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Premium member Presentation Transcript Nervous System Cells : Nervous System Cells Mr. Mullins OBJECTIVES : OBJECTIVES THE STUDENTS WILL UNDERSTAND: THE ORGANIZATION OF THE NERVOUS SYSTEM; DIVISION OF THE NERVOUS SYSTEM; CELLS OF THE NERVOUS SYSTEM; BLOOD-BRAIN BARRIER; RELEX ARC; WHITE MATTER AND GRAY MATTER; NERVE IMPULSE; REPAIR OF NERVES; ACTION POTENTIAL; SYNAPTIC CLEFT; NEUROTRANSMITTERS; ANESTHETICS; ANTIDEPRESSANT; EEG; PERFORM A LAB IN BUILDING A NEURON AND SHOWING THE ACTION POTENTIAL; AND CAREERS DEALING WITH THE NERVOUS SYSTEM materials : materials Video on nervous system Textbook Diagrams College funds : College funds www.hsf.net ($1000-$3000 awards) http://www.fafsa.ed.gov/ (pell grants) Stanford loans RATIONAL FOR LEARNING : RATIONAL FOR LEARNING Students will learn the function of the nervous system because it plays a major role in every aspect of our lives. Without the nervous system functions and performances could not be accomplished WARM-UPS : WARM-UPS BRAIN HIEROGLPHICS which will assist students in understanding important terms On your table you will find a few slips. You and your lab group must determine the correct answer and then place them into your journal. Brain jokes for the day!! Homework assignments : Homework assignments Complete handout notes Complete drawing/labeling handouts Build or poster draw a complete nerve cell; or synaptic cleft, or action potential Organization Of The Nervous System : Organization Of The Nervous System Organized to detect changes (stimuli) in the internal and external environment Evaluates the information Possibly respond by initiating changes in the muscles or glands Division of the Nervous System : Division of the Nervous System The nervous system is divided into smaller “systems” or “divisions” The nervous system can be divided in various ways: According to structure, Direction of information flow, or Control of effectors Central & Peripheral Nervous System : Central & Peripheral Nervous System Central & Peripheral Nervous System : Central & Peripheral Nervous System One way to subdivide the nervous system is based on the gross dissections of early anatomists They categorized all nervous system tissues according to their relative positions in the body: Central Peripheral Central Nervous System (CNS) : Central Nervous System (CNS) Is the structural and functional center of the entire nervous system Consisting of the brain and the spinal cord The CNS: Senses information—then evaluates the information—and initiates a response Peripheral Nervous System (PNS) : Peripheral Nervous System (PNS) Nerve tissues that lie in the periphery (outer regions) of the nervous system Nerves that originate from the brain are termed CRANIAL NERVES Nerves that originate form the spinal cord are termed SPINAL NERVES More about “central” and “peripheral” : More about “central” and “peripheral” These two terms are often used as directional terms in the nervous system Central fibers If they extend from the cell body toward the CNS Peripheral fibers If they extend from the cell body away from the CNS Afferent & Efferent Divisions : Afferent & Efferent Divisions Afferent & Efferent Divisions : Afferent & Efferent Divisions The tissues of both the CNS and PNS include nerve cells that form incoming information pathways and outgoing pathways Therefore, it is easier to categorize the nervous pathways into divisions according to the direction in which they carry information Afferent Division : Afferent Division Are all the incoming SENSORY PATHWAYS Literal meaning “carry toward” Efferent division : Efferent division Are all the outgoing MOTOR PATHWAYS Literally meaning “carry away” Somatic & Autonomic Nervous System : Somatic & Autonomic Nervous System Somatic & Autonomic Nervous System : Somatic & Autonomic Nervous System This is another way to organize the nervous system by categorizing them according to the type of effectors they regulate Types of effectors: Somatic Nervous System (SNS) Autonomic Nervous System (ANS) Somatic Nervous System (SNS) : Somatic Nervous System (SNS) Carry information to the somatic effectors The skeletal muscles These motor pathways make up the somatic motor division The SNS also includes the afferent pathways, which provide feedback from the somatic effectors The SNS also includes the integrated centers that receive the sensory information and generate the efferent response signal Autonomic Nervous System (ANS) : Autonomic