Neuron

• Neurons


  The basic elements of behavior, the basic parts of the nervous system
• Dendrites


  • Branching fibers that get narrower near their ends
  • Surface is lined with specialized synaptic receptors, receive information from other neurons
  • Greater surface area means more information can be received
  • Many contain dendritic spines that increase surface area for synapses
• Cell Body or Soma


  • Contains the nucleus, ribosomes, and mitochondria
  • Covered with synapses on its surface in many neurons
• Nucleus


  • Oval shaped membrane-bound structure found in the soma
  • Contains the nucleolus and chromosomes, necessary for the coded production of proteins within the cell
• Axon


  • Thin fiber of constant diameter
  • Conveys an impulse toward other neurons, an organ, or a muscle
• Myelin Sheath


  • Insulating layer that forms around the nerves
  • Made up of protein and fatty substances
  • Allows electrical impulses to transmit quickly and efficiently along the nerve cells
  • If damaged, impulses slow down
• Nodes of Ranvier


  • Periodic gaps in the insulating sheath (myelin) on the axon
  • Facilitate the rapid conduction of nerve impulses
  • First discovered in 1878 by French histologist and pathologist Louis-Antoine Ranvier
• Schwann Cells


  • Also called neurilemma cells
  • Cells in the peripheral nervous system that produce the myelin sheath around neuronal axons
  • A myelinating Schwann cell wraps around a single axon
• Axon Terminal


  • The very end of a branch of a nerve's axon
  • Conducts electrical signals to a nerve synapse (the gap between nerve cells)
  • Signal then moves across the synapse to another axon by means of a neurotransmitter (an electrochemical substance)
• Types of neurons according to number of processes

  • Unipolar
  • Pseudo-unipolar
  • Bipolar
  • Multipolar
• Sensory (or Afferent) Neurons


  Nerve cells within the nervous system responsible for converting external stimuli from the organism's environment into internal electrical impulses
• Interneuron (or Association) Neurons


  Found exclusively in the central nervous system, passes signals between neurons
• Motor (or Efferent) Neurons


  Cell body located in the motor cortex, brainstem or the spinal cord, axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands
• Unipolar


  Typically sensory neurons with receptors located within the skin, joints, muscles, and internal organs. In addition to pain and touch, they also carry information about temperature, taste, proprioception (body position) and visceral organ activity.
• Pseudo-unipolar


  A kind of sensory neuron in the peripheral nervous system. This neuron contains an axon that has split into two branches; one branch runs to the periphery and the other to the spinal cord.
• Bipolar


  Has two extensions (one axon and one dendrite). This are specialized sensory neurons for the transmission of special senses. As such, they are part of the sensory pathways for smell, sight, taste, hearing and vestibular functions.
• Multipolar


  A type of neuron that possesses a single axon and many dendrites, allowing for the integration of a great deal of information from other neurons. These processes are projections from the nerve cell body.
• SYNAPSE •Junctions between the neurons •Functional connection
• TYPES OF SYNAPSE

  1. Axosomatic synapse: One between the axon of one neuron and the body of another.

  2. Axodendritic synapse: One between the axon of one neuron and the dendrites of another.

  3. Axoaxonic synapse: One between the axon of one neuron and the axon of another neuron.3. Axoaxonic synapse: One between the axon of one neuron and the axon of another neuron.
• NEUROGLIA (or GLIAL CELLS)

  •Cells in the central nervous system and the peripheral nervous system

  •Play the role of supportive cells to neurons, which are responsible for all nervous system

  functions

  •Form a support network for the brain

  •More glial cells than nerve cells in the brain cells
• Types of Neuroglia found in CNS

  • Astrocytes/Astroglia
  • Oligodendrocytes/Oligodendroglia
  • Ependymal cells
  • Microglia/Mesoglia
• Astrocytes / Astroglia


  • Provide protection and support to neurons
  • Exchange nutrients and other important chemicals
  • Have many cell extensions called processes used for chemical exchanges that branch out like the points of stars
  • Processes connect with neurons, other tissue like blood vessels, and the blood brain barrier
• Blood brain barrier


  A protective membrane surrounding the spine and brain that allows small molecules like respiratory gases to pass through, while blocking anything larger
• Oligodendrocytes/Oligodendroglia


  • Wrap around the axons of CNS neurons to provide electrical insulation called myelin sheaths
  • Allows the signal to move quickly enough for proper functioning
  • In neurodegenerative diseases like multiple sclerosis, the myelin sheaths are damaged, slowing the signals of affected neurons
• Ependymal cells


  • Line the empty cavities called ventricles in the brain
  • Have access to nearby blood vessels
  • Filter materials out of the vessels to manufacture cerebrospinal fluid (CSF)
  • Use cilia to circulate CSF through the ventricles and into the rest of the CNS
• Microglia/Mesoglia 


  The final type of glial cell are small ones. Like macrophages in the blood,

  The final type of glial cell are small ones. Like macrophages in the blood, they surround and digest damaged or invading cells. They are considered the immune cells of the CNS.mmune cells of the CNS.

  • Considered the immune cells of the CNS
• Satellite cells


  • Function to provide nutrients and protection to neurons in the PNS
  • wraps itself around the neuron's cell body
  • The cell body is a rounded section that contains the nucleus and other key organelles common to most somatic cells
• Schwann cells


  • Wrap themselves around the axons of neurons in the PNS
  • The axon is the long, thin part of the neuron, along which the electrical signal passes
  • The Schwann cell forms a protective layer called the myelin sheath
  • The myelin sheath operates like the insulated coating on electrical wiring
  • Without the myelin sheath, the electrical signal can be disrupted, slowed or stopped altogether
• nervous system

  An electrochemical communication network consisting of all nerve cells of the peripheral and central nervous system.
• nervous system

  It communicates between the brain and body.
• central nervous system

  It connects sensory and motor fibers within the nervous system.
• spinal cord

  It is a long, slender, and flexible structure that extends from the base of the brain down to the lower back.
• spinal cord

  It transmits signals from sensory receptors to the brain and from the brain to muscles and glands.
• spinal cord

  It regulates reflexes and controls posture and movement.
• peripheral nervous system

  It connects the brain and spinal cord to everything else in the body.
• somatic system

  It includes the sensory system and motor nerves that activate skeletal muscles responsible for movements.
• autonomic system

  It is also called the vegetative nervous system.
• autonomic system

  It is concerned with activities of the body that keep us alive, such as glands and internal organs.
• sympathetic system

  It creates arousal and channels resources to muscles for the fight or flight response.
• parasympathetic system

  It calms the body and channels resources to internal organs.