Sensory systems

  1. Pathway for sensation (for example infared vision)
    • 1st: we have to have sensory cells with the receptor proteins that can be modulated by the stimuli
    • 2nd: we have to take that stimuli and turn it into something that neurons can understand like voltages & neurotransmitter (the voltage change leads to the neurotransmitter change)
    • This process is called sensory transduction
  2. Do stretch receptors fire action potentials or do photoreceptors fire action potentials?
    stretch receptors
  3. Intensity of stretch depends on whether we become ______ of it.
  4. Order in sequence of minimal hearing loss to complete hearing loss if damaged:
    tympanic membrane, ossicles, pinna
    • pinna
    • tympanic membrane
    • ossicles
  5. Sense: hearing story (8)
    • Vibratory energy approaches the ear
    • Pinna collect waves (vibratory energy) and focuses it down the auditory canal toward tympanic membrane
    • Tympanic membrane will vibrate or move and attached to it are the ossicles (malleus, incus & stapes)
    • Ossicles job is to translate the vibrations by making the stapes pound on the oval window (cochlear)
    • This will move the translated vibratory energy into the cochlear aka oval window (done in the middle canal
    • The Eustachean tube is an equalizer for the air pressure
    • That vibratory moves into the upper canal and wants to take a short cut and be alleviated at the round window
    • But the basilar membrane in the middle is stiff and thick but luckily as the vibratory energy makes its way down the basilar membrane becomes less argumentative and the energy is allowed to make its way to the round window and is alleviated. END
  6. W/out the ____ _____ the energy would not be alleviated, instead it would just bounce back/ reverberate and cause an echo
    round window
  7. The  vibratory energy has to be strong enough to deflect our basilar membrane _____ or it won't be heard. Higher pitch sounds are deflected _____ along the basilar membrane while lower pitch sounds are deflected _____
    • upward
    • nearer 
    • farther
  8. Deflection causes the stereocilia aka hair cells to move _____ and connect to the _____  membrane.  That movement opens up ion channels, allowing ___ in and drives our voltage upward. We get more positive and _____ is released as well.  The end result is that in the depolarized form, the sensory neuron can detect the ______ and sends the sensory info the brain
    • upward
    • tectorial 
    • K+
    • Ca++
    • glutamate
  9. Once the wave passes, the basilar membrane resumes form, the hair cells kick off, ion channels close, and we experience a _______
  10. The cochlea is fluid in both upper and lower canal but not the ____ canal. ______ membrane is the only movable membrane
    • middle 
    • basilar
  11. Which doesn't fire action potentials: 
    Sensory neurons or Sense Cells
    Sense cells
  12. Proprioception story:
    Muscle spindle fiber (9)
    • Muscle fibers that generate force are the extrafusal muscle fibers (activated by and alpha motor neuron)
    • These extrafusal muscle fibers will have intrafusal muscle fibers, both are efferent
    • Wrapped around the intrafusal muscle fibers are sensory neurons containing receptor proteins
    • SO when we stetch the whole muscle, the extrafusal muscles are not responsible for the sensation of proprioception
    • If we stretch the muscle, receptor proteins along the sensory neurons on the intrafusal muscles are mechanically opened. The voltage of the sensory neuron will become more positive and if the stretch is strong enough, they will fire action potentials.
    • Those are processed in the CNS and we perceive our own bodies stretching (proprioception)
    • While extrafusal muscle fibers generate motor outputs, intrafusal muscle fibers are almost there just to be stretched for the sensory neurons wrapped around them to initiate proprioception. That isn't completely true
    • Intrafusals also have gamma efferent motor neurons so they contract as well and this makes even smaller stretches of the muscle more easily detectable.
    • They will be less active during rest & digest
  13. All sensory neurons are located ______ of the ____ except for _______. Olfaction relies on ______ that are _____ ____
    • outside of the CNS
    • thermoreceptors
    • chemoreceptors 
    • g-protein coupled
  14. chemotaxis
    We move toward or away from smells
  15. Signaling cascade for odorants (g-protein cpld) gs signaling
    • Odorant (ligand) binds to olfactory receptor protein
    • Specific odorants bind to specific receptor protein because sensory neurons can only express one type of receptor proteins for a specific range of odors. So for example the fragrance of pizza can only bind to a specific receptor protein.
