Neurons & Nervous System part 1

  1. 2 categories of cells in the nervous system
    • neurons
    • glia (glial cells)
  2. __, or nerve cells, are excitable - They generate & transmit electrical signals called __
    Neurons; action potentials
  3. cells that provide support in the nervous system & maintain extracellular environment
    Glia (glial cells)
  4. contains the nucleus & majority of cell organelles; is the site of synthesis of most of the proteins, carbs, & lipids in the neuron
    cell body
  5. receive the signals & transmit them toward the cell body
  6. conduct signals away from the cell body to another neuron or effector
  7. Ligand-gated ion channels are at __ (part of the neuron).
  8. Voltage-gated ion channels are found at __ (part of the neuron).
    axon terminals
  9. In __, the plasma membranes of the presynaptic & postsynaptic cells are in direct contact & communication across such synapses occurs by the direct flow of an __
    electrical synapses; electrical signal

    • allow the most rapid conduction
    • found in cardiac muscle & retina of the eye

    (page 13 on slide)
  10. When an electrical impulse arrives at the axon terminal, __ allow ions to flow directly between the 2 cells, leading to unbroken transmission of electrical signal
    gap junctions

    (page 13 on slide)
  11. In __, the plasma membranes of the presynaptic & postsynaptic cells are separated by a narrow gap called the __. Communication across such synapses occurs by means of a __
    • chemical synapses;
    • synaptic cleft;
    • neurotransmitter

    (page 11 & 12 on slide)
  12. bundle of axons from different neurons
  13. structural classification of neurons
    • multipolar: possess more than 2 processes (numerous dendrites, 1 axon. most common. all motor are multipolar)
    • bipolar: possess 2 processes (rare, found in some special sensory organs. i.e. retina)
    • unipolar (pseudounipolar): possess 1 short, single process (dorsal root ganglia)

    (page 17 & 18 on slide)
  14. functions of glial cells
    • release & re-uptake neurotransmitter
    • support neurons (provide nutrients & maintain the extracellular environment)
    • immune functions
    • contribute to the blood-brain barrier
    • myelinate axons in the CNS (oligodendrocytes) & PNS (schwann cells)
  15. the electrical potential, the charge difference across the membrane
    membrane potential
  16. Outside the cell, the net charge is __ & the inside of the cell is __
    positive; negative

    This charge separation produces voltage
  17. the membrane potential of a resting neuron
    resting membrane potential
  18. An __, or nerve impulse, is a rapid, large change in membrane potential
    action potential
  19. Action potentials are generated by __
    openings & closings of ion channels
  20. changes from the resting potential; a means of integrating input - the membrane can respond proportionally to depolarization or hyperpolarization
    graded membrane potential
  21. EPSP (excitatory postsynaptic potential) & IPSP (inhibitory postsynaptic potential) are types of __ potentials
  22. The direction & size of ion movement depends on the __ & __ of the membrane. These 2 forces acting on an ion are its __
    • concentration gradient;
    • voltage difference;
    • electrochemical gradient
  23. If a membrane were permeable to only K+ or Na+ then..
    K+ or Na+ would diffuse down its concentration gradient until the electrical potential across the membrane countered the diffusion

    (page 37 & 41 on slide)
  24. The electrical potential that counters net diffusion of K+ or Na+ is called the __
    • K+ equilibrium potential (Ek = -90 mV)
    • Na+ equilibrium potential (ENa = +55 mV)

    (page 38, 41, & 43 on slide)
  25. Why are cells negative?
    • DNA
    • Na+/K+ pump
    • K+ leak channels
  26. Why is Vm (resting membrane potential) so close to Ek (K+ equilibrium potential)?
    The membrane is far more permeable to K than Na

    (page 45 on slide)
  27. If an equilibrium potential is close to the resting potential, there will be __
    little ion movement even if the membrane is freely permeable to the ion

    (See example on page 889 in book)
  28. driving force =
    Vm (membrane/resting membrane potential) - Eion (equilibrium potential of ion)

    ex. If the driving force = +70 mV (RMP) minus -90 mV (EK+), the driving force is +20mV

    (In this case, K+ will leave the cell.)
  29. If the driving force = -70mV (RMP) minus +55mV (ENa+), the driving force = -125 mV. What happens to the ionic flow Na+?
    Since the driving force is negative, there is inward movement of positive current.

    (negative driving force = more negative inside the cell, so + ions will enter)

    Therefore, Na+ will enter the cell.
  30. If the driving force = +75mV (MP) minus +55mV (ENa+), the driving force is +15mv. What happens to the ionic flow of Na+?
    Since the driving force is positive, there is an outward movement of positive current.

    (positive driving force = more positive inside the cell, so + ions will leave)

    Therefore, Na+ will leave the cell.
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Neurons & Nervous System part 1