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

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 How neurones communicate Action potential

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

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Reception

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Stimulus processing and information coding

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

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Coding All-or-none (binary) Frequency vs. interval coding Ensemble coding (a combination of more receptors codes for a single feature) Non-spiking coding (cells in the retina) There are 10 kinds of people: Those who Understand binary and those who don’t. 10 means 1x x2 0 = 2 There are 10 kinds of people: Those who Understand binary and those who don’t. 10 means 1x x2 0 = 2

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Olfactory system LampreySharkFrog

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

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

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Olfactory receptor

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Olfactory pathway

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Gustatory system Sweet Salty Sour Bitter Umami

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Tongue Papilla Taste buds

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Taste buds

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Taste receptor

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Taste receptor Receptor binding G-protein Second messengers Opening of TRPM5 Depolarisation

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

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Gustatory pathway

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Retina

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Rods and cones - photoreceptors

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 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 Sensory transduction Neurophysiology page 1 Photo-transduction in rods rhodopsin

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 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 Sensory transduction Neurophysiology page 1 Auditory and vestibular system

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Auditory and vestibular system

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Organ of Corti

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Organ of Corti

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Stereocilia glutamate

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 Vestibular system Semicircular canals

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

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

Department of Physiology, 2 nd Faculty of Medicine, Charles University Copyright © 2011 Luděk Nerad Sensory transduction Neurophysiology page 1 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 Sensory transduction Neurophysiology page 1 Pain receptors Nerve endings Non-adapting

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