Signal Transmission is chemicals that move throughout the body. These signals can be transported into two ways: Intercellular and Intracellular. Intracellular allows signals to move from cell to cell. Intracellular allows signals to move within the cell itself.
Stimuli
The base for a signal transmission is the transformation of a certain stimulus into a chemical signal.
Ligands
Majority of the pathways involve the binding so signaling molecules, also known as ligands, to receptors that trigger events inside of the cell. Combination of a ligand with a receptor causes a change in the conformation of the receptor , also known as receptor activation. Lingands typically bind to the cell surface receptors.
Receptors
Receptors can be divided into two categories: intracellular and extracellular.
Intracellular: Intracellular receptors are soluable solutions. First, to initiate signal transmission, the ligand must pass through the plasma membrane by passive diffusion. When binding with the receptor, the ligands pass through the nuclear membrane into the nucleus, altering gene expression.
Extracellular: Extracellular receptors are integral transmembrane proteins and make up most of these receptors. Signal transmission occurs as a result of the ligand binding to the outside part of the receptor. It then induces change in the conformation of the inside of the receptor.