The Brain and Cranial Nerves
One of the most complex and fascinating things in the human body is the brain. The body is "capable of almost everything, but it would not be possible, without the brain receiving information, and analyzing the information."
The brain is aware of its surroundings, via input from the spinal cord and cranial nerves. Cranial nerves with sensory functions allow us to smell and see. Nerves with both motor and sensory functions are responsible for everything from tasting and chewing, to breathing and the heating of your heart. Many of the little things we take for granted are also made possible by cranial nerves.
Solving problems, feeling hungry, laughing. Each of these activities occurs in a different region of the brain. The portion of the central nervous system is contained in the cranium. About one hundred billion neurons and ten to fifty trillion neuralgia make up the brain. In adults, the brain has a mass of about three pounds.
The four major parts of the brain are the Brain Stem, Cerebellum, Diencephalons, and the Cerebrum.
The brain stem is continuous with the Spinal Cord and consists of the Meclulla Oblongata, Pons, and the Mid Brain.
Posterior to the Brain Stem is the Cerebellum. Superior to the Brain Stem is the Diencephalon. The Diencephalons consists mainly of the Thalamus and Hypothalamus.
Supported on the Diencephalon of the Brain Stem, the Cerebrum which is the largest part of the brain.
Since the brain does not store oxygen, it needs a constant flow to prevent it shutting down.
Blood flows to the brain mainly via, the internal Caroticl and Vertebral Arteries. The internal Tugular Veins return blood from the head to the heart.
In adults, the brain is only two percent of the total body weight, but it consumes about two percent of the oxygen and glucose used at rest.
When activity of neurons and neuralgia increases in a region of the brain, blood flow to that area also increases. Even a brief slowing of brain blood flow may cause unconsciousness.
Typically an interruption in blood flow for one or two minutes impairs neuronal function. Should total deprivation of oxygen incur for about four minutes, perminate damage can occur. Because virtually no glucose is stored in the brain, the supply of glucose also must be continuous. If the blood entering the brain has a low level of glucose, mental confusion, dizziness, convulsions, and loss of consciousness may occur.
The blood brain barrier protects brain cells from harmful substances, as well as, pathogens, by preventing passage of many substances from blood into brain tissue.
Tight junctions seal together the enclothelial cells of brain capillaries, which also are surrounded by a thick basement membrain. The process of many astrocyties pressing up against the capillaries is known as the Astrocyties Process. This process selectively passes some substances from the blood to the neurons, at the same time, inhibiting the passage of others.
A few water soluble substances, like glucose, cross the brain blood barrier by active transport. Other substances like creatinine, vrea, and most ions, cross very slowly. Other substances and protions, including most antibiotic drugs, do not pass at all from the blood into brain tissue. Trauma, certain toxins, and inflammation, can all cause a breakdown of the Brain blood barrier.
The cranium and the Cranial Meniges surround and protect the brain. The Cranial meninges are continuous with the Spical meninges. Both have the same basic structure.
Cerebrospinal fluid is a clear, colorless, liquid that protects the brain and spinal cord against chemical and physical injuries. It also carries oxygen, glucose, and other needed chemicals from the flood to neurons, and neurogla.
The brain stem is the part of the brain between the spinal cord and the Diencephalon. The brain stem is made up of three structurally and functionally connected regions. These...
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