Physiopsych m1-2

• Types of Cells of the Nervous System

  • Neurons
  • Glia (or Neuroglia)
• Neurons


  • Receives and transmits information to other cells
  • Adults approx. have 86 billion neurons
  • Exact number of neurons varies from person to person
  • Neurons are the nerve cells
  • The structural and functional units of the NS
  • Conducts impulses that enable the body to interact with its internal and external environments
• Glia


  • Derived from the Greek word meaning "glue"
  • Holds the neurons together
• Types of neurons


  • Motor Neurons
  • Sensory Neurons
  • Interneurons
• Motor Neurons


  Causes muscle contractions and controls secretions from glands and organs controlling body functions
• Sensory Neurons


  • Does not have true dendrites
  • Are attached to sensory receptors and transmits impulses to the CNS, which then stimulates the interneurons, and then motor neurons
• Interneurons


  • Located within the CNS
  • Intercepts the impulses from the sensory neurons and transmits the signals to the motor neurons
• Nerve fibers


  • There are no Schwann cells on nerve fibers in the CNS, therefore damage to those nerve fibers are irreversible
  • A bundle of nerve fibers is called 'a nerve'
  • AFFERENT nerves - conducts impulses to the CNS
  • EFFERENT nerves - conducts impulses to the muscles, organs, and glands
• Types of Glia


  • Astrocytes
  • Microglia
  • Oligodendrocytes
  • Radial Glia
• Astrocytes


  • Are star-shaped
  • Wraps around the synapses of functionally related axons
  • Shields axons from chemicals circulating
  • Helps synchronize closely related neurons which enables their axons to send messages in waves
  • Important for generating rhythms (eg. breathing)
  • Dilates blood vessels to bring more nutrients into brain areas that have heightened activity
• Microglia


  • Acts as part of the immune system, removing viruses and fungi from the brain
  • Removes dead or damaged neurons
  • Contributes to learning by removing weak synapses
• Oligodendrocytes


  • Builds the myelin sheath that surrounds and insulates certain vertebrate axons
  • Supplies an axon with nutrients necessary for proper functioning
• Radial Glia


  • Guides the migration of neurons and their axons and dendrites during the embryonic dev
  • Most radial glia differentiate into neurons after embryological dev
  • Smaller numbers differentiate into astrocytes and oligodendrocytes
• Blood-Brain Barrier


  • When a virus invades a cell, mechanisms within the cell extrude virus particles through the membrane so that the immune system can find them
  • When the virus is discovered, the immune system kills it and the cell that contains it
  • To minimize the risk of irreparable brain damage, The body lines the brain's blood vessels with tightly packed cells that keep out most viruses, bacteria, and harmful chemicals
  • Certain viruses do cross the blood-brain barrier, such as Rabies and Syphilis
  • The microglia is more effective against several other viruses that enter the brain, mounting an inflammatory response that fights the virus
• How the Blood-Brain Barrier works

  1. It depends on the endothelial cells that form the walls of the capillaries

  2. Outside the brain, such cells are separated by small gaps, but in the brain, they are joined so tightly that they block viruses, bacteria, and other harmful chemicals from passage

  3. The barrier keeps out useful chemicals as well as harmful ones

  4. No special mechanism is required for small uncharged molecules such as oxygen and carbon dioxide that cross through cell walls freely

  5. Molecules that dissolve in the fats of the membrane cross easily

  6. For certain other chemicals, the brain uses active transport, a protein-mediated process that expends energy to pump chemicals from the blood into the brain
• The BBB is essential to health. In people with Alzheimer's disease or similar conditions, the endothelial cells lining the brain's blood vessels shrink, and harmful chemicals enter the brain
• The barrier poses a difficulty for treating brain cancers, because nearly all the drugs used for chemotherapy fail to cross the BBB
• Nerve Impulses