Nervous System (ANS) Carry information to the autonomic or visceral effectors Smooth muscles, Cardiac muscle, and Glands. Important to note is that this system seems autonomous of voluntary control without any conscious knowledge However, today we know now that we can also influence it by the conscious mind Further division of the ANS : Further division of the ANS The efferent pathways of the ANS can be divided into the Sympathetic division, and Parasympathetic division Sympathetic Division : Sympathetic Division Made up of pathways that exit the middle portions of the spinal cord Involved in preparing the body to deal with immediate threats to the internal environment FIGHT-OR-FLIGHT RESPONSE Parasympathetic Division : Parasympathetic Division Exit at the brain or lower portions of the spinal cord Coordinate the body’s normal resting activities REST-AND-REPAIR DIVISION Afferent pathways of the ANS : Afferent pathways of the ANS Belong to the VISCERAL SENSORY DIVISION Carries feedback information to the autonomic integrating centers in the CNS CELLS OF THE NERVOUS SYSTEM : CELLS OF THE NERVOUS SYSTEM Cells of the Nervous System : Cells of the Nervous System Two main types of cells Neurons, and glia Neurons : Neurons Neurons : Neurons Are excitable cells Conduct the impulses that make possible all nervous system functions They are the WIRING of the nervous system’s information circuits The human brain is estimated to contain about 100 billion, or about 10% of the total number of nervous system cells in the brain The Make-up of Neurons : The Make-up of Neurons All neurons consist of: Cell body Also termed SOMA OR PERIKARYON Dendrites Process Are thread like and often known as nerve fibers Axon Process Are also thread like and often known as nerve fibers Cell body of a Neuron : Cell body of a Neuron Largest part of the nerve Contains a nucleus, cytoplasm, and various organelles such as mitochondria and a Golgi apparatus The cytoplasm also extends into the processes and a plasma membrane encloses the entire neuron The rough ER (endoplasmic reticulum) has ribosome's that can be stained to form easily apparent structures call NISSL BODIES, which provide protein molecules needed for the transmission of nerve signals and are useful in maintaining and regenerating nerve fibers Dendrites of a Neuron : Dendrites of a Neuron Usually branch extensively from the cell body (like a tree) (which the name comes form the Greek word for tree) The distal ends of dendrites of sensory neuron may be termed receptors because the receive the stimuli that initiate nerve signals They receive stimuli and conduct electrical signals toward the cell body and/or axon of the neuron. Axon of the Neuron : Axon of the Neuron Is a single process Usually extends form a tapered portion of the cell body at a location termed AXON HILLOCK Axons conduct impulses away from the cell body Even though neurons have only one axon, that axon often has one or more side branches termed axon collaterals The distal tips of axons form branches called telodendria, which each terminate in a synaptic knob, which contain mitochondria and numerous vesicles Size of Axons : Size of Axons Some are a meter long and some are only a few millimeter Their diameter also varies. The larger the diameter the faster the impulse An axon can be myelinated or not However only axons can have myelin sheath, dendrites do not. Classification of neurons : Classification of neurons Classifying Neurons : Classifying Neurons Two ways: Structural functional Structural Classification of Neurons : Structural Classification of Neurons Can be classified according to the number of extensions form the cell body, there are three types Multipolar Bipolar unipolar Multipolar Neurons : Multipolar Neurons one axon Several dendrites Found in the brain and spinal cord Bipolar Neurons : Bipolar Neurons one axon Branched dendrites Are the least numerous kind of neuron Found in the: retina, inner ear, and olfactory pathway. Unipolar Neurons : Unipolar Neurons Also termed pseudounipolar neurons They only have a single process extending form the cell body Are always sensory neurons, conducting information toward the CNS This single process branches to form a central process toward the CNS and a peripheral process (away from the CNS), which together for an axon It conducts impulses away form the dendrites found at the distal end of the peripheral process Functional Classification of Neurons : Functional Classification of