It also causes the adrenal glands at the top of the kidneys to release adrenaline, a hormone that helps give extra power to the muscles for a quick getaway. This process is known as the body's "fight or flight" response. The parasympathetic nervous system does the opposite: It prepares the body for rest. It also helps the digestive tract move along so our bodies can efficiently take in nutrients from the food we eat.
Sight probably tells us more about the world than any other sense. Light entering the eye forms an upside-down image on the retina. The retina transforms the light into nerve signals for the brain. The brain then turns the image right-side up and tells you what you're seeing. Every sound you hear is the result of sound waves entering your ears and making your eardrums vibrate.
These vibrations then move along the tiny bones of the middle ear and turn into nerve signals. The cortex then processes these signals, telling you what you're hearing. The tongue contains small groups of sensory cells called taste buds that react to chemicals in foods.
Taste buds react to sweet, sour, salty, bitter, and savory. The taste buds send messages to the areas in the cortex responsible for processing taste. Olfactory cells in the mucous membranes lining each nostril react to chemicals you breathe in and send messages along specific nerves to the brain. The skin contains millions of sensory receptors that gather information related to touch, pressure, temperature, and pain and send it to the brain for processing and reaction.
Reviewed by: Larissa Hirsch, MD. Larger text size Large text size Regular text size. What Does the Brain Do? What Are the Parts of the Nervous System? The nervous system is made up of the central nervous system and the peripheral nervous system: The brain and the spinal cord are the central nervous system. The nerves that go through the whole body make up the peripheral nervous system.
What Are the Parts of the Brain? The brain has three main sections: the forebrain, the midbrain, and the hindbrain. When these signals reach the end of a neuron, they stimulate the release of chemicals called neurotransmitters.
Neurotransmitters travel across synapses , spaces between neurons or between neurons and other body tissues and cells. Neurotransmitters can be classified as two types: excitatory or inhibitory. Excitatory neurotransmitters stimulate electrical signals in other neurons and encourage responses from body cells. Inhibitory transmitters discourage signals and cellular responses.
Through these chemicals, the nervous system regulates the activity of muscles, glands, and its own nerve pathways. The spinal cord is an elongated cylinder of neuron cell bodies, bundles of axons and other cells, protected by connective tissue and bone.
It connects to the brain at the medulla oblongata and runs down the vertebral column, the hollow tunnel enclosed within the vertebrae of the spine.
The spinal cord is part of the central nervous system and serves as a kind of superhighway. Sensory information and motor commands travel up and down, heading to and from the brain. Some incoming signals demand a simple, immediate response. The spinal cord can shoot out a reflex command without bothering the brain. They are involved in decision-making, memory, and emotional responses; particularly negative emotions. The spinal cord, running almost the full length of the back, carries information between the brain and body, but also carries out other tasks.
Along its length, it connects with the nerves of the peripheral nervous system PNS that run in from the skin, muscles, and joints. Motor commands from the brain travel from the spine to the muscles and sensory information travels from the sensory tissues — such as the skin — toward the spinal cord and finally up to the brain.
The spinal cord contains circuits that control certain reflexive responses, such as the involuntary movement your arm might make if your finger was to touch a flame. The circuits within the spine can also generate more complex movements such as walking. Even without input from the brain, the spinal nerves can coordinate all of the muscles necessary to walk.
For instance, if the brain of a cat is separated from its spine so that its brain has no contact with its body, it will start spontaneously walking when placed on a treadmill.
The brain is only required to stop and start the process, or make changes if, for instance, an object appears in your path. The CNS can be roughly divided into white and gray matter. As a very general rule, the brain consists of an outer cortex of gray matter and an inner area housing tracts of white matter. Both types of tissue contain glial cells, which protect and support neurons. White matter mostly consists of axons nerve projections and oligodendrocytes — a type of glial cell — whereas gray matter consists predominantly of neurons.
Also called neuroglia, glial cells are often called support cells for neurons. In the brain, they outnumber nerve cells 10 to 1. Without glial cells, developing nerves often lose their way and struggle to form functioning synapses.
The following are brief descriptions of the CNS glial cell types:. Astrocytes: these cells have numerous projections and anchor neurons to their blood supply. They also regulate the local environment by removing excess ions and recycling neurotransmitters. Oligodendrocytes: responsible for creating the myelin sheath — this thin layer coats nerve cells, allowing them to send signals quickly and efficiently. The cranial nerves are 12 pairs of nerves that arise directly from the brain and pass through holes in the skull rather than traveling along the spinal cord.
These nerves collect and send information between the brain and parts of the body — mostly the neck and head. Of these 12 pairs, the olfactory and optic nerves arise from the forebrain and are considered part of the central nervous system:. Olfactory nerves cranial nerve I : transmit information about odors from the upper section of the nasal cavity to the olfactory bulbs on the base of the brain.
Home Brain and nerves. Nervous system. Actions for this page Listen Print. Summary Read the full fact sheet. On this page. Neurones are the building blocks Central nervous system The peripheral nervous system Problems of the nervous system Where to get help Things to remember.
Neurones are the building blocks The basic building block of the nervous system is a nerve cell, or neurone. Central nervous system The brain and the spinal cord make up the central nervous system. The spinal cord The spinal cord is connected to the brain and runs the length of the body. The peripheral nervous system Nerves connect the brain and spinal cord to the peripheral nervous system, which is what nerve tissue outside of the central nervous system is called.
The autonomic nervous system The autonomic nervous system is part of the peripheral nervous system. The somatic nervous system The somatic nervous system is also a part of the peripheral nervous system. Symptoms include shaking and problems with movement Sciatica — pressure on a nerve caused by a slipped disc in the spine or arthritis of the spine and, sometimes, other factors Shingles — infection of sensory nerves caused by the varicella-zoster virus Stroke — a lack of blood to part of the brain.
Where to get help Your doctor Things to remember The nervous system uses electrical and chemical means to help all parts of the body to communicate with each other. The brain and spinal cord make up the central nervous system. Nerves everywhere else in the body are part of the peripheral nervous system. More information here.
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