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Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell.

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Presentation on theme: "Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell."— Presentation transcript:

1 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Chapter 50 Sensory and Motor Mechanisms

2 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: Sensing and Acting Detection/processing of sensory information and generation of motor output provides physiological basis for all animal activity – Bats use sonar to detect their prey – Moths, a common prey for bats, can detect the bats sonar and attempt to flee – Both organisms have complex sensory systems that facilitate survival that include diverse mechanisms that sense stimuli and generate appropriate movement

3 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 50.1: Sensory receptors transduce stimulus energy and transmit signals to the central nervous system All stimuli represent forms of energy Sensation involves converting energy into change in membrane potential of sensory receptors – Sensations are action potentials that reach brain via sensory neurons Brain interprets sensations, giving perception of stimuli

4 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sensory Pathways Stimulation of stretch receptor in crayfish is first step in sensory pathway 4 functions of sensory pathways Bending activates stretch receptor in muscle Stretch receptor converts muscle deflection to change in membrane potential in cell body (receptor potential) Receptor potential triggers action potentials that travel along axon of stretch receptor Processing of action potentials that reach brain via axon of stretch receptor produces perception of body bending

5 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sensory Reception and Transduction sensory receptionSensations/perceptions begin with sensory reception (detection of stimuli by sensory receptors) – Sensory receptors – Sensory receptors (usually specialized neurons/epithelial cells that respond to specific stimuli) detect stimuli outside (heat/light/pressure/ chemicals) and inside body (blood pressure/body position) Most are specialized neurons/epithelial cells Sensory transduction receptor potentialSensory transduction is conversion of physical/chemical stimulus energy into change in membrane potential of sensory receptor (receptor potential) – Receptor potential are graded potentials (magnitude varies w/strength of stimulus) – Many sensory receptors are very sensitive (detect smallest physical unit of stimulus, light photon of light by light receptors)

6 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Transmission transmission transmissionAfter energy has been transduced into receptor potential, some sensory cells whose axons extend into CNS generate transmission of action potentials (nerve impulses) to CNS transmission – Sensory cells without axons release neurotransmitters at synapses with sensory neurons Larger receptor potentials generate more frequent action potentials if receptor is sensory neuron (more neurotransmitter released if not, increasing production of action potentials by postsynaptic neuron) IntegrationIntegration (processing of sensory information) of sensory information begins when information is received – Some receptor potentials are integrated through summation

7 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Perception PerceptionsPerceptions are brains construction of stimuli (color, smells, sounds, tastes) Stimuli from different sensory receptors travel as action potentials along different neural pathways Brain distinguishes stimuli from different receptors by area in brain where action potentials arrive

8 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Amplification and Adaptation Transduction of stimuli by sensory receptors subject to two types of modifications – Amplification – Amplification is strengthening of stimulus energy by cells in sensory pathways to produce action potentials or release neurotransmitter at synapse w/sensory neuron neurotransmitter Often require signal transduction pathways involving second messengers Amplify signal strength through formation of many product molecules by single enzyme molecule May also take place in accessory structures of complex sense organ – Sensory adaptation – Sensory adaptation is decrease in responsiveness to continued stimulation (dont sense stimuli after while)

9 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 50-UN1 Stimulus Sensory receptor Stimulus Afferent neuron Sensory receptor cell Afferent neuron To CNS Neuro- transmitter Receptor protein for neuro- transmitter (a) Receptor is afferent neuron.Receptor(b) Receptor regulates afferent neuron.Receptor Stimulus leads to neuro- transmitter release

10 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Types of Sensory Receptors Based on energy transduced, sensory receptors fall into five categories – Mechanoreceptors – Chemoreceptors – Electromagnetic receptors – Thermoreceptors – Pain receptors

11 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Mechanoreceptors MechanoreceptorsMechanoreceptors sense physical deformation caused by stimuli such as touch, pressure, stretch, motion, sound – Bending/stretching of external structure (cilia) tension that alters permeability of ion channels membrane potential altered depolarization or hyperpolarization Sense of touch in mammals relies on mechanoreceptors that are dendrites of sensory neurons, often embedded in layers of connective tissue – Structure of connective tissue/location of receptors affect type of mechanical energy (light touch, vibration, strong pressure) that best stimulates them

12 Fig. 50-3 Connective tissue Heat Strong pressure/ Vibration Hair movement (like whiskers providing detailed information about nearby objects) Nerve Dermis Epidermis Hypodermis Gentle touch (Responds to light touch or vibration) Pain Cold Hair http://www.sumanasinc.com/webcontent/animations/content/skinreceptors.html

13 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chemoreceptors chemoreceptorsGeneral chemoreceptors transmit information about total solute concentration of solution Specific chemoreceptors respond to individual kinds of molecules (glucose/oxygen/carbon dioxide/amino acids) When stimulus molecule binds to chemoreceptor, initiates changes in ion permeability (becomes more or less permeable to ions) Antennae of male silkworm moth have very sensitive specific chemoreceptors

