Chapter 3

Chapter 3 - Chapter 3 NEURONS: Specialized cells, newurons...

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Chapter 3 NEURONS: Specialized cells, newurons ar ethe basic building blocks of the nervous system. -Nervous cells are linked together in circuits, not unlike the electrical circuits in a computer. At birth you have 100 billion neurons. -If each neuron were 1 cm in length and were placed end to end, the resulting chain would circle the earth more than 24 times. -Neurons have three main parts, dendrites, cell body and an axon. -Thye cell body or “soma” contains the biochemical structures needed to keep the neron alive, and its nucleus carries the genetic information that determines how the cell develps and functions. DENDRITES: Specialized receiving units are like antennas that collect messages from neighbouring neurons and send them to the cell body. Branches of the dendrites can receive input from 1,000 or more neighbouring neurons. AXON: Extends from the cell body. The axon conducts electrical impulses away from the cell body to other neurons, muscles, or glands. Each axon may connect with dendritic branches from numerous neurons. -Neurons are supported in their actions by glial cells. These cells surround the neurons and hold them in place. Glial cells manufacture nurient chemicals that neurons need, form the myelin sheath around some axons, and absorb toxins and waste materials that might damage the neuron. Glial cells help to protect the brain from toxins. BLOOD- BRAIN BARRIER: prevents many substances, including a wide range of toxins, from entering the brain. The walls of the blood vessels within the braincontain smaller gaps than elsewhere in the body. -one type of glial cell can exchange chemicals with adjacent neurons and help to synchronize the activity of axons. Glial cells have also been known to have mechanisms necessary to allow them to communicate with other glial glial cells and with neurons.
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-neurons do two important things: Generate electricity and they release chemicals. The electrical properties of neurons have been known for more than a century. -Neurons function like bateries and their own chemical substances are a source of energy. Neurons are surrounded by a cell membrane that not only protects the inner structure but also operates as a filter that allows specific fluids into the cell. -Neurons are surrounded by a salty liquid environment This environment has a large concentration of positively charged particles, or ions. -The neuron has a resting potential of -70 millivolts, when it is in resting state the neuron is said to be polarized. -Neurons, like muscle cells, have a unique property among body cells: Sudden and extreme changes can occur in their restin potential voltage. ACTION POTENTIAL: or nerve impulsem, is a sudden reversal in the neurons membrain voltage, during which the membrane voltage momentarily moves from -70 to +40 millivolts. DEPOLORIZATION:
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Chapter 3 - Chapter 3 NEURONS: Specialized cells, newurons...

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