24 The middle chamber of the fluid-filled cochlea contains hair cells. Figure 46-5 The middle chamber of the fluid-filled cochlea contains hair cells.CochleaAuditory nerveThree fluid- filled chambersTectorial membraneNeurons (to auditory nerve)Hair cellsHair cells are sandwiched between membranes.StereociliaTectorial membraneOuter hair cellsAxons of sensory neuronsInner hair cellsBasilar membrane24
251. Arrival of pressure wave bends stereocilia. Figure 46-3Hair cells have many stereocilia and one kinocilium.WHEN STEREOCILIA BEND, A SEQUENCE OF EVENTS RESULTS IN THE RELEASE OF NEUROTRANSMITTER.Kinocilium1. Arrival of pressure wave bends stereocilia.Pressure waveStereociliaPotassium channels joined by threadsK+2. Potassium channels open in response to bending.K+3. Membrane depolar-izes due to influx of K+.NucleusDepolarizationHair cellSynaptic vesicle4. Depolarization triggers inflow of calcium ions.Afferent sensory neuronCalcium channel5. Ca2+ causes synaptic vesicles to fuse with plasma membrane.Ca2+Ca2+Efferent sensory neuron6. Neurotransmitter is released and diffuses to afferent neuron.Neurotransmitter released into synapseAfferent neuron (to brain)25
26Sound-receptor cells depolarize in response to sound. Figure 46-2Sound-receptor cells depolarize in response to sound.Sound stimulusDepolarizedSound-receptor cells respond more strongly to louder sounds.Highest response occurs at a characteristic frequencyLouder soundSofter sound26
27Uncoiled cochlea (to show basilar membrane) Figure 46-6Semicircular canalsCochleaWide part of basilar membrane is flexible— vibrates in response to low frequenciesOval windowUncoiled cochlea (to show basilar membrane)500 Hz1 kHzBasilar membrane)Human Hearing ranges from 20 Hz to 20 kHz2 kHz4 kHzBase of cochlea (near oval window)16 kHzNarrow part of basilar membrane is stiff— vibrates in response to high frequencies27
34Responses to StimuliTactile SensesChemical SensesWave Senses
35Light: An Energy Waveform With Particle Properties Too wavelengthvioletbluegreenyelloworangerednmwavelength (nm)10-9 metermeter!
36Light: An Energy Waveform With Particle Properties Too wavelengthvisible spectrumnmwavelength (nm)10-9 metermeter!
37White light: all the colors humans can see at once
38Which side of our brains are we using? Which side of our brains are we using?
39Leaf Pigments Absorb Most Colors White LightGreen is reflected!Leaf Pigments Absorb Most Colors
40Light: An Energy Waveform With Particle Properties Too amplitudebrightnessintensityMany metric units for different purposesWe will use an easy-to-remember English unit: foot-candle0 fc = darkness100 fc = living room1,000 fc = CT winter day10,000 fc = June 21, noon, equator, 0 humidity
42Ommatidia are the functional units of insect eyes. Figure 46-7Ommatidia are the functional units of insect eyes. Ommatidia contain receptor cells that send axons to the CNS.OmmatidiaLensReceptor cellsAxons42
43Copyright Norton Presentation Manager Human vs Insect VisionCopyright Norton Presentation Manager
55Figure 46-8 55 The structure of the vertebrate eye. In the retina, cells are arranged in layers.Pigmented epitheliumGanglion cellsConnecting neuronsPhotoreceptor cellsScleraRetinaIrisDirection of lightPupilCorneaFoveaLensOptic nerve (to brain)Axons to optic nerve55
56Figure 46-9The Cephalopod EyeRetina (photoreceptors are on the inside surface)CorneaLensSensory nerves to brainThis “design” is “more intelligent” than that of mammals (humans) because it lacks the blind spot and maximizes light exposure to receptors56
59Rods and cones contain stacks of membranes. Figure 46-10Rods and cones contain stacks of membranes.Rhodopsin is a transmembrane protein complex.Opsin (protein component)Retinal (pigment)ConeRod0.5 µmRhodopsinLightLightThe retinal molecule inside rhodopsin changes shape when retinal absorbs light.trans conformation (activated)cis conformation (inactive)OpsinOpsinLight59
60The disk of a photoreceptor cell (a rod) before stimulation Figure 46-11The disk of a photoreceptor cell (a rod) before stimulationcGMP-gated sodium channel (open)RhodopsinGDPcGMPcisTransducin (inactive)PhosphodiesterasePlasma membrane of rodDisk membraneThe same disk after stimulation (light)cGMP-gated sodium channel (closed)Rhodopsin (activated)GTPtransLack of Na+ current hyperpolarizes membraneTransducin (activated)Light60
70Colors indicate protein subunits Figure 46-21Myosin headColors indicate protein subunitsATP binding siteActin binding site
71CHANGES IN THE CONFORMATION OF THE MYOSIN HEAD PRODUCE MOVEMENT. Figure 46-22CHANGES IN THE CONFORMATION OF THE MYOSIN HEAD PRODUCE MOVEMENT.1. ATP bound to myosin head. Head releases from thin filament.Myosin head of thick filamentActin in thin filament4. ADP released. Cycle is ready to repeat.2. ATP hydrolized. Head pivots, binds to new actin subunit.3. Pi released. Head pivots, moves filament (power stroke).
72Thick filaments (myosin) Thin filaments (actin) Figure 46-24Motor neuronMuscle cellHOW DO ACTION POTENTIALS TRIGGER MUSCLE CONTRACTION?Motor neuronAction potential1. Action potential arrives; acetylcholine (Ach) is released.AChACh receptorAction potentials2. ACh binds to ACh receptors on the muscle cell, triggering depolari-zation that leads to action potential.3. Action potentials propagate across muscle cell’s plasma membrane and into interior of cell via T tubules.T tubule4. Proteins in T tubules open Ca2+ channels in sarcoplasmic reticulum.Sarcoplasmic reticulum5. Ca2+ is released from sarcoplasmic reticulum. Sarcomeres contract when troponin and tropomyosin move in response to Ca2+ and expose actin binding sites in the thin filaments (see Figure 46.23).Thick filaments (myosin)Thin filaments (actin)Ca2+ ions