Sensory Physiology PDF

TOPIC 09: SENSORY Jafferent division PHYSIOLOGY (CHAPTER 7)  Sensory Receptors graded Specialized cells that generate ______________ potentials (called receptor potentials) in response to a stimulus. – These a...

TOPIC 09: SENSORY Jafferent division PHYSIOLOGY (CHAPTER 7)  Sensory Receptors graded Specialized cells that generate ______________ potentials (called receptor potentials) in response to a stimulus. – These are cells, not simply protein receptors. – Many receptor cells have receptor proteins. 5 types of sensory receptors: 1. Mechanoreceptors => physical change 2. Thermoreceptors=> temperature change 3. Photoreceptors => light 4. Chemoreceptors => Chemical ligano gater] 5. Nociceptors => pain [llgand gater ______________: Stimulus energy or chemical that activates receptor Sensory __________________: transduction transformation of environmental stimuli into electrical (neural response)  Not every touch : action Types of Sensory Receptors potential ↳ has to be strong enough for graded to hit threshold I cell => receptor membrane and afferent neuron touch lons flow Voltage gut er = grades ↳ potential reaches threshold : action potential channels triggered to open at open channels threshold = (t) lons flow in depolarization action potential ! mechanically gated Loading… 2-cells : [separate) - receptor cell afteven , taste E graded potential > (t) - Ions flow in > - + 10n5 "graved potential. opening Hit threshold of voltage neurotransmitten get releaier, gated S 1st cell determines : graded amt. pot of neurotr. bino to 2nd receptor (ligani gate o chemoreceptor stimulate opening of How are they different? voltage gated cat channels * Voltage gated cast channels = exocytosis of neurotransmitter 1-cell = Stimulation of Afferent Neuron carrying signals to CNs afferent neuron : sensory neuron As Stimulus intensity (T), in amplitude = (4) frequent action grades potential (PC Dotential = (4) neurotransmitters action potentials  Stimulus Intensity How do we distinguish a strong stimulus from a weak one? ↑ frequency of action potentials stronger stimulus a given receptor = in action potentials increase in freq. S from an afferent neuron increase of stimulus mechanare [ Loading… more pressure = more activated newve fiber receptor activation (4) pressure (4) skin = Increased frequency of action potentials from one receptor (area) Stronger stimuli usually affect a larger area stimulating more receptors. This is called recruitment. can affect neighboring receptors = * Diff body parts = different contact sensitivity levels Stimulus Location How do we determine the location of a stimulus? Labeled Lines high acuity receptive field = Y lips high precision in detection of multiple stimuli [denser nerve endings _ Acuity = precision with which we distinguish multiple stimuli Depends on – 1 size of receptive field – z Convergence acuity. less more convergence = low acuity : less precision travel distinct from receptor to CNS sensory signals along pathways info from specific areas of neural pathways "lines" carrying brain determine where Stimulus 15 coming from body to brain (helps * free ended nerves detecting painful stimuli deformation , temp, unmylineated signaling = NIA sheath = slower Pain Receptors /Chemical changes = cell damage Free axon-terminal unmyelinated nociceptors stimulated by extreme signal Reacher Brain deformation, temperature or chemicals associated with cell damage. pain signal A) pain Transmission Pathway travels/ends here = pain 1. Pain Stimulus sensation felt. - detection of harmful stimulus Interneurons Ap. Synapse in CNS 3 holceptor pain signal transmitted from afferent neuron neuron to secondary. Afferent Pain Fiber [Sub 1 2 using 1 T N... ↳ travel from PNS to CNS (thi afferent pain & Glutamate] Fiber) brain 1. Modulate/Reduce Pain into Spinal coro a up the NT = pass pain ↳ signal carried thru synapses is) Descending pathway axo-axunic ↓ ↑ · release of endogenous us exogyneous " pict occurs w ! (l-Channel -- Neurotransmitter made outside ~ (the Ion enter tell your body Inatural by body , makes it ex : morphine release · prevents. neurot of blue 4. Inhibition of Pain Signal oplates binding to Inhibits pain pathway > receptor = Inhibit release of excitator/ neurotransmitter NIA pain. 3 Exogenous Morphine hyperpolarization : mimics body's. Oplate Neurotransmitter 2 + Channel natural pain-relieving ↓ neurons release endorphins llg and chemicals by binding (Endogenous oplated) to bind to same oplate receptors to oplate receptors  Referred Pain sensory nerve fibers from heart & y spinal at cord Skin converge due to same sensory pathway to brain Brain does not distinguish = N/A differentiation = referred pain ! stimuli coming from visceral and somatic branches of the same spinal nerve. Internal organa body surface share same nerve pathways to brain confusion in brain's Interpretation of pain location Feel pain from an internal organ as another area of the surface of the body. in I arm heart attack : pain