1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings http://www.youtube.com/watch?v=SCasruJT- DU action potential video (review)http://www.youtube.com/watch?v=SCasruJT- DU

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 49 Types of Sensory Receptors Based on the energy they transduce, sensory receptors fall into five categories – Mechanoreceptors – Chemoreceptors – Electromagnetic receptors – Thermoreceptors – Pain receptors

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The mammalian sense of touch – Relies on mechanoreceptors that are the dendrites of sensory neurons Figure 49.3 Heat Light touch Pain Cold Hair Nerve Connective tissue Hair movement Strong pressure Dermis Epidermis

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exploring the structure of the human ear Figure 49.8 Pinna Auditory canal Eustachian tube Tympanic membrane Stapes Incus Malleus Skull bones Semicircular canals Auditory nerve, to brain Cochlea Tympanic membrane Oval window Eustachian tube Round window Vestibular canal Tympanic canal Auditory nerve Bone Cochlear duct Hair cells Tectorial membrane Basilar membrane To auditory nerve Axons of sensory neurons 1 Overview of ear structure 2 The middle ear and inner ear 4 The organ of Corti 3 The cochlea Organ of Corti Outer ear Middle ear Inner ear

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vibrations of the ear bones and oval window create pressure waves in the fluid in the cochlea – That travel through the vestibular canal and ultimately strike the round window Figure 49.9 Cochlea Stapes Oval window Apex Axons of sensory neurons Round window Basilar membrane Tympanic canal Base Vestibular canal Perilymph

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The cochlea can distinguish pitch Because the basilar membrane is not uniform along its length Test your hearing: http://video.google.com/videosearch?q=hearing+test&hl=en&sitesearch= http://video.google.com/videosearch?q=hearing+test&hl=en&sitesearch Cochlea (uncoiled) Basilar membrane Apex (wide and flexible) Base (narrow and stiff) 500 Hz (low pitch) 1 kHz 2 kHz 4 kHz 8 kHz 16 kHz (high pitch) Frequency producing maximum vibration Figure 49.10

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Taste pore Sugar molecule Sensory receptor cells Sensory neuron Taste bud Tongue G protein Adenylyl cyclase —Ca 2 + ATP cAMP Protein kinase A Sugar Sugar receptor SENSORY RECEPTOR CELL Synaptic vesicle K+K+ Neurotransmitter Sensory neuron Taste Transduction in taste receptors – Occurs by several mechanisms Figure 49.14 4The decrease in the membrane’s permeability to K + depolarizes the membrane. 5Depolarization opens voltage-gated calcium ion (Ca 2+ ) channels, and Ca 2+ diffuses into the receptor cell. 6The increased Ca 2+ concentration causes synaptic vesicles to release neurotransmitter. 3Activated protein kinase A closes K + channels in the membrane. 2Binding initiates a signal transduction pathway involving cyclic AMP and protein kinase A. 1A sugar molecule binds to a receptor protein on the sensory receptor cell.

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Smell When odorant molecules bind to specific receptors – A signal transduction pathway is triggered, sending action potentials to the brain Brain Nasal cavity Odorant Odorant receptors Plasma membrane Odorant Cilia Chemoreceptor Epithelial cell Bone Olfactory bulb Action potentials Mucus Figure 49.15

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structure of the Eye The main parts of the vertebrate eye are – The sclera, which includes the cornea – The choroid, a pigmented layer – The iris, which regulates the pupil – The retina, which contains photoreceptors – The lens, which focuses light on the retina Ciliary body Iris Suspensory ligament Cornea Pupil Aqueous humor Lens Vitreous humor Optic disk (blind spot) Central artery and vein of the retina Optic nerve Fovea (center of visual field) Retina Choroid Sclera

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The structure of the vertebrate eye Figure 49.18 Ciliary body Iris Suspensory ligament Cornea Pupil Aqueous humor Lens Vitreous humor Optic disk (blind spot) Central artery and vein of the retina Optic nerve Fovea (center of visual field) Retina Choroid Sclera

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The human retina contains two types of photoreceptors – Rods are sensitive to light but do not distinguish colors – Cones distinguish colors but are not as sensitive

