The nervous system is the body’s communication system. It processes everything from sight to taste and interprets the information from its surroundings. The main organs of your nervous system are the brain and spinal cord. Some organisms have a much simpler nervous system consisting of just a few cells, such as a jellyfish. This system determines what is going on around the body and helps to facilitate a response.

The below image shows a diagram of the cross-section of a brain.

cross-section of a brain

Top 20 Fun Facts

  1. The basic unit of the nervous system is the neuron. These specialized cells have a cell body or soma, axons, and dendrites.
  2. The brain uses more of the body’s energy than the rest of the organs, using over 20% of the energy reserves in the body.
  3. The brain is hard at work even when you’re sleeping.
  4. The brain’s structure is constantly changing as we learn. New neuronal connections are made which increases the density of the brain.
  5. Some neurons have an insulating layer known as the myelin sheath. This allows nervous impulses to travel faster, with less energy lost.
  6. Involuntary reflexes are not controlled by your brain. They are controlled by a reflex arc.
  7. The fastest signal transmission in the body occurs in the alpha motor neurons within the spinal cord. They transmit a signal at 268 miles per hour. The slowest signal transmission is within the skin at 1 mile per hour.
  8. Neurons can’t divide or replace themselves. This means that nerve damage is often permanent.
  9. We lose neurons as we age, starting at around 20 years old in humans. 1/10 of our neurons are gone by the time we turn 75.
  10. Electrical impulses within the nervous system are triggered by ions or chemical signals that pass through channels in the neuron.
  11. Ions that are important in chemical signaling include sodium, potassium, chloride, and calcium.
  12. As we age, our brain shrinks by about 1-2 grams every year due to the loss of neurons.
  13. Males and females have different brain compositions. Males have more grey matter, while females have more white matter.
  14. The optic nerve crosses over in the brain. This means that the right optic nerve crosses to the left side of the brain and vice versa. This allows an image to be produced by the brain.
  15. Primates, including humans, have a group of neurons called mirror neurons. These are responsible for some behaviors being contagious, such as yawning.
  16. The longest nerve in the body is the sciatic nerve. It runs from the spinal cord to the toes on each side of the body.
  17. Neurons can look very differently from each other depending on their function. For example, sensory neurons have dendrites on both sides of their body, rather than on one side.
  18. The bowel is controlled by a separate part of the nervous system known as the enteric nervous system. It regulates digestion and bowel movements.
  19. Glial cells are support cells for neurons. They can make myelin to surround part of the neuron. They can also get rid of microbes and help supply nutrients to the neurons.
  20. The brain has approximately 100 billion neurons. In contrast, the spinal cord only has roughly 13.5 million neurons throughout its length.