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04-01 Brain and Nervous System - Biology 105 The Nervous...

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Biology 105 The Nervous System I. The Nervous System A. Has many essential functions 1. It allows _____________________ communication from one part of the body to another. 2. It receives a flood of information from internal and external environments. 3. It quickly makes __________________ of and responds to these communications and information. But in doing so, it can sometimes fool you… B. _____________________ carry out the functions of the nervous system. 1. Neurons are big cells, with a very long extension -- the _______________ -- coming from the main cell body, and several bushy branches at the other end called dendrites (dendro means tree). a. Axons extend from the brain to the furthest reaches of the body 2. There are 3 kinds of neurons: a. __________________ neurons carry information to the brain and spinal cord (Central Nervous System, or CNS) b. motor neurons carry information from the CNS to the body c. ___________________ go between parts of the brain and spinal cord 3. The job of a neuron is to receive an electrical signal at the dendrite and ____________________ it through the cell body and down the axon. From there is will be transferred to another neuron or cause a muscle or gland to __________________. a. Nerve impulses consist of these tiny electrical charges moving from one end of a neuron to the other and then transmitted to another neuron. It is strictly a one-way trip! b. Nerve messages can only be sent to neurons in physical contact, called a ______________________, through their axons and dendrites. Synapses are of central importance in the nervous system; they are the physical manifestation of thought! 4. Neurons do not divide after childhood, so adults can't get additional neurons (and in fact lose many), but new synapses are constantly made throughout life, especially when ________________________ occurs. a. People whose occupations require thought and complex skills have more dendrites, and more synapses, than those in occupations which don't require such skills. b. Older people who maintain ____________________ mental lives retain more connections and show less age-related mental impairment than those who just vegetate. c. Learning new skills at any age results in increased neural connection and enhanced brain function, and physical activity has also been shown to help improve memory and cognition. THE BRAIN -- USE IT OR LOSE IT!! 5. The human brain contains billions of neurons! a. The neurons of one human cerebral cortex would reach over ______________________ miles if placed end to end. b. Each neuron makes as many as _________________ contacts with other neurons! The total number of nerve-nerve connections is up to 10 15 . C. Neuron function 1. The original work was done on __________________, which have the largest neurons in the world. 2. All cells (not just neurons) have an electrical ______________________ across their membranes. That means that there is an electrical imbalance due to different numbers of positively and negatively charged ions on the two sides of the cell membrane. All cells are negative inside and positive outside.
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