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings spot the sixes visual test http://video.google.com/videosearch?q=visual+test+sixes&hl=en&sitesearch= http://video.google.com/videosearch?q=visual+test+sixes&hl=en&sitesearch – Figure 49.24 Left visual field Right visual field Left eye Right eye Optic nerve Optic chiasm Lateral geniculate nucleus Primary visual cortex

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vertebrate Skeletal Muscle Vertebrate skeletal muscle – Is characterized by a hierarchy of smaller and smaller units Figure 49.28 Muscle Bundle of muscle fibers Single muscle fiber (cell) Plasma membrane Myofibril Light band Dark band Z line Sarcomere TEM 0.5  m I band A band I band M line Thick filaments (myosin) Thin filaments (actin) H zone Sarcomere Z line Nuclei

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sliding filament theory – The I band and the H zone shrink Figure 49.29a–c (a) Relaxed muscle fiber. In a relaxed muscle fiber, the I bands and H zone are relatively wide. (b) Contracting muscle fiber. During contraction, the thick and thin filaments slide past each other, reducing the width of the I bands and H zone and shortening the sarcomere. (c) Fully contracted muscle fiber. In a fully contracted muscle fiber, the sarcomere is shorter still. The thin filaments overlap, eliminating the H zone. The I bands disappear as the ends of the thick filaments contact the Z lines. 0.5  m Z H A Sarcomere

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Myosin-actin interactions underlying muscle fiber contraction Figure 49.30 Thick filament Thin filaments Thin filament ATP ADP P i Cross-bridge Myosin head (low- energy configuration) Myosin head (high- energy configuration) + Myosin head (low- energy configuration) Thin filament moves toward center of sarcomere. Thick filament Actin Cross-bridge binding site 1Starting here, the myosin head is bound to ATP and is in its low- energy confinguration. 2 The myosin head hydrolyzes ATP to ADP and inorganic phosphate ( I ) and is in its high-energy configuration. P 1The myosin head binds to actin, forming a cross- bridge. 3 4 Releasing ADP and ( i ), myosin relaxes to its low-energy configuration, sliding the thin filament. P 5 Binding of a new mole- cule of ATP releases the myosin head from actin, and a new cycle begins.

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings When a muscle is at rest – The myosin-binding sites on the thin filament are blocked by the regulatory protein tropomyosin Figure 49.31a Actin Tropomyosin Ca 2+ -binding sites Troponin complex (a) Myosin-binding sites blocked

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings http://www.youtube.com/watch?v=DK7Z-Z7kKEY http://www.youtube.com/watch?v=WRxsOMenNQM http://www.youtube.com/watch?v=ZscXOvDgCmQ Figure 49.31b Ca 2+ Myosin- binding site (b) Myosin-binding sites exposed

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The stimulus leading to the contraction of a skeletal muscle fiber – Is an action potential in a motor neuron that makes a synapse with the muscle fiber – Acetylcholine depolarizes – Ca++ released from sarcoplasmic reticulum – Ca++ binds to troponin/ tropomyosin complex exposing myosin binding sites Figure 49.32 Motor neuron axon Mitochondrion Synaptic terminal T tubule Sarcoplasmic reticulum Myofibril Plasma membrane of muscle fiber Sarcomere Ca 2+ released from sarcoplasmic reticulum

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ACh Synaptic terminal of motor neuron Synaptic cleft T TUBULE PLASMA MEMBRANE SR ADP CYTOSOL Ca 2  P2P2 Cytosolic Ca 2+ is removed by active transport into SR after action potential ends. 6 Review of contraction in a skeletal muscle fiber Figure 49.33 Acetylcholine (ACh) released by synaptic terminal diffuses across synaptic cleft and binds to receptor proteins on muscle fiber’s plasma membrane, triggering an action potential in muscle fiber. 1 Action potential is propa- gated along plasma membrane and down T tubules. 2 Action potential triggers Ca 2+ release from sarco- plasmic reticulum (SR). 3 Myosin cross-bridges alternately attach to actin and detach, pulling actin filaments toward center of sarcomere; ATP powers sliding of filaments. 5 Calcium ions bind to troponin; troponin changes shape, removing blocking action of tropomyosin; myosin-binding sites exposed. 4 Tropomyosin blockage of myosin- binding sites is restored; contraction ends, and muscle fiber relaxes. 7