The simplest reaction is called a reflex, defined as an automatic reaction to a
A pathway of the human nervous system is the series of neurons or other
structures used to transmit an item of information. In general, we consider two major
types of pathways--the general sensory pathways and the motor pathways.
At some specific level in the neuraxis, all of these pathways cross to the opposite
side. Each crossing is called a decussation. Thus, the right cerebral hemisphere
communicates with the left half of the body. The left cerebral hemisphere
The general senses include pain, touch, temperature, and proprioception ("body
A general sensory pathway extends from the point where the stimulus is received
to the postcentral gyrus (fold) of the cerebral hemisphere. This gyrus is the site of
conscious sensation of a stimulus.
Corresponding to each location in the body, there is a specific location in the
Pain is an ancient protective mechanism which generally helps us to avoid injury.
Endorphins are chemicals found naturally within the body which tend to block the
sensation of pain.
The pain receptor is not a specific receptor organ. It is referred to as a free nerve
The body has two different mechanisms for sensing temperature. Detecting
warmth and cold in the periphery of the body are specific sensory receptors. Special
heat-sensitive neurons in the hypothalamus detect increases in the temperature of the
The pacinian corpuscles are typical of the receptors which detect deep pressure.
Another term for muscle sense is proprioception. For this, there is a special
receptor organ to monitor the stretch of the muscle. These receptor organs are called
muscle spindles or stretch receptors. They detect relative muscle length.
Another stretch receptor associated with the skeletal muscle is the Golgi tendon
organ. As its name implies, this organ is located within the tendon of the muscle. It