14 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Electromagnetic Receptors Electromagnetic receptorsElectromagnetic receptors detect electromagnetic radiation such as – Light (photoreceptors) – Electricity (electroreceptors of some fish/platypus to detect presence of prey) – Magnetism (Earths magnetic field for migration/ iron-containing magnetite) – Heat (infrared receptors of some snakes to detect body heat of prey)

15 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Thermoreceptors ThermoreceptorsThermoreceptors, which respond to heat or cold, help regulate body temperature by signaling both surface and body core temperature – Located in skin/anterior hypothalamus – Send information to bodys thermostat (posterior hypothalamus) Capsaicin (jalapeno/cayenne peppers) activates chemoreceptors AND thermoreceptors (why we think spicy food is hot) Mammals have at least 6 different thermoreceptors, each for particular temperature range

16 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Pain Receptors pain receptorsnociceptorsIn humans, pain receptors, or nociceptors, are class of naked dendrites in epidermis (some also associated w/other organs) Respond to excess heat (thermal), pressure (mechanical), or chemical stimuli (prostaglanins) released from damaged or inflamed tissues

17 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 50-UN2 Sensory receptors More receptors activated Low frequency of action potentials (b) Multiple receptors activated Fewer receptors activated (a) Single sensory receptor activated High frequency of action potentials Gentle pressure More pressure Gentle pressure Sensory receptor

18 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 50.2: The mechanoreceptors responsible for hearing and equilibrium detect moving fluid or settling particles Hearing and perception of body equilibrium (balance) are related in most animals Settling particles or moving fluid are detected by mechanoreceptors, produce receptor potentials

19 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sensing Gravity and Sound in Invertebrates statocysts Most invertebrates maintain equilibrium using sensory organs called statocysts statoliths Contain mechanoreceptors that detect movement of granules called statoliths (grains of sand/other dense granules) found in chamber surrounded by layerok of ciliated receptor cells Gravity causes statoliths to settle to low point in chamber, stimulating mechanoreceptors

20 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Many arthropods sense sounds with – Body hairs that vibrate in response to sound waves Hairs of different stiffnesses/lengths vibrate at different frequencies – Localized ears consisting of tympanic membrane receptor cells nerve impulses to brain

21 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Hearing and Equilibrium in Mammals Hearing In most terrestrial vertebrates, sensory organs for hearing and equilibrium are closely associated in ear Vibrating objects create percussion waves in air that cause tympanic membrane to vibrate – Hearing – Hearing: perception of sound in brain from vibration of air waves – Vibrations of moving air three bones of middle ear oval window on cochlea pressure waves in fluid in cochlea vestibular canal vibrates basilar membrane, bending its hair cells depolarizes membranes of mechanoreceptors action potentials to brain auditory nerve

22 Fig. 50-8a Auditory canal Eustachian tube (equalizes pressure between middle ear/ atmosphere) Pinna Tympanic membrane Oval window Round window Stapes Cochlea (hearing) Incus Malleus Semicircular canals (equilibrium) Auditory nerve to brain Skull bone Outer ear Middle ear Inner ear http://www.sumanasinc.com/webcontent/animations/content/soundtransduction.html

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24 Fig. 50-9 Hairs of hair cell Neuro- trans- mitter at synapse Sensory neuron More neuro- trans- mitter (a) No bending of hairs(b) Bending of hairs in one direction depolarization increases neurotransmitter released and frequency of action potentials to brain along auditory nerve (c) Bending of hairs in other direction hyperpolarization reduces neurotransmitter released and frequency of auditory nerve sensations Less neuro- trans- mitter Action potentials Membrane potential (mV) 0 –70 0 1 2 3 4 5 6 7 Time (sec) Signal –70 –50 Receptor potential Membrane potential (mV) 0 –70 0 1 2 3 4 5 6 7 Time (sec) –70 –50 Membrane potential (mV) 0 –70 0 1 2 3 4 5 6 7 Time (sec) –70 –50 Signal With each vibration, hairs bend when surrounding fluid moves Mechanoreceptors in hair cells respond by opening/closing ion channels in plasma membrane Each hair cell releases an excitatory neurotransmitter at synapse w/sensory neuron, which conducts action potential to CNS http://bcs.whfreeman.com/thelifewire/content/chp45/4502001.html

25 perilymphVibrations of stapes against oval window produce pressure waves in perilymph (fluid of cochlea) Waves travel to apex of cochlea through vestibular canal and back toward base through tympanic canal Energy in waves causes basilar membrane to vibrate, stimulating hair cells round windowFluid waves dissipate when they strike round window at end of tympanic canal Prevents reverberation within ear and prolonged sensation/ resets apparatus for next vibration http://highered.mcgraw-hill.com/sites/dl/free/0072421975/196644/sound_waves_cochlear.html

