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NERVOUS SYSTEM

NERVOUS SYSTEM. HONORS ANATOMY & PHYSIOLOGY. excitable characteristic of nervous tissue allows for generation of nerve impulses (action potentials) that provide communication & regulation of most body tissue. together with endocrine system: responsible for maintaining homeostasis.

erica-hardin
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NERVOUS SYSTEM

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  1. NERVOUS SYSTEM HONORS ANATOMY & PHYSIOLOGY

  2. excitable characteristic of nervous tissue allows for generation of nerve impulses (action potentials) that provide communication & regulation of most body tissue. • together with endocrine system: responsible for maintaining homeostasis Nervous Tissue & Homeostasis

  3. NERVOUS ENDOCRINE • rapid responder • action potentials • slow, prolonged response • releases hormones Differences in Nervous & Endocrine Control of Homeostasis

  4. total mass of 2 kg (~3% of total body mass) • Skull • Spinal Cord • Spinal Nerves • Cranial Nerves • Ganglia • Enteric Plexus • Special Senses & other Sensory Receptors Structures of the Nervous System

  5. Major Structures of the Nervous System

  6. 3 basic functions: • Sensory • Integrative • Motor Functions of the Nervous System

  7. sensory receptors detect internal & external stimuli • sensory (afferent) neurons carry this sensory information to spinal cord & brain thru cranial & spinal nerves Sensory Function

  8. integrate: process • nervous system takes information from sensory neurons & processes that information, analyzes it, stores some of it & makes decisions for appropriate responses • served by interneurons (connect 1 neuron to another neuron • Perception: • conscious awareness of sensory stimuli • occurs in brain Integrative Function

  9. served by motor (efferent) neurons • carry info from brain/spinal cord  effectors (muscle or gland) thru cranial or spinal nerves • results in muscles contraction or gland secreting Motor Function

  10. What terms are given to neurons that carry input  spinal cord & brain? • What terms are given to neurons that carry output out of the brain & spinal cord? Quick Quiz

  11. Organization of the Nervous System

  12. 2 cell types • Neurons • Neuroglia Histology of the Nerrvous System

  13. nerve cells that possess electrical excitability: • ability to respond to a stimulus & convert it into an action potential • stimulus: any change in environment that is strong enough to initiate an action potential Neurons

  14. Direction Action Potential Travels

  15. electrical signal that propagates along surface of neurolema (membrane) • begins & travels due to movement of ions between interstitial fluid & inside of neuron thru specific ion channels • once begun it travels rapidly @ constant strength Action Potential

  16. Parts of a Neuron

  17. contains nucleus, cytoplasm, typical organelles, • + Nissl bodies clusters of RER • make materials for: • growth of neuron • regenerate damaged axons in PNS Parts of Neuron: Cell Body

  18. general term for any neuronal process or extension that emerges from cell body • most neurons have 2: • Dendrites • Axons Nerve Fiber

  19. “little trees” • input portion of neuron • usually, short, tapering, highly branched • their cytoplasm contains Nissl bodies, mitochondria Dendrites

  20. propagates action potentials  • another neuron • muscle fiber • gland cell Axon

  21. joins cell body @ cone-shaped elevation: axon hillock • part of axon closest to hillock = initial segment • jct of axon hillock & initial segment where action potential arises so is called the trigger zone Parts of an Axon

  22. axoplasm: cytoplasm of an axon • axolemma: plasma membrane of axon • axon collaterals: side branches along length of axon (most @ 90°) • axon terminals: axon divides into many fine processes Parts of an Axon

  23. site of communication between 2 neurons or between a neuron & effector cell • synaptic end bulbs: tips of some axon terminals swell into bulb-shaped structures • synaptic vesicles: store neurotransmitter • many neurons have >1 neurotransmitter, each with different effects on postsynaptic cell Synapse

  24. 2 types: • for moving materials from cell body  axon terminals • slow • 1-5 mm/d • replenishes new axoplasm to developing or regenerating axons • fast • 200 – 400 mm/d • moves materials to/from cell body • organelles or membranes needed in axon terminal Axonal Transport

  25. Functional Classification Structural Classification • Sensory • Interneurons • Motor • use # processes extending from cell body • Multipolar neurons • Bipolar neurons • Unipolar neurons Types of Neurons

  26. several dendrites with 1 axon • includes most neurons in brain & spinal cord Multipolar Neurons

  27. 1 main dendrite & 1 axon • retina, inner ear, olfactory area of brain Bipolar Neuron

  28. are sensory neurons that begin in embryo as bipolar • during development axon & dendrite fuse then divide into 2 branches (both have characteristic structure & function of an axon) • 1 branch ends with dendrites (out of CNS) • 2nd branch ends in axon terminal (in CNS) • cell bodies of most found in ganglia Unipolar Neuron

  29. Unipolar Neuron

  30. found in cerebellum Purkinje Cells

  31. in cerebral cortex of brain Pyramidal Cells

  32. ~50% vol of CNS • “glue” • do not generate or propagate action potentials • multiply & divide in mature nervous systems • glioma: • brain tumors derived from glial cells • very malignant, grow rapidly Neuroglia (Glia)

  33. ASTROCYTES • OLIGODENDROCYTES • MICROGLIA • EPENDYMAL CELLS Glial Cells of the CNS

  34. star-shaped • largest & most numerous of glial cells • functions: • physically support neurons • assist in blood-brain-barrier (bbb) • in embryo: regulate growth, migration, &interconnections between neurons • help maintain appropriate chemical environment for propagation of action potentials Astrocytes

  35. “few trees” • smaller & fewer branches than astrocytes • Functions: • form & maintain myelin sheath on axons in CNS • 1 oligo. myelinates many axons Oligodendrocytes

  36. small cells with slender processes giving off many spine-like projections • function: • phagocytes • remove cellular debris made during normal development • remove microbes & damaged nervous tissue Microglia

  37. single layer of cuboidal to columnar cells • ciliated & have microvilli • function: • line ventricles of brain & central canal of spinal cord • produce, monitor, & assist in circulation of cerebrospinal fluid (CSF) • form bbb Ependymal Cells

  38. Schwann cells • Satellite cells Neuroglial Cells of the PNS

  39. functions: • myelinate axons in PNS • 1 Schwann cell myelinates 1 axon • participate in axon regeneration Schwann Cells

  40. flat cells that surround cell bodies of neurons in PNS ganglia • functions: • structural support • regulate exchange of materials between neuronal cell bodies & interstitial fluid Satellite Cells

  41. myelin sheath: made up of multilayered lipid & protein (plasma membrane) covering • function: • electrically insulates axon • increases speed of nerve impulses Myelination

  42. Myelinated & Unmyelinated Axons

  43. gaps in myelin sheath • 1 Schwann cell wraps axon between nodes of Ranvier Nodes of Ranvier

  44. Sheath of Schwann = Neurolemma

  45. amount increases from birth to maturity • infant‘s responses slower & less coordinated as older child or adult in part because myelination is a work in progress thru infancy Myelin

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