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THE NERVOUS SYSTEM (Peripheral Nervous System (PNS) = composed of all the…

- - - - Sympathetic Division:
        
        mobilizes the body into action and gets it all fired up
      - Parasympathetic Division:
        
        relaxes the body and talks it down
- - - - Dendrites = receive message from other neurons via neurotransmitter (they pick up messages from other cells and convey that info into the cell body) e.g. 'listener'
      - Axon = they transmit electrical impulses away from the cell body to other cells. e.g. 'talker'
      - The Soma (or cell body) = neuron life support, contains nucleus, DNA, mitochondria, ribosomes, cytoplasme
        
        The Nucleus of the cell is round or oval and is enclosed by the nuclear membrane. The nucleolus and chromosome reside here:
        
        Chromosome = a strand of DNA, with associated proteins, found in the nucleus; carries genetic information
        
        DNA (Deoxyribonucleic acid) = a long, complex macromolecule consisting of 2 interconnected helical strands; along with associated proteins. --> strands of DNA constitute the chromosomes.
        Contains the organism's genetic information
        
        Gene = portions of chromosomes . When the DNA is active, the genes cause the production one another complex molecule called mRNA.
        The gene is the functional unit of the chromosome, which directs synthesis of 1 or more proteins.
        
        mRNA (messenger ribonucleic acid) = a macromolecule that delivers genetic information concerning the synthesis of a protein from a portion of a chromosome to a ribosome.
        
        Nucleolus = a structure within the nucleus of a cell that produces the ribosome
        
        Ribosome = a cytoplasmic structure, made of protein, that serves as the site of production of protein translated from mRNA (small structure involved in protein synthesis)
      - terminal buttons = when an action potential traveling down the ax reaches the terminal button, they secrete a chemical called a neurotransmitter.
    - - Sensory neurons =
        (Afferent neurons)
        
        Pick up messages and transmit impulses from sensory receptors (skin or internal organs) towards the CNS
        
        Most sensory neurons are Unipolar
      - Motor neurons =
        (Efferent neurons)
        
        Do the opposite: transmit impulses away from the CNS and out to your body's muscles and glands
        
        Most Multipolar
      - Interneurons =
        (Association neurons)
        
        Live in the CNS and transmit impulses between those sensory and motor neurons
        
        They are the most abundant of your body's neurons
        
        Mostly Multipolar
        
        Local interneurons = form circuits with nearby neurons and analyses small pieces of information
        
        Relay interneurons = connect circuits of local interneurons in one region of the brain with those in other regions
  - - - MicroGlial Cells = act as the main source of immune defense against invading microorganisms in the brain and spinal cord (defend)
      - Ependymal Cells = line cavities in your brain and spinal cord and create, secrete and circulate cerebrospinal fluid that fills those cavities and cushions those organs.
      - Astrocytes = most abundant and versatile glial cells. They anchor neuron to their blood supply (support), and govern the exchange of materials between neurons and capillaries (regulate ions)
      - Oligodendrocytes Cells = wrap around neurons, producing an insulating barrier called the myelin sheath
    - - Satellite Cells = do mainly in the PNS what Astrocytes do in the CNS, they surround and support neuron cell bodies
      - Schwann Cells = similar to Oligodendrocytes --> insulate, help form myelin sheath