The most important part of a human nervous system is the human brain.
Different Facts about the human brain
- The human brain is the largest brain of all vertebrates relative to body size.
- It weighs about 3.3 lbs.
- The average male has a brain volume of 1,274 cm
- The average female brain has a volume of 1,131 cm
- The brain makes up about 2 percent of a human's body weight.
- The cerebrum makes up 85 percent of the brain's weight.
- It contains about 86 billion nerve cells (neurons) — the "gray matter."
- It contains billions of nerve fibers (axons and dendrites) — the "white matter."
- These neurons are connected by trillions of connections, or synapses.
Main parts of the brain
The brain has three main parts:
- Brain stem
The cerebrum, the large, outer part of the brain, controls reading, thinking, learning, speech, emotions and planned muscle movements like walking. It also controls vision, hearing and other senses.
The cerebrum is divided two cerebral hemispheres (halves): left and right. The right half controls the left side of the body. The left half controls the right side of the body.
The brain stem
The brain stem, at the bottom of the brain, connects the cerebrum with the spinal cord. It is what controls our fundamental body functions such as breathing, eye movements, blood pressure, heartbeat, and swallowing.