Muscle Spindle and GTO Flashcards
(30 cards)
Muscle Contracture
Individual with a complete C7 SCI with a elbow flexion contracture due to prolonged positioning in an elbow flexed position
C7 SCI : key muscles still functionally working
-C4: Upper trapezius, Accessory neck muscles, Deep neck muscles, Diaphragm
C 1, 2, 3: need ventilator to breathe
- C5: Biceps, Wrist extensors (ASIA – elbow flexors)
- C6: Wrist Extensors, Serratus Anterior, Latissimus Dorsi (ASIA – wrist extensors)
- C7: Triceps, Intercostals /muscles of first seven rib muscles, upper slips of abdominal muscles (poor trunk control) (starts at T6), Back/neck Extensors C-1-7 (ASIA – elbow extensors)
For this individual with C7 SCI, which of the following is likely the BEST stretching choice?
Active Stretching (for biceps) bc they can use their antagonist muscle (aka triceps) to try to change their contracture of the biceps muscle --Strengthen the triceps as well
Passive Stretching –There are no functioning muscles around the joint. Neither agonist, synergist, or antagonist muscle function is present.
- Example for this patient: hip flexion contracture in an individual with C7 quadriplegia (tetraplegia)
- Active stretching is NOT possible in this case since there are NO functioning muscles
Passive Stretching – The contracture has a soft tissue endfeel. Soft tissue endfeels mean that the restriction may be due to…
-Muscle endfeel: medium-soft; compliant to a point (example, hamstring muscles) –Intervention – Most appropriate to use active stretching technique to stretch the muscle (more later)
-Myofascial endfeel: medium; firmer than muscle endfeel (soft endfeel)
Intervention – Most appropriate to use Myofascial release techniques
-Skin adhesion or scar tissue endfeel: soft, compliant to a point, observe skin restriction or scar tissue stop–Intervention – Most appropriate: Soft tissue mobilization (superficial to deep); scar tissue mobilization; functional massage
Passive Stretching – Prolonged stretching time or if equipment is available
- Manual stretching - long duration (“when a relatively low force is sustained for a long period of time, most materials will deform in a time-dependent manner.” “creep” is a result of the viscoelastic properties.)
- Equipment (such as Dynasplint) is available for the patient.
- Not always effective unless pt is using it outside of PT
Passive Stretching– The restriction is due to a joint or capsular issue (firmer endfeel)
Not really a passive stretching technique, but joint mobilization is the most appropriate intervention.
What causes contractures?
- not moving the joint through full ROM
- prolonged positioning in a shorten position
- not have the antagonist to elongate
Other ways to deal with contractures….
- Dynasplint: Can stop wearing it when you strengthen the antagonist (triceps)
- –Hard end feel = bony end feel, Intervention: none, not likely to respond to stretch; potentially surgery, but controversial
Why is active stretching the BEST CHOICE for this individual patient case? (C7 SCI)
- Active stretching uses the neuromuscular system
- There usually is high tone (hypertonicity) in the biceps muscle (tone end feel – medium feel and responds to active stretching techniques)
- Active stretching has better immediate & long term results than passive stretching
- –Debatable*- seen in literature but it depends on the tissue
- This individual with C7 SCI has functioning muscles around the elbow joint
- –Both biceps and triceps
Contract-Relax Active Stretching
Contract – Relax
concentric
Contract-relax through range near point of restriction- active concentric (moving) contraction of the agonist (biceps) may induce relaxation of the agonist (biceps) (muscle spindle neurophysiology)
Hold-Relax Active Stretching
Hold – Relax
isometric
Hold-relax at the point of the restriction - strong contraction of the biceps may trigger the GTO to inhibit the agonist (biceps) (GTO neurophysiology) or may induce immediate relaxation of the agonist (biceps) after the strong agonist contraction (muscle spindle neurophysiology)
Reciprocal Inhibition Active Stretching
Activate antagonist muscle
