Tuesday oct 23 lecture chandler axon contains many

This preview shows page 6 - 8 out of 10 pages.

Tuesday Oct 23 Lecture (Chandler): Axon contains many voltage-gated sodium channels – electrical impulse is faithfully propagated till axon terminal, triggering release of neurotransmitter into synaptic gap Action Potential - Explosive change in membrane potential that briefly changes voltage from negative to positive (depolarization) Positive feedback Hodgkin cycle?? Leakage channels – always open, even at equilibrium K delayed-rectifier channel – suddenly produces outward current, counters inward current, they do not inactivate – they’re voltage-gated, but don’t immediately turn off (it is a molecular property) Can mimic synaptic input by injecting impulse using electrode, to simplify experimental setup Supra threshold pulse Myelinated axons are much more metabolically efficient than unmyelinated axons Action potential propagation in MS patients: there is lost current where myelin (insulator) is missing, so takes longer to initiate action potential or not at all Clinical correlation: conduction block: lidocaine
Image of page 6

Subscribe to view the full document.

Sid Baphna Thursday, September 27, 2018 Axonal propagation failure Binds to S6 region of sodium channel protein -single polypeptide -cocaine (molecular structure similar to lidocaine – blocks sodium conduction, when someone snorting says they can’t feel anything and their nose gets red, it’s because sodium channels in tip of nose are blocked) Synaptic potentials are great for short-distance communication but decay over long distance, action potentials propagate faithfully over the axon and thus are great for long-distance communication Neuronal Communication Intra-neuronal (within) Inter-neuronal (between) Circuits
Image of page 7
Sid Baphna Thursday, September 27, 2018 Thursday Oct 25 Lecture (Chandler): Synaptic integration at central synapses – Spatial summation + temporal summation = initiate action potentials Summation of individual synaptic inputs, if juxtaposition of timing is right Spatial summation – multiple inputs for different cells Temporal summation – multiple inputs for one cell Spatial and temporal work together (understand properly??) Tuesday Oct 30 Lecture (Knowlton): Perception is a creation of the brain based on inputs (reality is a construct) Sensory receptor organs detect specific type of stimuli Receptor neurons in organ convert stimulus to electrical signal Can only detect energies/substances we have receptors for Some species can detect electrical or magnetic fields we can’t sense (forms of energy we don’t have receptors for): Rays – snakes – infrared radiation pigeons – Even for senses for which we have receptors, can only detect stimuli within limited range : Many animals can detect frequencies outside range of human hearing (elephants hear lower freqs., cats hear higher freqs. that humans don’t) Bees – UV light Rats – taste receptor that detects starch As frequency increases, our auditory cells are more sensitive so less intensity (dB) is required to detect, but after ~4000 Hz, need higher intensity to detect
Image of page 8
You've reached the end of this preview.
  • Fall '15
  • S.H.Chandler
  • Sid Baphna

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern