Textbook notes-Chapter 8 Neurons-Cellular and Network Properties

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Biological Sciences
Ingrid L.Stefanovic

MAMMILIAN PHYSIOLOGY Chapter 8 Neurons: Cellular and Network Properties Emergent Properties: Complex processes, such as consciousness, intelligence, emotion, that cannot be predicted from the properties of individual nerve cells The nervous system can be divided into two parts: The central nervous system (the brain and spinal cord; CNS) and the peripheral nervous system (afferentsensory neurons and efferent neurons; PNS) Efferent neurons can also be divided into two subgroups: somatic motor division (controls skeletal muscles) and autonomic division (controls smoothcardiac muscles, exocrine and some endocrine glands, as well as adipose tissue) The autonomic division, also called the visceral nervous system, is further subdivided into the sympathetic and parasympathetic branches The nervous system is composed primarily of two types of cells: neurons and glial cells Neurons Neurons are the functional unit of the nervous system; they consist of dendrites (which receive incoming signals), a cell body (called the soma where the nucleus of the cell is found), and the axon (which carries outgoing signals) Neurons can be classified structurally, based on the presence or lack of axons and dendrites 1. Pseudounipolar: A neuron where the axon and the dendrite fuse during development. They are both found on the same single body. The soma is to the side of the dendriteaxon fuse 2. Bipolar: There is a single, separate axon and a separate dendrite on the neuron. Both are about the same length and are separated by the cell body 3. Multipolar: There are many branched dendrites and axons on the neuron 4. Anaxonic: There is no distinguishable axon on the neuron www.notesolution.comAxons can also be functionally classified: 1. Sensory (afferent): Neurons that carry information about temperature, pressure, light, etc. From sensory receptors to the CNS; usually they are found close to the CNS with long bodies reaching the receptor in the limbs and organs Most sensory neurons have a pseudounipolar structure (the cell body is out of the direct path of signals along the axondendrite). However for smell and vision, they have a bipolar structure (signal travels through the cell body) 2. Interneurons: Neurons that lie completely within the CNS. They have complex branching systems that allow them to communicate with other neurons 3. Efferent neurons: IZ]K]o}ZZK}oL}L[~]2:-2, page 247). They usually are Bipolar In terms of afferent and efferent peripheral (sensory) neurons, many axons are bundled together with connective tissue to form a nerve. Some nerves carry afferent signals only, some only carry efferent signals, some carry both Dendrites receive incoming information for other cells. They increase the surface area of the neurons allowing them to communicate at different locations In the PNS, dendrites are used primarily to receive information and relay it to other areas of the neuron that can process the information (usually the soma) However in the CNS dendrites are more complex, sometimes acting as an independent compartment and communicating back and forth with other cells Peripheral neurons usually have one axon which branches off the soma at the axon hillock (area of the soma where the soma stops and the axon starts) The primary function of axons is to transmit outgoing electrical signals from the integrating center (axon hillock) to the end of the axon (axon terminal) The region where the axon terminal meets its target cell is called the synapse; the space between the two neurons is called the synaptic cleft The cytoplasm of the axon (called the axoplasm) lacks ribosomes and endoplasmic reticulum therefore it cannot produce proteins. Instead, proteins must be synthesized in the rough endoplasmic reticulum in the soma and transported down the axon via axonal transport. There are 2 types of axonal transport: 1) Slow Axonal Transport: Moves the materials through the axoplasm (axoplasmic flow) www.notesolution.com
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