- Mechanoreceptors respond to mechanical forces (touch and pressure). They
are located in muscles, tendons, ligaments, and joint capsules. They include muscle
spindles, Golgi tendon organs and joint receptors. - Nociceptors respond to pain (pain receptors).
- Chemoreceptors respond to chemical interaction (smell and taste).
- Photoreceptors respond to light (vision).
Muscle spindles are major sensory organs of the muscle.
- They are sensitive to change in length and rate of length of change.
- When a muscle is stretched, its spindles are also stretched.
- This information is transmitted to the brain and the spinal cord to update the
nervous system on the status of the muscle length, and the rate at which that muscle
is lengthening. - When excited, the muscle spindle will cause the muscle to contract – this prevents the
muscle from stretching too far, and/or too fast to prevent injury.
Golgi tendon organs are located within the musculotendinous junction.
- They are sensitive to changes in muscular tension and the rate of the tension change.
- When excited, the Golgi tendon organ will cause the muscle to relax, preventing it from
being placed under excessive stress, and thus resulting in injury. Prolonged Golgi tendon
organ stimulation provides an inhibitory action to muscle spindles – this neuromuscular
phenomenon is called autogenic inhibition (the contracting muscle is inhibited by its
own receptors).
Joint receptors are located in, and around the joint capsule. They:
- Respond to pressure, acceleration, and deceleration of the joint.
- Signal extreme joint positions and thus help to prevent injury.
- Initiate a reflexive inhibitory response in the surrounding muscles if there is too much
stress place on the joint.
Anatomy and Function of a Neuron
A neuron, or nerve cell, is the basic unit of the nervous system, and is how synapses
or messages are sent to various parts of the body. The nervous system is similar to an electric
circuit, in which the circuitry is all connected and relays messages back and forth aiding in
sensory and motor functions. Neurons are highly specialized cells, and are capable of responding
to stimuli, and conducting these stimuli from one part of the cell to another. They have a very
high requirement of oxygen; they can’t live without it for more than a few minutes. When we
are born, there are only a certain number of neurons that we have. They do not reproduce like
most other cells, but some can regenerate or repair specific parts if the cell body remains intact.