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Chapter 3

Chapter 3- Anatomy of the Nervous System.docx

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Psychology 2221B
Derek Quinlan

Chapter 3: The Anatomy of the Nervous System General Layout of the Nervous System: Central Nervous System (CNS) Brain (in the skull) Spinal Cord (in the spine) - Think of this system as the core Peripheral Nervous System (PNS) Located outside of the skull and spine Serves to bring information into the CNS and carry signals out of the CNS 1) Somatic NS - Afferent Nerves (Sensory)  into - Efferent Nerves (Motor)  out of - Have both of these nerves - Tie this back to CNS, afferent nerves into the CNS (touch, joint angles, muscles, internal organs sending signals to the CNS) - Efferent sensing signals out of the CNS, sending signals to the motor signals so you can move and adapt to the environment 2) Autonomic Nervous System a) Sympathetic Nerves b) Parasympathetic - Thoracic and Lumbar - Cranial (out of skull area) and sacral (low - “Fight or Flight” back) - Second stage- neurons are far from the - “Rest and Restore” target. - Out of the CNS - Second Stage -neurons are near the target organ - Both are efferent  sending signals to sweat glands, lungs, and heart, taking signals out of CNS to out of the organs so your body can react to the environment in appropriate ways. - Both have opposite effect - 2-stage neural Paths, neurons exiting the CNS synapses on a second-stage neuron before the target organ - Sympathetic- prepare body for demands, sympathetic to what you‟re going through and going to be sympathetic to the changes that need to happen. Telling body to get ready - Para- does the opposite; it counters the effect of the sympathetic nerves. Heart pounding, sweating-- slowly quiet things down. - The way the signals are carried, they use a 2-stage arrangement, signals coming out of spinal cord; those neurons are going to synapse on another neuron and then on an organ itself. - Fight or Flight- you saw the bear, blood flow pattern are going to change, you need all blood to go to muscles, instead to go to the digestive system for you to run away from the bear. I need stress hormones kicking in (adrenaline) pupillary response, breathing, and heart rate to make body ready. And once you get away. The Parasympathetic gets you down to an everyday state. Meninges, Ventricles and Cerebrospinal Fluid (CSF) - CNS ANATOMY - We have several layers of membrane that help protect the CNS Meninges/ Meninx  CNS encased in bone and covered by three meninges help protect the brain  If you want to investigate them in mammals, remove section of skull, we first hit a thick tough membrane called the Dura Mater Dura mater – tough outer membrane, and then below that directly underneath you have the arachnoid. Arachnoid membrane – web-like, also has a space underneath that house thins in that region- dorsal sinuses For keeping the brain from hitting the skull, we need this shock absorption system, web like fluid in it. From helping it slamming into the skull Pia mater – adheres to CNS surface  Cerebrospinal fluid (CSF) Fluid serves as cushion Act as a shock absorber that is created in the ventricles of the brain. We have 4 ventricles where the fluid passes We have internal and external shock absorption We need a certain amount of fluid to do that job. Anybody that has had a spinal tap done - you‟re removing the fluid and removing that natural absorption and you get a horrible headache. You can develop problems if you have tumors forming near the aqueduct Some researchers has investigated that neurogenesis can happen in the ventricles Protecting the Brain  Chemical protection The blood-brain barrier – tightly-packed cells of blood vessel walls prevent entry of many molecules We have ways to protect brain and spinal cord from calatogenes, can be chemicals, and can be proteins, viruses and other bacteria. So in our body the blood stream, the vascular that we have outside the CNS, the cells that make up these vessels are sloppy in nature, the cell spacing is larger, so many things can be leaked out and wastes can be go back in - the peripheral But in the spinal cord and brain the cells are more compact. This is a good thing because the immune function in the CNS is bad. If you get an infection in the CNS, you need aggressive treatment because there is not substantial immune response there Reason why we tell pregnant women to stay away form things is because some of these things are teratogens that can be passed through