Central nervous system

Your brain and spine are very special.

They are part of a big control center. The brain is the largest part. It helps you think and feel. The spine sits below the brain. It is safe inside your bones.

The brain and spine stay in a special bag. This bag keeps them safe from bad things. They also sit in a clear liquid. This liquid helps protect them too. Your body uses them to move and sense the world.

Your brain and spine are part of a big system. This is called the central nervous system. It is the main control center for your body.

The brain is the largest part. It helps you think, remember, and feel. The spinal cord sits below the brain. It runs down through your back. Your bones protect it.

Both parts stay inside a special layer called the meninges. This layer acts like a shield. It protects your brain from bad chemicals in your blood. Inside the meninges, the brain and spine sit in a clear liquid. This liquid helps keep them safe.

The brain has different parts that do different jobs. The brainstem helps you breathe and keeps your heart beating. The cerebellum helps you stay balanced and move smoothly. The cerebrum is the biggest part. It helps you plan tasks and feel emotions. Inside the brain, there are two kinds of tissue. There is gray matter and white matter. Gray matter is made of tiny cells called neurons. White matter helps parts of the brain talk to each other.

Your system also helps your eyes react to light.

The central nervous system is your body's main control center. It consists of the brain, the spinal cord, and the retina. The brain acts as the major processing unit for everything you do. It integrates information and tells the rest of your body how to react. This system is very important for animals with bodies that are symmetric. Most multicellular animals rely on this system to coordinate their movements.

This system works through a clever design of protection and communication. The brain and spinal cord are wrapped in layers called meninges. These layers act like a shield against harmful chemicals in the blood. Inside these layers, a clear liquid called cerebral spinal fluid bathes the tissues. The brain sits safely inside the skull, or cranium. The spinal cord stays protected inside the vertebral canal of your spine.

Scientists have studied these structures to understand how we function. They found that the central nervous system uses two main types of tissue. One is gray matter, which is made of neuron bodies. The other is white matter, which contains axons and supporting cells. There are also special cells called glia that act like glue. These cells provide support and help clean up waste in the brain.

Many different parts of the brain handle specific, important jobs. The brainstem includes the medulla, the pons, and the midbrain. The medulla helps you control breathing and your blood pressure. Behind the pons, the cerebellum helps you keep your balance. The cerebellum holds more neurons than any other part of the brain. The large cerebrum handles your memories, emotions, and complex thinking.

Your central nervous system connects to the world around you. The spinal cord uses nerves to talk to your skin and muscles. These nerves carry sensory signals in and motor signals out. Some nerves, called cranial nerves, connect directly to your head and neck. For example, your optic nerves connect your eyes straight to the brain. This allows your pupils to react quickly to changing light.

The central nervous system (CNS) is the primary control and integration center for vertebrates. It consists of the brain, the spinal cord, and the retina. The CNS is responsible for coordinating the activities of the entire body. This system is found in all bilaterally symmetric and triploblastic animals. These are multicellular animals that are not sponges or diploblasts. The brain integrates incoming information and influences how the body reacts.

Protection is a vital part of how the CNS functions. The brain and spinal cord are enclosed within protective membranes called meninges. These layers act as a barrier against chemicals in the blood. This protects the brain from neurotoxins that might be found in food. Inside the meninges, the tissues are bathed in cerebral spinal fluid. This fluid replaces the extracellular fluid found in other animals. The brain sits inside the cranial cavity within the skull. The spinal cord is housed in the spinal canal within the vertebrae.

On a microscopic level, the CNS is made of two distinct types of tissue. These are known as white matter and gray matter. White matter consists of axons and oligodendrocytes. Gray matter is composed of neuron bodies and unmyelinated fibers. Both tissues contain glial cells, which are often called neuroglia. The name comes from the Greek word for "glue." These cells provide essential support to the nervous system. For example, Bergmann glia act as scaffolding for neuroblasts during neurogenesis. Microglia act as specialized macrophages to support the immune system. Astrocytes help clear metabolites and transport fuel to neurons from capillaries.

The spinal cord serves as a major pathway for communication. It starts at the base of the skull near the foramen magnum. It continues down the vertebral canal and ends near the first or second lumbar vertebra. The spinal cord receives sensory signals through afferent pathways. It sends motor signals out through efferent pathways. There are 31 pairs of spinal nerves that project from the brain stem. These nerves connect the spinal cord to the skin, joints, and muscles. Sensory information travels up through spinal tracts to the thalamus and the cortex.

The brain is the largest and most complex part of the CNS. It is divided into several functional regions. The brainstem is the first major section. It includes the medulla, the pons, and the midbrain. The medulla controls vital functions like breathing and blood pressure. The pons helps transmit information between the cerebellum and the cerebral cortex. The midbrain contains nuclei that link different parts of the motor system. It also handles parts of the visual and auditory systems. The brainstem also contains the reticular formation, which manages arousal and alertness.

Other critical regions include the cerebellum and the diencephalon. The cerebellum is located behind the pons. It controls posture, balance, and the coordination of body movements. Interestingly, the cerebellum contains more neurons than any other brain structure. The diencephalon contains the thalamus and the hypothalamus. The thalamus acts as a linkage and sorts incoming information for the cerebral hemispheres. The hypothalamus regulates primitive emotions like hunger and thirst. It also controls the secretion of hormones via the pituitary gland.

The largest visible part of the brain is the cerebrum. It is made of two cerebral hemispheres connected by the corpus callosum. The cerebrum includes the cortex, the basal ganglia, the amygdala, and the hippocampus. The cerebral cortex is the outer layer of gray matter. It is responsible for planning and carrying out everyday tasks. The hippocampus manages the storage of memories. The amygdala helps with the perception and communication of emotion. The basal ganglia are essential for the coordination of voluntary movement.

Finally, the CNS includes unique structures like the cranial nerves. There are 12 cranial nerves located in the head and neck region. While most nerves connect to the CNS through intermediaries, some connect directly. The olfactory nerves and the optic nerves are considered part of the CNS. This is because they connect directly to brain neurons without intermediate ganglia. The olfactory epithelium is unique because it is CNS tissue in direct contact with the environment. This provides a pathway for certain therapeutic agents to enter the system.