Muscle spindles

Definition

Muscle spindles are sensory receptors located within muscles that detect changes in muscle length and the rate of that change. They play a crucial role in regulating muscle contraction and maintaining posture.

5 Must Know Facts For Your Next Test

1. Muscle spindles are composed of intrafusal fibers which are innervated by both sensory and motor neurons.
2. They provide feedback to the central nervous system about muscle stretch, enabling proprioception.
3. The primary afferent (Ia) fibers are responsible for transmitting rapid changes in muscle length.
4. Gamma motor neurons adjust the sensitivity of muscle spindles by altering the tension of intrafusal fibers.
5. Muscle spindle activity results in the stretch reflex, which helps prevent muscle damage from overstretching.

Review Questions

• What type of sensory information do muscle spindles provide to the central nervous system?
• How do gamma motor neurons influence muscle spindle sensitivity?
• What is the relationship between muscle spindles and the stretch reflex?

Related terms

Proprioception:

The sense of body position and movement mediated by proprioceptors including muscle spindles.

Intrafusal Fibers: Specialized muscle fibers found within a muscle spindle that detect changes in muscle length.

Stretch Reflex: A spinal reflex that involves the contraction of a stretched muscle to prevent overstretching, initiated by muscle spindle activity.