Nerv 1

• Organs and divisions of the nervous system

  • Central nervous system (CNS)
  • Brain
  • Spinal cord
  • Peripheral nervous system (PNS)
  • All nerves
  • Autonomic nervous system (ANS)
• Nervous system


  • Organized into the central and peripheral nervous system
  • Central nervous system (CNS): brain and spinal cord
  • Peripheral nervous system (PNS): nerve fibers
  • Afferent and efferent divisions
  • Enteric nervous system (ENS): nerve network of the digestive tract
• Divisions of the peripheral nervous system

  • Somatic nervous system: fibers of the motor neurons that supply the skeletal muscles
  • Autonomic nervous system (ANS): fibers that innervate smooth muscle, cardiac muscle, and glands
  • Further subdivided into the sympathetic and parasympathetic nervous system
• Neuron

  Each neuron consists of three main parts: cell body, dendrites, and axon
• Types of neurons

  • Sensory (afferent) neurons: Conduct impulses to the spinal cord and brain
  • Motor (efferent) neurons: Conduct impulses away from brain and spinal cord to muscles and glands
  • Interneurons: Conduct impulses from sensory neurons to motor neurons or among a network of interneurons
• Glial cells


  • Support cells, bringing the cells of nervous tissue together structurally and functionally
  • Three main types: Astrocytes, Microglia, Oligodendrocytes
• Nerve

  Bundle of peripheral axons
• Tract


  Bundle of central axons
• White matter

  Tissue composed primarily of myelinated axons (nerves or tracts)
• Gray matter


  Tissue composed primarily of cell bodies and unmyelinated fibers
• Nerve coverings


  • Endoneurium: Surrounds individual fibers within a nerve
  • Perineurium: Surrounds a group (fascicle) of nerve fibers
  • Epineurium: Surrounds the entire nerve
• Reflex arc


  Nerve impulses are conducted from receptors to effectors over neuron pathways or reflex arcs
• Nerve impulse


  Self-propagating wave of electrical disturbance that travels along the surface of a neuron membrane (also called action potential)
• Mechanism of a nerve impulse

  1. At rest, the neuron's membrane is slightly positive on the outside - polarized

  2. A stimulus triggers the opening of Na+ channels in the plasma membrane of the neuron

  3. Inward movement of Na+ depolarizes the membrane by making the inside more positive than the outside at the stimulated point

  4. The stimulated section of membrane immediately repolarizes, but by that time, the depolarization has already triggered the next section of membrane to depolarize, thus propagating a wave of electrical disturbances (depolarizations) all the way down the membrane
• Synapse


  The place where impulses are transmitted from one neuron to another (the postsynaptic neuron)
• Neurotransmitters


  • Acetylcholine (ACh)
  • Catecholamines: Norepinephrine, dopamine, and serotonin
  • Endorphins
  • Enkephalins
  • Nitric oxide (NO)
  • Other compounds