Discovery Science: Human Nervous System – Brain and Spinal Cord

Earth Science: Human Nervous System – Brain and Spinal Cord

The brain is an incredibly complex organ. It coordinates all incoming information. The spinal marrow receives and sends messages from the body to the brain.

Neurobiologists have long sought to understand the human brain. This high-performance organ processes all the sensory information arriving from the nervous system. The brain’s tissue consists of neurons and glial cells.

The skull bones, inner membranes, and cranial fluid all protect the brain.

Structure of the brain

The brain’s symmetrical halves are connected by nerve fibers. The left half, or hemisphere, houses the language centers and processes
analytical thinking. The right hemi- sphere processes intuitive and visual input. The brain’s outer layer, the cerebral cortex, is about as thick as a little finger and has the highest concentration of neurons.

Its surface area, and thus performance, is increased by having many folds. This outer layer is part f the cerebrum, the center of conscious- ness, perception, thought, emotion, and action. It is organized into lobes with specialized areas.

Another section is the interbrain-the interface between the sensory organs and the cerebrum—which filters out unnecessary input to protect the brain from overload. It also regulates the body’s fluid levels, temperature, and circadian rhythm. Some interbrain areas produce hormones to regulate important body functions. Beneath the interbrain, the midbrain-the brain’s internal switching station—transfers information to other brain areas.

The cerebellum, at the back of the head, coordinates body movements. Along with the inner ear, it maintains the body’s balance. Connected to the cerebellum is the medulla oblongata, which controls reflexes like swallowing and vomiting, and helps regulate the heart, breathing, and circulation.

The spinal marrow is part of the central nervous system and begins at the brain stem. From here it runs through the vertebral column to the lower back. Bunches of nerve fibers leave the spinal marrow at regular intervals and merge into spinal nerves.

The nerve cells of the spinal marrow transmit signals from the body and the central nervous system.


Pain is a warning signal of the body. Nervous receptor systems such as numerous trigger points in the skin are stimulated and pass the information to the brain and spinal cord.

This triggers reflexes to protect the body from the pain. This could be the quick pull back of a burnt hand from a hot stove. Complex vertebrates are most likely to have similar pain systems that are essential for survival.


SEX DIFFERENCE: An adult female brain weighs 2.6 lb (1.2 kg); an adult male’s brain weighs 2.8 lb (1.3 kg).

However, female brains have more convolutions (folds).

THE BRAIN makes up 2 percent of total body weight, but it uses 20 percent of the body’s blood volume.