At end range
This pt can use their triceps—see previous slides
Reciprocal inhibition at the point of the restriction would strengthen (facilitate) the triceps and inhibit the biceps (muscle spindle neurophysiology)
Cross fiber massage at the musculotendinous junction
Active Stretching
Find tendon and find where it meets the muscle and massage perpendicular
Not truly actively stretching but does use neuromuscular wiring to get the outcome
Cross fiber massage at the point of the restriction at the biceps musculotendinous junction – would inhibit the biceps (GTO neurophysiology)
What type of active stretching intervention is the BEST CHOICE for this individual with C7 SCI? (In Larson’s opinion)
1st: Reciprocal inhibition at the point of the restriction would strengthen (facilitate) the triceps and inhibit the biceps (muscle spindle neurophysiology)
2nd: Cross fiber massage at the point of the restriction at the biceps musculotendinous junction – would inhibit the biceps (GTO neurophysiology)
3rd: Hold-relax at the point of the restriction - strong contraction of the biceps may trigger the GTO to inhibit the agonist (biceps) (GTO neurophysiology) or may induce immediate relaxation of the agonist (biceps) after the strong agonist contraction (muscle spindle neurophysiology)
4th: Contract-relax through range near point of restriction- active concentric (moving) contraction of the agonist (biceps) may induce relaxation of the agonist (biceps) (muscle spindle neurophysiology)
C7 SCI: Use the arm functionally within the new (and previous) range of motion
- Reaching, rolling, PNF to encourage proximal scapula and shoulder muscle function with elbow extension
- Re-set muscle spindle bias
- Muscle spindle bias is the tendency for the muscle to resume its original length due to the idea that the muscle spindle wants to assume its original length
Muscles have two sensory receptors
Muscle spindles sense change in muscle length
—-Parallel to “regular muscle fibers” – fast, slow and intermediate fibers
GTOs sense change in muscle tension/force
Lie in series with the muscle (between tendon and muscle)
—-Actively contract or passively stretch= pull GTO to get info about how much force
**most important function is proprioception: where joints are or muscle length
Muscle Spindle
- complex intrafusal sense organ (4-10 mm in length)
- intrafusal muscle fiber of two types
- -nuclear bag - large diameter - clustered, central nuclei
- —two sub-types: static nuclear bag and dynamic nuclear bag
- -nuclear chain - smaller diameter and nuclei more spread out: 2 chain fibers for every bag fiber
Afferents
- Ias (both Ia phasic & Ia tonic) arise from primary (annulospiral) intrafusal muscle fibers
- Ia phasics arise from dynamic nuclear bag fibers
- Ia tonics arise from nuclear chain fibers
- IIs arise from the flower spray receptors on the polar ends of the muscle spindle
Ia phasics afferents
- primary annulospiral receptors
- arise from the dynamic nuclear bag central area
- sense both the rate of muscle lengthening (velocity) and muscle length changes
- Facilitory [+] to the agonist through the alpha MN
- inhibitory [-] to the antagonist (thru interneuron)
Ia tonics afferents
- primary annulospiral receptors
- arise from the nuclear chain area
- sense muscle length changes
- Facilitory [+] to the agonist through the alpha MN
- inhibitory [-] to the antagonist
Individual with C7 SCI and elbow flexion contracture…
Elicit contraction of the triceps (here agonist) which would facilitate (+) the agonist/triceps and inhibit the antagonist/biceps.
Reciprocal inhibition
GTOs
When the collagen fibers are pulled tight when the tendon is lengthened and it’ll cause a depolarization in the axon which will cause the muscle to contract. If the muscle contracts, it also elongates the tendon causing the GTO to fire.
Tells us where the joint is.
Ib afferents
- Arise from the golgi tendon organs (GTOs) which are encapsulated sense organs located in the tendons (near musculotendinous junction)
- In series with the extrafusal muscle fibers
- “braided” structure around Ib afferent neurons
- GTO is 1 mm long & 0.1 mm in diameter
