Revision SCT

What enhances the activity of Na+/K+ pump

• Insulin

• Aldosterone

• thyroxine

• Aldosterone

• Catecholamines (e.g. dopamine, epinephrine, norepinephrine).

What blocks Na+/K+ pump

• Ouabain

• Digitoxin

• Digoxin

What are the effects of the Na+/K+ blockers?

• Depolarisation

• Swelling of the cell

• Cardiac glycosides effect: POSTIVE INOTROPIC ACTION

Note: ouabain, digitoxin and digoxin are cardiac glycosides

what is the equation for showing permeability properties

SEE IN THE PICTURE ATTACHED

Note: Driving force = Vm - Vx

What are the properties of ion channels:

• Cannot be saturated thus has large Vmax

• Gating: Voltage, ligand, mechanical

• Selectivity: selectivity filter + ionic radius. Cation; non-selective cation channel; anion channel

• Inhibition: specific and non-specific blockers.

Structure of ion channels

Ligand gated channels:

What voltage gated channels are activated by depolarisation?

• Voltage gated sodium channels

• Voltage gated K+ channels

• Voltage gated calcium channels

What voltage gated channels are activated by Hyperpolarisation?

K_ir, I_f

States of an ion channel

Equation for osmotic pressure

Structure of the 7TM Metabotropic receptors

What are the functions of the various G proteins

Which enzymes are activated by the alpha subunits of the G proteins

• Adenylate cyclase

• Phospholipase C

• cGMP phosphodiesterase

Activated by the beta-gamma subunit

• Modulation of K+ and Ca2+ channels

• Membrane bound localised effects

NO …..

is responsible for cardio protection. It prevents/ opposes excessive ca2+ entry.

Beta 1 receptor

stimulates the PKA pathway

AKAP is a scaffold protein able to bind to:

•β-adrenergic receptor

•protein kinase A

•protein kinase C

•protein phosphatases

•cytoskeletal elements

•Ca2+-channels

•K+-channels

What is the magnitude of the donnan potential

-10mv. Thus this is too small and this cannot explain the highly negative resting potential of excitable cell.

the large negative potential comes mainly from the Na+/K+ pump not just the donnan potential

EQUATIONS TO REMEMBER

Characteristics of electrotonic potential

Rheobase and chronaxie

Rheobase: the minimum current needed to rogger an action potential if applied for a very long duration. UNIT OF RHEOBASE = PICOAMPERES

Chronaxie: the time required to reach the threshold if the current is twice the rheobase. UNIT OF CHRONXIE = Milliseconds

Equation for calculating the speed of conduction

Factors that affect the speed of conduction

TAKE NOTE: Myelination increases the membrane resistance but decreases the capacitance.

Differences between action potential and electrotonic potential