Intro to Neurophysiology Notes
Intro to Neurophysiology Notes BIOL 221
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Date Created: 04/03/16
Nervous System Lecture – Organization and Histology OUTLINE Spring 2015 Reading: 386398 Vocabulary: Afferent To the brain Efferent Away from brain Visceral Internal Innervate “are distributed to” Sensory Info about senses Motor Effector Peripheral gland or muscle cells innervated by a motor neuron Interstitial Fluid in tissues that fills space between cells Propagate “jumpy” flow of charge, like electricity in copper wire Regenerate Rebuild/ Repair Intro to the nervous system (Fig 12.1) Responsible for electrical signaling in the body Central nervous system Brain and spinal cord responsible for integration/processing/coordination of info Peripheral nervous system Bring sensory info to spinal cord and brain, or to carry motor commands out to body • Subdivided into o Afferent nervous system Brings sensory info to the brain Receptors ▪ Somatic Sensory Receptors • Monitor skeletal muscles, joints, and skin surface ▪ Visceral Sensory Receptors • Monitors internal organs (status and stretch of organs) ▪ Special Sensory Receptors • Monitors smell, taste, vision, balance, hearing o Efferent nervous system Effector ▪ Somatic nervous system Skeletal muscle ▪ Autonomic nervous system AUTOMATIC (no control) • Parasympathetic Rest & Digest o Smooth muscle o Cardiac Muscle o Glands • Sympathetic o Smooth Muscle o Cardiac Muscle o Glands o Adipose Tissue Cells that make up the nervous system (Fig 12.6, 12.5) Neuroglia or glial cells • Support neurons, • 10:1 ratio of neuroglia to neurons, • no signaling activity, • Clinical Note: Glioma, brain tumor or tumor in the Nervous System from glial cells, malignant • Six types CNS: astrocytes, oligodendrocytes, microglia, ependymal cells ▪ Astrocytes • Wrap around axons, Provide structural support • Regulate ion, nutrient, and dissolved gas concentrations • Protect neurons “nurse cell” • maintain bloodbrain barrier • Some repair work on brain tissue • Help with brain development • Maintain environment and fluids ▪ Oligodendrocytes • Myelinate axons • Provide strutural framework • myelination wrapping axon in lipids and proteins, • acts as insulation and isolates each axon from one another • makes signaling go faster ▪ Microglia • Picks up cellular debris and waste products by phagocytosis ▪ Ependymal cells o Three Types: ▪ Ependymocytes(cilia) aid in circulation of CSF ▪ Tancytes (no cilia)transport substances between CSF and brain ▪ Specialized CSFproducing ependymal cells • Line central canal and ventricles • Form EPENDYMA simple cuboidal columnar epithelium • Make cerebrospinal fluid PNS: Schwann cells, satellite cells ▪ Satellite cells • Regulate O2 and CO2, nutrient, and neurotransmitter levels • PNS version of astrocyte • ganglia ▪ Schwann cells • Surround all axons in PNS (wraps whole body to 1 axon) • myelinate peripheral axons • Repair • Better Oligodendrocyte Neurons (Fig 12.2) • Neurons respond to an action potential, a sudden change in electrochemical force that propagates on the membrane surface of a neuron • Parts of the neuron o Cell body or soma ▪ Nissl bodies bundled RER on the cell body, helpful with PNS damage o Dendrites “Antenna” ▪ Receives signals ▪ Transfer signals to axon hillock ▪ Telodendria connects to synapse o Axon ▪ Axon Hillock Initial point of axon ▪ Initial segment ▪ Axoplasm ▪ Axolemma Membrane of axon ▪ Axon collaterals ▪ Synaptic terminal (Fig 12.30 ▪ Axons are surrounded by a myelin sheath (Fig 12.7) In the Schwann cells o Nodes of Ranvier In the , oligodendrocytes • Unmyelinated – not completely myelinated (Fig 12.7) o Axoplasmic transport Transport between cell body and axon terminals ▪ From cell body axon terminal is anterograde flow (Kinesin) ▪ From axon terminal cell body is retrograde flow (Dynein) Types of neurons • Structural classification (Fig 12.4) o Multipolar neurons Multiple dendrites come off cell body, then axon o Bipolar neurons has two things coming off body (bi) RARE ▪ Occur in special sense organs (relay sight, smell, hearing from receptors) ▪ dendrite ▪ Axon o Unipolar neurons Cell body off to the side, dendrites and axon fused ▪ Most sensory neurons of PNS are unipolar o Anaxonic neurons No axon, only