Brain - Invertebrate Brain, Vertebrate Brain, Human Brain, The Brain Stem, The Diencephalon, The Cerebrum - The cerebellum
system coordinates functions controls
The brain is a mass of nerve tissue located in an animal's head that controls the body's functions. In simple animals, the brain functions like a switchboard picking up signals from sense organs and passing information to muscles. The brain is also responsible for a variety of involuntary behavior, including keeping the heart beating, and maintaining blood pressure and temperature. In more advanced forms, particularly vertebrates, a more analytical brain coordinates complex behaviors. In higher vetebrates, the brain coordinates thinking, memory, learning, and emotions. The brain is part of an animal's central nervous system, which receives and transmits impulses. It works with the peripheral nervous system, which carries impulses to and from the brain and spinal cord via nerves running throughout the body.
The cerebellum is located below the cerebrum and behind the brain stem, and is shaped like a butterfly. The "wings" are the cerebellar hemispheres, and each consists of lobes that have distinct grooves or fissures. The cerebellum controls the movements of our muscular system needed for balance, posture, and maintaining posture.
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Nematodes (roundworms) have a simple brain and nervous system consisting of approximately 300 nerve cells, or neurons. Sensory neurons located in the head end of the animal detect stimuli from the environment and pass messages to the brain. The brain then sends out impulses through a ventral nerve cord to muscles which respond to the stimulus. The way that the interneurons of the brain process the…
The central nervous system of vertebrates consists of a single spinal cord, which runs in a dorsal position along the back, and a highly developed brain. The brain is the dominant structure of the nervous system. It is the master controller of all body functions, and the analyzer and interpreter of complex information and behavior patterns. We can think of the brain as a powerful neural computer. …
The living human brain is a soft, shiny, grayish white, mushroom-shaped structure. Encased within the skull, it is a 3 lb (1.4 kg) mass of nerve tissue that keeps us alive and
A comparison of the brains of an earthworm, an insect, a bird, and a human. Illustration by Hans & Cassidy. Courtesy of Gale Group.
functioning. On average, the brain weighs 13.7 oz (390 g) at birth, and by a…
The brain stem is the stalk of the brain, and is continuous with the spinal cord. It consists of the medulla oblongata, pons, and midbrain. A part of the brain stem, the medulla oblongata is a continuation of the spinal cord. All the messages that are transmitted between the brain and spinal cord pass through the medulla via fibers in the white matter. The fibers on the right side of the medulla c…
The cerebrum, constituting about 87.5% of the brain weight, spreads over the diencephalon. The cerebral cortex is the outer layer of the brain and is composed of gray matter made up of nerve cell bodies. It is about 0.08 in (2 mm) thick and its surface area is about 5 sq ft (1.5 sq m)—around half the size of an office desk. White matter, composed of nerve fibers covered with myelin sheaths,…
At the end of the nineteenth century, Santiago Ramon y Cajal, a Spanish scientist, studied neurons using stain developed by Camillo Golgi. Cajal realized that the brain was made up of individual units and not a continuous net as was believed at the time. His studies uncovered a large variety of neurons that differed in size and shape. He explained that neurons received signals on dendrites and tra…
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