acetylcholine
A chemical substance in the body tissues that facilitates the transmission of nerve impulses from one nerve to another. It has a stimulant (or excitatory) effect on some parts of the body (such as skeletal muscles) and a depressant (or inhibitory) effect on other parts of the body (such as the heart muscle); also known as a neurotransmitter.
afferent nerves
Transmitters of nerve impulses toward the CNS; also known as sensory nerves
agnosia
Loss of mental ability to understand sensory stimuli (such as sight, sound, or touch) even though the sensory organs themselves are functioning properly. For example, the inability to recognize or interpret the images the eye is seeing is called optic agnosia.
agraphia
The inability to convert one's thoughts into writing.
alexia
The inability to understand written words.