HUMAN ANATOMY fourth edition MARIEB | MALLATT | WILHELM Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham 12 Fundamentals of the Nervous System and Nervous Tissue PART 1
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Nervous System Master control and communication system
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Nervous System: Functions Three overlapping functions Sensory receptors monitor changes inside and outside the body Change – a stimulus Gathered information – sensory input CNS Processes and interprets sensory input Makes decisions – integration Dictates a response by activating effector organs Response – motor output
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Basic Divisions of the Nervous System: CNS Central nervous system (CNS) Brain and spinal cord Integrating and command center
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Basic Divisions of the Nervous System: PNS Peripheral nervous system (PNS) Outside the CNS Nerves extending from brain and spinal cord Cranial nerves Spinal nerves Link all regions of the body to the CNS
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Sensory Input and Motor Output Sensory signals picked up by sensory receptors Carried by afferent nerve fibers of PNS to the CNS Motor signals are carried away from the CNS Carried by efferent nerve fibers of PNS to effectors Innervate muscles and glands
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Sensory Input and Motor Output Divided according to region they serve Somatic body region Visceral body region Results in four main subdivisions Somatic sensory Visceral sensory Somatic motor Visceral motor
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Somatic Sensory Somatic sensory General somatic senses – receptors are widely spread Touch, pain, vibration, pressure, and temperature Proprioceptive senses – detect stretch in tendons and muscle Body sense – position and movement of body in space Special somatic senses Hearing, balance, vision, and smell
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Visceral Sensory Visceral sensory General visceral senses – stretch, pain, temperature, nausea, and hunger Widely felt in digestive and urinary tracts, reproductive organs Special visceral senses – taste
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Somatic Motor Somatic motor General somatic motor – signals contraction of skeletal muscles Under voluntary control Often called “voluntary nervous system”
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Visceral Motor Visceral motor Regulates the contraction of smooth and cardiac muscle and gland secretion Makes up autonomic nervous system Controls function of visceral organs Often called “involuntary nervous system”
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Peripheral Nervous System Summary Figure 12.3
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Types of Sensory and Motor Information Figure 12.3
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Types of Sensory and Motor Information Figure 12.3
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue Cells are densely packed and intertwined Two main cell types Neurons – transmit electrical signals Support cells (neuroglial cells) – nonexcitable Surround and wrap neurons
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Neuron The human body contains billions of neurons Basic structural unit of the nervous system Specialized cells conduct electrical impulses along the plasma membrane Graded potentials Action potentials
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Neuron: Special Characteristics Longevity – can live and function for a lifetime Do not divide – fetal neurons lose their ability to undergo mitosis; neural stem cells are an exception High metabolic rate – require abundant oxygen and glucose
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Structure
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Cell Body or Soma (also called Perikaryon) Size varies from 5–140µm Contains nucleus, organelles plus other structures Chromatophilic bodies (Nissl bodies) Clusters of rough ER and free ribosomes Stain darkly and renew membranes of the cell Neurofibrils – bundles of intermediate filaments Form a network between chromatophilic bodies
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Nissl Body Staining
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Cell Body Most neuronal cell bodies Located within the CNS (clustered in nuclei) Protected by bones of the skull and vertebral column Ganglia – clusters of cell bodies in PNS
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Cell Body Structure Figure 12.4
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Processes: Dendrites Dendrites Extensively branching from the cell body Transmit electrical signals (graded potentials) toward the cell body Chromatophilic bodies – only extend into the basal part of dendrites Function as receptive sites
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Dendritic Spines
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Dendritic Spines
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Processes: Axons Axons (nerve fibers) Neuron has only one, but it can branch Impulse generator and conductor Transmits action potentials away from the cell body Chromatophilic bodies absent No protein synthesis in axon
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Processes: Axons Axons Neurofilaments, actin microfilaments, and microtubules Provide strength along length of axon Aid in the transport of substances to and from the cell body Axonal transport
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Processes Neuron Structure Axons Branches along length are infrequent Axon collaterals Multiple branches at end of axon Terminal branches (telodendria) End in knobs called axon terminals (also called end bulbs or boutons)