Neuromuscular

ION CHANNELS: Diagrams

Calcium Channels
Potassium Channels
Sodium Channels



SODIUM CHANNELS

Voltage gated Na+ channel: α-subunit
4 repeated domains.
Each domain has 6 membrane spanning subunits.
Subunit 4 acts as a voltage sensor.
From University of Toronto

Non-Voltage gated Na+ channel
Each subunit has 2 membrane spanning subunits.
The channel is a heterotrimer.
From Lake Forest College



POTASSIUM CHANNELS


CTX: Charybdotoxin
Ball & chain: Inactivation domain
From: Goldstein

Voltage-gated Shaker K+ channel
Inwardly rectifying K+ channel




CALCIUM CHANNELS

Voltage gated Ca++ channel

From Queens University
  • Contains voltage sensor & Ca++ selective pore
  • Consists of 4 internal repeated domains (I-IV)
    • Each domain contains 6 α-helical transmembrane regions (S1-S6)
    • Domain I: responsible for channel activation kinetics
    • S4: Positively charged; Forms part of the voltage sensor
    • 2 additional domains between S5 & S6: Form pore region of channel
    • Verapamil & nifedipine bind
      • Helix 5 & 6 regions of domain III
      • Sequence after helix 6 of domain 4


Excitation-Contraction Coupling: Muscle



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11/13/2013