    • Gs signaling activates the alpha sub unit
    • The alpha sub unit shuttles over to adenylyl cylcase (AC)
    • AC will convert ATP into cAMP
    • cAMP will bind to the ion channel
    • Na+ and Ca++ come in and Ca++ is a 2nd messenger that binds to a Ca++ gated chloride channel
    • Cl- will leave and the cell/neuron, according to its electrochemical gradient, will become more (+)
    • Sensory neuron's receptor potential will eventually become positive enough to elicit an action potential
    • Axons will go to the glomerulus (which have no cell bodies, just a place where axons meet with dendrites)
    • Glomerulus will release glutamate to the dendrites (possibly of a mitral cell)
    • Mitral cell axons go directly to cortex
  16. Animal that have cells containing rhodopsin we recognize as _____ & ____ that will translate indirectly into ______ _____
    • cones & rods
    • action potentials
  17. Purpose of the posterior portion of they eye is to translate photonic energy into _____ changes (retina...)
    voltage changes
  18. The front part of the eye's job (like the lens) is to focus photonic energy to the _____ _____ specifically to the _____ _____. Most of our ____ are there. It is by far the _____ dangerous part of the eye to have damaged
    • macula lutea
    • fovea centralis 
    • cones
    • most
  19. Cornea's job is ______ and ______ of light. The pupils are black to ______ light. Light does not enter through the iris, it is ______ or ______
    • protection & transmission
    • absorb
    • absorbed or reflect
  20. Vision pathway:
    retina story (6)
    • Light through the pupil, gets focused through the lens
    • The light will be transmitted to the retina where it will be absorbed
    • Retina pathway: The light will be transmitted through the axons of ganglion cells into the 1st excitable cells so far, the ganglion cell
    • The light will then be transmitted through the bipolar cells (* some amacrine and horizontal) into the photoreceptor (cones and rods) portion of the eye
    • The light will be transmitted through most of the photoreceptors until it gets to their outer segment.
    • Any light that escapes that is absorbed immediately after at the pigmented epithelium
    • NO light escapes
  21. The three parts of rods & cones
    • synaptic ending (carrying transmitter)
    • inner segment (contains nucleus and mitochondria, role: maintenance)
    • Outer segment (absorbs light, contains cytoplasm/membrane & discs)
  22. Rhodopsin story
    • Rhodopsin consist of an opsin protein and a retinal molecule
    • The retinal molecule changes it conformation and we are allowed translate the photonic energy
    • Retinal molecule within rhodopsin molecule is referred to as the 11-cis retinal.
    • Photonic energy hits rhodopsin and 11-cis-retinal and the retinal molecule will undergo a conformational change.
    • The conformational change will turn our retinal molecule into "all-trans-retinal"
    • This conformational change will activate the g-protein for vision, transducin
    • Like previous alpha sub units, transducin will shuttle over to the effector protein, phosphodiesterase
    • This phosphodiesterase is specific for cGMP and itll break it down into GMP
    • When [cGMP] is high, it binds to adjacent ion channels and allows Na+ & Ca++ into the cell, making the inside more (+)
    • The phosphodiesterase reduces [cGMP] and there will be less binding to the ion channel
    • Ion channels will close and voltage will become negative (hyperpolarization) END
  23. All ganglion cells have _______ receptors. Photoreceptors become more _____ in the dark (-35mV is high)
    • ionotropoic receptors
    • positive
  24. In the _____ a photoreceptor in the synaptic ending is releasing transmitter (glutamate) and stops doing so in the _____. Overload of glutamate in the synapse wouldn't necessarily blind someone, but ____ ____ would go down
    • dark 
    • light 
    • visual acuity
  25. In the dark story 
    On center: (6)
    • Cone will be depolarized
    • Glutamate will be released
    • On center bipolar cell has metabotropic glutamate receptors
    • When glutamate binds, there is a hyperpolarization and its glutamate release will be low
    • Its synaptically coupled on center ganglion cell will get no glutamate. (has ionotropic receptors)
    • It won't be able to fire an action potential
  26. In the dark:
    off center story
    • Off center bipolar cell has ionotropic (AMPA) glutamate receptors
    • When glutamate binds, Na+ enters and the cell depolarizes and the transmitter release is increased.
    • This is synaptically connected to an off-centered ganglion cell
    • The ganglion cell will be getting hit by a lot of glutamate, this will cause a lot of EPSPs aka depolarization.
    • The off-center ganglion cell will then fire action potential
    • That'll go through the optic nerve, to the thalamus, and then to the occipital lobe.
    • The ganglion cell is literally telling the brain, I'm in the dark
  27. In the light:
    on center story (4)
    • Cone will be hyperpolarized
    • Glutamate release will be decreased
    • On center bipolar cell
    • Depolarize and transmitter release will increase
    • Firing of on-center ganglion cell increased (now the brain knows its in the light)
  28. In the light:
    Off center story (2)
    • Off center bipolar cell
    • Off-center bipolar cell hyperpolarized and transmitter release is decreased
    • Firing of off center gang cell decreased
Card Set
Sensory systems
Audio breakdown