ELECTROPHYSIOLOGY & TRANSPORT: (Ion Channels (Examples of Interactions…
ELECTROPHYSIOLOGY & TRANSPORT:
Families of Ion Channels
Requires the K+ ion concentration to be greater inside cell.
Cell membrane must be permeable to K+ by having K+ ion channels that are open.
Closed, open active, open inactive (desensitised)
Gating of channels
Measurement of Channel Function by Patch Clamping
Capacitance changes as a result of vesicle exocytosis
Currents across single channels (open probability)
Intracellular Ion Concentrations
Distribution of Charges
Generating Resting Membrane Potentials
i. Cell membrane is permeable to K+
Evidence that K+ diffusion potential is involved.
Altering the K+ gradient by changing the K+ concentration outside the cell directly changes the RMP.
A K+ channel inhibitor such as Ba2+ ion (barium ion) causes a fall in the resting membrane potential (RMP) of a cell.
ii. Cell membrane is impermeable to Na+
iii. Na+, K+-pump maintains ion concentration gradients
iv. Na+ K+-pump is the main electrogenic transport pump. It pumps three Na+ ions out for every two K+ ions in.
Mechanically Gated Channel
Ca2+ release channel of SR (ryanodine receptor)
Stretch-activated Cl- channels (cell volume control)
Examples of Interactions Between Channels
Neuromuscular junction ion channels
Ion Channels in Muscle Contraction
Electrophysiology of Adaptation and Memory
Post-synaptic potentials (PSPs)
Ligand Gated Channel
Carriers and Pumps
"Master Pump" of Animal Cells - Na+ K+-ATPase (sodium pump)
"Master Pump" of Plant Cells and Bacteria
Families of Transporters
Sodium or Hydrogen Gradient-Driven Pumps - “Porter Systems”
Regulation of Transport Activity
Changes in Ion Concentrations, pH, or Voltage around Channel (Biochemical)
Control of Synthesis or Degradation - e.g. aldosterone, organic osmolyte transporters
Protein-Protein Interactions - K+ channel, sulfonyluria receptor, and Ca2+v channel
Control of Insertion or Removal - e.g. SGLT, GLUT4, ENaC, AP2
Phosphorylation or Dephosphorylation:
Transport Related Diseases
Ion Channel Diseases