Muscle Sensory Control Flashcards
What are the two types of muscle receptors?
Muscle spindles
Golgi tendon organs
What is the function of muscle spindles?
Signal joint position and movement by monitoring muscle length
Signal movement velocity
Located within the muscle
What is kinesthesia?
Conscious sense of body position and movement that depends upon signals from muscle receptors
What is the stretch reflex?
Stretch of muscle spindles that causes the contraction of a muscle (e.g. gastrocnemius)
Does not require conscious awareness
What type of motor neurons innervate muscle spindles?
Gamma motor neurons
What are golgi tendon organs?
Located in muscle tendons or connective tissue attachments
Sensitive to tension in the tendon and signals force
What type of neuron is responsible for skeletal muscle contraction?
Alpha motor neurons (Lower motor neurons)
What is muscle tonus?
The muscle tension at rest, due to activities in alpha motor neurons at rest
Where is the density of muscle spindles highest?
Highest in muscles that are used in fine control
E.g. muscles involved in finger and eye movements
How are muscle spindles different from normal muscle cells?
Nuclei are in the middle
Middle region does not contract (no contractile filaments), location of sensory innervation
The polar regions (ends) have contractile filaments and can contract, location of motor innervation
Describe gamma motor neurons
Smaller that alpha motor neurons
About 30% of all axons in ventral roots are gamma motor neurons
Firing contracts muscle spindle, but does not generate much force at the muscle tendon
What are Gamma dynamic motor neurons?
Innervate fast contracting muscle cells
What are Gamma static motor neurons?
Innervate slow contracting muscle cells
What are sensory Ia neurons?
1
per spindle; innervates all muscle cells
What are sensory II neurons?
1-5 per spindle; innervates only slow contracting muscle cells
How does a tendon tap cause a reflex?
Produces a brief fast stretch of the muscle, which in turn activates all spindle sensory neurons in the muscle
What do group II fibers encode about stretch?
Only encode magnitude of change in length
i.e. how long is the muscle
What do group Ia fibers encode about stretch?
Encode velocity of stretch and length
i.e. how fast is stretch
What is the function of gamma motor neurons?
Adjust spindle length to muscle length; reset sensitivity
What type of sensory neurons innervate golgi tendon organs?
Large, Type Ib sensory neurons
What type of contraction will cause a large discharge in the golgi tendon organ?
Isometric contractions