Neurons Can be classified according to the direction in which they conduct impulses, there are three types: Afferent Efferent Interneuron's Afferent Neurons : Afferent Neurons Are SENSORY Transmit nerve impulses to the spinal cord or brain Efferent Neurons : Efferent Neurons MOTOR Transmit nerve impulses away form the brain or spinal cord to or toward muscles or glands Interneuron's : Interneuron's Conduct impulses from afferent neurons to or toward motor neurons Located entirely within the CNS (brain and spinal cord) Glia Cells : Glia Cells Glia or Glial Cells : Glia or Glial Cells Do not usually conduct information themselves but support the function of neurons in various ways Major Types of Glia : Major Types of Glia Common term is NEUROGLIA Discovered by Italian cell biologist Camillo Golgi (whom also named the Golgi Apparatus in cells) He accidentally dropped a piece of brain tissue in a bath of silver nitrate. When he finally found it, golgi could see a vast network of various kinds of darkly stained cells surrounding the neurons—proof that glia existed Glia literally means “GLUE” Studies of glia is now one of the hottest areas in neurobiology Some say that there is well over 900 billion glia in the nervous system (9 times the amount of stars in the Milky Way) More About Glia : More About Glia Most important thing about glia is that unlike neurons they retain their capacity for cell division throughout adulthood However, even though this gives glia the ability to replace themselves, it also makes them susceptible to abnormalities of cell division, such as cancer Most benign and malignant tumors in the nervous system begin in glial cells So What is the Role of Glia Cells? : So What is the Role of Glia Cells? They serve as various roles in supporting the function of neurons! There are five major types of glia Astrocytes; Microglia; Ependymal cells; Oligodendrocytes; and Schwann cells Astrocytes : Astrocytes Star shaped (derived their name from the Greek astron, “star” Found only in the CNS Are the largest and most numerous Their long delicate “points” extend through the brain tissue, attaching to both neurons and the tiny blood capillaries Also termed “stars of the nervous system” What do astrocytes do? : What do astrocytes do? The “feed” the neurons by picking up glucose from the blood, converting it to lactic acid, and passing it along to the neurons that they are connected with Since astrocytes form tight sheaths around the brain’s blood capillaries they help form the BLOOD-BRAIN BARRIER (BBB) BBB : BBB Is a double barrier made up of astrocyte “feet” and the endothelial cells that make up the walls of the capillaries Small molecules (oxygen; carbon dioxide; water; and alcohol) diffuse rapidly through the barrier to reach brain neurons and other glia Large molecules penetrate it slowly or not al all (box 12-1) Recent news about astrocytes : Recent news about astrocytes Astrocytes may not only influence the growth of neurons and how the neurons connect to form circuits, but may also transmit information along “astrocyte pathways” themselves Microglia : Microglia Small Usually stationary cells found in the CNS In inflamed or degenerating brain tissue, microglia enlarge and move about and carry on phagocytosis Therefore microglia are functionally and developmentally unrelated to other nervous system cell Ependymal Cells : Ependymal Cells Resemble epithelial cells, forming thin sheets that line fluid-filled cavities in the brain and spinal cord Some take part in producing the fluid that fills these spaces Others have cilia that help keep the fluid circulating within the cavities Oligodendrocytes : Oligodendrocytes Smaller than astrocytes and have fewer processes Literally means “cell with few branches” (oligo few; dendro branch; cyte cell) Some lie clustered around nerve cell bodies Some are arranged in rows between nerve fibers in the brain and spinal cord Function is to help hold nerve fibers together and also serve another more important function—they produce the fatty myelin sheath around nerve fibers in the CNS (Box 12-2) Schwann Cells : Schwann Cells Only found in the PNS!!!!!!!!!!!!!!! Serve as the functional equivalent of the oligodendrocytes, supporting nerve fibers and sometimes forming a myelin sheath around them Many Schwann cells can wrap themselves around a single nerve fiber How do Schwann cells form myelin sheaths? : How do Schwann cells form myelin sheaths? The myelin sheath is formed by layers of Schwann cell