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The Cochlea • Hair Cells Bend in the Cochlea and Ion Channels Open • Action Potential Travel to the Brain

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Olfaction • Link between smell, memory, and emotion • Vomeronasal organ (VNO) in rodents – Response to sex pheromones • Olfactory sensory neurons – Olfactory epithelium in nasal cavity • Odorants bind to odorant receptors, G protein–linked membrane receptors © 2016 Pearson Education, Inc. Figure 10.13a The Olfactory System Olfactory Pathways The olfactory epithelium lies high within the nasal cavity, and its olfactory neurons project to the olfactory bulb. Sensory input at the receptors is carried through the olfactory cortex to the cerebral cortex and the limbic system. Cerebral cortex Limbic system Olfactory bulb Olfactory tract Olfactory cortex Cranial Nerve I Olfactory neurons in olfactory epithelium © 2016 Pearson Education, Inc. Figure 10.13b The Olfactory System The olfactory neurons synapse with secondary sensory neurons in the olfactory bulb. Olfactory bulb Secondary sensory neurons Bone Olfactory sensory neurons Olfactory epithelium FIGURE QUESTION Multiple primary neurons in the epithelium synapse on one secondary neuron in the olfactory bulb. This pattern is an example of what principle? © 2016 Pearson Education, Inc. Figure 10.13c The Olfactory System Olfactory neurons in the olfactory epithelium live only about two months. They are replaced by new neurons whose axons must find their way to the olfactory bulb. Olfactory neuron axons (cranial nerve I) carry information to olfactory bulb. Capillary Lamina propria Basal cell layer includes Olfactory (Bowman’s) gland stem cells that replace olfactory neurons. Developing olfactory neuron Olfactory sensory neuron Supporting cell Olfactory cilia (dendrites) contain odorant receptors. Mucous layer: Odorant molecules must dissolve in this layer. © 2016 Pearson Education, Inc. Gustation • Closely linked to olfaction • Taste is a combination of five basic sensations: sweet, sour, salty, bitter, umami. • Additional taste sensations may be linked to TRP pathways, same as thermoreceptors and nocireceptors: minty, hot spicy © 2016 Pearson Education, Inc. Gustation • Taste receptor cells are non-neural epithelium. • Each taste cell is sensitive to only one taste. • Taste transduction – Gustducin • Humans and animals may develop specific hunger, such as salt appetite. © 2016 Pearson Education, Inc. Figure 10.14a Taste Taste Buds. Each taste bud is composed of taste cells joined near the apical surface with tight junctions. Taste ligands create Ca2+ signals that release serotonin or ATP. Sweet Umami Bitter Sour Tight junction Type I support cells Taste buds are located may sense salt when on the dorsal surface Na+ enters through of the tongue. channels. Taste pore Salt? (Based on Tomchik et al., J Presynaptic Neurosci 27(40): cell (III) 10840–10848, 2007.) ATP Serotonin Receptor cells (type II) Light micrograph of a taste bud Primary sensory neurons © 2016 Pearson Education, Inc. Figure 10.14b Taste Slide 1 Sweet, umami, Sour Taste Transduction. Each taste cell or bitter ligand H+ senses only one type of ligand. Gustducin GPCR ? Presynaptic cells sense sour taste (H+) apparently when H+ enters the cell through channels. Receptor cells with G protein–coupled H+ membrane receptors bind either bitter, Signal sweet, or umami ligands and release transduction ATP as a signal molecule. ? Ligands activate the taste cell. Ca2+ Various intracellular pathways Ca2+ are activated. Taste GPCR Family Ca2+ Sweet T1R2 + 3 subunits Ca2+ Ca2+ signal in the cytoplasm Umami T1R1 + 3 subunits triggers exocytosis or ATP formation. Bitter T2R Neurotransmitter or ATP is ATP released. Primary Primary sensory neuron fires gustatory and action potentials are neurons sent to the brain. © 2016 Pearson Education, Inc. Figure 10.14b Taste Slide 2 Sweet, umami, Sour Taste Transduction. Each taste cell or bitter ligand H+ senses only one type of ligand. Gustducin GPCR ? Presynaptic cells sense sour taste (H+) apparently when H+ enters the cell through channels. Receptor cells with G protein–coupled H+ membrane receptors bind either bitter, sweet, or umami ligands and release ATP as a signal molecule. Ligands activate the taste cell. Ca2+ Taste GPCR Family Ca2+ Sweet T1R2 + 3 subunits Umami T1R1 + 3 subunits Bitter T2R Primary gustatory neurons © 2016 Pearson Education, Inc. Figure 10.14b Taste Slide 3 Sweet, umami, Sour Taste Transduction. Each taste cell or bitter ligand H+ senses only one type of ligand. Gustducin GPCR ? Presynaptic cells sense sour taste (H+) apparently when H+ enters the cell through channels. Receptor cells with G protein–coupled H+ membrane receptors bind either bitter, Signal sweet, or umami ligands and release transduction ATP as a signal molecule. ? Ligands activate the taste cell. Ca2+ Various