BIO LQ1 QT4

• Neurons


  Electrically excitable cells that contain ions or charged atoms, may exist in resting or stimulated state, and produce electrical impulses transmitted along the axon
• Neuron structure


  • Cell body
  • Axon
  • Dendrites
  • Myelin sheaths
  • Axon terminals
• Cell body


  Keeps the neuron functional, maintains the cell by holding the nucleus which produces RNA that directs the synthesis of proteins needed by the other parts of the neuron for functioning
• Axon


  Long extension of the cell that transmits the nerve impulses to another neuron or effector, may be myelinated or not
• Dendrites


  Tree-like extensions of the cell body which specialize in receiving chemical signals from other neurons, converted into electrical impulses transmitted toward the cell body
• Myelin sheaths


  Prevent ion flow across the neuron membrane, forcing the current to "jump" from node to node along the axon
• Axon terminals


  Located at the end of the neuron, send the signal on to other neurons, have a gap known as a synapse where neurotransmitters are released
• Types of neurons


  • Sensory neurons
  • Motor neurons
  • Interneurons
• Sensory neurons


  Transmit impulses from sensory receptors to other neurons, triggered by chemical and physical inputs
• Motor neurons


  Play an important role in movement, both voluntary and involuntary, transmit impulses from the Central Nervous System to muscles or glands
• Interneurons


  Neural intermediates found in the brain and spinal cord, carry impulses from sensory to motor neurons
• Types of glial cells in the CNS

  • Astrocytes
  • Oligodendrocytes
  • Microglia
  • Ependymal cells
  • Radial glia
• Astrocytes


  Star-like, most common type of glial cells, responsible for forming the blood-brain barrier, regulating neurotransmitters, cleaning up dead neurons, regulating blood flow, synchronizing axon activity, and regulating brain metabolism
• Oligodendrocytes


  Help information move faster along axons by wrapping them in a protective myelin sheath
• Microglia


  Tiny glial cells that act as the brain's immune system, detecting injuries and diseases, clearing away dead cells, and getting rid of pathogens
• Ependymal cells


  Make up the lining of the central canal of the spinal cord and the passageways of the brain, create cerebrospinal fluid
• Radial glia


  Believed to be a type of stem cell that produces astrocytes and oligodendrocytes in the developing brain
• Types of glial cells in the PNS

  • Schwann cells
  • Satellite cells
• Schwann cells


  Function like oligodendrocytes, help insulate axons and provide a protected path for new axons to form
• Satellite cells


  Regulate the environment around the neuron, deliver nutrition, absorb heavy metal toxins, detect and respond to injuries and inflammation
• The nervous system serves as the control and communicating system of the body
• Functions of the nervous system

  1. Detecting stimuli

  2. Interpreting them

  3. Initiating appropriate responses
• Central Nervous System (CNS)

  Composed of the brain and the spinal cord
• Peripheral Nervous System (PNS)


  Composed of nerves and ganglia outside the CNS
• Brain


  • Responsible for integration
• Spinal cord


  • Transmits messages to and from the brain, controls spinal reflexes
• Divisions of the PNS

  • Sensory Division
  • Motor Division
• Sensory (Afferent) Division


  Transmits information from peripheral organs to the CNS
• Motor (Efferent) Division


  Carries impulses from the CNS to the effectors for response or action
• Subdivisions of the Motor Division

  • Somatic Nervous System (SNS)
  • Autonomic Nervous System (ANS)
• Somatic Nervous System (SNS)


  Carries impulses to the voluntary (skeletal) muscles
• Autonomic Nervous System (ANS)


  Regulates visceral functions over which there is generally no conscious control
• Divisions of the ANS

  • Parasympathetic Division
  • Sympathetic Division
• Parasympathetic Division


  Causes "rest and digest" reaction, releases acetylcholine
• Sympathetic Division


  Causes "fight-or-flight" response, releases noradrenaline
• Enteric Division


  Active within the pancreas, gallbladder and digestive tract, regulates peristalsis and secretions
• Cooperation between the somatic and autonomic nervous systems

  Maintains homeostasis in the body
• Neurons


  Electrically excitable cells that contain ions or charged atoms, may exist in resting or stimulated state, and produce electrical impulses transmitted along the axon
• Neuron structure


  • Cell body
  • Axon
  • Dendrites
  • Myelin sheaths
  • Axon terminals
• Cell body


  Keeps the neuron functional, maintains the cell by holding the nucleus which produces RNA that directs the synthesis of proteins needed by the other parts of the neuron for functioning