NSC - Central Nervous System Lesson

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Central Nervous System

The function of the central nervous system is to interpret incoming sensory information and send out responses based on past experiences and current conditions. The brain and spinal cord are the organs of the CNS.  

Because they are so vitally important, these organs are carefully protected within the body. The brain and spinal cord are both are encased in bone for protection. They are also surrounded by a colorless liquid called cerebrospinal fluid (CSF). CSF is secreted from the blood into the lateral ventricles (hollow spaces in the brain), and functions to maintain uniform pressure within the brain and spinal cord and to provide basic mechanical and immunological protection to the brain inside the skull. Another line of protection is the three membranes of connective tissue which envelop the brain and spinal cord called meninges that include the arachnoid, dura mater, and pia mater.

Another line of protection is the three membranes of connective tissue which envelop the brain and spinal cord called meninges that include the arachnoid, dura mater, and pia mater.

Although considered to be two separate organs, the brain and spinal cord are continuous at the foramen magnum.   Let's take a closer look at the anatomy of these two organs.

A detailed anatomical view of the human brain.

The brain is found within the cranial cavity of the skull. The largest and outermost part of the brain is called the cerebral cortex. The exterior of this thick piece of nervous tissue is folded into hills called gyri (singular: gyrus) and valleys called sulci (singular: sulcus). The cerebral cortex is made up of two hemispheres, the right and left, and is divided by a large sulcus. A thick fiber bundle called the corpus callosum connects the hemispheres of the brain and allows information to be passed from one side to the other. Although there are some brain functions that are localized more to one hemisphere than the other, the functions of the two hemispheres are largely redundant.

Each hemisphere of the brain can be divided into four different lobes, which each have a unique function. The four lobes are the frontal lobe, the parietal lobe, the occipital lobe, and the temporal lobe.

 

The cerebral cortex, along with the cerebellum, diencephalon, epithalamus, and brainstem, make up the major components of the brain. Use the interactive below to learn the structure and function of these parts.  Download a copy of "The Brain - Anatomy and Function Note Guide Download The Brain - Anatomy and Function Note Guide." Complete the note guide using the interactive below.

Spinal Cord

The spinal cord extends from the base of the brain, down the middle of the back to the waist. The spinal cord is the major bundle of nerves that carry nerve impulses to and from the brain to the cells of the body. The spinal cord is surrounded by the bones of the spinal column.

The spinal cord sends and receives information from the body and the brain. Nerves traveling through the body relay the information from the spinal cord to target cells in all areas of the body.

A cross-section view of the spinal cord. White matter surrounds gray matter. Within the spinal nerves are motor neuron soma, sensory neuron soma, dorsal root ganglion, dorsal roots, and ventral roots.

 

An illustration of the human spine. The human spine is split up into different regions: the cervical, thoracic, and lumbar.

The spinal cord also controls motor reflexes. Motor reflexes are quick, unconscious movements, such as automatically removing a hand from a hot object.

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