26 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ear conveys information about – Volume – Volume (amplitude/loudness of sound wave) Large-amplitude sound wave more vigorous vibration of basilar membrane greater bending of hairs on hair cells more action potentials – Pitch – Pitch (frequency of sound wave)

27 Cochlea distinguishes pitch because basilar membrane is not uniform along its length Variations in stiffness of basilar membrane along its length tunes specific regions to specific frequencies Relatively narrow and stiff at base near oval Wider and more flexible at apex Different frequencies of pressure waves cause different portions to vibrate, stimulating particular hair cells and sensory neurons that leads to excitation of specific auditory area of cerebral cortex Selective stimulation of hair cells perceived in brain as sound of certain pitch

28 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Equilibrium Several organs of inner ear detect body position and balance – In vestibule behind oval window Utriclesaccule otoliths Utricle/saccule contain calcium carbonate granules (otoliths) that allow us to detect gravity/linear movement (acceleration) – Otoliths press on hairs protruding into gel when you tilt your head deflection of hairs transformed into change in output of sensory neurons brain signaled of angle change

29 Fig. 50-11 Vestibular nerve Semicircular canals detect angular movement of head (each canal has swelling at base containing cluster of hair cells) Saccule both tell brain which way is up/inform it of bodys position or linear acceleration Utricle & Body movement Bending of hairs increases frequency of action potentials in sensory neurons in direct proportion to amount of rotational acceleration Hairs Cupula Hairs of hair cells project into gelatinous cap (cupula) When head starts or stops rotating, fluid in semicircular canals presses against cupula, bending the hairs Flow of fluid Axons Hair cells Vestibule

30 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Three semicircular canals, connected to utricle Contain fluid Allow us to detect angular acceleration (turning head) Each canal in different spatial plane, allowing us to detect motion in any direction Each canal has hair cells in single cluster cupulaHairs project into cupula (gelatinous cap) Motion deflects hairs impulse sent to brain

31 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Hearing and Equilibrium in Other Vertebrates Unlike mammals, fishes have only pair of inner ears near brain (no external opening/eardrum/cochlea) – Water vibrations/vibrations in air-filled swim bladder conducted through heads skeleton to pair of inner ears, setting otholiths in motion and stimulating hair cells lateral line systemMost fishes/aquatic amphibians also have lateral line system along both sides of their body – Contains mechanoreceptors with hair cells that detect and respond to low-frequency waves Terrestrial vertebrates ears main organ of hearing/ equilibrium

32 Fig. 50-12 Surrounding water Lateral line enables fish to monitor water currents (direction/velocity), pressure waves produced by moving objects, low-frequency sounds conducted through water Lateral line canal Epidermis Hair cell Cupula Axon Sensory hairs Scale Lateral nerve Opening of lateral line canal Segmental muscles Fish body wall Water flowing through system bends hair cells transduce energy into receptor potentials (depolarizes hair cells) action potentials conveyed to brain Supporting cell

33 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 50.3: The senses of taste and smell rely on similar sets of sensory receptors In terrestrial animals, chemoreceptors needed to detect specific chemicals in environment – Gustation tastants – Gustation (taste) is dependent on detection of chemicals (tastants) – Olfactionodorant – Olfaction (smell) is dependent on detection of odorant molecules – Chemicals must be dissolved to bind to proteins on plasma membrane No distinction between taste/smell in aquatic animals sensillaInsects taste receptors in sensory hairs (sensilla) located on feet/in mouth parts/are capable of smelling airborne odorants using olfactory hairs located in antennae

34 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Taste in Mammals taste budsIn humans, receptor cells for taste are modified epithelial cells organized into taste buds Five taste perceptions: sweet, sour, salty, bitter, and umami (elicited by glutamate) – Each type of taste can be detected in any region of tongue that has taste buds Each taste cell has only one type of receptor and detects tastants representing only one of five tastes When taste receptor is stimulated, signal transduced to sensory neuron

35 Fig. 50-13 G protein Binding initiates signal transduction path- Way involving G protein/phospholipase C Sugar molecule binds to receptor protein on sensory receptor cell Phospholipase C Tongue Sodium channel opened, allowing Na + to diffuse into taste receptor cell PIP 2 Phospholipase C activity generates second messenger IP 3 which binds to calcium channel in ER, opening it. Ca 2+, another second messenger flows into cytosol Na + Depolarization activates sensory neuron through process not fully understood IP 3 (second messenger) Sweet receptor ER Nucleus Taste pore SENSORY RECEPTOR CELL Ca 2+ (second messenger) IP 3 -gated calcium channel Sensory receptor cells Taste bud Sugar molecule Sensory neuron

