Neurophysiology page 1 Department of Physiology 2 nd

Neurophysiology page 1 Sensory transduction Reception, perception, and transmission of information The brain creates

Neurophysiology Sensory transduction page 1 How neurones communicate Action potential Department of Physiology, 2

Neurophysiology page 1 Sensory transduction Action potential Na+ K+ K+ Voltage-gated Na+ and K+

Neurophysiology page 1 Sensory transduction Postsynaptic potentials Source of excitation is another neurone Neurotransmission

Neurophysiology page 1 Sensory transduction Reception Department of Physiology, 2 nd Faculty of Medicine,

Neurophysiology page 1 Sensory transduction Stimulus processing and information coding Department of Physiology, 2

Neurophysiology page 1 Sensory transduction Sensory receptors Anatomical classification Nerve endings Sensory neurones Classification

Neurophysiology page 1 Sensory transduction . . Common to all types of sensory receptors

Neurophysiology page 1 Sensory transduction Adaptation Decrease in amplitude of the generator potential during

Neurophysiology page 1 Sensory transduction Coding All-or-none (binary) Frequency vs. interval coding Ensemble coding

Neurophysiology page 1 Sensory transduction Sensory systems Visual system Auditory system Vestibular system Olfactory

Neurophysiology page 1 Sensory transduction Olfactory system Department of Physiology, 2 nd Faculty of

Neurophysiology Sensory transduction page 1 Olfactory system Lamprey Shark Department of Physiology, 2 nd

Neurophysiology page 1 Sensory transduction Olfactory system Receptor cells Mitral cells Periglomerular cells Granule

Neurophysiology page 1 Sensory transduction Olfactory receptor Department of Physiology, 2 nd Faculty of

Neurophysiology page 1 Sensory transduction Olfactory receptor Odorant binding protein Odorant receptor (one type

Neurophysiology page 1 Sensory transduction Olfactory pathway Department of Physiology, 2 nd Faculty of

Neurophysiology page 1 Sensory transduction Gustatory system Sweet Salty Sour Bitter Umami Department of

Neurophysiology Sensory transduction page 1 Tongue Taste buds Tongue Papilla Department of Physiology, 2

Neurophysiology page 1 Sensory transduction Taste buds Department of Physiology, 2 nd Faculty of

Neurophysiology page 1 Sensory transduction Taste receptor G-protein coupled receptor Sweet Bitter Umami Ion

Neurophysiology page 1 Sensory transduction Taste receptor Department of Physiology, 2 nd Faculty of

Neurophysiology page 1 Sensory transduction Taste receptor Receptor binding G-protein Second messengers Opening of

Neurophysiology page 1 Sensory transduction Taste receptor Na+ enter cell Depolarisation Low p. H

Neurophysiology page 1 Sensory transduction Taste receptor ATP Department of Physiology, 2 nd Faculty

Neurophysiology page 1 Sensory transduction Gustatory pathway Department of Physiology, 2 nd Faculty of

Neurophysiology page 1 Sensory transduction Visual system Department of Physiology, 2 nd Faculty of

Neurophysiology page 1 Sensory transduction Retina Department of Physiology, 2 nd Faculty of Medicine,

Neurophysiology page 1 Sensory transduction Rods and cones - photoreceptors Department of Physiology, 2

Neurophysiology page 1 Sensory transduction Retinal cells Rods Cones Bipolar cells Ganglion cells Horizontal

Neurophysiology page 1 Sensory transduction Photo-transduction in rods rhodopsin Department of Physiology, 2 nd

Neurophysiology page 1 Sensory transduction Rhodopsin cycle rhodopsin scotopsin all-trans retinal Metarhodopsin II triggers

Neurophysiology page 1 Sensory transduction Rod receptor potential In the dark, the outer segment

Neurophysiology page 1 Sensory transduction Action potentials in the retina The only type of

Neurophysiology page 1 Sensory transduction Auditory and vestibular system Department of Physiology, 2 nd

Neurophysiology page 1 Sensory transduction Organ of Corti Department of Physiology, 2 nd Faculty

Neurophysiology page 1 Sensory transduction Stereocilia glutamate Department of Physiology, 2 nd Faculty of

Neurophysiology page 1 Sensory transduction Vestibular system Semicircular canals Department of Physiology, 2 nd

Neurophysiology page 1 Sensory transduction Somatosensory system Department of Physiology, 2 nd Faculty of

Neurophysiology page 1 Sensory transduction Somatosensory system Mechanoreceptors Thermoreceptors Nociceptors Department of Physiology, 2

