Nervous System Functions: TEAS Practice Question with Answer & Explanation

Understanding the Role of Motor Neurons

In the nervous system, information generally flows in a specific loop: detection, processing, and action. To master this concept for the TEAS, you must distinguish between Sensory and Motor pathways.

Why Choice B is Correct

Choice B is correct because motor neurons are efferent neurons. The term "efferent" comes from "exit." These neurons carry nerve impulses away from the central nervous system (the brain and spinal cord) toward effectors. An effector is any organ or tissue that receives a signal to act—most commonly skeletal muscles (to move), cardiac muscles, or glands (to secrete hormones).

Analyzing the Incorrect Options

• Choice A: This describes a sensory (afferent) neuron. These neurons bring information "into" the system from the environment.
• Choice C: This describes interneurons. Interneurons are located entirely within the central nervous system and act as the "middlemen" that connect sensory input to motor output.
• Choice D: This is another description of a sensory pathway. Sensory neurons enter the spinal cord through the dorsal (back) root, while motor neurons exit through the ventral (front) root.

TEAS Concept: Afferent vs. Efferent

The TEAS exam frequently tests your ability to identify the direction of signal travel.

1. Afferent (Sensory): Receives stimuli (heat, touch, light) and sends it toward the brain/spinal cord.
2. Efferent (Motor): Takes the "command" from the brain/spinal cord and sends it out to the body to cause a reaction.

Study Tip: The "SAME" Acronym

To remember the directions of these nerves and where they enter/exit the spinal cord, use the acronym SAME DAVE:

• Sensory = Afferent
• Motor = Efferent
• Dorsal = Afferent (Sensory enters the back)
• Ventral = Efferent (Motor exits the front)

Thinking of "E" for Efferent and Exit will help you remember that motor neurons exit the CNS to perform an action.