Mod 1: action potential

Question 1

Action potential: Cell membranes become more permeable to___, enters _____ period

Answer 1

Sodium, absolute refractory

Question 2

Action potential: what happens to cell? What needs to happen to generate AP?

Ion movement
Polarity

Answer 2

Cell becomes less negative- depolarizes
Depolarizes until threshold potential met (depolarizes by 15-25mV)
Na Voltage gated channels open

Question 3

What happens when threshold potential is met

Answer 3

Action potential created, no further stimulus needed

Question 4

Action potential: what happens when membrane potential reaches 0?

Na+k voltage gated channels do what?
What changes in permeability?
What refractory period?
Na k pumps do what?

Answer 4

Polarity is neutralized, Cell repolarizes-needs to get more negative
Na voltage gated channels close
k voltage gated channels open

Membrane Na permeability decreases
Membrane K permeability increases
—-relative refractory period
K moves out

To return to rmp:
Na K pump pumps 2K in and 3Na out using atp to go against ion polarity gradient restoring normal icf/ecf na and K concentration

Question 5

Hyperkalemia
RMP? Effect on cells excitability?

Clinical effects

Continued hyperkalemia?

Answer 5

RMP more positive, k doesn’t diffuse out
More excitable bc closer to TP

Peak T waves

If continued-RMP = TP == no AP

Card standstill, paralysis/parasthesia, widening qrs

Question 6

Hypokalemia effects on polarity
Excitability
Clinical effects

Answer 6

K diffuses to ecf
More negative -hyperpolarized
Need stronger stimulus to depolarize, less excitable

Weakness, smooth muscle atony, parasthesia, dysrhythmias

Question 7

Hypercalcemia

Effect on permeability, excitability, clinical effects

Answer 7

Decreases cell permeability to Na

Increases RMP and TP distance
Less excitable

Weakness, hyporeflexia, fatigue/lethargy/confusion, encephalopathy

Shortened qt segment
Depressed widened t waves

Question 8

Hypocalcemia

Effect on permeability, polarity, excitability, clinical effects

Answer 8

Increased permeability to Na
Progressive depolarization
RMP and TP closer
More likely to =AP (v excitable)

Tetany hyper reflexia , circumoral parasthesia, seizures, dysrhythmias

Question 9

RMP maintained by

Answer 9

-70- -85mV

NaKATPase protein=3Na out 2Kin

Question 10

Threshold potential

Answer 10

-55 - -65mV

Question 11

Hyperpolarized

hypopolarized

Answer 11

-85mV Super negative

less than -65mV closer to 0