Brain + nerv

• Central Nervous System (CNS)


  The division of the nervous system located within the skull and spine
• Peripheral nervous system (PNS)


  The division of the nervous system located outside the skull and spine
• Divisions of the central nervous system

  • Brain
  • Spinal cord
• Divisions of the peripheral nervous system

  • Somatic nervous system (SNS)
  • Autonomic nervous system (ANS)
• Somatic nervous system (SNS)


  Part of PNS that interacts with the external environment
• Afferent nerves


  Nerves that carry sensory signals from skin, skeletal muscles, joints, eyes, ears and so on
• Efferent nerves


  Nerves that carry motor signals from CNS to skeletal muscles
• Autonomic nervous system (ANS)


  Part of peripheral nervous system that regulates the body's internal environment
• Sympathetic nerves (efferent nerves)

  Autonomic motor nerves that project from the CNS in lumbar and thoracic regions of spinal cord
• Parasympathetic nerves (efferent nerves)


  Autonomic motor nerves that project from the brain and sacral region of the spinal cord
• Cranial nerves


  Project from the brain, include sensory nerves (e.g. Olfactory nerves), optic nerves (but most contain sensory and motor fibers)
• Blood-brain barrier


  A mechanism impeding the passage of many toxic substances from the blood into the brain
• The blood-brain barrier is a consequence of the special structure of cerebral blood vessels
• Difference between blood vessels in the brain and the rest of the body

  • In the rest of the body, the cells that compose the walls of blood vessels are loosely packed; as a result, most molecules pass readily through them into surrounding tissue. In the brain, however, the cells of the blood vessel walls are tightly packed, thus forming a barrier to the passage of many molecules—particularly proteins and other large molecules.
• The degree to which therapeutic or recreational drugs can influence brain activity depends on the ease with which they penetrate the blood–brain barrier
• The blood–brain barrier does not impede the passage of all large molecules. Some large molecules that are critical for normal brain function (e.g., glucose) are actively transported through cerebral blood vessel walls.
• Many CNS disorders are associated with impairment of the blood-brain barrier
• Sympathetic and parasympathetic neurons

  • Project from the CNS and go only part of the way to the target organs before they synapse on other neurons (second-stage neurons) that carry the signals the rest of the way. However, the sympathetic and parasympathetic systems differ in that the sympathetic neurons that project from the CNS synapse on second-stage neurons at a substantial distance from their target organs, whereas the parasympathetic neurons that project from the CNS synapse near their target organs on very short second-stage neurons.
• Sympathetic and parasympathetic systems

  • Sympathetic nerves stimulate, organize, and mobilize energy resources in threating situation, whereas parasympathetic nerves act to conserve energy.
  • Each autonomic target organ receives opposing sympathetic and parasympathetic input, and its activity is thus controlled by relative levels of sympathetic and parasympathetic activity
  • Sympathetic changes are indicative of psychological arousal, whereas parasympathetic changes are indicative of psychological relaxation
• Meninges


  Three protective membranes covering the brain and spinal cord: Dura mater, arachnoid membrane, pia mater
• Cerebrospinal fluid (CSF)


  Fluid that fills the subarachnoid space, the central canal of the spinal cord, and the cerebral ventricles of the brain
• The central canal is a small central channel that runs the length of the spinal cord
• Cerebral ventricles


  • Two lateral ventricles
  • Third ventricle
  • Fourth ventricle
• The subarachnoid space, central canal, and cerebral ventricles are interconnected by a series of openings and thus form a single reservoir
• Cerebrospinal fluid is produced by the choroid plexuses (networks of capillaries, or small blood vessels that protrude into the ventricles from the pia mater)
• Excess cerebrospinal fluid (CSF) is absorbed from the subarachnoid space into large blood-filled spaces called dural sinuses
• Hydrocephalus is a condition where a tumor blocks the flow of cerebrospinal fluid (CSF) in the brain, causing the ventricles and the brain to swell
• Neurons


  Cells that are specialized for reception, conduction, and transmission of electrochemical signals
• Glial cells


  Cells that regulate neurotransmission and help form the blood-brain barrier, providing physical and chemical support to neurons and maintaining their environment
• External features of a neuron

  • Cell body/soma
  • Cell membrane
  • Dendrites
  • Axon hillock
  • Axon
  • Myelin
  • Nodes of Ranvier
  • Buttons
  • Synapses
• Classes of neurons


  • Multipolar
  • Unipolar
  • Bipolar
  • Interneurons
• Oligodendrocytes


  Glial cells with extensions that wrap around the axons of some neurons of the central nervous system (CNS)
• Schwann cells


  Glial cells that consist of one myelin segment and can guide axonal regeneration (regrowth) after damage in the peripheral nervous system (PNS)
• Microglia


  Glial cells that respond to injury or disease by multiplying, engulfing cellular debris or even entire cells, and triggering inflammatory responses
• Astrocytes


  Glial cells that allow the passage of some chemicals from the blood into CNS neurons and block other chemicals, and have the ability to contract or relax blood vessels based on the blood flow demands of particular brain regions
• Golgi stain


  A silver staining technique used to visualize nervous tissue under light microscopy
• Nissl stains


  Use variety of dyes (cresyl violet) to show charged structures in the sum of neurons and glia
• Anterograde tracing methods


  Used when an investigator wants to trace the paths of axons projecting away from cell bodies located in a particular area
• Effective axonal regeneration in the mammalian nervous system is restricted to the PNS because only Schwann cells can guide axonal regeneration (regrowth) after damage
• Microglia play a role in the regulation of cell death, synapse formation, and synapse elimination