36 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Smell in Humans Olfactory receptor cells are neurons (unlike gustation) that line upper portion of nasal cavity Binding of odorant molecules to receptors triggers signal transduction pathway, sending action potentials along axons extend directly to olfactory bulb of brain – >1000 genes code for membrane proteins that bind to specific classes of odorants/each receptor cell appears to expreess only one of those genes – Receptive ends contain cilia that extend into layer of mucus coating nasal cavity – Odorant diffuses into region binds to specific GPCR protein (odorant receptor/OR) on plasma membrane of olfactory cilia transduction cAMP production Na + /Ca 2+ channels open depolarization of membrane action potential

37 Fig. 50-15 Olfactory bulb Odorants Bone Epithelial cell Plasma membrane Odorant receptors Odorants Nasal cavity Brain Chemo- receptor Cilia Mucus Action potentials

38 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 50.4: Similar mechanisms underlie vision throughout the animal kingdom Many types of light detectors have evolved in the animal kingdom – Simple cluster of cells that detect direction and intensity of light – Complex organs that form images

39 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Vision in Invertebrates Most invertebrates have light-detecting organ ocellusOne of simplest is ocellus (eyecup or eyespot of planarians) – Light-sensitive photoreceptors determine direction of light/planaria moves away from source

40 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Two major types of image-forming eyes have evolved in invertebrates compound eyes – Image-forming compound eyes found in insects/crustaceans/ some polychaete worms ommatidia Consist of up to several thousand light detectors (ommatidia) Each has light-focusing lens Very effective at detecting movement Excellent color vision/some see UV range

41 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Single-lens eyesSingle-lens eyes found in some jellies/polychaetes, spiders, many mollusks – Work on camera-like principle: Iris changes diameter of pupil to control how much light enters focuses on layer of photoreceptors

42 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Vertebrate Visual System Structure of the Eye In vertebrates, eye detects color/light, but brain assembles information and perceives image Main parts of vertebrate eye – Scleracornea – Sclera: white outer layer, including cornea (transparent front/ lets light in/acts as fixed lens) – ChoroidIris pupil – Choroid: pigmented inner layer which includes Iris (colored portion of eye/regulates size of pupil) – Retina – Retina: innermost layer/has layers of neurons/photoreceptors – Lens – Lens: focuses light on retina – Optic diskblind spot – Optic disk: blind spot (no photoreceptors) in retina where optic nerve attaches to eye

43 Fig. 50-18 Optic nerve Fovea (center of visual field) Lens Vitreous humor Optic disk (blind spot) Central artery and vein of the retina Iris Retina ChoroidSclera Ciliary body Suspensory ligament Cornea Pupil Aqueous humor

44 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings lens ciliary bodyEye divided into two cavities separated by lens (transparent disk of protein used to focus by changing its shape) and ciliary body aqueous humor – Anterior cavity filled with watery aqueous humor Ciliary body produces aqueous humor Glaucoma Glaucoma: blockage of ducts that drains aqueous humor, increasing pressure that can damage optic nerve/cause blindness vitreous humor – Posterior cavity filled with jellylike vitreous humor Most of eyes volume

45 Fig. 50-19 Ciliary muscles relax. Retina Choroid (b) Distance vision (a) Near vision (accommodation) Suspensory ligaments pull against lens. Lens becomes flatter. Lens becomes thicker and rounder. Ciliary muscles contract. Suspensory ligaments relax.

46 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Human retina contains two types of photoreceptors – Rods – Rods: light-sensitive but dont distinguish colors Enable us to see at night Humans have ~125 million fovea In humans, concentrated in fovea (center of visual field- ~150,000 cones/mm 2 ) – Cones – Cones: distinguish colors but are not as sensitive to light 3 types, each w/different sensitivity across visual spectrum Humans have ~6 million In humans, more concentrated around periphery of retina

47 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sensory Transduction in the Eye retinal opsinEach rod/cone contains visual pigments consisting of light- absorbing molecule (retinal, derivative of vitamin A) bonded to protein (opsin) rhodopsinRods contain pigment rhodopsin (retinal combined w/specific opsin), which changes shape when absorbing light Absorption of destabilizes/activates rhodopsin (turns it purple to yellow, called bleaching)

48 Fig. 50-21 Light Sodium channel Inactive rhodopsin Active rhodopsin Phosphodiesterase Disk membrane INSIDE OF DISK Plasma membrane EXTRACELLULAR FLUID Light Transducin CYTOSOL GMP cGMP Na + Dark Time Hyper- polarization 0 Membrane potential (mV) –40 –70 1. Light isomerizes retinal, activating rhodopsin 2. Active rhodopsin activates G protein (transducin) 3. Transducin activates phosphodiesterase (activates G protein) 4. Activated phosphodiesterase detaches cGMP from Na + channels in plasma membrane by hydrolyzing cGMP to GMP 5. Na + channels close when cGMP detaches. Membranes permeability to Na + decreases, rod hyperpolarizes (response in rods saturated). Remains bleached in very bright light and takes minutes to regain full responsiveness once light decreases (rhodopsin returns to inactive form when enzymes convert retinal back to cis form)

