MEMBRANE POTENTIAL(Part-1)

Husan BanoAssistant ProfessorDeptt. Physiology

SMC,DUHS

BY THE END OF THIS LECTURE YOU SHOULD BE ABLE TO :

• COMPARE THE CHRACTERSTIC OF EXCITABLE AND NON EXCITABLE CELLS

• DEFINE THE RESTING MEMBRENE POTENTIAL

• EXPLAIN THE GENERATION AND MAINTAINANCE OF RESTING MEMBRANE POTENTIAL.

TYPES OF CELLS

1. EXCITABLE CELLS

2. NON-EXCITABLE CELLS

EXCITABLE CELLS

1. EXSIST HIGH ELECTRICAL POTENTIAL DIFFERENCE ACROSS THE MEMBRANE

2. GENERATE ACTION POTENTIAL

3. PROPAGATE ACTION POTENTIAL

e.g. Nerve & Muscle

EXCITABLE CELL

NON-EXCITABLE CELLS

• LOW POTENTIAL DIFFERENCE ACROSS THE MEMBERANE.

• DO NOT GENERATE AND PROPAGATE ACTION POTENTIAL.

e.g. Glandular cells, Macrophages, Blood cells etc

RESTING STATE

GENERATION OF RESTING MEMBERANE POTENTIAL

• IONIC DESTRIBUTION OF ICF AND ECF

Substance and Units

Extracellular

Fluid

Intracellular

Fluid*

Na+ (mEq/L) 140 10

K+ (mEq/L) 3-5 140

PROTEIN(-) ABSENT 200

Cl- (mEq/L) 103-105 3-5

ION FLUXES IN RESTING STATE• Na+142meq/L PO4-- 4meq/L

• K+ 5 -10 P- absent

• Cl- 103-105 ECF

• -------------------------------------------------------------

• Na+ 10meq/L PO4- -75 m.eq/L ICF

• K+142 P- 200 mg%

• Cl– 3-5

• ------------------------------------------------------------

SODIUM-POTASSIUM PUMP

SODIUM-POTASSIUM PUMP

ION FLUXES

REASONS OF RMP

1. ACTIVE TRANSPORT OF SODIUM IONS FROM ICF TO ECF.

2. PASSIVE TRANSPORT OF POTASSIUM IONS FROM ICF TO ECF.

3. PASSIVE TRANSPORT OF CHLORIDE IONS FROM ECF TOICF.

~~~ Cont.

4. PRESENCE OF NEGATIVELY CHARGED PROTEIN IONS AND PHOSPHATE IONS IN ICF

RMP OF DIFFERENT EXCITABLE CELL

• Due to the combine reason. the RMP of an excitable cell ranges from -60mv to -90 mv

eg.

• -60 mv ( Smooth muscle)

• -90 mv ( Skeletal muscle)

• -90 mv ( Nerve fiber )

• -85mv to -90mv (Cardiac muscle)

DEFINATION OF RMP

• The potential difference accrose the membrane in resting condition is called resting membrane potential (RMP).

THE END