MUSCLE SPINDLES OR GOLGI TENDON ORGANS?

MUSCLE SPINDLES OR GOLGI TENDON ORGANS?ORMuscle spindles -respond to stretch(changes in LENGTH)Golgi Tendon Organs -respond to FORCE,muscle tension

1. What are discharges of Muscle Spindlesand Golgi Tendon Organs when youpassively stretch a relaxed muscle(rapidly)?

PASSIVE STRETCH RELAXED MUSCLE (rapidly)LENGTH1LENGTH2PULLONTENDON O O FORCEINCREASEDISCHARGELITTLE ORNOINCREASEWhen relaxed, muscle cells are easily stretched, tendon is stiff;MUSCLE SPINDLE - stretch excites muscle spindleGOLGI TENDON ORGAN - little or no increase as muscle easilystretched; exerting force but not a lot.

2. What are discharges of Muscle Spindlesand Golgi Tendon Organs when you try tostretch a contracted muscle (attempted)?

STRETCH CONTRACTED MUSCLE (attempted)LENGTHSTAYSSAMEFORCEONTENDONLARGELENGTH2LENGTHwhen pulledPULLONTENDON1 lb1 lbFORCE+100 lbPULLNODISCHARGEINCREASEDISCHARGEWhen contracted, muscle cells are stiff, tendon is pulled tautMUSCLE SPINDLE - no stretch, no dischargeGOLGI TENDON ORGAN - increases discharge; frequency of actionpotentials encodes amount of force applied.

3. What are discharges of Muscle Spindlesand Golgi Tendon Organs in an IsotonicContraction if you only activate Alpha MotorNeurons?

ISOTONIC CONTRACTION - MUSCLE CONTRACTS ANDMOVES MODERATE (CONSTANT) LOADISO = sameTONIC = forceLENGTH1LENGTH2LENGTH 1 > LENGTH 2FORCE 1 = FORCE 2FORCE1= 1 lbFORCE2= 1 lbDISCHARGEENCODESLOADex. Lifting an Object - Muscle shortens, tension on tendon stays about same;GOLGI TENDON ORGAN - discharge constant, reflects load (force on tendon);GTO same in all circumstances

ISOTONIC CONTRACTION BY ACTIVATING ONLY ALPHAMOTONEURONSPrimary IaRESTSecondary IISensory neuronsstop firing (Ia) or decrease (II)Primary IaSecondary IIFLEXSHORTENSMUSCLEMUSCLE SPINDLE - goes slack; Ia discharge stops;II discharge decreases

4. What are discharges of Muscle Spindlesand Golgi Tendon Organs in an IsotonicContraction produced by Alpha-Gamma coactivation?

ISOTONIC CONTRACTION - MUSCLE CONTRACTS ANDMOVES MODERATE (CONSTANT) LOADISO = sameTONIC = forceLENGTH1LENGTH2LENGTH 1 > LENGTH 2FORCE 1 = FORCE 2FORCE1= 1 lbFORCE2= 1 lbDISCHARGEENCODESLOADex. Lifting an Object - Muscle shortens, tension on tendon stays about same;GOLGI TENDON ORGAN - discharge constant, reflects load (force on tendon);GTO same in all circumstances; activating Gamma motor neurons does notgenerate additional force.

ISOTONIC CONTRACTION (WITH ALPHA GAMMACOACTIVATION)RESTALPHAONLYALPHA +GAMMAOverall spindlelength gets shorterbut middle partstretched enough sonot go slackMUSCLE SPINDLE - maintain discharge; means discharge at rest does notdecrease.

5. What are discharges of Muscle Spindlesand Golgi Tendon Organs in an Isometriccontraction?

ISOMETRIC CONTRACTION - MUSCLECONTRACTS AGAINST IMMOVABLE LOADISO = sameMETRIC = lengthLENGTH 1 = LENGTH 2FORCE 1 < FORCE 2LENGTH1LENGTH2FORCE 1 FORCE 2NODISCHARGEINCREASEDISCHARGEMuscle length stays about same, force increases greatly; tendon stretchesslightly (tension on tendon is proportional to force);MUSCLE SPINDLE - no discharge (no change length)GOLGI TENDON ORGAN - increase discharge (encodes force)

6. What are discharges of Muscle Spindlesand Golgi Tendon Organs if only Gammamotor neurons are activated?

ONLY ACTIVATE GAMMA MOTOR NEURONGAMMA DYNAMICMOTOR NEURONDYNAMIC BAGSTATIC BAGGAMMA STATICMOTOR NEURONSCHAINSPINDLEMUSCLE CELLGETS SHORTERMIDDLE OFCELL GETSLONGERACTIVATEGAMMA DYNAMICMOTORNEURON,GAMMA STATICMOTOR NEURONWhen activate gamma motor neurons, intrafusal cells contract; they getshorter but the middle of the cell stretches; this can actually producea discharge of MUSCLE SPINDLES; little force generated so no GTO discharge