Nervous centers
Nervous Centers (Brain and Spinal Cord)
The brain is located inside the skull, and the spinal cord lies within the spinal canal. These two organs function like a command center. While receiving and processing information, they analyze it and, if necessary, send commands to various parts of the body.
The brain includes the cerebral hemispheres, the cerebellum, and the brainstem.
These components play a vital role in processing sensory input and coordinating body functions.
Quick Fact
The brain is protected by the skull, and the spinal cord by the vertebral column—both essential for safeguarding the central nervous system.
Cerebrum
Most of the brain’s volume is made up of the two cerebral hemispheres. These hemispheres receive sensory information from organs such as the eyes, ears, skin, nose, and tongue. They also send out commands necessary for voluntary body movements, like moving muscles.
The cerebral hemispheres are also involved in thinking, speaking, and problem-solving. The left hemisphere controls the right side of the body, while the right hemisphere controls the left side (this is called contralateral control).
Although each hemisphere specializes in some tasks, they also work together and share functions. For example, both eyes and both cerebral hemispheres are involved when we look at something.
The outer surface of the cerebrum, called the cerebral cortex, is responsible for many voluntary functions of the body. This area is divided into four main lobes: frontal, parietal, temporal, and occipital.
Each lobe of the cerebrum plays a distinct role in processing different kinds of information and responses.
Important Concept
The cerebral cortex is the outer layer of the cerebrum and is divided into four lobes—each responsible for specific tasks like movement, vision, reasoning, and memory.
Cerebellum
When you exercise, your body moves in different directions and still needs to maintain its balance. But how is balance preserved during motion? Sensory signals from organs such as the eyes, ears, and skin are sent to a specialized part of the nervous system: the cerebellum.
The cerebellum receives and analyzes this information and sends appropriate commands to muscles for maintaining coordination and balance. In every movement—whether standing, walking, sitting, or jumping—the cerebellum helps regulate body balance. Athletes and gymnasts who train frequently strengthen their cerebellum’s function.
Left: athletes training balance and coordination.
Center and right: cerebellum
The cerebellum includes two hemispheres (left and right) and a central area called the vermis, all crucial for balance and smooth movement.
Example
A gymnast on a balance beam constantly adjusts their posture using signals processed by the cerebellum. This organ fine-tunes muscle movements in real time to prevent falling.
Brainstem
The brainstem is a stem-like structure located beneath the cerebrum. It connects the brain and cerebellum to the spinal cord. A part of the brainstem is called the medulla oblongata.
The medulla oblongata sits just above the spinal cord and serves as the control center for many involuntary actions, such as breathing, heart rate, and blood pressure. Due to its vital role in regulating life-sustaining processes, it is often referred to as the life center.
Damage to the brainstem can severely affect vital functions and may lead to life-threatening conditions.
Common Mistake
The brainstem is sometimes mistaken as part of the spinal cord, but it is actually a part of the brain that directly connects to it. It is critical for controlling involuntary survival functions.
Spinal Cord
The spinal cord is a white, rope-like structure located inside the vertebral column. It extends from the medulla oblongata to the lower back. The spinal cord connects the brain with the rest of the nervous system and transmits sensory input and motor commands between the brain and the body.
The spinal cord is also the center for certain reflexes that do not require direct involvement from the brain.
The figure below shows spinal nerves. These nerves control the activity of muscles and different parts of the body. For example, nerves that exit from the lower back region control movement and sensation in the legs.
In individuals with spinal cord injuries, the specific type of damage depends on which region is affected. This may result in different types of sensory and motor impairments. Some people may lose only sensation or movement in their legs, while others may lose both sensation and movement in their hands as well.
Safety Warning
Spinal cord injuries, unlike most other body parts, are often irreversible. Using helmets and back protectors can greatly reduce the risk of this type of serious damage.
Did You Know?
43 pairs of nerves connect the spinal cord to the rest of the body. 31 of these pairs originate from the spinal cord, and 12 pairs originate from the brain.
Example
When you accidentally touch something hot, spinal nerves quickly detect the pain and signal your muscles to pull away. This happens without the brain's involvement—it's a spinal reflex.