CBIO 2200 1nd Edition Lecture 18 Outline of Last Lecture I. ATP SourcesII. Cardiac MuscleIII. Smooth MuscleIV. Neuromuscular Toxins and Paralysis V. Tension Production by Muscle ContractionVI. Behavior of Whole MusclesVII. Contraction Strength of TwitchesVIII. StimulusIX. Isometric vs. Isotonic ContractionOutline of Current Lecture I. Overview of the Nervous SystemII. Subdivisions of the Nervous SystemIII. Nervous TissueIV. Classes of NeuronsV. Types of CNS NeurogliaVI. Types of PNS NeurogliaVII. MyelinVIII. Regeneration of PNS Nerve FibersThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.IX. Electrophysiology of NeuronsCurrent LectureCHAPTER 12 – Nervous TissueI. Overview of the Nervous Systema. Nervous system carries out its task in three basic steps:i. Receives information through sensory receptors and coding it into a messageii. Brain/spinal cord processes that information iii. Sends out information to the rest of the bodyII. Subdivisions of the Nervous Systema. Centrali. Brainii. Spinal cordb. Peripheral (Nerves and Ganglia)i. Sensory division (afferent division) – receives info from receptors1. Visceral sensory division – info about internal environment2. Somatic sensory division – info about external environmentii. Motor division (efferent division) – send out commands to body1. Visceral motor division – info being sent to internal environment/organs (autonomic nervous system); visceral reflexesa. Sympathetic division – arousing the body; putting into actioni. Accelerated heart beat, respiration, etc.b. Parasympathetic division – calming effect on bodyi. Digestion2. Somatic motor division – info being sent to external environmentIII. Nervous Tissuea. Two cell types in nervous tissuei. Neurons – basic cell of nervous systemii. Glial cells – support cellsb. Universal properties of nerves/neuronsi. Excitability (irritability)ii. Conductivityiii. Secretionc. Classes of neuronsi. Afferent/ Sensory – synapse on interneuronsii. Interneurons – processing iii. Motor/efferent d. Anatomy of neuroni. Neuro-soma – cell bodyii. Nucleusiii. Neurofilament – structural supportiv. Mitochondrionv. Nissl bodies – important in regenerationvi. Dendritesvii. Axonviii. Axolemma – cytoplasm of axonix. Axon hillock – generate action potentiale. Nissl Bodiesi. Protein synthesis takes place hereii. Many neurotransmitters are protein based moleculesIV. Classes of Neuronsa. Multiple neuron – one axon and many dendritesb. Bipolar neuron – one axon and one dendrite; found in eye, ear, and nosec. Unipolar neuron – one process leading off the soma, and it then branchesd. Anaxonic neuron – no axon; just multiple dendrites; seen in part of the visual pathwayV. Types of CNS Neurogliaa. Oligodendrocytes – synthesize myelin in CNSb. Ependymal – line cavities in brain; help make cerebrospinal fluidc. Astrocyte – most abundant; responsible for malignant brain tumors; help form the blood brain barrieri. Send out projections called perivascular feet that wrap around blood vesselsd. Microglial – macrophages of CNS; make sure nothing is there that shouldn’t be; increased number in cerebrospinal fluid diagnosis meningitisVI. Types of PNS Neurogliaa. Schwann cells – make the myelinb. Satellite cells – surround soma of the neuron, providing protectionVII. Myelina. Myelin sheathi. Formed by oligodendrocytes in CNS and Schwann cells in PNSb. Myelination: process of forming myelini. During this process, the myelin coats the nerve in segmentsc. Myelin sheath is segmentedi. Nodes of Ranvier – spots on nerve that are not covered by myelinii. Internodes – segments of myelin covered nervesd. Speed up conduction of nerve signal e. Diameter of nerve fiber affects conduction; larger = more rapidf. Diseases of the myelin sheathi. Multiple sclerosis1. Autoimmune disease2. Oligodendrocytes attacked by immune cells3. Myelin replaced by hardened scar tissue (sclerosis)a. Reduces speed of conduction in nerves 4. No cure; live 20-30 yrs after diagnosisii. Tay-Sachs disease1. Hereditary disorder (need two recessive copied of the gene)2. Found mostly in people with eastern European Jewish ancestry 3. Abnormal accumulation of a glycolipid (GM2) due to absence of lysosomal enzyme (hexosaminidase A)4. Caused by defect on chromosome 155. No cure; fatal by age 4iii. Guillain-Barre syndrome1. Loss of myelin from the peripheral nerves and spinal nerve roots2. Ascending paralysis3. Usually preceded by a flu-like illness4. Most people recover all neurologic function with little medical interventionVIII. Regeneration of PNS Nerve Fibers (regeneration cannot occur in CNS)a. Regeneration can occur if:i. Its soma is in tactii. At least some neurilemma remainsb. Denervation atrophyIX. Electrophysiology of Neuronsa. Establishing and maintaining the resting membrane potential (RMP)i. Cytosol (ICF) – high concentration of potassiumii. ECF – high concentration of sodiumiii. Sodium potassium pump corrects leaking of ionsb. Neuron responsei. Receptive segment – receives informationii. Initial segment – action potential initiatediii. Conductive segment – axon; propagation of action potentialiv. Transmissive segment – dendrites; releases neurotransmitters c. Local potentialsi. Need enough local potentials to fire an action potential at the axon hillocks ii. Differences in local potentials vs. action potentials1. Graded – they can vary in magnitude; the stronger the stimulus, the more gates it can open2. Decremental – get weaker the farther away they are from the stimulus3. Reversible – if no action potential is initiated, then the already open gates close; stops local potential; can’t stop action potential once they’ve started4. Either excitatory or inhibitory – some neurotransmitters make the membrane potential more negative; depends on action of neurotransmitter that is releaseda. Glycine, GABA, and chlorine are inhibitory neurotransmitters usuallyd. Action Potentials in Neuronsi. Soma (50 – 75 gates per micron squared)ii. A rapid up-and-down shift in the membrane voltageiii. Characteristics of action potentials vs. local potentials1. Follows all or none law2. Nondecremental3. Irreversiblee. In un-myelinated fiber, the nerve is polarized in segments (that portions charges will be reversed of what is