What Are the Proprioceptors and Proprioception?

Proprioception is a sense of body and limb position awareness

Woman In Physical Therapy, France
Proprioceptors involve your sensory nerves being aware of your body's movements - like in physical therapy. BSIP/UIG/Getty Images

Proprioceptors are specialized sensory receptors on nerve endings found in muscles, tendons, joints, and the inner ear. These receptors relay information about motion or position and make you aware of your body position and movement in space. Proprioceptors detect subtle changes in movement, position, tension, and force, within the body.

What is Proprioception?

Proprioception allows a person to sense his or her body's orientation in its environment.

Thanks to proprioception, you can move about without consciously focusing on where you are in your environment. 

For instance, if you raise your arm above your head with your eyes closed, you're still aware of where your arm is even though you can't see it. If you're walking on a sidewalk and the surface changes (say from concrete to grass), your body knows how to adjust your stride even if you're not looking at the ground.

Proprioception comes from sensory nerve endings that communicate information from your limbs. You have nerves in your muscles and joints that tell the brain which positions your joint is in.

Proprioceptors in the Body

The proprioceptors of the musculoskeletal system are found in the tendons and the muscle fibers. These proprioceptors include:

  • Muscle spindles (stretch receptors). These are the primary proprioceptors in the muscles that are sensitive to changes in muscle length. These allow you to know when to stretch your legs while walking or your arms when reaching for something.
  • Golgi tendon organs. These proprioceptors are found in the tendons near the end of the muscle fiber. They are sensitive to changes in muscle tension. For example, for a weightlifter, the Golgi tendon organs sense how much tension the muscles in the arms are exerting. If the muscle has too much tension, the Golgi tendon organs will prevent it from creating any force (it's at this point that the weightlifter would probably drop the weight or realize he has to place it down). This helps prevent injury.
  • The Pacinian corpuscles. These proprioceptors are responsible for detecting changes in movement and pressure within the body. They're found in parts of the body such as the fingertips and are very useful in helping you detect textures, for instance.

How Proprioceptors Protect You From Injury

In addition to providing information about the movement and positioning of your body, head, arms, and legs, the proprioceptors can trigger certain protective reflexes. The "stretch reflex," for example, is activated when the proprioceptors sense too much stretch or force on a muscle or tendon. To resist an unsafe change in muscle length that may lead to a torn muscle or tendon, the reflex causes the stretched muscle to contract, shorten, and protect the muscle or tendon from injury.

What Happens When Proprioceptors Fail?

Although it's not possible to lose all proprioception, for people with multiple sclerosis (MS), there's a slowdown in nervous system communication, known as demyelination. MS leaves people less aware of their bodies, in a way, with balance control issues an early sign of the condition.

An ankle sprain can impair your sense of proprioception and you may feel the joint is unstable and about to give out.

Proprioceptive exercises are a common rehabilitation therapy to help you relearn how to control the position of the joint.

Source:

Purves D. Neuroscience. New York: Oxford University Press; 2018.