49 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings photopsinsIn humans, three pigments (photopsins) detect light of different wave lengths – Formed from binding of retinal to three distinct opsin proteins – Absorption spectrums of visual pigments (red, green, blue) overlap, so brains perception of intermediate hues depends on different stimulation of two or more classes of cones – Abnormal color vision typically results from alterations in genes for one or more photopsin protein Genes for red/green on X chromosome

50 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Processing of Visual Information Processing of visual information begins in retina, where absorption of light triggers signal transduction pathway bipolar cells – In dark, rods/cones are depolarized and continually release neurotransmitter glutamate into synapses with neurons (bipolar cells) Some bipolar cells hyperpolarized/others depolarized in response to glutamate Response determined by glutamate receptor present on surface at synapse – In the light, rods/cones hyperpolarize, shutting off release of glutamate (release less neurotransmitter) Depolarized bipolar cells hyperpolarize/hyperpolarized one depolarize

51 Fig. 50-22 Light Responses Rod depolarized Rhodopsin inactive Rhodopsin active Dark Responses Na + channels open Na + channels closed Glutamate released Bipolar cell either depolarized or hyperpolarized Rod hyperpolarized No glutamate released Bipolar cell either hyperpolarized or depolarized

52 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Three other types of neurons contribute to information processing in retina – Ganglion cells – Ganglion cells transmit signals from bipolar cells to brain along optic nerves (made of ganglion cell axons) – Horizontal cellsamacrine cells – Horizontal cells/amacrine cells help integrate visual information before it is sent to brain lateral inhibitionInteraction among different cells results in lateral inhibition – When horizontal cells illuminated, they inhibit more distant photoreceptors/bipolar cells not illuminated – Light spot appears light/dark surroundings even darker – Form of integration sharpens edges/enhances contrast of image http://www.sumanasinc.com/webcontent/animations/content/receptivefields.html

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54 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Many rods/cones information sent to single ganglion cell – Reception field – Reception field (part of visual filed to which ganglion can respond) Smaller reception field = sharper image (more precise information going to retina) – Ganglion cells of fovea very small, high visual acuity

55 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings optic chiasmOptic nerves (each contain ~million axons) meet at optic chiasm near cerebral cortex – Here, axons from left visual field (from both left/right eye) converge and travel to right side of brain – Axons from right visual field travel to left side of brain lateral geniculate nucleiMost ganglion cell axons lead to lateral geniculate nuclei primary visual cortex – Relays information to primary visual cortex in cerebrum – Several integrating centers in cerebral cortex are active in creating visual perceptions

56 Neural Pathways for Vision Fig. 50-24 Neural Pathways for Vision Right visual field Right eye Left visual field Left eye Optic chiasm Primary visual cortex Lateral geniculate nucleus Optic nerve

57 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Evolution of Visual Perception Photoreceptors in diverse animals likely originated in earliest bilateral animals – All photoreceptors contain similar pigment molecules – Many invertebrates/vertebrates share genes associated w/embryonic development of photoreceptors MelanopsinMelanopsin (pigment in ganglion cells) may play role in circadian rhythms in humans

58 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 50.5: The physical interaction of protein filaments is required for muscle function Muscle activity is response to input from nervous system Microfilament movements bring about contraction – Extension occurs only passively

59 Fig. 50-25 Bundle of muscle fibers TEM Muscle Muscle consists of bundle of long fibers running parallel to length of muscle Thick filaments Thick filaments are composed of myosin staggered arrays of myosin molecules M line Single muscle fiber Single muscle fiber is single cell w/multiple nuclei Nuclei Z lines Plasma membrane Myofibril Muscle fiber contains bundle of smaller Myofibril arranged longitudinally. Each myofibril is composed of thin filaments and thick filaments. Functional (contractile) unit of muscle Borders lined up in adjacent myofibrils and contribute to striations Z lines Thin filaments attached at Z lines and project toward center of sarcomere, while thick filaments M lines attached at M lines centered in sarcomere At rest, thick/thin filaments only partially overlap (near edge, only thin/center only thick)Sarcomere Z line Thin filaments Thin filaments consist of two strands actin of actin and two strands of regulatory protein coiled around one another Sarcomere 0.5 µm Vertebrate Skeletal Muscle Vertebrate Skeletal Muscle characterized by hierarchy of smaller and smaller units striated muscle Skeletal muscle also called striated muscle because regular arrangement of myofilaments creates pattern of light/dark bands

