Physiology Module 8

Question 1

What is Excitable Tissue?

Answer 1

• consist of cells with the ability to receive and respond to stimuli by converting them into electrical signal
• mainly nerve cells and muscle cells

Question 2

What is resting membrane potential ?

Answer 2

• voltage difference between the inside and the outside of the
  cell at rest

Question 3

All cells, excitable and non- excitable have resting membrane potential

TRUE/ FALSE ?

Answer 3

True 👍

Question 4

What does excitable tissue have that non-excitable tissue don’t have

Answer 4

-gated ion channels (to produce action potential)

Question 5

What is membrane potential ?

Answer 5

• voltage difference between inside and outside of cells due to
  unequal distribution of ion

Question 6

a) According to Fick ‘s law of diffusion ?

b) Formula in Fick’s law of diffusion ?

Answer 6

a) ion flux depends on membrane permeability to ion, the surface area of membrane and concentration gradient
b) dn/ dt = P x A x ( dC/dx )

where :
dn / dt = rate of flux
A = membrane surface area
P = permeability constant
dC/ dx = electrochemical gradient across the membrane 

more info @ page 24 of module 8

Question 7

Factors that influence membrane permeability ?

Answer 7

• size of solute particles
• electrical charge of ion
• solubility in lipid
• presence of channels on membrane

Question 8

What do you know about ;
a) Leaky channels/pores

b) Voltage-gated channels
c) Ligand-gated/chemical -gated channels
d) Mechanical-gated channels

Answer 8

a) no. of K+ leaky channel > Na+ , so cell membrane more permeable to K+ than Na+
b) regulated by voltage difference (open when membrane depolarized)
c) open and close in response to neurotransmitters, hormones and particular ions establishing receptor potential
d) open or close in response to mechanical stimulation, establishing electrical signal

Question 9

What is dynamic equilibrium?

Answer 9

• net movement of particles is zero

Question 10

There is no dynamic equilibrium for large particles ( protein)

TRUE/ FALSE ?

Answer 10

• TRUE

- and a concentration gradient is maintained by the impermeability of the membrane

Question 11

Increasing surface area of diffusion (dendrites and subneural clefts) affect lon flux

TRUE / FALSE?

Answer 11

TRUE 👍

Question 12

Energy difference is due to ?

Answer 12

• chemical forces /gradient / concentration gradient
  ▪︎ move down their concentration gradient
• electrical forces/ gradient
  ▪︎ions tendency to be pushed in one director or the other by membrane potential
• electrochemical forces / gradient
  ▪︎direction depends on the net direction of both forces

Question 13

Equilibrium potential of ion =

Answer 13

• membrane potential that produces electrica l force that counters chemical force such that the electrochemical force is zero
• no net force for ion to move across membrane

Question 14

What is used to measure potential difference between the inside and outside of a cell ?

Answer 14

voltmeter

Question 15

Can channels vary the conductance of cell membrane for different ions ?

Answer 15

Yes 👌

Question 16

What is the value of Resting Membrane Potential ?

Answer 16

-70 to -90 mV

Question 17

Equilibrium potential of an ion can be calculated using What equation ?

Answer 17

Nernst equation

E = 61.5 X log10 ( [ ion outside cell ] / [ ion inside cell ] )

Question 18

Membrane potential can be calculated using What equation?

Answer 18

Goldman - Hodgkin - Katz equation
 Formula Refer page 63 module 8

Question 19

What causes

a) hyperkalemia
b) hypokalaemia

Answer 19

a) increase in K+

b) decrease in K+

Question 20

Pseudohyperkalaemia is due to ?

Answer 20

• release of potassium from RBC lysis
• blood drown from the side of IV infusion or a central line without previous flushing
• prolonged use of tourniquet

Question 21

Hyperkalaemia leads to

Answer 21

• cardiac arrhythmias
• muscle weakness , paralysis
• Decreased deep tendon reflexes

Question 22

Hypokalemia leads to ?

Answer 22

• same like hyperkalaemia

- Fatigue

Question 23

Is Resting Membrane potential affected by hyperkalaemia ?

Answer 23

Nope but regulation of heart rate ❤ and cardiac Output is Affected