Motor 1: Monosynaptic (stretch) reflex Flashcards
Nucleur Bag fiber is responsible for detection of
Dynamic stretch
Nuclear chain fiber is responsbile for detection of
Static stretch
Type of Afferent fiber of Nuclear bag Intrafusal Muscle fiber
Primary ending (annulospiral)
* Group Ia
* Thick
* myelinated
Type of Afferent fiber of Nuclear chain Intrafusal Muscle fiber
Both Primary ending & secondary ending
Dynamic response is done by
primary ending (annulospiral) fibers of Nuclear Bag
Dyanmic response is the base of
Tendon jerk (sudden contraction & relaxation)
Static Response is done by
Primary ending (annulospiral) & secondary ending of Nuclear Chain
Static response is the base of
Muscle tone
primary ending (annulospiral) responds to
both change in length & change in rate of stretch
Enumerate physiological Importances of Stretch reflex
- Maintain muscle length
- Control of Voluntary movement
- Base of Muscle tone & tendon jerk
Describe Servo-assistant function of the voluntary control of movement done by stretch reflex
- Descending fibers from cortex stimulate both Alpha and gamma motor neurone
- Alpha neurone causes contraction of extrafusal Muscle fibers, while Gamma motor neurone causes contraction of peripheral contractile part of Intrafusal Muscle fibers, causing intrafusal Fibers to stretch
- Stretch in infrafusal fibers Causes afferent (primary and secondary Ending) to stimulate Alpha neurone more, causing more contraction
Describe Damping function of the voluntary control of movement done by stretch reflex
- Impulses ariving from the cortex cause ausculatory jerky contractions
- Afferent fiber (primary and sencondary ending) sends signals to the cortex to readjust and smoothen the contraction
Despite rest, explain why muscle spindle is always stretched
- Attachement of the muscle further than its actual length
- Gravity
- Activity of Gamma motor Neurone
Explain why muscle tone doesnt cause fatigue
- Alternating contractions
- Sub-tetanic
- Red fibers
Functions of Muscle tone
- Maintain body temperature
- Aid in venous return
- Maintain posture
- Background for voluntary movement
Facilitatory reticular formation sends facilitatory signals to Gamma motor Neurone through
Ventral reticulospinal Tract
Facilitatory reticular formation Recieves facilitatory signals from
- primary motor Area
- Neocerebellum
+ intrisic activity
Facilitatory reticular formation is located in the
Pons
Vestibular Nucleus sends facilitatory signals to gamma motor neurone through
Vestibulospinal tract
Site of Inhibitory reticular formation
Medulla
Inhibitory reticular formations sends Inhibtory signals to gamma motor neurone through
Lateral reticulospinal tract
Inhibitory reticular formations recieves signals from
- Paleocerebellum
- Cortical Suppressor Area
- Basal Ganglia
Red nucleus sends inhibtory Signals to gamma motor neurone through
Rubrospinal Tract
Explain what will happen to Stretch reflex if there was a cut between midbrain & pons
- Facilitatory: still working, as facilitatory RF has intrinsic activity
- Inhibitory: Not working, no intrinsic activity
Causing Decerbrate Rigidity
Causes of Areflexia/Atonia
- Tebes dorsalis
- Polimyelitis
- Peripheral Neuritis
Causes of Hyperreflexia/Hyper atonia
- Anxiety (high reticular formation activity)
- UMNL
- Hyperthyroidism
Causes of Hyporeflexia/Hypotonia
(defect in facilitation):
* Neocerebellar Syndrome
* Myxoedema (opposite hyperthyroidism)
* Sleep (no reticular formation activity)
Golgi tendon organ is stimulated by
- Active contraction
- Passive tension
Receptor of Inverse stretch reflex
Golgi tendon organ
Afferent of Inverse stretch reflex
Group I-b
Center of inverse stretch reflex
Bisynaptic Center
Efferent of inverse stretch reflex
Alpha motor neurone
Response of inverse stretch reflex
Inhibitory (relaxation of muscle)
Importance of inverse stretch reflex
to protect muscle from exessive Contraction