and can go to the brain. Protects chemicals form getting through. But again not all things are kept out, THC and weed, cocaine goes right through but if it stayed there then nothing would happen  Physical protection Skull Meninges Cerebrospinal fluid (CSF) Cells of the Nervous System: Neurons  Specialized cells for the reception, conduction, and transmission of electrochemical signals in CNS AND PNS  That collect signals from other neurons and send signals to other neurons. They receive and transmit. By electrical signals and chemical  Many sizes and shapes Cell Membrane - composed of a lipid bilayer, or 2 layers of fat molecules. - Protein molecules are embedded in the bilayer and are the basis of the membrane‟s functional properties - Some membranes are channel proteins, through whithc molecules can pass - Others, are signal proteins, which transfer a signal to the inside of the neuron when some molecules bind to them on the outside of the membrane Neuroanatomical Structure - in general, there are 2 gross neural structures: 1) those composed primarily of cell bodies and 2) those primarily composed of axons. - In the CNS, clusters of cell bodies are called nuclei - In the PNS, clusters of cell bodies are called ganglia - in the CNS bundles of axons are called tracts - in the PNS bundles of axons are called nerves Glial Cells- the forgotten ones - supportive cells - Originally we thought they were outnumbering, but now it‟s said to have equal numbers of cells. - We thought they just supported the neurons, 1 they help create the blood barrier, they myelinated axons, they create a structure that the neurons can grow on and keep them arrange properly. But they also do other things - We found that there are signals between them and between neurons, and a neuron modulatory affect, can turn up and down  Outnumber neurons 10:1  Support neurons  Recent evidence for glial communication and modulatory effects of glia on neuronal communication Four classes of Glial cells:  Oligodendrocytes – extensions rich in myelin create myelin sheaths in CNS have long processes and have pancake ends that wrap around the axons of nerves in the CNS, create the installation in the axon only in the CNS. Help neurotransmission to go faster.  Schwann cells – similar to function of oligodendrocytes but in PNS, can guide axonal regeneration In the PNS, its not done by one cell that sends many msgs to different cells, but its multiple cells sending msgs to other many cells.  If we damage a neuron and it dies, some neuron can continue growth of axon and regenerate itself. In the PNS the Schwann cells, if it dies, the Schwann cells are still there. After other glial cells come in and take away the dead tissue. You have a channel for regeneration to follow. In the PNS but doesn‟t happen in the CNS  Astrocytes – largest glia, star-shaped, many functions  Microglia – involved in response to injury or disease  In the CNS we don‟t refer to it as nerve we refer to them as Tracts. Terminology Note CNS PNS Myelin-providing gilia Oligodendrocytes Schwann cells Clusters of Cell bodies Nuclei Ganglia Clusters of Axons Tracts Nerves - Only difference between the two (uni and bi) is how many processes are coming off of it - Bipolar- Multipolar interneuron is just the cell body Neuroanatomical Techniques and Directions - We have astrocytes, all these cells and when you look at it under a microscope its hard to see. Your magnification is limited because the more you magnify the more it dims, and their all tissue of the same colour - So you can stain cells to know what it is there. - They do two different contrast way of making special cells stand out more. - Golgi Stain: allows for visualization of individual neurons, they will stain the entire neuron. But doesn‟t stain all of them stains selectively ones here and there. Silver chromate. - They will stain the whole neuron, which is good you can see the dendrites and the whole picture. But the problem there is you don‟t know how many there are or cell densities. This is where nissl stains come in - In the picture, it does not show all the neurons that are actually there. - Nissl Stain: selectively stains cell bodies, stains all the cells but ONLY the cell bodies. Now you can see the cell densities. And see different layers. And can identify the different layers because they have different shapes. But I can‟t really get at the synapse to see what‟s going on there. - In the pic, you don‟t see the axons or the dendrites but you se
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