question 5

Biggest ion contributor to membrane potential

Answer 5

Potassium motherfucker, CRSS up in that bitch

Question 6

Passive diffusion factors

Answer 6

Electrochem gradient

Channel conductance

Question 7

Role of ion pump

Answer 7

Concentration gradient maintenance

Question 8

Cable properties

Answer 8

Amplitude of potential change decreases exponentially as it moves away from the source, bidirectionally

Question 9

Length constant

Answer 9

Distance by which the potentials falls by 63% (1-1/e)

Depends on membrane (directly) and longitudinal (indirectly) resistance

Question 10

Action potential

Answer 10

Active propogation
Threshold with all-or-none response
Shows latency
Refractory period
Upper limit of frequency is 1 KHz

Question 11

Gate states

Answer 11

Sodium: Resting to Open to Inactive to Resting
Potassium: Resting to Open to Resting

Question 12

Recording devices

Answer 12

Intracellular: Electrode pierces membrane

Patch clamp: Electrode surrounds a single channel

Question 13

Channel types and blockers

Answer 13

Leak channel - TEA
Na+ - TTX
Ca2+ - Verapamil, D600, Co, Cd, Mn, Ni, La ions
K+ - TEA, amino pyridines
Ca2+ dep. K+ - Extracellular TEA

Question 14

Hyperkalemic periodic paralysis

Answer 14

Episodes of weakness and decreased muslce tone, (following exercise or kalemic food)
Unable to fire APs, cell depolarized by 30-40 mV
Mutation of the muscle voltage-gated Na channels that prevents some percentage of them from being clompletely inactive after depolarization
Small and constant inward current, causing normal Na channel to be inactivated

Question 15

Myotonia

Answer 15

Difficulty of reaxing muscle upon contraction
Thomsen’s and Becker’s disease
Myotonic goats from chloride channel abnormality
Skeletal muscles have high Cl permeability
Decreased Cl permeability lowers threshold for depolarization