Neuroanatomy

  • Neuroanatomy 

    • Neuroanatomy – the study of the parts and functions of neurons 

    • Neurons – Individual nerve cells 

    • Dendrites – root like parts of the cell that stretch out from the cell body. Dendrites grow to make synaptic connections with other neurons 

    • Cell Body (soma) - contains nucleus and other parts of the cell needed to sustain life 

    • Axon – wire like structure ending in the terminal buttons that extends from the cell body 

    • Myelin sheath – a fatty cover around the axon of some neurons that speeds neural impulses 

    • Terminal buttons – the branched end of the axon that contains neurotransmitters 

    • Neurotransmitters – chemicals contained in terminal buttons that enable neurons to communicate. Neurotransmitters fit into receptor sites on the dendrites of neurons like a key fits into a lock 

    • Synapse – the space between the terminal buttons of one neuron and the dendrites of the next neuron. 

  • When a neuron is in resting state, it has a slightly negative charge because there are mostly negative ions within the cell and mostly positive ions surrounding it. 

  • How a neuron fires 

    • When the terminal buttons of the first neuron are stimulated, they release neurotransmitters into the synapse. If enough neurotransmitters are received, the cell membrane of the second neuron becomes permeable and positive ions run into the cell 

      • These neurotransmitters fit into receptor sites on the dendrites of the second neuron.  

    • Action potential - The change in charge spreads down the length of the second neuron like a bullet from a gun.  

      • The charge travels at 120 meters per second 

    • A neuron fires in only one direction, from dendrites to terminal buttons 

    • When the charge reaches the terminal buttons of the second neuron, the buttons release their neurotransmitters into the synapse 

      • This process begins again if enough neurotransmitters are received by the next cell. 

    • All-or-none principle – A neuron either fires completely or not at all 

      • A neuron cannot fire a little or a lot, the impulse is the same every time 

  • Neurotransmitters 

    • Neurotransmitters - chemicals held in the terminal buttons that travel through the synaptic gap between neurons 

    • There are different types of neurotransmitters 

      • Excitatory neurotransmitters – they excite the next cell into firing 

      • Inhibitory neurotransmitters – they inhibit the next cell from firing 

    • To determine if the neuron will fire or not depends on the amount and type of neurotransmitters 

      • Acetylcholine – Motor movements 

      • Dopamine – Motor movements and alertness 

      • Endorphins – Pain control 

      • Serotonin – Mood control