60 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Sliding-Filament Model of Muscle Contraction sliding-filament modelAccording to sliding-filament model, filaments slide past each other longitudinally, producing more overlap between actin of thin/myosin of thick filaments, which never change length – Head of myosin molecule energized by ATP binds to actin filament, forming cross-bridge and pulling thin filament toward center of sarcomere Each of ~350 heads of thick filament forms/reforms ~5 cross- bridges/sec Energy for repeated contractions comes from – Creatine phosphate transfers phosphate group to ADP to synthesize additional ATP (sustained contractions for ~15 sec) – Glycogen glucose by glycolysis (~1 minute of sustained contraction)/aerobic respiration (up to hour of sustained contractions) generate ATP needed to sustain muscle contraction http://uccpbank.k12hsn.org/courses/APBioII/course%20files/multimedia/lesson55/lessonp.html

61 Fig. 50-26 Z Relaxed muscle M Z Fully contracted muscle Contracting muscle Sarcomere 0.5 µm Contracted Sarcomere http://www.rattlerscience.com/life/classes/apbiology/documents/ Unit%204/49_Lectures_PPT/media/sarcomere_shortening_2.swf

62 Fig. 50-27-4 Thin filaments ATP Myosin head (low- energy configuration Thick filament 1. Starting here, myosin head bound to ATP/in low-energy conformation Thin filament Thick filament Actin Myosin head (high- energy configuration 3. Myosin head binds to actin, forming cross-bridge 2. Myosin head hydrolyzes ATP ATD/P i /in high- energy configuration Myosin binding sites ADP P i Cross-bridge ADP P i Myosin head (low- energy configuration 4. Releasing ADP/P i, myosin returns to low-energy configuration, sliding the thin filament 5. Binding of new molecule of ATP releases myosin head from actin, new cycle begins Thin filament moves toward center of sarcomere. ATP ADP P i +

63 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Role of Calcium and Regulatory Proteins Skeletal muscle fiber contracts only when stimulated by motor neuron tropomyosinWhen muscle is at rest, myosin-binding sites on thin filament are blocked by regulatory protein tropomyosin, preventing actin/myosin from interacting

64 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings For muscle fiber to contract, myosin-binding sites must be uncovered troponin complex – Occurs when calcium ions (Ca 2+ ) bind to set of regulatory proteins (troponin complex) – Actin strands shift position and expose myosin-binding sites on thin filament – Muscle fiber contracts when concentration of Ca 2+ is high; muscle fiber contraction stops when concentration of Ca 2+ is low http://www.rattlerscience.com/life/classes/apbiology/documents/Unit%204/49_Lectures_PPT/media/myofilament.swf http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter47/breakdown_of_atp_and_cross- bridge_movement_during_muscle_contraction.html

65 Fig. 50-29a Sarcomere Ca 2+ released from SR Synaptic terminal T tubule Motor neuron axon Plasma membrane of muscle fiber Sarcoplasmic reticulum (SR) Myofibril Mitochondrion

66 Fig. 50-29b Ca 2+ ATPase pump Synaptic terminal of motor neuron Synaptic cleft T (transverse) Tubule Plasma membrane Ca 2+ CYTOSOL SR ATP ADP P i ACh Stimulus leading to contraction of muscle fiber is action potential in motor neuron that makes synapse with muscle fiber 1. Acetylcholine released at synaptic terminal of motor neuron diffuses across synaptic cleft/binds to receptor proteins on muscle fibers plasma membrane depolarization action potential 2. Action potential propagated along plasma membrane/down T tubules 3. Action potential triggers Ca 2+ release from sarcoplasmic reticulum (SR) 4. Calcium ions bind to troponin in thin filament; myosin-binding sites exposed 5. Myosin cross-bridges alternately attach to actin/detach, pulling thin filament toward center of sarcomere; ATP powers sliding of filaments 6. Cytosolic Ca 2+ removed by active transport into SR after action potential ends 7. Tropomyosin blockage of myosin- binding site is restored; contraction ends/muscle fiber relaxes http://highered.mcgraw- hill.com/sites/9834092339/student_view0/chapter43/action_potentials_and_muscle_contraction.html http://bcs.whfreeman.com/thelifewire/content/chp47/4702001.html

67 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Diseases causing paralysis – Amyotrophic lateral sclerosis (ALS), formerly called Lou Gehrigs disease Interferes with excitation of skeletal muscle fibers Usually fatal – Myasthenia gravis Autoimmune disease that attacks acetylcholine receptors on muscle fibers As number of receptors decreases, synaptic transmission between motor neurons/muscle fibers declines Treatments exist for this disease

68 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Nervous Control of Muscle Tension Contraction of whole muscle is graded (extent/strength of its contraction can be voluntarily altered) Two basic mechanisms by which nervous system produces graded contractions – Varying number of fibers that contract – Varying rate at which fibers are stimulated

