Which nervous systems are responsible for voluntary motor function: the Central Nervous System (CNS) and/or the Peripheral Nervous System (PNS)?

Voluntary Motor Function Depends on Both the Central Nervous System and Peripheral Nervous System

Voluntary motor function depends on both the central nervous system (CNS) and the peripheral nervous system (PNS), making the correct answer D.

Neuroanatomical Basis of Voluntary Motor Function

Central Nervous System (CNS) Components

• The CNS (brain and spinal cord) contains the motor neurons that originate the signals for voluntary movement 1
• Motor commands are initiated in the motor cortex of the brain
• These signals travel through descending pathways in the spinal cord

Peripheral Nervous System (PNS) Components

• The PNS contains the motor nerves that extend from the CNS to innervate skeletal muscles throughout the body 1
• Specifically, the somatic motor division of the PNS is responsible for voluntary movement 1
• The neuromuscular junction serves as the connection point where motor neurons communicate with skeletal muscle fibers 2, 1

Functional Division of the Nervous System

Somatic Nervous System

• The somatic nervous system is part of the PNS that controls voluntary muscle movements
• It uses acetylcholine as the neurotransmitter at the neuromuscular junction 1
• While the somatic nervous system is involved in voluntary movement, it cannot function independently of the CNS

Autonomic Nervous System

• The autonomic nervous system controls involuntary functions
• It is not primarily involved in voluntary motor control
• Therefore, option C (somatic AND autonomic nervous systems) is incorrect

Enteric Nervous System

• The enteric nervous system regulates gastrointestinal function
• It is not involved in voluntary motor control
• Therefore, option E (ONLY the enteric nervous system) is incorrect

The Complete Motor Pathway

For voluntary motor function to occur, a complete pathway is required:

1. Signal initiation in the motor cortex of the brain (CNS)
2. Signal transmission through descending tracts in the spinal cord (CNS)
3. Synaptic transmission to lower motor neurons in the spinal cord (CNS)
4. Signal conduction through peripheral motor nerves (PNS)
5. Neuromuscular junction activation and muscle contraction (PNS interface with muscle)

This complete pathway demonstrates why both the CNS and PNS are essential for voluntary motor function. Neither system alone is sufficient.

Clinical Evidence Supporting CNS and PNS Integration

• Studies examining patients with HIV-1 infection have shown that CNS and PNS functions can be independently disturbed, highlighting that both systems are normally required for proper motor function 3
• Research on peripheral nerve injuries shows that damage to either the CNS or PNS components can disrupt voluntary motor function 1
• The American Journal of Respiratory and Critical Care Medicine confirms that voluntary motor control requires intact pathways from the CNS through the PNS to the muscles 2

Common Misconceptions

• Some may incorrectly believe that only the CNS (option A) is responsible for voluntary movement because it initiates the commands
• Others might think only the somatic nervous system (option B) is responsible because it directly controls the muscles
• However, both systems must work together for voluntary motor function to occur

Therefore, the correct answer is D: The central nervous system (CNS) AND the peripheral nervous system (PNS).