Muscle Sensors And Spinal Reflexes Flashcards
Muscle sensors
Muscle spindles
Golgi tendon organs
Muscle spindles
In parallel with muscle
Respond to changes in length (static length and the rate of change of length)
Golgi tendon organs
In series with muscle
Respond to changes in tension
Capsules of tendons, “braided”
1mm long and 100 micrometers in diameter
Intertwined never fibres are distorted during tension
Innervated by Ib afferent nerve endings
Location of Golgi tendon organs
Within tendons, near the muscle tendon junction
What are Golgi tendon organs?
Encapsulated nerve endings that have numerous terminal branches; small swellings associated with bundles fo collagen fibres in the tendons
When are Golgi tendon organs stimulated?
As the tendon is stretched during muscle contraction
2 types of muscle spindles
Nuclear bag fibres (dynamic response)
Nuclear chain fibres (static response)
What are muscle spindles innervated by?
Gamma motoneurone
How long are muscle spindles?
~10 micrometers
What does intrafusal mean?
Within spindle
What does non-contractile mean?
Lack of myofibrils
Chain fibre
Four to ten per spindle
Nuclei are formed in a line
Found in the central region of the muscle
Underlying sensory nerve (Ia fastest in the body)
Bag fibre
Usually two per spindle
Bunch of about 100 nuclei
Found in the central region
Underlying the sensory nerve endings
Muscle spindles - dynamic response
Response during stretch
Related to velocity of stretch
Muscle spindles - static response
Response following he stretch
Decrease in afferent discharge (related to muscle length)
Firing rate is dependent on the length of the muscle
Gamma motor neurones
These originate in the spinal cord and they control the contractions of the ends of the muscle spindle cells.
Non-contractile centres of the muscle spindle cells are innervated by afferent neurons.
Carry impulses to the spinal cord.
Synapse directly with a motor neurones
