Introduction to the Nervous System
Introduction to the Nervous System NROSCI 1000 - Intro to Neuroscience
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This 3 page Class Notes was uploaded by Svena Verma on Saturday September 24, 2016. The Class Notes belongs to NROSCI 1000 - Intro to Neuroscience at University of Pittsburgh taught by Linda Rinaman in Summer 2015. Since its upload, it has received 3 views. For similar materials see Intro to Neuroscience in Neuroscience at University of Pittsburgh.
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Date Created: 09/24/16
1. Introduction to the Nervous System Important early innovators that helped found neuroscience Golgi most famous for his technique (his theories turned out to be wrong); developed silver impregnation/stain; revealed structure of neurons and glial cells Golgi stain only labels a subset of neurons (randomly), which helps you see them better No explanation as to why this happens This is valuable because if you look at a block of a Golgi stained tissue, you can see the individual cell bodies, dendrites, axons At this time they thought neuron signals traveled through the shared cytoplasm; communication through a shared network He developed a technique to prove himself wrong; he wasn’t able to make that intellectual leap Cajal Golgi’s adversary Cajal used Golgi’s technique against him/improved it, and used it to prove the neuron doctrine: each neuron is an individual independent cell, and communicates with other cells but not through shared cytoplasm, but through gaps between cells linked by synapses. Work followed up by Charles Sherrington who further reﬁned the neuron doctrine Both Sherrington and Cajal are credited for the doctrine Cells in the nervous system 2 main types of cells in the nervous system neurons (nerve cells) glia (glial cells): support cells for the nervous system oligodendricites make myelin (insulating tissue) microglia are scavengers astrocytes participate in the blood brain barrier and buﬀer the pH and osmotic content of the extracellular ﬂuid vascular endothelial cells make up the blood vessels of the brain hundreds of thousands of miles of blood vessels in the brain capillaries make up more bulk of tissue than any other type in the brain “Brainbow" cassette will express the primary colors; random expression of colors (some cells are red, some are blue, etc) Nervous system has two major components central (CNS) - brain & spinal chord - brain protected by skull and spinal chord is protected in the vertebral column peripheral (PNS) - not protected by bone (everything else) cranial nerves, spinal nerves, peripheral ganglia in heart/pancreas, autonomic nervous system one exception to the rule: the retina; the origin of the optic nerve. not protected by bone. Major components of the nervous system CNS: areas that are primarily motor; control how to make the body move sensory components: bring information from the outside world AND from within the body into the brain (internal and external environmental signals that travel through sensory pathways into the system) motor components will control skeletal muscles or smooth muscles of the bladder/uterus/heart (autonomic) cranial nerves are in charge of the head and neck the spinal nerves are in charge of the shoulders down exception: vagus nerve is a cranial nerve but controls some things below the neck General neuron categories sensory neurons take environmental signals (temp, pressure, sound waves, photons of light) and traduces them into neural signals that neurons can understand. they are aﬀerent neurons because they bring information into the nervous system motor neurons contract muscles to move the body around, or to control visceral functions (glands, hormone secretion, cardiac muscle). they are eﬀerent neurons because they take information out of the CNS and into the body. some of the motor neurons are endocrine neurons because they secrete hormones (control the release of hormones) interneurons communicate signals between neurons usually between the same region of the nervous system/close by. sharing information with a neuron of group of neurons nearby. projection neurons have long axons within the CNS (if they left they’d be motor neurons), and communicate with other neurons located in a distant area in the nervous system. how far away is the signal going to be delivered? close = interneuron; distant = projection neuron. mass of nerves at the end of spinal chord reﬂex arc: knee jerk reﬂex tests the transition of signals from sensory receptors in a tendon in the knee and a sensory signal that can travel up to the spinal chord through a long nerve impact the ﬁring activity cause the activation of motor neurons that project back out down to the muscles that move the knee. knee jerk reﬂex is an example of the sensory in, motor out. common neurological test of function for injury in nerve pathway or spinal regions, myelin is appropriate, etc. tap the patellar tendon, physically stretches and pulls on incense muscle, turns on sensory neuron send its signal that enters the spinal chord, and the signal gets delivered to interneurons and motor neurons in the spinal chord. motor neuron gets excited; becomes activated and sends a neural signal to control a muscle; muscle is stretched and tells the motor neuron to ﬁre and contract a muscle; back to its original place; knee jerks. interneuron is also excited and silences the opposing muscle. turns the other motor neuron oﬀ (the one that keeps your leg from ﬂailing). so the motor neuron excites and activates the jerk muscle, and the interneuron excites and activates the opposing muscle. neurons are diﬀerent every neuron is unique; like trees every oak tree has morphological features, but no two trees are identical. birch, oak, maple; many diﬀerent types/categories of neurons. diﬀerent types with diﬀerent functions. shape, size, structure, location, dictates function of neurons things they have in common: cell bodies, all (exceptions) have dendrites dendrites are involved with receiving signals; increase the surface area for receiving input of a neuron. they would not have as many diﬀerent inputs with just the cell body. every single aspect of the dendrite is available to receive synaptic input; neuron can now receive more complex input. only one axon that comes oﬀ the cell body (but the axon can branch): axon delivers the signal to another target, to another neuron or a group of neurons, or if its a motor neuron it might be to muscle. as many axon branches as there are that will provide a way for an individual neuron to target diﬀerent neuron or muscle targets. neurons’ major features neurons are made to communicate by electrical and chemical signaling (unique bc they do both) intracellular signaling (within neurons) intercellular signaling (between neurons) cell body is called the soma lots of ribosomes because they are so highly specialized to secrete neurotransmitters, making so many proteins, so they have extra ribosomes dendrites all along the dendrites there are many instances of axon terminals (synapse) and it has the ability to signal to the dendrite axon only one that leaves the cell body but will often branch; delivers signals to other targets close or far away; covered in insulation called myelin to increase the speed of the electrical signal being sent axon terminal; synaptic ending this is a synapse; the point of contact; very thin space; cleft; membrane of axon terminal and membrane of the dendrite; synapse is a point of chemical signaling
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