Muscle Spindle and Golgi Tendon Organ Lecture Review

A set of 20 vocabulary flashcards covering muscle spindle mechanics, afferent nerve types, and sensory receptor functions based on lecture notes.

Alpha Motor Neurons

Efferent neurons that innervate extrafusal fibers to produce force and cause voluntary skeletal muscle contraction.

Group $Ia$ Afferent

Primary endings that detect speed and size of rapid stretch (velocity of muscle length) and initiate the stretch reflex.

Group $II$ Afferent

Secondary endings that detect sustained muscle length and static stretch to maintain posture and joint position.

Group $Ib$ Afferent

Tension receptors that travel to the spinal cord to detect muscle tension and force, most active during active contraction.

Muscle Spindle

A proprioceptor and intrafusal stretch sensor located within the muscle belly, arranged parallel with extrafusal muscle fibers.

Golgi Tendon Organ (GTO)

A proprioceptor and tension receptor located within the tendon near the myotendinous junction, arranged in series with extrafusal muscle fibers.

Autogenic Inhibition

Also known as the Inverse Stretch Reflex, where the $Ib$ interneuron inhibits the Alpha Motor Neuron to cause the muscle to relax and prevent injury.

Gamma Motor Neurons

Efferent neurons that innervate intrafusal fibers to keep the spindle taut and maintain sensitivity during muscle contraction.

Afferent

Signals that 'arrive' at the Central Nervous System (CNS) from sensors like muscle spindles.

Efferent

Signals that 'exit' the Central Nervous System (CNS) to go toward targets like tendons or muscles.

Extrafusal muscle fibers

The 'worker' muscle fibers responsible for producing force and contraction.

Intrafusal fibers

Specialized muscle fibers within the spindle that function as stretch sensors and receive innervation from Gamma Motor Neurons.

Dynamic Function

A muscle spindle function involving Group $Ia$ afferents that detects the rate of muscle stretch.

Static Function

A muscle spindle function involving Group $II$ afferents that detects sustained muscle length, such as holding an elbow at $90$ degrees.

Joint Receptors

Sensors that respond to the chemical deformation of the joint capsule and ligament.

Ruffini Endings

A type of joint receptor classified as Type $II$ afferents.

Paciniform Corpuscles

A type of joint receptor classified as Type $II$ afferents.

Free Nerve Endings

Joint receptors classified as Type $III$ and Type $IV$ afferents.

Ligament Receptors

Receptors similar to the Golgi Tendon Organ (GTO) that use Type $Ib$ afferents to detect force.

Patellar tendon reflex

A monosynaptic stretch reflex where $Ia$ fibers fire rapidly, causing the quadriceps to suddenly stretch.