Both- the textbook and your teacher are right.
The most obvious function of the pars intermedia in lower vertebrates is the secretion of melanocyte-stimulating hormone (MSH) for the purpose of pigmentary control.
In human fetal life as well, this area produces MSH which causes the release of melanin pigment in skin melanocytes.
The human ...
Voltage-gated sodium channels have three basic states that represent different conformations of the protein: closed, open, and inactivated.
When a voltage-gated sodium channel is open at depolarized voltage, there is space for part of the channel to shift into a position that blocks the pore. When this happens, it gets stuck blocking the flow of sodium, and ...