17.1 Stretch Reflex

[@MainEv3nt13]

Extremely helpful please continue the great job! A student from Greece

[@GreekLietuvos]

Same! Thank you! from another student from Greece!

[@yeppy013]

She teaches very well and to the point!

[@IsmailKhan-vx7mb]

Thanks a million ma'am, mesmerising lecture !

[@L0n30pium]

amazing lecture!! Keep up the good work Ma’am! - student from india

[@ninkazee]

excellent. Thankyou for explaining this so well.

[@mariaelenajimenez9120]

Very nicely put. I enjoy watching your videos.

[@abeer6187]

Brilliant !

[@joannperez-fc8qu]

God bless you so And Thank you

[@hrushicatey]

Excellent Madam. Thxx

[@elenajehrlich3796]

How it is work prezisely: kontrakt of the polarregion means at the same time stretch of aquatorislregion? And what happen than with synergist, how they are interconnected in the time and stretch/contraction avtion in relation to each other

[@aliganji8122]

brilliant!

[@fahmisyarif]

Thank you Profesor, student from Indonesia

[@iyappans5259]

Wow nice explanation

[@hussainbushehab2629]

Great appreciation to you

[@sabiaabidi]

Amazing teacher!

[@ahmedelsakka9548]

all that regarding stretch reflex which is involuntary so what is the role of gamma motor neurons in voluntary muscle contraction ??

[@nusinvanwinkle8774]

Same thing, it goes to the muscle spindle making sure that muscle is contracted when muscle is contracted...

[@ahmedelsakka9548]

@@nusinvanwinkle8774 I mean, when i tend to move my bicieps forexample, my cerebral cortex orders goes to anterior horn of the spinal cord then from anterior horn which is supplied next ? Alpha or gamma motor neurons ?

[@ishtaiwemoftah6602]

@@ahmedelsakka9548 goes to both, alpha & gamma neurons simultaneously, it synapse on alpha MN to contract the muscle bulk (Extrafusal fibers) & synapse also on Gamma MN to keep the muscle spindle taut. if the descending pathways synapse on alpha MN only, Extrafusal fibers contract , contraction mean shortening of the muscle, so muscle spindle which is a stretch receptor is not activated b/c there is no gamma MN which contract the polar part of the muscle spindle, therefore the central part of the muscle spindle which is a stretch receptor stretched , so, muscle spindle will become slack (turned off) --> If the muscle were to be stretched again, the muscle spindle would not be able to signal this stretch & muscle spindle will be temporarily insensitive to stretch after the muscle has contracted. so there will be contraction , relaxation, contraction, relaxation & so on --> that is mean there will be jerky contraction not smooth contraction. Remember, muscle spindle is a proprioceptor, so it should inform the CNS about the muscle contraction via spinocerebellar & DCML pathways, if there is no Gamma MN --> so the CNS at some time didn't know anything about the muscle. Note: 1. the higher center (pyramidal tract) sends the impulse in irregular fashion → so contraction supposed to be in irregular fashion , But in presence of stretch reflex → it will convert the jerky contraction to smooth contraction. that is called (Damping effect of stretch reflex). conclusion: the essential role of gamma MN is to prevent the spindle from falling silent when the muscle shortens as a result of active contraction , thus enabling it to signal length changes over the full range of muscle lengths --> This will maintains the spindle firing rate within an optimal range for signaling length changes.

[@barbapapaplouf5419]

Amazing! But a question: how come the stretch reflex does not oppose WILLED movement and stretch? eg i want to flex my arm. my agonist muscle contracts, my antagonist stretches. But if the stretch reflex activates, my antagonist will be contracted, opposing the contraction of my agonist, and I will never be able to flex my arm. So how come the stretch reflex does not render impossible any action? best

[@nusinvanwinkle8774]

The tap to the patellar ligament is unexpectedly causing a rapid stretch in the quadriceps extrafusal fibers that does not originate from voluntary movement. In order to prevent any possible injury from too much stretch, the reflex is to contract the quadriceps. With the willed movements the stretch is not unexpected and not rapid.

[@malak2858]

I'm subscribing

[@georgen9755]

1a inhibitory neuron , .....motor ...muscles ... wasting of the muscles ..... occupational hazards .... in construction labours who are frequently using the reflex motion to stretch their muscles frequently ....... addressing the health related issues of muscles affecting the nervous system and the motor unit ....... many labour contractors do not provide adequate health care to the construction labourers who are deployed through the railways and metropolitan services ...... incurring damage to their daily wages ................. chief engineer , ignou , igcar, Anna university campus , account subhash Chandra Bose , ....... technical training ........ public works department