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Chapter 20 Lecture 1 (Structures of the Central Nervous System (The…

- - - - Blood infections hard to cross but so are many antimicrobial drugs so it is difficult to treat once CNS is infected
- - - - Sensory nerves: carry signals toward the CNS
      - Motor nerves: carry signals away from the CNS
      - Mixed nerves: carry signals toward and away from
  - - - Neuroglia
        
        Provide support, insulation, nutrients
        
        Phagocytize microbes
      - Neurons
        
        Carry nerve impulses
        
        Nucleus lies in a region called the cell body
        
        Ganglion is collection of many neurons' cell bodies
        
        Dendrites and axons extend from the cell body
    - - Junction at the terminal ends of axons
      - Facilitates signal transfer to postsynaptic cell
      - Synaptic cleft stops transmission of electrical signals- because the signals between cells is chemical
    - - Chemical
      - May be either stimulatory or inhibitory
        
        Stimulate a muscle to contract, a glad to secrete or another neuron to carry a nerve impulse
        
        Stops the activity
  - - - It has no normal microbiota
    - - Breaks in the bones and meninges
      - Medical procedures
      - Travel in peripheral neurons to the CNS
      - Infect and kill cells of the meninges, causing meningitis
      - Inflammation can alter the permeability of the blood-brain barrier
- - - - Sudden high fever, severe meningeal inflammation, and increased white blood cells in the CSF
      - Inflammation causes most signs and symptoms . Swelling slows the normal flow of CSF which puts pressure on the organs
        
        Severe nausea, vomiting, pain, drowsiness, confusion, fretfulness or irritability, stiffness of the neck
      - Infection of the brain causes encephalitis
        
        Can result in behavioral changes, coma, and death, deafness, blindness
      - Can develop rapidly- can kill within 6 hours of initial s/s
  - - - Sometimes you will see petechiae in the skin
    - - Researchers have shown that more than 50 species of bacteria can cause meningitis
      - Five species cause 90% of bacterial meningitis cases
        
        Neisseria meningitidis
        
        Streptococcus pneumoniae
        
        Haemophilus influenzae
        
        Listeria monocytogenes
        
        Streptococcus agalactiae
      - Opportunistic members of the normal microbiota can also cause meningitis
      - Streptococcus pneumoniae- Louis Pasteur Discovered
        
        Gram-positive coccus and is encapsulated which forms short chains, or pairs
        
        92 different strains of S. Pneumoniae are known to infect humans as normal members of the microbiome of the throat that grow in the lungs, sinuses and middle ear and from those locations move into the meninges via the blood
        
        Leading cause of meningitis in children and elderly
        
        Polysaccharide capsule protects bacteria from digestion by phagocytes (encapsulated) the unencapsulated strains DO NOT cause disease
        
        Enzymes and toxins enable bacteria to counteract immune defenses
        
        Phosphorylcholine triggers endocytosis by cells
- - - - Meningitis- the most common bacterial infection of the nervous system
      - Leprosy- disease of cells found in the PNS
    - - Botulism
      - Tetanus