Page 200 - The Miracle of Hormones

Stimulus
transmitter Receiver
hormone Endothelial cell
Smooth muscle cells
Nitric oxide

Nucleus

Constricted
artery
GC
GC

Storage area
GC

GTP cGMP
Actin
Myosin

Dilated artery

Amessage-bearing hormone binds with receptors on the artery. As a result of this
bond, NO is produced. The NO molecules travel towards the smooth muscles and
activate the GC enzyme there. This worker enzyme converts the GTP, the energy
carrying molecules into cGMP. The cGMP causes calcium ions to go to the storage
areas in the cell. As a result of these operations, the smooth muscle cells relax and
the blood vessels dilate.