biology

• Organs and divisions of the nervous system

  • Central nervous system (CNS)—brain and spinal cord
  • Peripheral nervous system (PNS)—all nerves
  • Autonomic nervous system (ANS)

  
• Neurons


  • The basic unit of structure and function in the nervous system
  • Cells that conduct impulses
  • Made up of dendrites, cell body and an axon

  
• Neuron response to someone tapping your shoulder

  1. Receptors in the skin sense touch or other stimuli

  2. Sensory neurons transmit the touch message

  3. Information is sorted and interpreted in the brain

  4. A response is determined by interneurons

  5. Motor neurons transmit a response message to the shoulder muscles

  6. The shoulder muscles are activated, causing the head to turn
• Resting potential


  The neuron moves Na+ ions to the outside of the cell and K+ ions to the inside of the cell, maintaining a negative charge

  
• Action potential


  A large change in membrane potential that is an "all or none" response, caused by the opening and closing of voltage gated ion channels

  
• Action potentials are generally very rapid (as brief as 1–4 milliseconds) and may repeat at frequencies of several hundred per second
• The ability to generate action potentials is known as excitability, possessed by neurons, muscle cells and some other types of cells
• Local anesthetics inhibit action potential generation

  They block voltage-gated Na+ channels, preventing graded signals from reaching the brain and causing pain

  
• Synapse


  The gap between two neurons that controls the transmission of signals, using neurotransmitters

  
• Some neurotransmitters


  • Acetylcholine
  • Dopamine
  • Epinephrine
  • Serotonin
  • Endorphins
  • Nitric Oxide
• Electrical synapse


  • The electrical activity of the presynaptic neuron affects the electrical activity of the postsynaptic neuron

  
• Chemical synapse


  • Neurotransmitters cross the synapse and stimulate the next neuron
• Glia (neuroglia) are support cells that bring the cells of nervous tissue together structurally and functionally
• Main types of glia

  • Astrocytes
  • Microglia
  • Oligodendrocytes
• Multiple sclerosis is characterized by myelin loss in central nerve fibers and resulting conduction impairments
• Most nervous system tumors are gliomas, glial tumors
• Four basic operations of information processing

  • Determine type of stimulus
  • Signal the intensity of a stimulus
  • Integrate responses from many sources
  • Initiate and direct operations
• Intensity of stimulus


  Intensity = frequency of action potentials
• Convergence


  Many signals arrive through many neurons, but several may pass their signal to a single connecting neuron
• Neural pathways


  Consist of sensory neurons, association neurons, and motor neurons

  
• Reflex arc

  The simplest neural pathway, involving one or more sensory neurons, association neurons in the spine, and motor neurons
• Central Nervous System


  • Consists of brain and spine
  • Receives sensory signals and determines appropriate response
  • Stores memory
  • Carries out thought

  
• Spinal cord


  • Protected by the vertebrae
  • Gray matter contains cell bodies, white matter contains myelinated fibers
  • PNS nerves extend outside of the vertebrae
• Brain regions


  • Hindbrain
  • Midbrain
  • Forebrain
• Peripheral Nervous System


  • Nerves, neurons, and sensory organs outside the central nervous system
  • Sends signals to the CNS
  • Receives and transmits motor signals from the CNS
  • Stimulates effectors

  
• Nerves in the PNS

  • Cranial nerves
  • Spinal nerves

  
• Somatic Nervous System


  Motor neurons that control voluntary movements by activating skeletal muscles
• Autonomic Nervous System


  Motor neurons that control involuntary responses involving the organs, glands, and smooth muscles
• Divisions of the Autonomic Nervous System

  • Sympathetic Division
  • Parasympathetic Division

  
• Sympathetic Division


  • Produces the "fight or flight" response
• Parasympathetic Division


  • Produces the "rest and ruminate" response
• Many visceral effectors are doubly innervated, influenced in opposite ways by the sympathetic and parasympathetic divisions
• Stress-induced disease can disrupt normal functioning throughout the body
• Neuroblastoma is a highly malignant tumor of the sympathetic nervous system, primarily affecting young children
• Mammalian brain


  • Highly complex, containing many specialized regions that carry out specific functions
  • Generally divided into hindbrain, midbrain, and forebrain

  
• Hindbrain


  • Medulla controls autonomic functions
  • Pons controls sleep stages
  • Cerebellum coordinates movement and stores some motor memory
• Midbrain


  • Reticular formation filters sensory input, allowing concentration
• Forebrain


  • Thalamus relays sensory information
  • Limbic system controls basic emotions, drives, and behaviors
  • Cortex controls higher thought

  
• Limbic system


  • Hypothalamus is the master controller of the endocrine system
  • Amygdala processes sensations of pleasure or fear, recognizes fear in others
  • Hippocampus forms memories

  
• While there is some specialization to each brain hemisphere, the idea of "right brain" and "left brain" functions has been oversimplified