- Excitability.

-Def:- is the ability of cells to respond to stimuli.

-Excitability of cells and tissues is a basic function of life,as it is necessary for the functioning of nerves, muscles, and hormones,etc...

-The basis for the excitability of cells is their ion distribution, and the distribution of ions and molecules is determined by transport mechanisms associated with their plasma membrane structure.
-This structure permits and regulates various forms of ionic and molecular transport.

-Stimuli which induce Excitability are classified into two types:-
1-electrical. (galvanic ,faradric)
2-chemical.( ions , chemical transmitters, gases,……etc)

-you must know that:-
Excitable cells are those that can be stimulated to create a tiny electric current which in turn is transformed into physiological function and excitable cells are of three types:-

• Muscle cells.
• Nerve cells (neurons).
• Glandular cells.