membrane containing the whit, fatty substance “MYELIN” Microscopic gaps in the sheath, between adjacent Schwann cells are termed NODES OF RANVIER The myelin sheath and its tiny gaps are important in the proper conduction of impulses along nerve fibers in the PNS Neurilemma : Neurilemma As each Schwann cell wraps around nerve fibers, its nucleus and cytoplasm are squeezed to the perimeter to form the NEURILEMMA (sheath of Schwann) The neurilemma is essential to the regeneration of injured nerve fibers Nerve fibers with many Schwann cells forming a thick myelin sheath are called MYELINATED FIBERS OR WHITE FIBERS When several nerve fibers are held by a single Schwann cell that does not wrap around them to form a thick myelin sheath, the fibers are termed UNMYELINATED FIBERS OR GRAY FIBERS Satellite cell : Satellite cell Is a type of Schwann cell They surround the cell body of a neuron They support neuronal cell bodies in regions called GANGLIA in the PNS Ganglion Block Shots: are how doctors numb an entire limb or portion of the body such as epidurals. Reflex Arc : Reflex Arc What is Reflex Arc? : What is Reflex Arc? Neurons are often arranged in a pattern called reflex arc. Reflex arc is a signal conduction route to and from the CNS Most common is the three-neuron arc Three-Neuron Arc : Three-Neuron Arc Consist of an afferent, an interneuron, and an efferent In essence, a reflex arc is a signal conduction route from receptors to the CNS and out to effectors as a feedback loop (fig 12-8 pg 351) Reflex arc is called an ipsilateral reflex arc because the receptors and effectors are located on the same side of the body Contralateral reflex arc are ones whose receptors and effectors are located on opposite sides of the body Nerves and Tracts : Nerves and Tracts Nerves : Nerves Nerves are bundles of peripheral nerve fibers held together by several layers of connective tissues (fig 12-9, p 351) Surrounding each nerve fiber (axon) is a layer of fibrous connective tissue termed endoneurium Bundles of these fibers are called fascicles which are held together by tissue termed perineurium Numerous fascicles along with blood vessels are held together to form a complete nerve by a fibrous coat termed the epineurium Nerves only in PNS What are tracts : What are tracts In the CNS bundles of nerve fibers are termed tracts rather than nerves Tracks only in CNS White Matter and Gray Matter : White Matter and Gray Matter White matter : White matter Is creamy white color of myelin which distinguishes bundles of myelinated fibers from surrounding unmyelinated tissues Bundles of myelinated fibers make up white matter in the PNS, white matter consists of myelinated nerves; in the CNS white matter consists of myelinated tracts Gray Matter : Gray Matter Cell bodies and unmyelinated fibers make up the darker gray matter of the nervous system CNS are usually called nuclei PNS, regions of gray matter is termed ganglia Repair of Nerve Fibers : Repair of Nerve Fibers Can Nerve Fibers be Repaired : Can Nerve Fibers be Repaired Mature neurons are incapable of cell division, damage to nervous tissue can be permanent. Damaged neurons cannot be replaced; the only option for healing injured or diseased nervous tissue is repairing the neurons that are already present. Is there any hope? : Is there any hope? Nerve fibers can sometimes be prepared if the damage is not extensive. That is when the cell body and neurilemma remain intact, and scarring has not occurred. Axons can grow up to 3 to 5 mm per day and if all goes well the axon will reconnect with the other end of the axon However, in the CNS, similar repair of damaged nerve fibers is very unlikely. Mainly because they lack the neurilemma needed to form the guiding tunnel from the point of injury to the distal connection. Second astrocytes quickly fill damaged areas and thus blow regrowth of the axon with scar tissue. NERVE IMPULSES : NERVE IMPULSES Nerve Impulses : Nerve Impulses NEURONS EXHIBIT BOTH EXCITABILITY AND CONDUCTIVITY MEMBRANE POTENTIALS : MEMBRANE POTENTIALS One way to describe a nerve impulse is as a wave of electrical fluctuation that travels along the plasma membrane. Electrical nature of the plasma membrane : Electrical nature of the plasma membrane All living cells maintain a difference in the concentration of ions across their membranes There is a slight excess of positive ions on the outside of the membrane and a slight excess of negative ions on the inside of the membrane. This causes a difference