intracellular pathways are activated. Taste GPCR Family Ca2+ Sweet T1R2 + 3 subunits Umami T1R1 + 3 subunits Bitter T2R Primary gustatory neurons © 2016 Pearson Education, Inc. Figure 10.14b Taste Slide 4 Sweet, umami, Sour Taste Transduction. Each taste cell or bitter ligand H+ senses only one type of ligand. Gustducin GPCR ? Presynaptic cells sense sour taste (H+) apparently when H+ enters the cell through channels. Receptor cells with G protein–coupled H+ membrane receptors bind either bitter, Signal sweet, or umami ligands and release transduction ATP as a signal molecule. ? Ligands activate the taste cell. Ca2+ Various intracellular pathways Ca2+ are activated. Taste GPCR Family Ca2+ Sweet T1R2 + 3 subunits Ca2+ Ca2+ signal in the cytoplasm Umami T1R1 + 3 subunits triggers exocytosis or ATP formation. Bitter T2R ATP Primary gustatory neurons © 2016 Pearson Education, Inc. Figure 10.14b Taste Slide 5 Sweet, umami, Sour Taste Transduction. Each taste cell or bitter ligand H+ senses only one type of ligand. Gustducin GPCR ? Presynaptic cells sense sour taste (H+) apparently when H+ enters the cell through channels. Receptor cells with G protein–coupled H+ membrane receptors bind either bitter, Signal sweet, or umami ligands and release transduction ATP as a signal molecule. ? Ligands activate the taste cell. Ca2+ Various intracellular pathways Ca2+ are activated. Taste GPCR Family Ca2+ Sweet T1R2 + 3 subunits Ca2+ Ca2+ signal in the cytoplasm Umami T1R1 + 3 subunits triggers exocytosis or ATP formation. Bitter T2R Neurotransmitter or ATP is ATP released. Primary gustatory neurons © 2016 Pearson Education, Inc. Figure 10.14b Taste Slide 6 Sweet, umami, Sour Taste Transduction. Each taste cell or bitter ligand H+ senses only one type of ligand. Gustducin GPCR ? Presynaptic cells sense sour taste (H+) apparently when H+ enters the cell through channels. Receptor cells with G protein–coupled H+ membrane receptors bind either bitter, Signal sweet, or umami ligands and release transduction ATP as a signal molecule. ? Ligands activate the taste cell. Ca2+ Various intracellular pathways Ca2+ are activated. Taste GPCR Family Ca2+ Sweet T1R2 + 3 subunits Ca2+ Ca2+ signal in the cytoplasm Umami T1R1 + 3 subunits triggers exocytosis or ATP formation. Bitter T2R Neurotransmitter or ATP is ATP released. Primary Primary sensory neuron fires gustatory and action potentials are neurons sent to the brain. © 2016 Pearson Education, Inc. The Ear: Hearing • Perception of energy carried by sound waves • Frequency is translated into pitch • Loudness is an interpretation of intensity, a function of wave amplitude © 2016 Pearson Education, Inc. Figure 10.15 The Ear The Ear EXTERNAL EAR MIDDLE EAR INNER EAR The pinna The oval window and the round window separate directs sound the fluid-filled inner ear from the air-filled middle ear. waves into the ear. Malleus Semicircular Oval Incus canals window Nerves Stapes Cochlea Vestibular apparatus Ear canal Tympanic Round membrane window To pharynx Eustachian tube © 2016 Pearson Education, Inc. Figure 10.16a Sound waves Sound waves alternate peaks of compressed air and valleys where the air is less compressed. Wavelength Tuning fork © 2016 Pearson Education, Inc. Figure 10.16b Sound waves Sound waves are distinguished by their frequency, measured in hertz (Hz), and amplitude, measured in decibels (dB). (1) 1 Wavelength Intensity Amplitude (dB) (dB) 0 0.25 Time (sec) (2) FIGURE QUESTIONS Intensity Amplitude 1. What are the frequencies of the (dB) (dB) sound waves in graphs (1) and (2) in Hz (waves/second)? 2. Which set of sound waves would be interpreted as having lower pitch? 0 0.25 Time (sec) © 2016 Pearson Education, Inc. Sound Transduction • Sound waves to mechanical vibrations when striking the tympanic membrane (ear drum) • Three middle bones vibrate and transfer to membrane in oval window • Vibrations generate fluid waves in the cochlea • Hair cells bend in the cochlea and ion channels open • Action potential travel to the brain © 2016 Pearson Education, Inc. Figure 10.17 Sound transmission through the ear Slide 1 Sound waves The sound The stapes is The fluid waves push on Neurotransmitter Energy from the waves strike the wave energy is attached to the the flexible membranes release onto sensory transfers across the tympanic transferred to membrane of the oval of the cochlear duct. Hair neurons creates action cochlear duct into the membrane the three bones window. Vibrations of cells bend and ion potentials that travel tympanic duct and is and become of the middle the oval window channels open, creating an through the cochlear dissipated back into vibrations. ear, which create fluid waves electrical signal that alters nerve to the brain. the middle ear at the vibrate. within the cochlea. neurotransmitter release. round window. Cochlear nerve Incus Oval Ear canal Malleus
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