Transcellular Pathway

Water and solutes can be transported through the cell membranes by passive diffusion or active transport.

TLS Online TPP Program

#Id: 4014

#Unit 7. System Physiology – Animal

Membrane ion channels that play important roles in generation of the action potential:

T (transient) channels 

L (long-lasting) channels Voltage gated potassium ion channel

TLS Online TPP Program

#Id: 4015

#Unit 7. System Physiology – Animal

Between heartbeats, influx of positively charged sodium ions causes a slow rise in the resting membrane potential in the positive direction. 

TLS Online TPP Program

#Id: 4018

#Unit 7. System Physiology – Animal

When the potential reaches a threshold voltage of about −40 millivolts, the L-type calcium channels become “activated,” causing the action potential

TLS Online TPP Program

#Id: 4019

#Unit 7. System Physiology – Animal

L-type calcium channels become inactivated (i.e., they close) within about 100 to 150 milliseconds after opening

TLS Online TPP Program

#Id: 4022

#Unit 7. System Physiology – Animal

When the L-type calcium channels become inactivated at about the same time, greatly increased numbers of potassium channels open.

TLS Online TPP Program

#Id: 4025

#Unit 7. System Physiology – Animal

Large quantities of positive potassium ions diffuse out of the SA node.