Bio Notes

Bio Notes - Goals for Chapter 28b Nervous system By the end...

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Goals for Chapter 28b – Nervous system By the end of this chapter, you should be able to: 28.2 Describe the structure and functions of neurons. Know the role of neuroglia in the nervous system; know the function of Schwann cells and myelin, and a disorder that arises due to its loss. - The structure of a neuron comprised of a cell body, in which most of a neuron’s organelles, including the nucleus are found. From the cell body, there are two types of extensions: a great # of dendrites and one axon. - Dendrites are highly branched extensions that receive signals from other neurons and convey this info toward the cell body. Dendrites are often short. - The Axon is typically a much longer extension that transmits signals to other cells, which may be other neurons or effector cells. Some axons, such as the one that reach from your spinal cord to muscle cells in your feet can be over a meter long - The neuroglia is a supporting cell that outnumbers neurons 50 to 1 and it is essential for the structural integrity and normal functioning of the nervous system. - A Schwann cell is found in the PNS. A Schwann cell is what forms the myelin sheaths of nerve fibers. - Myelin sheath is a chain of oblong beads. Axons that convey signals very rapidly are enclosed along most of their length by a thick insulating material called the myelin sheath. Each bead is a Schwann cell and the myelin sheath is a chain of Schwann cells that each are wrapped many times around the axon. A disorder that arises due to the loss of myelin is Multiple Sclerosis which leads to a gradual destruction of myelin sheaths by the individual’s own immune system. 28.6 Compare the structures, functions, and locations of electrical and chemical synapses. - Electrical synapses pass electrical current directly from one neuron to the next. - The receiving neuron is stimulated quickly and at the same frequency of action potentials at the sending neuron. - The function of the electrical synapse is to transmit info from a synaptic terminal to another cell. - Electrical synapses are found in the heart and digestive tract, where nerve signals maintain steady, rhythmic, muscle contractions. - Chemical synapses have a narrow gap, called the synaptic cleft, separating a synaptic terminal of the sending neuron from the receiving neuron. -
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Bio Notes - Goals for Chapter 28b Nervous system By the end...

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