The two proprioceptors that tell the spinal cord what a muscle is doing: the spindle, which reports its length and how fast that length is changing, and the tendon organ, which reports the force it is developing. The spindle is a full long question here, with a labelled diagram and the γ motor neuron; the tendon organ usually comes as a short note or an MCQ.
Topics, in the book’s order
- Muscle spindle · pp. 1048–1051 · asked 5 times
- Golgi tendon organ · p. 1052 · asked twice
When you’ve read them: Quiz 127 · Muscle Spindle and Golgi Tendon Organ, 15 questions.
After this chapter you should be able to
- say why the muscle spindle and the Golgi tendon organ matter in motor physiology
- draw and label a schematic diagram of the muscle spindle
- describe what the muscle spindle does
- explain how γ motor neurons set muscle tone
- describe the structure and function of the Golgi tendon organ
Going further: the wider part γ motor neurons play in motor control, and the part the tendon organ plays in it.
Viva checklist
- Structure of the muscle spindle, and the fibres inside it
- Intrafusal versus extrafusal fibres
- Bag 1, bag 2 and chain fibres compared
- Afferent and efferent supply of the spindle
- Primary versus secondary endings: annulospiral and flower-spray
- Functions of the muscle spindle
- Fusimotor neurons: size, share of the ventral root, what they supply
- Static and dynamic γ motor neurons; plate and trail endings
- Static and dynamic spindle responses
- What controls γ efferent discharge
- Jendrassik’s maneuver, and how it works
- α–γ coactivation, and why the spindle still fires in a contracting muscle
- Structure and function of the Golgi tendon organ
- Length feedback versus force feedback