69 Fig. 50-30 Spinal cord Motor neuron cell body Motor neuron axon Each branched motor neuron may form synapses w/many muscle fibers Nerve Muscle Muscle fibers Each muscle fiber controlled by only one motor neuron Synaptic terminals Tendon Motor unit 1 Motor Motor unit consists of single motor unit 2 neuron/all muscle fibers it controls

70 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings When motor neuron produces action potential, all muscle fibers in its motor unit contract as group – Strength of resulting contraction depends on how many muscle fibers motor neuron controls – Nervous system regulates strength of contraction by determining how many motor units are activated recruitment – Force developed by muscle progressively increases (contraction stronger) as more motor neurons controlling muscle are activated (recruitment) Some muscles always partially contracted – To prevent fatigue, nervous system alternates activation among motor units, reducing length of time any one set of fibers is contracted

71 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Gradation also achieved by varying rate of muscle fiber stimulation – Twitch results from single action potential in motor neuron (lasts ~100msec) – If second action potential arrives before muscle fiber completely relaxed, two twitches add up, resulting in greater tension – More rapidly delivered action potentials produce graded contraction by summation – Tetanus – Tetanus is state of smooth and sustained contraction produced when motor neurons deliver volley of action potentials (not jerky like individual twitches)/muscle fiber cannot relax at all between stimuli

72 Fig. 50-31 Summation of two twitches Tetanus Single twitch Time Tension Pair of action potentials Single action potential Dashed lines show tension that would have developed if only first action potential occurred Series of action potentials at high frequency

73 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Types of Skeletal Muscle Fibers Skeletal muscle fibers can be classified – As oxidative or glycolytic fibers, by source of ATP – As fast-twitch or slow-twitch fibers, by speed of muscle contraction

74 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Oxidative and Glycolytic Fibers Oxidative fibersOxidative fibers use aerobic respiration to generate ATP (dark meat in chicken) myoglobin – Have many mitochondria, rich blood supply, and much myoglobin (protein that binds oxygen more tightly than hemoglobin does) Glycolytic fibersGlycolytic fibers use glycolysis as primary source of ATP (light meat in chicken) – Have larger diameter, less myoglobin, fatigue much more readily

75 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fast-Twitch and Slow-Twitch Fibers Muscle fibers vary in speed with which they contract Slow-twitch fibersSlow-twitch fibers contract more slowly, but sustain longer contractions (~5x as long) – All are oxidative – Often found in muscles that maintain posture Fast-twitch fibersFast-twitch fibers contract more rapidly (2-3x faster), but sustain shorter contractions – Can be either glycolytic or oxidative – Used for brief, rapid, powerful contractions Most skeletal muscles contain both in varying ratios

76 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Other Types of Muscle In addition to skeletal muscle, vertebrates have – Cardiac muscle – Cardiac muscle (only in heart) consists of striated cells Have ion channels in plasma membrane that cause rhythmic depolarizations, triggering action potentials without neural input (unlike skeletal muscle fibers) intercalated disks Plasma membranes of adjacent cardiac muscle cells interlock at intercalated disks that provide direct electrical coupling between cells – Action potential generated by specialized cells in one part of heart spread to all other cardiac muscle cells, causing whole heart to contract – Long refractory period prevents summation and tetanus

77 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings – Smooth muscle – Smooth muscle (mainly in walls of hollow organs) Actin/myosin filaments not regularly arrayed along length of cell, so no striations Contractions are relatively slow – May be initiated by muscles themselves, without neural input (electrically coupled to one another) – May also be caused by stimulation from neurons in autonomic nervous system http://bcs.whfreeman.com/thelifewire/content/chp47/4702002.html

78 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 50.6: Skeletal systems transform muscle contraction into locomotion Skeletal muscles are attached in antagonistic pairs, with each member of pair working against other Skeleton provides rigid structure to which muscles attach Skeletons function in support (maintains shape), protection, and movement

79 Fig. 50-32 GrasshopperHuman Biceps contracts Triceps contracts Forearm extends Biceps relaxes Triceps relaxes Forearm flexes Tibia flexes Tibia extends Flexor muscle relaxes Flexor muscle contracts Extensor muscle contracts Extensor muscle relaxes

80 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Types of Skeletal Systems Three main types of skeletons are – Hydrostatic skeletons (lack hard parts) – Exoskeletons (external hard parts) – Endoskeletons (internal hard parts)

81 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Hydrostatic Skeletons Hydrostatic skeletonHydrostatic skeleton consists of fluid held under pressure in closed body compartment Main type of skeleton in most cnidarians, flatworms, nematodes, annelids peristalsis – Annelids use their hydrostatic skeleton for peristalsis (type of movement on land produced by rhythmic waves of muscle contractions) Well suited for aquatic life, cushion internal organs from shocks, provide support for crawling/burrowing in terrestrial animals Cannot support terrestrial activities when body held off ground (walking, running) http://uccpbank.k12hsn.org/courses/APBioII/course%20files/multimedia/lesson54/lessonp.html

