Key Takeaways

  • The nervous system includes billions of neurons that communicate through electrical and chemical signals. It’s divided into the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves throughout the body).
  • Neurons come in three types: sensory neurons that carry signals from the body to the brain, motor neurons that send commands to muscles, and interneurons that relay messages between neurons.
  • The autonomic nervous system regulates involuntary functions like heart rate and digestion through three divisions: sympathetic (action and stress), parasympathetic (rest and relaxation), and enteric (digestive control).

Nerve cells take in information through the body’s senses: touch, taste, smell, sight, and sound. The brain interprets these sensory cues to understand what’s going on outside and inside the body.

This allows a person to use their body to interact with their surrounding environment and control their body functions.

The nervous system is very complex. We rely on it every day to help us stay healthy and safe. Why should we appreciate our nervous system? Read these 11 fun facts and you’ll know why:

Every person’s body contains billions of nerve cells (neurons). There are billions of neurons in the brain and millions in the spinal cord. The body’s neurons take up and send out electric and chemical signals to other neurons.

Neurons receive signals in a short, antennae-like part called the dendrite, and send signals to other neurons with a long, cable-like part called the axon. Axons and dendrites vary in size, but axons are generally longer and sometimes an axon can be up to a meter long.

In some neurons, axons are covered with a thin layer of fat called myelin, which acts as an insulator. It helps transmit nerve signals, or impulses, down a long axon. All neurons have a cell body.

The cell body contains important structures, such as genetic material, energy-producing organelles, and more.

Neurons come in a variety of shapes and sizes depending on where they’re located in the body and what they’re programmed to do.

Most neurons have several axons and dendrites, and the position of the cell body and the length and numbers of the axons and dendrites can vary.

  • Sensory: Sensory neurons deliver electrical signals from glands, muscles, and skin throughout nerve pathways, eventually to reach the CNS.
  • Motor: Motor neurons carry signals from the CNS throughout the spinal cord and peripheral nerves to eventually reach the muscles.
  • Interneurons: Interneurons sends messages between neurons.

The human nervous system is defined as two parts. They are the central nervous system (CNS) and the peripheral nervous system (PNS).

The CNS is located in the skull and vertebral canal of the spine. It includes the nerves in the brain and spinal cord. The sensory and motor nerves that run through the extremities and internal organs are defined as the PNS.

The CNS and PNS control voluntary and involuntary functions. Voluntary (somatic) nerve control sensation and movement a person is aware of and can control consciously, such as moving their head, arms, legs, or other body parts.

The body’s involuntary (autonomic) nervous system controls processes in the body that a person doesn’t consciously control. These nerves are always functioning for survival, regulating a person’s heart rate, breathing, metabolism, and other critical body processes.

The PNS nerves that control involuntary actions include the sympathetic, parasympathetic, and enteric nervous systems. The sympathetic, parasympathetic, and enteric nervous systems work together to balance out your body’s functions.

The sympathetic nervous system and parasympathetic nervous system work together, balancing the activity of your body’s internal organs and functions.

Usually, the hormones upregulated by the parasympathetic nerves promote relaxation, learning, and sleep.

The hormones upregulated by the sympathetic nerves have actions such as increasing your ability to manage urgent matters and exerting intense physical effort.

The enteric nervous system controls your digestive system, and it is regulated by the sympathetic and parasympathetic nervous systems.

The sympathetic nervous system prepares the body for physical and mental activity. It causes the heart to beat harder and faster and opens the airways for easy breathing. It also temporarily slows digestion so the body can focus on fast action.

The parasympathetic nervous system promotes a resting state. Some of its activities include stimulating digestion, activating metabolism, and helping the body relax.

The enteric nervous system is composed of nerves embedded in the organs of the digestive system that control the breakdown of food, the absorption of nutrients, and the elimination of waste. These actions are regulated by hormones of the parasympathetic and sympathetic nervous system.

Scientists are now developing ways to “hack” into the nervous system, gaining the ability to control brain cells with the flash of a light. The cells can be programmed to react to light through genetic alteration. However, it should be noted that these studies were performed using mouse cells only.

Hacking can help scientists learn about the functions of different groups of neurons. They can activate several brain cells at the same time and observe their effects on the body.

The nervous system handles the body’s communication needs through complex nerve signaling pathways. It is responsible for regulating and processing sensory inputs, controlling muscles, and facilitating all bodily processes.