dendrites ▪ Found in brain ▪ Dont produce action potentials ▪ Poorly understood function • Functional classification o Sensory (afferent) neurons – transmit nerve impulses from receptors in the skin, sense organs, muscles, joints and viscera toward the CNS Carry from sensory receptors CNS ▪ somatic sensory neurons (monitors external environment) ▪ visceral sensory neurons (monitors internal environment) ▪ Interoreceptors monitor, and provide sensation of stretch, deep pressure, and pain • digestive • respiratory • cardiovascular • urinary • reproductive ▪ Exteroreceptors Provide information about external environment • Temperature • pressure sensations • complex senses of taste, smell, sight, balance ▪ Proprioceptors monitor the movement of skeletal muscles and joints o Motor (efferent) neurons – transmit nerve impulses from the CNS to effectors ▪ somatic motor neurons – innervate skeletal muscles ▪ visceral motor neurons – innervate smooth muscle, cardiac muscle, glands and adipose tissue o Interneurons (association neurons) – distribute sensory information and coordinate motor activity; information processing; memory, planning and learning; brain and spinal cord Where processing is done o Damage and Repair o PNS – dendrites and myelinated axons can be repaired if cell body is intact and Schwann cells are active ▪ Wallerian Degeneration axon distal to injury degenerates and macrophages clean debris ▪ Schwann cells remain intact and act as REGENERATION TUBE guiding new axon o CNS – little or no repair even if the cell body is intact ▪ more axons are likely to be involved ▪ scar tissue and chemicals produced by astrocytes can prevent axon growth Review questions from your book: 1. What is a receptor? Sensory structures that detect changes in the enironment (internal or external) to respond to specific stimuli. What is an effector? Target organs of the integration system, which in turn do something in response to the issue at hand. 2. Distinguish between the central and peripheral nervous systems and between visceral and somatic divisions of the sensory and motor systems. CNS Brain and Spinal cord PNS Receptors and effectors Viseral Peripheral muscle (motor) Internal (sensory) Somaticskeletal muscle (motor) External (sensory) 3. What is another name for the visceral motor nervous system? What are its two subdivisions? What are their functions? 4. Sketch a multipolar neuron and label its soma, dendrites, axon, synaptic knobs (bulbs), myelin sheath, and the nodes of Ranvier. 5. Explain the difference between a sensory neuron, a motor neuron, and an interneuron. Sensory neuron senses change, carries to CNS Motor Neurons transmit info from CNS to effectors Interneuron Integration Center 6. What is the functional difference between a dendrite and an axon? 7. How do proteins and other chemicals synthesized in the soma get to the synaptic knobs? By what process can a virus that invades a peripheral nerve fiber get to the soma of that neuron? Axoplasmic transport and reverse axoplasmic transport 8. How is a glial cell different from a neuron? List the six types of glial cells and discuss their functions.CNS: astrocytes, oligodendrocytes, microglia, ependymal cells ▪ Astrocytes • Wrap around axons, Provide structural support • Regulate ion, nutrient, and dissolved gas concentrations • Protect neurons “nurse cell” • maintain bloodbrain barrier • Some repair work on brain tissue • Help with brain development • Maintain environment and fluids ▪ Oligodendrocytes • Myelinate axons • Provide strutural framework • myelination wrapping axon in lipids and proteins, • acts as insulation and isolates each axon from one another • makes signaling go faster ▪ Microglia • Picks up cellular debris and waste products by phagocytosis ▪ Ependymal cells • Make cerebrospinal fluid PNS: Schwann cells, satellite cells ▪ Satellite cells • Regulate O2 and CO2, nutrient, and neurotransmitter levels • PNS version of astrocyte • ganglia ▪ Schwann cells • Surround all axons in PNS (wraps whole body to 1 axon) • myelinate peripheral axons • Repair • Better Oligodendrocyte 9. How is myelin produced? How does myelin production in the CNS differ from that in the PNS? 10. How can a severed peripheral nerve fiber find its way back to the cells it originally innervated? Regeneration tube