Neurophysiology page 1 Sensory transduction Somatosensory receptors Ruffini’s corpuscle – pressure sensor Merkel’s cells

Neurophysiology page 1 Sensory transduction Pain receptors Nerve endings Non-adapting Department of Physiology, 2

Neurophysiology page 1 Summary Sensory transduction in general Receptor neurones Receptor potential Specific sensory

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Neurophysiology page 1 Sensory transduction Reception, perception, and transmission of information The brain creates subj. experience Department of Physiology, 2 nd Faculty of Medicine, Charles University Our actions are based on what we perceive, i. e. the brain can ”read” it. Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Action potential Na+ K+ K+ Voltage-gated Na+ and K+ ion channels Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Postsynaptic potentials Source of excitation is another neurone Neurotransmission at a chemical synapse Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Sensory receptors Anatomical classification Nerve endings Sensory neurones Classification based on physical stimulus Mechanoreceptors Thermoreceptors Photoreceptors Chemoreceptors Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction . . Common to all types of sensory receptors Change of membrane potential -> Generation of receptor (“generator”) potential Similar to postsynaptic potentials -> Threshold for action potential must be crossed Receptor potential is graded, i. e. , it is proportional to stimulus strength Receptor potentials decrease with distance Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction . . Common to all types of sensory receptors The number of action potentials per time unit is linearly proportional to the receptor potential Receptor potential [m. V] Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction . . Common to all types of sensory receptors The number of action potentials per time unit is linearly proportional to the receptor potential Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction . . Common to all types of sensory receptors Receptor membrane becomes permeable for all small ions (however Na+ prevail) Receptor membrane is not electrically excitable Action potentials are generated down the line (even in different neurones, such as in vision) Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction . . Common to all types of sensory receptors Summation of receptor potentials in time Summation of receptor potentials in space Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Adaptation Decrease in amplitude of the generator potential during a prolonged sustained stimulation Stimulation Department of Physiology, 2 nd Faculty of Medicine, Charles University Stimulation Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Coding All-or-none (binary) Frequency vs. interval coding Ensemble coding (a combination of more receptors codes for a single feature) There are 10 kinds of people: Those who Non-spiking coding (cells in the retina) Understand binary and those who don’t. 10 means 1 x 21 + 0 x 20 = 2 Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Sensory systems Visual system Auditory system Vestibular system Olfactory system Gustatory system Somatosensory s. Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Olfactory system Receptor cells Mitral cells Periglomerular cells Granule cells Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Olfactory receptor Odorant binding protein Odorant receptor (one type for each cell) Olfactory G-protein Increase of c. AMP Opens Na+, K+, Ca 2+ ch. Cell depolarisation Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Taste receptor G-protein coupled receptor Sweet Bitter Umami Ion channels Salty Sour Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Taste receptor Receptor binding G-protein Second messengers Opening of TRPM 5 Depolarisation Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Taste receptor Na+ enter cell Depolarisation Low p. H opens H+ ch. H+ enter cell Depolarisation Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Taste receptor ATP Department of Physiology, 2 nd Faculty of Medicine, Charles University Depolarisation Ca 2+ channels open Ca 2+ causes neurotransmitter release Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Retinal cells Rods Cones Bipolar cells Ganglion cells Horizontal cells Amacrine cells Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Rhodopsin cycle rhodopsin scotopsin all-trans retinal Metarhodopsin II triggers cell hyperpolarisation Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Rod receptor potential In the dark, the outer segment suffers from the leakage of Na+ This reduces resting potential to -40 m. V Light produces metarhodopsin II Metarhodopsin II reduces inward flow of Na+ in outer segment Resting potential drops to as low as -70 m. V Glutamate release is reduced Department of Physiology, 2 nd Faculty of Medicine, Charles University glutamate Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Action potentials in the retina The only type of retinal cell that generates action potentials are ganglion cells Other cells conduct signals by simple electric conduction Retinal ganglion cells produce action potentials repeatedly (40 Hz), even if not stimulated. Visual signal is formed by ‘extra’ action potentials. Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Somatosensory system Mechanoreceptors Thermoreceptors Nociceptors Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Sensory transduction Somatosensory receptors Ruffini’s corpuscle – pressure sensor Merkel’s cells – pressure receptor Meissner’s corpuscle – light touch Hair follicle receptor – analog. to Meissner’s c. Pacinian corpuscle – fast-adapting pressure sensor Cold and warmth sensors Pain sensor – free nerve ending Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad

Neurophysiology page 1 Summary Sensory transduction in general Receptor neurones Receptor potential Specific sensory systems Olfactory Gustatory Visual Auditory Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad