Ch.13-Anatomy

• Nervous system


  Includes all of the neural tissue in the body
• Anatomical subdivisions of the nervous system

  • Central nervous system (CNS)
  • Peripheral nervous system (PNS)
• Central nervous system (CNS)


  • Consists of the brain and spinal cord
  • Responsible for integrating, processing, and coordinating sensory input and motor input
  • Seat of higher functions like intelligence, memory, learning, emotion
• Central canal


  Narrow cavity in the spinal cord
• Ventricles


  Expanded chambers found in specific regions of the brain
• Cerebrospinal fluid (CSF)


  Fills the central canal, ventricles, and surrounds the CNS
• Peripheral nervous system (PNS)


  • Includes all neural tissue outside the CNS
  • Provides sensory information to the CNS and carries motor commands from the CNS to peripheral tissues and systems
• Divisions of the PNS

  • Afferent division
  • Efferent division
• Afferent division


  Brings sensory information to the CNS
• Efferent division


  Carries motor commands to muscles and glands
• Components of the afferent and efferent divisions

  • Somatic
  • Visceral
• Afferent division


  • Carries information from somatic sensory receptors, visceral sensory receptors, and special sense organs
• Efferent division


  • Includes the somatic nervous system (SNS) which controls skeletal muscle contractions and the autonomic nervous system (ANS) which regulates smooth muscle, cardiac muscle, and glandular activity
• Somatic nervous system activities


  May be voluntary or involuntary
• Autonomic nervous system activities


  Usually outside our awareness and control
• Neurons


  • Responsible for the transfer and processing of information in the nervous system
  • Have a cell body, dendrites, and an axon
• Dendritic spines


  Fine processes where a neuron receives information from other neurons
• Neuroglia


  • Isolate neurons, provide a supporting framework for neural tissue, help maintain the intercellular environment, and act as phagocytes
  • Have the ability to divide
• Types of glial cells in the CNS

  • Astrocytes
  • Oligodendrocytes
  • Microglia
  • Ependymal cells
• Astrocytes


  • Largest and most numerous glial cells
  • Control the interstitial environment
  • Maintain the blood-brain barrier
  • Create a three-dimensional framework for the CNS
  • Perform repairs in damaged neural tissue
  • Guide neuron development
• Oligodendrocytes


  • Provide a membranous coating called myelin that improves the speed of action potential conduction along an axon
  • Myelinated axons have small gaps called myelin sheath gaps between adjacent oligodendrocyte processes
• White matter


  Regions dominated by myelinated axons
• Gray matter


  Regions dominated by neuron cell bodies, dendrites, and unmyelinated cells
• Microglia


  • Smallest of the glial cells
  • Act as a roving security force
  • Phagocytic cells of the CNS
  • Increase in number during infection or injury
• Ependymal cells


  • Cuboidal to columnar in form
  • Make direct contact with glial cells in the surrounding neural tissue
  • Ciliated ependymal cells may assist with the circulation of cerebrospinal fluid
  • Specialized ependymal cells participate in the secretion of cerebrospinal fluid
• Neuroglia of the PNS


  • Neuron cell bodies are usually clustered together in masses called ganglia
  • Peripheral nerves have axons bundled together and wrapped in connective tissues
• Glial cell types in the PNS

  • Satellite cells
  • Schwann cells
• Satellite cells


  • Regulate exchange of nutrients and waste products between the neuron cell body and extracellular fluid
  • Help isolate the neuron from stimuli other than those provided at synapses
  • Surround neuron cell bodies in peripheral ganglia
• Schwann cells


  • Cover every peripheral axon
  • Provide the axolemma (plasmalemma of the axon) and neurolemma (superficial cytoplasmic covering)
• Perikaryon


  • Contains the cytoskeleton with neurofilaments and microtubules
  • Contains organelles that provide energy and perform biosynthetic activities
• Specialized neurons lost to injury or disease cannot be replaced
• Resting membrane potential


  Transmembrane potential property resulting from the unequal distribution of ions across the neuron membrane
• Axon hillock


  Specialized region where the initial segment of the axon connects to the soma
• Axoplasm


  Cytoplasm of the axon, containing neurofibrils, microtubules, vesicles, lysosomes, mitochondria, and enzymes
• Collaterals


  Side branches of the axon
• Terminal arborizations


  The main trunk and collateral ends of the axon in a series of fine terminal extensions
• Synaptic terminal


  Where the neuron makes contact with another neuron or effector
• Axoplasmic transport


  Movement of organelles, nutrients, synthesized molecules, and waste products between the cell body and synaptic terminals
• Synapse


  Specialized site where a neuron communicates with another cell
• Terminal button (synaptic knob)


  The site where one neuron synapses on another