Neurons and Action Potentials (Exam 2)

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Neurons and Action Potentials (Exam 2)
2015-04-08 03:42:19
Physiology Lecture
Neurons and action potentials
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  1. What is a neuron?
    Specialized nerve cells to transmit messages
  2. Dendrites
    Receive information
  3. Soma
    • cell body
    • site of metabolism
  4. Processes
    • Fibers that extend from the soma
    • Dendrites and axon
  5. Functional properties of neurons
    • Irritability: Ability to respond to a stimulus
    • Conductivity: ability to transmit and impulse
  6. When a nuron is at rest...
    • High [na+] outside
    • High [K+] inside
    • Fewer + ions inside cell vs outside
    • RMP = -70
  7. How is RMP maintained?
    Through Na+ and K+ pumps (requires most energy) or through leak channels
  8. Intake/outtake of Na+/K+ pumps
    • 3 Na+ moves out
    • 2 K+ moves in
    • Cost 1 ATP
  9. Ligand gated channels
    • Open or close when ligand binds to receptors on the membrane 
    • Usually located on dendrites or soma
  10. Voltage gated channels
    • Open or closes when membrane potential changes
    • Most located on axon, but throughout
  11. Depolarization
    • Na+ gates open -> Na+ rushes in
    • RMP increases from -70mV to +30mV
  12. Repolarization
    • K+ gates open -> K+ rushes out
    • Na+ gates close 
    • RMP goes from 30mV to -70mV
  13. Hyperpolarization
    • K+ gates closing after RMP goes back to -70mV
    • Slow closing gates cause a drop in RMP to below -70mV
  14. Myelination and its types
    • Insulating layer of plasma membrane
    • Formed by schwann cells and oligodendrocytes
  15. Schwann cells
    • In peripheral nervous system
    • One cell can myelinate an axon (one part of an axon)
  16. Oligodenrocytes
    • In central nervous system
    • One cell can myelinate several axons
  17. Nervous system functions
    • Sensory imput: Gather info (stimuli) about the environment
    • Integration: Response to stimuli and sends information to brain
    • Motor Output: Response to stimuli (muscle or gland)
  18. Nervous system classifications
    • Sensory (afferent) Division: Carries infotoward CNS from receptors 
    • Motor (efferent) Division: Carries information away from CNS and to effectors
  19. Neurons
    • Nerve cells
    • Carry electrical impulses (AP)
    • Processes information
  20. Neuroglia
    • Glial cells 
    • Support and protect neurons 
    • Types: Ependymal cells, microglia, astrocytes, oligodendrocytes
  21. Ependymal Cells
    • Types of neuroglia cell
    • Bathes brain and spinal cord with cerebral spinal fluid (CSF)
    • CSF: nourishes and protects brain tissue
  22. Microglia
    • Type of neuroglia cell
    • Removes waste and debris
  23. Astrocytes
    • Type of neuroglia cell
    • Forms the blood-brain barrier 
    • BBB: Protective layer around blood vessels
  24. Steps of action across a synapse
    • 1. Action Potential arrives as axon terminal 
    • 2. Voltage Ca+ gated channels open
    • 3. Ca+flows in -> exocytosis of synaptic vesicles 
    • 4. NT diffuse across cleft -> Binds to receptors
    • 5. Postsynaptic cell responds
    • 6. Response is eventually stops through degradation, re-uptake, or diffusion of NT
  25. Effects of Neurotransmitters
    Change in membrane potential in post-synaptic cell
  26. EPSP and IPSP
    • Excitatory postsynaptic potential (depolarize neurons)
    • Inhibitory postsynaptic potential (Hyperpolarizing neurons)
    • IPSP drops membrane potential to -55mV
    • IPSP is also membrane stabilizing
  27. Divergence and Convergence
    • Divergence: One presynaptic neuron -> several postsynaptic neurons
    • Convergence: Several presynaptic neurons -> One postsynaptic neuron
  28. Graded potentials
    Small changes in membrane potential due to ion channels opening and closing in response to stimuli (Determines in you get AP)
  29. Summation
    • Graded potential only
    • Can combine effects of stimuli (Add or cancel)
  30. Temporal summation
    Same stimulus or repeated close together in time to create graded potential
  31. Spatial Summation
    • Due to different stimuli
    • Overlapping in time