Exercise Physiology Chapter 11 Quiz

The somatic nervous system is responsible for controlling voluntary movements and actions. It innervates skeletal muscles, which are responsible for voluntary movements, such as walking or picking up objects. It does not innervate involuntary muscles, such as smooth muscles found in organs, or cardiac muscle, which controls the beating of the heart. Therefore, the correct answer is that the somatic nervous system innervates skeletal muscle and voluntary muscles.

The gradation of force principle states that the force of muscle action can vary from slight to maximal. This is achieved by two mechanisms: increasing the number of motor units and increasing the frequency of motor unit discharge. By recruiting more motor units and increasing the frequency of their discharge, the muscle can generate a greater force. Therefore, the correct answer is both a and c.

Muscle spindles are sensory receptors located within the muscle fibers that provide information about changes in muscle fiber length and tension. They are responsible for detecting the stretch and contraction of muscles, allowing the body to have proprioception and awareness of the position and movement of the muscles. This information is crucial for coordinating muscle contractions and maintaining balance and posture.

Less complex movements such as forearm supination and elbow flexion have a higher ratio of muscle fibers to motor nerves compared to complex eye and hand movements. This means that these movements require a smaller number of motor nerves to control a larger number of muscle fibers. This suggests that the muscles involved in forearm supination and elbow flexion are more efficient and capable of producing stronger contractions with fewer motor nerves.

A slow oxidative motor unit would probably be activated while the aerobic oxidative phosphorylation system is activated. This is because slow oxidative motor units are specialized for endurance activities and rely on the aerobic energy system to produce ATP. The aerobic oxidative phosphorylation system utilizes oxygen to break down glucose and produce ATP, which is ideal for sustained, low-intensity activities. Therefore, it is likely that a slow oxidative motor unit would be activated during this energy system.

Pacinian corpuscles are specific sensory receptors located in the skin and other tissues. They are responsible for detecting changes in movement or pressure. When pressure is applied to the skin, these corpuscles generate electrical signals that are transmitted to the brain, allowing us to perceive and respond to changes in our environment. Joints, ligaments, and motor units are not directly involved in detecting changes in movement or pressure, making them incorrect options.