Muscle Spindles vs. Golgi Tendon Organs

Muscle Spindles

• Location:
  • Found within the contractile fibers of the muscle (intramuscular).
• Structure:
  • These are intrafusal fibers, meaning they are located within the muscle fibers.
  • Appear as white fibers within the muscle.
• Function:
  • Sensory organs that sense muscle stretch.
  • When a muscle stretches, muscle spindles send signals via nerves to the spinal cord.
  • Communicate with the muscle fibers to facilitate a muscle contraction.
  • Example: In a baseball pitch, stretching of the shoulder muscle is sensed, leading to muscle contraction.

Golgi Tendon Organs

• Location:
  • Located within the tendons (which connect muscles to bones).
• Structure:
  • Represented as black dots within the tendons.
  • Present in thousands within tendons.
• Function:
  • Sense muscle tension or tendon stretch.
  • During heavy muscle activation (e.g., lifting a one-rep max), the tendon stretches.
  • Golgi tendon organ senses this stretch and aims to protect the muscle by inhibiting overactivation.
  • Causes muscle inhibition to reduce force through the tendon, thereby decreasing tendon stretch.

Summary

• Muscle Spindles:
  • Detect muscle stretch and promote muscle contraction.
• Golgi Tendon Organs:
  • Detect intense muscle activation and promote muscle relaxation or inhibition to prevent damage.

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