Muscle Spindle Outcomes Flashcards
What is the myotatic reflex?
When a muscle is pulled, it pulls back
What innervates the intrafusal muscle fibres?
- sensory afferents
- gamma motor neurone efferents
Supinator reflex
C5-C6
Biceps reflex
C5-C6
Triceps reflex
C7
Quadriceps reflex (knee)
L3-L4
Gastrocnemius reflex? (ankle)
S1
What innervates the non-contractile region of intrafusal fibres?
Ia afferents
What innervates the contractil region of intrafusal fibres?
Gamma motor neurones
What causes the spindle to contract?
Stimulation of the gamma fibres
What are Nuclear bag 1 (dynamic) fibres sensitive to?
Rate of change of muscle length
innervated by dynamic gamma neurones
What are nuclear bag 2 (static) fibres sensitive to?
Absolute length of muscle
innervated by static gamma neurones
What are chain fibres sensitive to?
The absolute length of the muscle
innervated by gamma neurones
Where are golgi tendon organs located?
At the junction between the muscle and tendon
What do golgi tendon organs monitor?
The changes in muscle tension
What innervates golgi tendon organs?
Ib fibres
What do golgi tendon organs do?
Regulate muscle tension (i.e. protect muscle from overload and make sure that muscle tension is in optimal range)
What do proprioceptive axons do?
Respond to changes in angle, direction and velocity of movement of a joint. Also prevent excessive flexion, or extension
Function of free nerve endings?
Nociceptive role
Function of golgi endings
Protective role
Function of paciniform endings
Acceleration detectors
Function of ruffini endings
Sense static position and speed of movments
What do spinal interneurones do?
Integrate incoming information ro generate an output
- they mediate the inverse myotatic reflex
- reciprocal inhibition between extensors and flexors
Give an example of reciprocal inhibition
Myotatic reflex causes the homonymous extensor muscle (quadriceps) to contract, but for the leg to extend the antagonist flexor muscle (hamstring) must simultaneously relax
What is the flexor reflex?
Noxious stimulus causes limb to flex by:
contraction of flexor muscles via excitatory interneurones
relaxation of extensor muscles via excitatory and inhibitory interneurones
What is the crossed extensor reflex?
Noxious stimulus causes limb to extend by:
contraction of extensor muscles via excitatory interneurones
relaxation of flexor muscles via excitatory and inhibitory interneurones
This reflex enhances postural support during withdrawal of a foot from a painful stimulus (you do not fall over!)
