Certified Rehabilitation Registered Nurse (CRRN) Practice Exam

What is the primary function of the lateral corticospinal tract?

1. Transmit impulses for voluntary motion

2. Regulate autonomic nervous system activities

3. Control reflex actions

4. Facilitate sensory information processing

The correct answer is: Transmit impulses for voluntary motion

The primary function of the lateral corticospinal tract is to transmit impulses for voluntary motion. This tract is a major pathway in the central nervous system that conveys motor commands from the cerebral cortex to the spinal cord, specifically targeting the spinal motor neurons that innervate skeletal muscles. This pathway is crucial for the execution of fine motor skills and voluntary movements, such as those required for intricate tasks like writing or playing a musical instrument. The fibers of the lateral corticospinal tract decussate (or cross over) at the level of the medulla, which allows each hemisphere of the brain to control the opposite side of the body; this finer motor control is especially significant for the limbs and distal muscle groups. The other choices pertain to different functions that are not related to the primary role of the lateral corticospinal tract. The autonomic nervous system's regulation primarily involves other pathways, while reflex actions are managed through different spinal cord circuits that do not require direct involvement from the cortex. Sensory information processing is also mediated by distinct pathways that are focused on transmitting sensory signals to the brain rather than motor commands.