MNSR 13

Question 1

describe everything about current

Answer 1

• Current is the rate of flow of charge Q.
• It has units Amperes [A]:
• 1 Ampere = 1 Coulomb charge/ second
• 1 A = 1 C/s
• Charge can be electrons (e.g. in wire) or ions (e.g. in neurons)

Question 2

describe everything about voltage

Answer 2

• In order to move charges from one position to another (i.e. to
  produce a current), energy must be expended.
• Voltage can be defined as follows:
  A potential difference, or voltage, of 1 Volt means that 1 Joule
  of energy has been expended in moving 1 Coloumb of charge.
• Voltage is measured in Volts[V].
• In living systems, voltages are on the order of (tens of)
  millivolts [mV].

Question 3

describe everything about resistance

Answer 3

• Electrical resistance is measured in Ohms [Q].
• Ohms Law:
  or
  voltage = current × resistance
  V = IR

Question 4

what are conductors

Answer 4

• Materials which allow easy movement of charge

Question 5

what are insulators

Answer 5

while materials which do not allow easy flow of charge are insulators.

Question 7

what happens When a voltage is applied across a
resistor

Answer 7

1. A current flows which is
   proportional to the resistance
2. A current flows which is
   proportional to the voltage
3. The resistance of the resistor
   changes

Question 8

what happens when electrical charges accumulate on one side of the insulator

Answer 8

a voltage builds up across the insulator.
capacitance = charge / voltage
C = Q/V

Question 9

what does capacitance depend on

Answer 9

Capacitance depends on the permitivity of the insulator and the distance between the conductor plates.

Question 10

how does lipid bilayer form a capacitance

Answer 10

• Insulates inside from outside. Ions cannot pass.
• If ions accumulate on one side (surplus of charge Q),
  a voltage builds up: V = Q/C.
• This is called the membrane potential VM.

Question 10

what is membrane potential

Answer 10

voltage difference between the inside and the outside of the neuron measured at a certain location.

Question 11

lon pumps use chemical energy (ATP) to continuously

Answer 11

transport ions against their concentration gradient.
Establish and maintain different ion concentrations.

Question 12

compare and contrast Voltage-gated ion channels with ligand gated

Answer 12

• lon channels are tiny pores in the cell membrane which can let ions pass (no active transport).
• Hundreds to thousands of ion channels of the same type are found in the membrane of a neuron. Together, they determine the permeability (or
  resistance) of the membrane to one ion type.
• In contrast to ‘ligand-gated’ ion channels which open
  when a ligand is bound, ‘voltage-gated’ ion channels open and close in response to the membrane voltage.

Question 13

Selectivity filter:

Answer 13

only lets pass ions of a specific type

Question 14

Gates:

Answer 14

determines permeability/resistance and can be open or closed

Question 15

which transition states are favored/disfavored by membrane potential

Answer 15

favored(+57 mV) = opening, innactivation

disfavored(-91 mV) = closing and recovery

(only open state is conducting)

Question 16

what is a drift

Answer 16

Drift is a movement driven by difference in electric potential(voltage)

Question 17

what causes drift

Answer 17

coulombs force

Question 18

How will ions move
between two compartments
due to both drift and diffusion?

Answer 18

that is, when a potential difference and a concentration difference exist at the same time? - described by nerst equation