Question

Put your pen or pencil down and then pick it up again. Identify and describe the parts of the nervous system that caused those movements to happen.

Short answer

The key parts of the nervous system involved here are the brain (more specifically, the motor cortex), motor neurons in the peripheral nervous system, the spinal cord, the somatic portion of the peripheral nervous system controlling voluntary movements, and the hand and finger muscles that respond to the impulse by contracting to allow the grabbing and lifting.

Step-by-step solution

Identify the Starting Point

Recognize that this procedure begins with the brain. The decision to pick up a pen or pencil initiates in the brain, specifically, in the motor cortex, which sends an impulse to motor neurons.

Understand the Role of Motor Neurons

The motor neurons, which are part of the peripheral nervous system (PNS), receives the signal from the brain. These neurons transmit impulses from the central nervous system (CNS, which includes the brain) to the muscles.

Relation between Neuron Impulses and Actual Movement

These impulses are sent down the spinal cord, from where they enter the parts of the peripheral nervous system which controls voluntary actions - the somatic nervous system. This nervous impulse arrives at the specific muscles (hand and finger muscles in this case) which are commanded to contract.

Muscle Contraction

The end result of this series of neural impulses, transformations and synapses is muscle contraction in the hand and fingers, enabling one to pick up the pencil.

Key concepts

Motor Neurons

Motor neurons are vital components that serve as messengers between the brain and muscles. They belong to the peripheral nervous system (PNS) and have a special role in transmitting signals. When you decide to move, such as picking up a pencil, the brain sends a command through the motor cortex.

• The motor cortex engages by sending electrical signals.
• These signals travel down the spinal cord to motor neurons.
• Motor neurons then pass this message on to your muscles.

When a motor neuron carries a signal, it results in muscle contractions. For instance, if you're picking up a pencil, specific neurons associated with your hand and wrist muscles are activated. Without motor neurons, the brain’s commands couldn’t be carried out efficiently, demonstrating their crucial role in movement.

Motor Cortex

The motor cortex is a key area in the brain that controls voluntary movements. Located in the frontal lobe, it acts like a command center. This is where the brain decides to initiate actions like picking up a pencil. The motor cortex has several responsibilities:

• Planning movements: Deciding how a movement will be executed.
• Initiating movements: Sending commands to motor neurons to carry out the action.
• Coordinating complex movements: Ensuring the body parts work together smoothly.

By interpreting signals and planning precise movements, the motor cortex ensures that the desired outcome, such as a smooth hand motion, is achieved. When you decide to move, this area wakes up, coordinating with other parts of the brain to make your action happen.

Peripheral Nervous System

The peripheral nervous system (PNS) encompasses all the nerves outside of the brain and spinal cord. It acts as a communication network, connecting the central nervous system (CNS) to the limbs and organs. In our scenario of picking up a pencil, the PNS includes crucial components: motor neurons that deliver signals to your muscles. The PNS consists of:

• Somatic Nervous System: Controls voluntary muscle movements. It connects the CNS with the muscles you move consciously, such as your fingers when picking up a pencil.


• Autonomic Nervous System: Manages involuntary movements and regulates bodily functions not consciously controlled.

In essence, the PNS ensures that the brain can communicate its decisions to the muscles and organs of the body. Without it, actions like grasping a pencil or even simple movement would not be possible.