As a person squats, the quadriceps muscles contract. At the same time, the respective Golgi tendon organs _______ their firing rate, and the intrafusal muscle fibers _______ their firing rate.Group of answer choicesincrease; increaseincrease; decreasedecrease; decreasedecrease; increasedecrease; level off

Sure, let's break down the question step by step.

1. Understanding the Quadriceps Contraction:

   • When a person squats, the quadriceps muscles (located at the front of the thigh) contract to control the movement and provide stability.

2. Role of Golgi Tendon Organs (GTOs):

   • Golgi tendon organs are sensory receptors located at the junction of muscles and tendons. They monitor tension within the muscle.
   • When the muscle contracts, the tension increases, and the GTOs respond by increasing their firing rate to prevent potential muscle damage from excessive force.

3. Role of Intrafusal Muscle Fibers:

   • Intrafusal muscle fibers are part of the muscle spindle, which detects changes in muscle length and the rate of change in length.
   • When the muscle contracts, the muscle spindle's intrafusal fibers typically decrease their firing rate because the muscle is shortening, reducing the stretch on these fibers.

Now, let's match this understanding with the given options:

• Increase; increase: This would mean both GTOs and intrafusal fibers increase their firing rate, which is not correct because intrafusal fibers typically decrease their firing rate during muscle contraction.
• Increase; decrease: This matches our understanding. GTOs increase their firing rate due to increased tension, and intrafusal fibers decrease their firing rate due to muscle shortening.
• Decrease; decrease: This would mean both GTOs and intrafusal fibers decrease their firing rate, which is incorrect because GTOs should increase their firing rate.
• Decrease; increase: This is incorrect because intrafusal fibers should decrease their firing rate during muscle contraction.
• Decrease; level off: This is incorrect because GTOs should increase their firing rate.

Therefore, the correct answer is:

Increase; decrease