  • Action potential transmits information without loss of intensity over distance. The cost is a delay between the stimulus and its arrival in the brain
  • Inside of a resting neuron has a negative charge with respect to the outside, mainly because of negatively charged proteins inside the neuron
  • The sodium-potassium pump moves sodium ions out of the neuron, and potassium ions in
  • When the membrane is at rest, both the electrical gradient and the concentration gradient would act to move sodium ions into the cell, except that its gates are closed
  • The all-or-none law: for any stimulus greater than the threshold, the amplitude and velocity of the action potential are independent of the size of the stimulus that initiated it
  • When the membrane is sufficiently depolarized to reach the cell's threshold, sodium and potassium channels open
  • As an action potential occurs at one point on the axon, enough sodium enters to depolarize the next point to its threshold, producing an action potential at that point. In this manner the action potential flows along the axon, remaining at equal strength throughout. Behind each area of sodium entry, potassium ions exit, restoring the resting potential
• Cajal and Sherrington are regarded as the great pioneers of modern neuroscience, and their nearly simultaneous discoveries supported each other: If communication between neurons is special in some way, then there can be no doubt that neurons are anatomically separate from one another
• Sherrington's discovery was an amazing feat of scientific reasoning, as he used behavioral observations to infer the major properties of synapses half a century before researchers had the technology to measure those properties directly
• Types of Neurotransmitters


  • Amino Acids
  • Modified Amino Acid
  • Monoamines
  • Neuropeptides
  • Purines
  • Gasses
• Amino Acids


  Glutamate, GABA, glycine, aspartate, etc.
• Monoamines


  • Indoleamines: Serotonin
  • Catecholamines: Dopamine, Norepinephrine, Epinephrine
• Neuropeptides


  Endorphins, Substance P, Neuropeptide Y
• Purines

  ATP, adenosine
• Gasses

  NO (Nitric oxide)
• The Meninges


  • Membranes of CNS
  • Protect the CNS
• Ventricles


  • Interconnected cavities within cerebral hemisphere and brain stem
  • Continuous with the central canal of the spinal cord
  • Filled with cerebrospinal fluid
• Cerebrospinal Fluid


  • Secreted by the choroid plexus
  • Circulates in ventricles, central canal of spinal cord, and the subarachnoid space
  • Completely surrounds the brain and spinal cord
  • Excess or wasted CSF is absorbed by the arachnoid granulations
  • Clear fluid
  • Volume is about 140 ml
  • Nutritive and protective
  • Helps maintain stable ion concentrations in the CNS
• Nervous System


  • Consists of two divisions: the central nervous system containing the brain and spinal cord, and the peripheral nervous system which is a network of nerves and neural tissues branching out throughout the body
• Central Nervous System


  • Contained in the cranial cavity of the skull
  • Includes the cerebral cortex, limbic system, basal ganglia, thalamus, hypothalamus, and cerebellum
• Functions of the brain


  • Interprets sensations
  • Determines perception
  • Stores memory
  • Reasoning
  • Make decisions
  • Coordinates muscular movements
  • Regulates visceral activities
  • Determines personality
• Major parts of the brain

  • Cerebrum
  • Frontal lobes
  • Parietal lobes
  • Occipital lobes
  • Temporal lobes
• Cerebrospinal fluid (CSF)

  • Completely surrounds the brain and spinal cord
  • Excess or wasted CSF is absorbed by the arachnoid granulations
  • Clear fluid
  • Volume is about 140 ml
  • Nutritive and protective
  • Helps maintain stable ion concentrations in the CNS
• Nervous System


  Consists of two divisions: the central nervous system containing the brain and spinal cord, and the peripheral nervous system which is a network of nerves and neural tissues branching out throughout the body
• Central Nervous System (CNS)


  • Contained in the cranial cavity of the skull
  • Includes the cerebral cortex, limbic system, basal ganglia, thalamus, hypothalamus, and cerebellum
• Functions of the brain

  • Interprets sensations
  • Determines perception
  • Stores memory
  • Reasoning
  • Make decisions
  • Coordinates muscular movements
  • Regulates visceral activities
  • Determines personality
• Major parts of the brain

  • Cerebrum
  • Diencephalon
  • Cerebellum
  • Brainstem
• Cerebral Cortex

  • The outmost part of the brain
  • A thick piece of nervous system
  • Folded into hills called gyri
  • Valleys call sulci
  • The cortex is made up of two hemisphere right and left, which is separated by a large sulcus. A thick fiber bundle called corpus callosum
• Four lobes of the brain


  • Frontal lobe
  • Parietal lobe
  • Occipital lobe
  • Temporal lobe