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Sensory system, remember the sensory info on one side travels to the…

- - - - eardrum (tympanic membrane)
      - ear ossicles
        
        malleus
        
        incus
        
        stapes
      - Eustachian tube
    - - vestibular apparatus
        
        used for sense of balance
      - cochlea
        
        sound processing
        
        structure
        
        cochlear duct
        
        scala tympani
        
        scala vestibuli
        
        basilar membrane
        
        separates cochlear duct and scala tympani
        
        organ of corti
        
        hair cells convert sound waves to ac here
        
        these hair cells are embedded in the tectorial membrane
        
        they will bend when sound waves cause the basilar membrane to vibrate
    - - auricle
      - external auditory canal
  - - - number of sound waves per unit time
    - - expresses how loud that sound wave is
    - - airwaves hit the outer year
        
        the waves go into the external auditory canal
        
        hit tympanic membrane (back and fourth motion)
        
        ear ossicles have levering action that amplify the waves that hit the tympanic membrane
        
        oval window(found under stapes) vibrates
        
        amplify the waves 15-20x
        
        fluid in cochlea (perilymph) transmit waves to the hair cells in the basilar membrane
        
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        creates a traveling wave in the basilar membrane
        
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- - - - Meissner's corpuscles
        
        detects low frequency (30-40 cycles/sec) vibrations
        and touch
      - Ruffini's corpuscles
        
        detects touch
      - Free nerve endings
        
        responds to pain and temperature
        
        only receptor that does not detect fine touch
      - Pacinian corpuscles
        
        detects high frequency (250-300 cycles/s) vibrations and touch
      - Hair follicle
        
        sensitive to fine touch and vibration
  - - - i.e. a potential applied outside the region (receptor field) will not trigger an ac
  - - - transmits pain, temperature and crude touch
      - pathway
        
        info from sensory neuron (first order neuron) enters spinal cord
        
        synapses with second order neuron
        
        cross to contralateral(opposite) side
        
        goes up to the thalamus
        
        relay station for almost all sensory info
        
        synapse with third order neuron
        
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    - - transmits more advanced sensation of fine touch, proprioception and vibration
      - pathway
        
        info from sensory neuron (first order neuron) enters spinal cord
        
        IMMEDIATELY travels up the spinal cord
        
        in upper spinal cord, synapses with second order neuron
        
        crosses to contralateral side
        
        thalamus
        
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- - - - detects linear and rotational motion/position of the head relative to the body
  - - - detect angular/rotational accelerations
      - 3 different ones for linear acceleration in each plane (x,y,z) of motion
      - filled with endolymph(fluid)
      - ampula
        
        crista ampullaris
        
        sensory region in ampula
        
        contains sensory hair cells
        
        hair cells are embedded in a gel material (cupula)
      - process
        
        head rotates to left
        
        endolymph hits cupula
        
        bends the hair cells that are in it
        
        bending in one direction causes depolarization, leading to an ac
        
        bending in opposite direction causes hyperpolarization and no info is sent to brain
        
        endolymph lags behind a bit and looks like it moves in opposite direction
    - - detect linear acceleration/deccelerations
      - also detect head position when tilted
      - structure
        
        utricle
        
        detect horizontal acc/decel
        
        have hair cells anchored and have cilia embedded in a gelatinous membrane
        
        this membrane has otolith crystals stuck inside for weight and inertia when it moves
        
        act together to detect head tilts
        
        saccule
        
        detect vertical acc/decel
      - process
        
        at rest
        
        regular series of ac produced in vestibular nerve
        
        during acc in vertical/horizontal plane
        
        otolith crystals lag behind and appear to move in opposite direction to the acc at first
        
        cilia bend in opposite direction
        
        increase ac frequency in vestibular nerve
        
        constant velocity
        
        hair cells are in resting state
        
        ac frequency is same as when at rest
        
        during deceleration
        
        hair cells bend in other direction
        
        ac frequency decreases further from resting state
        
        the hair cell
        
        have a large cilia called the kinocilium and small cilia called stereocilia
        
        at rest, neurotransmitters are released onto the sensory nerve, creating an ac
        
        when small stereocilia bends towards the large kinocilium, more neurotransmitters are released
        
        higher freq ac fired
        
        when small stereocilia bends away from the large kinocilium, less neurotransmitters are released
        
        lower freq ac fired
- - - - normally in the dark, constantly depolarizes (Na+ goes in), releasing inhibitory neurotransmitter
        
        turns off bipolar cells
        
        light hits the retina
        
        hyperpolarization of rod and cone cells
        
        Na+ channels close when light hits
        
        K+ starts leaking out
        
        cause hyperpolarization
        
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  - - - lens
        
        flips the light to focus it onto the retina
      - retina
        
        at the back of the eye
        
        photoreceptors
        
        rods
        
        very sensitive to light
        
        function best in low light conditions
        
        only have 1 type of photopigment
        
        cannot detect color
        
        found mostly outside and around the fovea
        
        don't have axons, so cannot generate axon potentials
        
        instead, generates receptor potentials, causing depolarization (no light conditions)
        
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        cones
        
        function best in bright light
        
        ideal to detect detail
        
        have 3 different photopigments sensitive to one primary color
        
        allow for color detection
        
        found in region of fovea in large concentrations
        
        vision is focused on the fovea (part of retina) with high concentration of cone cells
        
        have pigment layer at back to absorb excess light
        
        have other cell types
        
        bipolar, ganglion, horizontal and amacrine cells
        
        these cells integrate info from rods and cones and produce ac
        
        types of eye movement
        
        smooth pursuit
        
        smooth movement of the eyes, following the object of interest and keeping it within the fovea
        
        vestibular ocular reflex
        
        focusing your eye on an object and moving head, while still watching the object
        
        saccades
        
        rapid, jerky eye movements to the object of interest
        
        vergence
        
        eye diverging (moving away) or converging (coming towards you) when an object is moving towards or away from you
      - iris
        
        regulates amount of light passing through
        
        constrict in bright light
        
        dilate in low light
- - - - requires environment stimuli (heat, touch, smell,etc) to be detected by sensory receptors
        
        types of environmental stimuli
        
        chemical
        
        taste
        
        pain
        
        odors
        
        electromagnetic
        
        light
        
        mechanical
        
        touch
        
        vibrations
        
        proprioception
        
        pressure
        
        other
        
        motion
        
        acceleration
        
        gravity
        
        heat
        
        adequate stimulus
        
        environmental stimulus the sensory receptor is MOST sensitive to
        
        Example
        
        adequate stimulus of rod + cone cells is light
        
        can respond to pressure, but not optimal
        
        receptor potentials
        
        local depolarization caused by sensory receptor stimulated by environmental stimulus
        
        to fire ac, receptor potential must travel to the first node de Ranvier where voltage-gated ion channels are present
        
        ac travels along axon, into the spinal cord
        
        for receptors with no axons, depolarization must spread to the synapse for release of a neurotransmitter
        
        similarities to EPSPs/IPSPs
        
        caused by higher permeability to Na+ ions (or K+ for hyperpolarization)
        
        they are local potentials and spread similarly, decreasing with time and distance
        
        can be depolarizing or hyperpolarizing
        
        stronger receptor potential makes it more likely to fire an ac
        
        larger receptor potentials triggers more ac
        
        used for situations where holding heavy object