Fundamentals Of The Nervous System And Nervous Tissue PDF

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky Fundamentals of the Nervous System and Nervous Tissue Part A...

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky Fundamentals of the Nervous System and Nervous Tissue Part A 11 Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Nervous System ▪ The master controlling and communicating system of the body ▪ Functions ▪ Sensory input – monitoring stimuli occurring inside and outside the body ▪ Integration – interpretation of sensory input ▪ Motor output – response to stimuli by activating effector organs Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Nervous System Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11.1  Organization of the Nervous System ▪ Central nervous system (CNS) ▪ Brain and spinal cord ▪ Integration and command center ▪ Peripheral nervous system (PNS) ▪ Paired spinal and cranial nerves ▪ Carries messages to and from the spinal cord and brain Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Peripheral Nervous System (PNS): Two Functional Divisions ▪ Sensory (afferent) division ▪ Sensory afferent fibers – carry impulses from skin, skeletal muscles, and joints to the brain ▪ Visceral afferent fibers – transmit impulses from visceral organs to the brain ▪ Motor (efferent) division ▪ Transmits impulses from the CNS to effector organs Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Motor Division: Two Main Parts ▪ Somatic nervous system ▪ Conscious control of skeletal muscles ▪ Autonomic nervous system (ANS) ▪ Regulates smooth muscle, cardiac muscle, and glands ▪ Divisions – sympathetic and parasympathetic Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Histology of Nerve Tissue The two principal cell types of the nervous system are: ▪ Neurons – excitable cells that transmit electrical signals ▪ Supporting cells – cells that surround and wrap neurons Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Supporting Cells: Neuroglia ▪ The supporting cells (neuroglia or glial cells): ▪ Provide a supportive scaffolding for neurons ▪ Segregate and insulate neurons ▪ Promote health and growth Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Astrocytes ▪ Most abundant, versatile, and highly branched glial cells ▪ They cling to neurons and their synaptic endings, and cover capillaries ▪ Functionally, Astrocytes: ▪ Support and brace neurons ▪ Anchor neurons to their nutrient supplies ▪ Guide migration of young neurons ▪ Control the chemical environment Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Astrocytes Figure 11.3a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Microglia and Ependymal Cells ▪ Microglia – small, ovoid cells with spiny processes ▪ Phagocytes that monitor the health of neurons ▪ Ependymal cells – range in shape from squamous to columnar ▪ They line the central cavities of the brain and spinal column Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Microglia and Ependymal Cells Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11.3b, c  Oligodendrocytes, Schwann Cells, and Satellite Cells ▪ Oligodendrocytes – branched cells that wrap CNS nerve fibers ▪ Schwann cells – surround fibers of the PNS ▪ Satellite cells – surround neuron cell bodies with ganglia Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Oligodendrocytes, Schwann Cells, and Satellite Cells Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11.3d, e  Neurons (Nerve Cells) ▪ Structural units of the nervous system ▪ Composed of a body, axon, and dendrites ▪ Long-lived, amitotic, and have a high metabolic rate ▪ Their plasma membrane functions in: ▪ Electrical signaling ▪ Cell-to-cell signaling during development Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Neurons (Nerve Cells) Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11.4b  Nerve Cell Body (Perikaryon or Soma) ▪ Contains the nucleus and a nucleolus ▪ Is the major biosynthetic center ▪ Is the focal point for the outgrowth of neuronal processes ▪ Has well-developed Nissl bodies (rough ER) ▪ Contains an axon hillock – cone-shaped area from which axons arise Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Processes ▪ Arm-like extensions from the soma ▪ Called tracts in the CNS and nerves in the PNS ▪ There are two types: axons and dendrites Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Dendrites of Motor Neurons ▪ Short, tapering, and diffusely branched processes ▪ They are the receptive, or input, regions of the neuron Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Axons: Structure ▪ Slender processes of uniform diameter arising from the hillock ▪ Long axons are called nerve fibers ▪ Usually there is only one unbranched axon per neuron Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Axons: Function ▪ Generate and transmit action potentials ▪ Secrete neurotransmitters from the axonal terminals Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Myelin Sheath ▪ Whitish, fatty (protein-lipoid), segmented sheath around most long axons ▪ It functions to: ▪ Protect the axon ▪ Electrically insulate fibers from one another ▪ Increase the speed of nerve impulse transmission Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Myelin Sheath and Neurilemma: Formation ▪ Formed by Schwann cells in the PNS ▪ A Schwann cell: ▪ Envelopes an axon in a trough ▪ Encloses the axon with its plasma membrane ▪ Has concentric layers of membrane that make up the myelin sheath ▪ Neurilemma – remaining nucleus and cytoplasm of a Schwann cell ▪ Nodes of Ranvier: Gaps in the myelin sheath between adjacent Schwann cells Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Myelin Sheath and Neurilemma: Formation Figure 11.5a-c Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Axons of the CNS ▪ Both myelinated and unmyelinated fibers are present ▪ Myelin sheaths are formed by oligodendrocytes ▪ Nodes of Ranvier are widely spaced Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Regions of the Brain and Spinal Cord ▪ White matter – dense collections of myelinated fibers ▪ Gray matter – mostly soma and unmyelinated fibers Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Neuron Classification ▪ Structural: ▪ Multipolar — three or more processes ▪ Bipolar — two processes (axon and dendrite) ▪ Unipolar — single, short process Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Neuron Classification ▪ Functional: ▪ Sensory (afferent) — transmit impulses toward the CNS ▪ Motor (efferent) — carry impulses away from the CNS ▪ Interneurons (association neurons) — shuttle signals through CNS pathways Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Comparison of Structural Classes of Neurons Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Table 11.1.1  Comparison of Structural Classes of Neurons Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Table 11.1.2  Comparison of Structural Classes of Neurons Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Table 11.1.3