82 Fig. 50-33 Circular muscle contracted Circular muscle relaxed Longitudinal muscle relaxed (extended) Longitudinal muscle contracted Bristles Longitudinal muscles contracted/circular muscles relaxed making body Segments at head/rear short/thick and anchored to ground. Other segments thin/elongated (circular muscles contracted/ longitudinal muscles relaxed) Head moves forward because circular muscles in head segments have contracted. Segments behind head/at read now thick/anchored, preventing worm from slipping backward. Head segments thick again/anchored in new positions. Rear segments Released hold on ground/pulled forward. Head end

83 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Exoskeletons ExoskeletonExoskeleton is hard encasement deposited on surface of animal and found in – Most mollusks (calcium carbonate shell secreted by mantle) cuticle – Arthropods (made of cuticle secreted by epidermis, can be strong/flexible, polysaccharide chitin is often found in cuticle)

84 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Endoskeletons EndoskeletonEndoskeleton consists of hard supporting elements, such as bones, embedded within animals body and are found in – Sponges – Echinoderms (hard plates composed of magnesium carbonate/calcium carbonate crystals called ossicles beneath skin) – Chordates (consists of cartilage, bone) Bones reinforced by inorganic material/softer fibers made of protein Mammalian skeleton has >200 bones, some fused; others connected at joints by ligaments that allow freedom of movement

85 Fig. 50-34 Examples of joints Humerus Ball-and-socket joint Radius Scapula Head of humerus Ulna Hinge joint Ulna Pivot joint Skull Shoulder girdle Rib Sternum Clavicle Scapula Vertebra Humerus Phalanges Radius Pelvic girdle Ulna Carpals Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges 1 1 2 3 3 2

86 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Size and Scale of Skeletons Animals body structure must support its size – Body posture (position of legs relative to main body) more important in support body weight than leg size relative to body size – Size of animals body scales with volume (function of n 3 ), while support for that body scales with cross-sectional area of legs (function of n 2 ) – As objects get larger, size (n 3 ) increases faster than cross-sectional area (n 2 ); this is principle of scaling

87 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The skeletons of small and large animals have different proportions because of the principle of scaling In mammals and birds, the position of legs relative to the body is very important in determining how much weight the legs can bear

88 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Types of Locomotion locomotionMost animals are capable of locomotion (active travel from place to place) to search for food, escaping from danger, finding mate In locomotion, energy is expended to overcome friction and gravity

89 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Swimming In water, friction is bigger problem than gravity Fast swimmers usually have streamlined shape to minimize friction Animals swim in diverse ways – Paddling with their legs as oars – Jet propulsion – Undulating their body and tail from side to side, or up and down

90 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Locomotion on Land Walking, running, hopping, or crawling on land requires animal to support itself and move against gravity – Air poses little resistance (up to moderate speeds) – Powerful muscles (must overcome inertia by accelerating from standing start, must propel/keep from falling down)/strong skeletal support important Diverse adaptations for locomotion on land have evolved in vertebrates Maintain balance Energy to overcome friction problem w/crawling

91 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Flying Flight requires that wings develop enough lift to overcome downward force of gravity – Wing shape is key – All types of wings are airfoils (structures whose shape alters air currents to help object stay afloat) Many flying animals have adaptations that reduce body mass – For example, birds lack teeth/urinary bladder and have relatively large bones w/air-filled spaces to lessen weight

92 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Energy Costs of Locomotion Energy cost of locomotion – Depends on mode of locomotion/environment Running expends more energy to overcome gravity Swimming most energy-efficient (if animal specialized for it) Flying uses more energy than swimming/running Larger animals more efficient than smaller ones specialized for same mode of locomotion – Can be estimated by rate of oxygen consumption or carbon dioxide production – Energy in food used for locomotion not available for other activities (growth/reproduction) Structural/behavioral adaptations that maximize efficiency of locomotion increase evolutionary fitness of organism

93 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings You should now be able to: 1.Distinguish between the following pairs of terms: sensation/perception; sensory transduction/receptor potential; tastants/odorants; rod/cone cells; oxidative/glycolytic muscle fibers; slow-twitch/fast-twitch muscle fibers; endoskeleton/exoskeleton 2.List the five categories of sensory receptors and explain the energy transduced by each type 3.Explain the role of mechanoreceptors in hearing and balance 4.Give the function of each structure using a diagram of the human ear 5.Explain the basis of the sensory discrimination of human smell 6.Identify and give the function of each structure using a diagram of the vertebrate eye 7.Identify the components of a skeletal muscle cell using a diagram 8.Explain the sliding-filament model of muscle contraction 9.Explain how a skeleton combines with an antagonistic muscle arrangement to provide a mechanism for movement


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