in electrical charge across their plasma membranes termed membrane potential + ions outside membrane plus – ions inside membrane = electrical charge difference (membrane potential) Why is it called potential? : Why is it called potential? This difference in electrical charge is called a potential because it is a type of stored energy called potential energy. Whenever opposite electrical charges are separated by a membrane, they have the potential to move toward one another if they are allowed to cross the membrane. So there is a “potential” What else about membrane potential? : What else about membrane potential? A membrane that exhibits a membrane potential is said to be polarized meaning that its membrane has a negative pole and a positive pole. The magnitude of potential difference between the two sides of a polarized membrane is measure in volts (V) or millivolts (mV) measured with a voltmeter. Resting Membrane Potentials : Resting Membrane Potentials When a neuron is not conducting electrical signals it is said to be “resting” Resting is typically at -70 mV The membrane potential maintained by a nonconducting neuron’s plasma membrane is called the resting membrane potential (RMP) Via gated channels (fig 12-12 pg 354) Or sodium-potassium pump (fig 12-13 pg 355) Local Potentials : Local Potentials A slight shift away from the RMP in a specific region of the plasma membrane is often called a local potential Inhibition is a stimulus that triggers the opening of stimulus-gated K+ channels Hyperpolarization: movement of the membrane potential away from zero Excitation of a neuron occurs when a stimulus triggers the opening of stimulus-gated NA+ channel Stimulus-gated channels open in response to a sensory stimulus from another neuron Depolarization: movement of the membrane potential toward zero ACTION POTENTIAL : ACTION POTENTIAL Action Potential : Action Potential Action Potential is the membrane potential of an active neuron. It is one that is conducting an impulse Synonym commonly used is nerve impulse It is an electrical fluctuation that travels along the surface of the neuron’s plasma membrane Step-by-Step Description of Action Potential (fig 12-15 pg 356) : Step-by-Step Description of Action Potential (fig 12-15 pg 356) Step 1 : Step 1 Adequate stimulus is applied to a neuron, then the stimulus-gated Na+ channels at the point of stimulus open, Na+ diffuses rapidly into the cell producing a local depolarization Step 2 : Step 2 If the magnitude of the depolarization surpasses a limit termed THRESHOLD POTENTIAL (-59 mV), the voltage-gated Na+ are stimulated to open Step 3 : Step 3 As more Na+ rushes into the cell, the membrane moves toward 0 mV, then continues to a peak of +30 mV (the + indicates that there is an excess of +ions inside the membrane If the local depolarization fails to cross -59 mV the voltage-gated Na+ do not open and the membrane simply recovers back to the resting potential of -70 mV without producing an action potential Step 4 : Step 4 Voltage-gated Na+ stays open for only about 1 ms before automatically closing. This means that once they are stimulated the Na+ always allow sodium to rush in. therefore the action potential is an all-or-nothing response Step 5 : Step 5 Once the peak is reached the membrane potential begins to move back toward the resting potential termed REPOLARIZATION surpassing the threshold not only triggers the opening of voltage-gated Na+ but also the voltage-gated K+ these are slow to respond, however, and thus do not begin opening until the inward diffusion of Na+ has caused the membrane potential to reach +30 mV once the K+ are open it rapidly diffuses out of the cell. The outward rush of K+ restores the original excess of + ions on the outside of the membrane, thus repolarizing the membrane Step 6 : Step 6 Because the K+ channels remain open as the membrane reaches its resting potential, too many K+ may rush out of the cell. This causes a brief period of hyperpolarization before the resting potential is restored by the action of the Na+-K+ pump and the return of ion channels to their resting state REFRACTORY PERIOD : REFRACTORY PERIOD Refractory Period : Refractory Period Is a brief period during which a local area of an axon’s membrane resists restimulation, for about ½ ms after the membrane surpasses the threshold potential IT WILL NOT RESPONSD TO ANY STIMULI NO MATTER HOW STRONG Termed ABSOLUTE REFRACTORY PERIOD REFRACTORY PERIOD : REFRACTORY PERIOD The RELATIVE REFRACTORY