If the P2 cell is removed at the early 4-cell stage, the EMS cell will divide into two MS cells, and no endoderm will be produced.

TLS Online TPP Program

#Id: 5455

#Unit 7. System Physiology – Animal

The spatial distribution of ion channels along the axon plays a key role in the initiation and regulation of the action potential

TLS Online TPP Program

#Id: 5456

#Unit 7. System Physiology – Animal

Voltage-gated Na+ channels are highly concentrated in the nodes of Ranvier and the initial segment in myelinated neurons. 

TLS Online TPP Program

#Id: 5457

#Unit 7. System Physiology – Animal

The number of Na + channels per square micrometer of membrane in myelinated mammalian neurons has been estimated: 

50–75 in the cell body, 350–500 in initial segment, less than 25 on the surface of the myelin, 2000–12,000 at the nodes of Ranvier & 20–75 at the axon terminals 

TLS Online TPP Program

#Id: 5458

#Unit 7. System Physiology – Animal

The number of Na + channels along the axons of unmyelinated neurons, is about 110.

TLS Online TPP Program

#Id: 5459

#Unit 7. System Physiology – Animal

Depolarization in myelinated axons travels from one node of Ranvier to the next, this “jumping” of depolarization from node to node is called

saltatory conduction

TLS Online TPP Program

#Id: 5460

#Unit 7. System Physiology – Animal

Saltatory conduction is a rapid process that allows myelinated axons to conduct up to 50 times faster than the fastest unmyelinated fibers