PERIOD occurs a few ms after the absolute refractory period This is the time in which the membrane is repolarizing and restoring the resting membrane potential Will only respond to very strong stimuli CONDUCTION OF THE ACTION POTENTIAL : CONDUCTION OF THE ACTION POTENTIAL Conduction of the Action Potential : Conduction of the Action Potential Never backwards always pulses forward Synaptic Transmission : Synaptic Transmission Synaptic Transmission : Synaptic Transmission Synaptic is the place where signals are transmitted from one neuron (presynaptic neuron) to another neuron (postsynaptic neuron) A postsynaptic neuron can be an effector such as a muscle. There are two types of Synapses Two Types of Synapses : Two Types of Synapses Electrical synapses Chemical synapses Electrical synapses : Electrical synapses Occur where two cells are joined end-to-end by gap junctions (fig 12-20, A; pg 359) Chemical Synapses : Chemical Synapses Use chemical transmitter called a neurotransmitter to send a signal from the presynaptic cell (Fig 12-20, B, pg 359) Three structures make up a chemical synapse Three Structures Making up the Chemical Synapse : Three Structures Making up the Chemical Synapse Synaptic Knob Synaptic cleft Plasma membrane of a postsynaptic neuron More about Synaptic Knob : More about Synaptic Knob Is a tiny bulge at the end of a terminal branch of a presynaptic neuron’s axon (Fig 12-21, pg 360) Each knob contains about 10,000 molecules of a chemical compound known as NEUROTRANSMITTER What About the Synaptic Cleft : What About the Synaptic Cleft Is a space between a synaptic knob and the plasma membrane of a postsynaptic neuron The narrow space is about 1 millionth of an inch in width Fig 12-21, pg 360 Finally the Plasma Membrane of a Postsynaptic Neuron : Finally the Plasma Membrane of a Postsynaptic Neuron Has protein molecules embedded in it opposite each synaptic knob Serve as receptors to which neurotransmitter molecules bind MECHANISMS OF SYNAPTIC TRANSMISSION : MECHANISMS OF SYNAPTIC TRANSMISSION Step 1 : Step 1 1. when an action potential reaches a synaptic knob, voltage-gated Ca++ open and allow Ca++ to diffuse into the know rapidly Step 2 : Step 2 The increase in intracellular Ca++ triggers movement of neurotransmitter vesicles to the plasma membrane of the synaptic knob Once there they fuse with the membrane to release their neurotransmitter via exocytosis Thousands of neurotransmitter molecules spurt out into the synaptic cleft Step 3 : Step 3 The released neurotransmitter molecules diffuse across the narrow synaptic cleft and contact the postsynaptic neuron’s plasma membrane They briefly bind to receptor molecules that are also the gated channels, which triggers them to open Step 4 : Step 4 The opening of ion channels in the postsynaptic membrane may produce a local potential termed POSTSYNAPTIC POTENTIAL Excited neurotransmitters cause both Na+ and K+ to open Because Na+ rushes inward faster than K+ rushing outward there is a temporary depolarization termed EXCITATROY POSTSYNAPTIC POTENTIAL (EPSP) Inhibitory neurotransmitter cause K+ and/or Cl- to open. Either event makes the inside of the membrane more negative causing a temporary hyperpolarization termed INHIBITORY POSTSYNAPTIC POTENTIAL (IPSP) Step 6 : Step 6 Once neurotransmitter binds to its postsynaptic receptors, its action is quickly terminated Fig 12-22, pg 361 Summation : Fig 12-22, pg 361 Summation Neurotransmitters : Neurotransmitters What Are Neurotransmitters : What Are Neurotransmitters They are a means for neurons to talk to one another They act to facilitate, stimulate, or inhibit postsynaptic neurons and effector cells There are over 50-100 known neurotransmitters Neurotransmitter can be classified Classification of Neurotransmitters : Classification of Neurotransmitters Classification of Neurotransmitters : Classification of Neurotransmitters Commonly classified by their function or by their chemical structure Some can have inhibitory effects and other excitation Because the functions of neurotransmitters vary by location it is often useful to classify them according to their chemical structure Therefore they can be grouped into two main groupings Two Main Groupings of Neurotransmitters : Two Main Groupings of Neurotransmitters Small-molecule transmitters Large-molecule transmitters Small-molecule Neurotransmitters : Small-molecule Neurotransmitters Are smaller Are amino acids or are derived from amino acids Are divided into four chemical classes Acetylcholine Amines Amino acids Other small molecules Acetylcholine : Acetylcholine Ach Made in neurons by combining acetate (acetyl-CoA) with choline (B vit) Found in motor effectors (muscles, glands) and many parts of the brain Function as excitatory (in muscles) or inhibitory (in heart) and involved in memory Amines : Amines Made from amino acid such as tyrosine, tryptophan, or histidine Amines are neurotransmitters such as SEROTONIN and HISTAMINE Also included are neurotransmitters of the CATECHOLAMINE class such as DOPAMINE, EPINEPHRINE, and NOREPINEPHRINE More about Amines : More about Amines Serotonin Found in CNS Function: involved in moods and emotions; and sleep Histamine Found in brain Function: involved in emotions and regulation of body temp and water balance Dopamine Found in brain, ANS Function: involved in emotions/moods and in regulating motor control Epinephrine Found in CNS and sympathetic division Function: acts as hormone when secreted by sympathetic cells of the adrenal gland Norepinephrine Found in CNS and sympathetic division Function: regulates sympathetic effectors; in brain, involved in emotional responses Amino Acids : Amino Acids Most common neurotransmitter in CNS Glutamate is responsible for up to 75% of the excitatory signals in the brain Gamma-aminobutyric acid (GABA) is derived from glutamate and is the most common inhibitory neurotransmitter in the brain Glycine is found in the spinal cord and is an inhibitory neurotransmitter Large-molecule Neurotransmitters : Large-molecule Neurotransmitters Made up of chains of 2 to 40 amino acids Are all neuropeptides (chains of amino acids strung together by peptide bonds Vasoactive intestinal peptide (VIP) Retina; gastrointestinal tract; brain, and some ANS Cholecystokinin (CCK) Retina; brain Substance P (transmits pain info) Brain; spinal cord; pain pathways; and gastrointestinal tract Enkephalins (block pain) Regions of CNS; retina; intestinal tract Endorphins (block pain) CNS; retina; intestinal tract Antidepressants : Antidepressants Box 12-6 pg 366 Read and write a response in your own words Anesthetic : Anesthetic Box 12-4, pg 358 Write a response to what you have learned in your own words Mechanisms of Disease : Mechanisms of Disease Disorders of Nervous System Cells Tumors in the Central Nervous System Tumors in the Peripheral Nervous System Disorders of the Nervous System Cell : Disorders of the Nervous System Cell Involve glia rather than neurons Multiple sclerosis (MS) is one of the myelin disorders (read pg 347) Neuroma is tumors arising in the nervous system structures. Come from glia, membrane tissue, and blood vessels. A common brain tumor (GLIOMA) occurs in glia Usually benign Can be life threatening because the develop in deep areas of the brain and difficult to treat. Can cause secondary tumors in the lungs breast, or other organs causing cancer. Tumors of CNS : Tumors of CNS ASTOCYTOMA is a type of glioma that originates from astrocytes Slow growing, infiltrating tumor of the brain appearing during the fourth decade of life Symptoms: seizures, headaches, or neurological deficits Glioblastoma multiforme is highly malignant form of astrocytic tumor Spreads throughout the white matter and surgical removal is difficult and average survival is less than 1 year Ependymoma is a glial tumor arising from ependymal cells which line the fluid filled cavities (ventricles) of the brain and spinal cord Most common glioma in children Causes increased pressure Average post-op survival is 5 years Oligodendroglioma is a tumor that commonly occurs in the anterior portion of the brain Peaks at 40 years of age Average survival is 10 years after onset of symptoms Tumors of the PNS : Tumors of the PNS Glial tumors can also develop in or on the cranial nerves Acoustic neuroma A lesion of the sheath of Schwann cells surrounding the 8th cranial nerve (hearing and balance) Size of a pea or walnut Experiences difficulty deciphering speech through the affected ear, dizziness, tinnitus (ringing of the ear) and slow progressive hearing loss Removed surgically with some nerve damage Multiple neurofibromatosis is an inherited disease that has numerous fibrous neuromas throughout the body are benign Appears first as small nodules in the Schwann cells in the skin Spreads as large disfiguring tumors in many areas of the body Elephant Man (David Merrick) You do not have the permission to view this presentation. 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