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Muscles, Locomotion & Sensation (Ch. 50)

Muscles, Locomotion & Sensation (Ch. 50). Overview of information processing by nervous systems. Sensory input. Integration. Sensor. Motor output. Effector. Peripheral nervous system (PNS). Central nervous system (CNS). Animal Locomotion. What are the advantages of locomotion?.

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Muscles, Locomotion & Sensation (Ch. 50)

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  1. Muscles, Locomotion & Sensation (Ch. 50)

  2. Overview of information processing by nervous systems Sensory input Integration Sensor Motor output Effector Peripheral nervoussystem (PNS) Central nervoussystem (CNS)

  3. Animal Locomotion What are the advantages of locomotion? sessile motile

  4. Lots of ways to get around…

  5. Lots of ways to get around… mollusk mammal bird reptile

  6. Lots of ways to get around… bird arthropod mammal bird

  7. Muscle involuntary, striatedauto-rhythmic voluntary, striated heart moves bone multi-nucleated involuntary, non-striated digestive systemarteries, veins evolved first

  8. All cells have a fine network of actin and myosin fibers that contribute to cellular movement. But only muscle cells have them in such great abundance and far more organized for contraction. • SMOOTH MUSCLESmooth muscle was the first to evolve. Lining of blood vessels, wall of the gut, iris of the eye.Some contract only when stimulated by nerve impulse. Others generate electrical impulses spontaneously and then are regulated by nervous system. • CARDIAC MUSCLESmall interconnected cell with only one nucleus. Interconnected through gap junctions. Single functioning unit that contract in unison via this intercellular communication. Mostly generate electrical impulses spontaneously. Regulated rather than initial stimulation by nervous system. • SKELETAL MUSCLEFusion of many cells so multi-nucleated. Attached by tendon to bone. Long thin cells called muscle fibers.

  9. Organization of Skeletal muscle skeletal muscle plasma membrane nuclei tendon muscle fiber (cell) myofibrils myofilaments

  10. Human endoskeleton 206 bones

  11. Muscles movement • Muscles do work by contracting • skeletal muscles come in antagonistic pairs • flexor vs. extensor • contracting = shortening • move skeletal parts • tendons • connect bone to muscle • ligaments • connect bone to bone

  12. Structure of striated skeletal muscle • Muscle Fiber • muscle cell • divided into sections = sarcomeres • Sarcomere • functional unit of muscle contraction • alternating bands of thin (actin) & thick (myosin) protein filaments

  13. Muscle filaments & Sarcomere • Interacting proteins • thin filaments • braided strands • actin • tropomyosin • troponin • thick filaments • myosin

  14. Thin filaments: actin • Complex of proteins • braid of actin molecules & tropomyosinfibers • tropomyosin fibers secured with troponin molecules

  15. Thick filaments: myosin • Single protein • myosin molecule • long protein with globular head bundle of myosin proteins: globular heads aligned

  16. Thick & thin filaments • Myosin tails aligned together & heads pointed away from center of sarcomere

  17. Interaction of thick & thin filaments sarcomere sarcomere • Cross bridges • connections formed between myosin heads (thick filaments) & actin (thin filaments) • cause the muscle to shorten (contract)

  18. Where is ATP needed? formcrossbridge releasecrossbridge shortensarcomere binding site CleavingATP ADP allows myosin head to bind to actin filament thin filament(actin) myosin head ADP thick filament(myosin) 1 2 ATP So that’s where those10,000,000 ATPs go! Well, not all of it! 1 1 3 1 1 4

  19. Closer look at muscle cell Sarcoplasmicreticulum Transverse tubules(T-tubules) Mitochondrion multi-nucleated

  20. Muscle cell organelles Ca2+ ATPase of SR • Sarcoplasm • muscle cell cytoplasm • contains many mitochondria • Sarcoplasmic reticulum (SR) • organelle similar to ER • network of tubes • stores Ca2+ • Ca2+ released from SR through channels • Ca2+ restored to SR by Ca2+ pumps • pump Ca2+ from cytosol • pumps use ATP There’sthe restof theATPs! But whatdoes theCa2+ do? ATP

  21. Muscle at rest • Interacting proteins • at rest, troponin molecules hold tropomyosin fibers so that they cover the myosin-binding sites on actin • troponin has Ca2+ binding sites

  22. The Trigger: motor neurons • Motor neuron triggers muscle contraction • release acetylcholine (Ach) neurotransmitter

  23. Nerve trigger of muscle action • Nerve signal travels down T-tubule • stimulates sarcoplasmic reticulum (SR) of muscle cell to release stored Ca2+ • flooding muscle fibers with Ca2+

  24. Ca2+ triggers muscle action • At rest, tropomyosin blocks myosin-binding sites on actin • secured by troponin • Ca2+ binds to troponin • shape changecauses movement of troponin • releasing tropomyosin • exposes myosin-binding sites on actin

  25. How Ca2+ controls muscle • Sliding filament model • exposed actin binds to myosin • fibers slide past each other • ratchet system • shorten muscle cell • muscle contraction • muscle doesn’t relax until Ca2+ is pumped back into SR • requires ATP ATP ATP

  26. Put it all together… 1 2 3 ATP 7 4 6 ATP 5

  27. How it all works… • Action potential causes Ca2+ release from SR • Ca2+ binds to troponin • Troponin moves tropomyosin uncovering myosin binding site on actin • Myosin binds actin • uses ATP to "ratchet" each time • releases, "unratchets" & binds to next actin • Myosin pulls actin chain along • Sarcomere shortens • Z discs move closer together • Whole fiber shortens  contraction! • Ca2+ pumps restore Ca2+ to SR relaxation! • pumps use ATP ATP ATP

  28. Fast twitch & slow twitch muscles • Slow twitch muscle fibers • contract slowly, but keep going for a long time • more mitochondria for aerobic respiration • less SR  Ca2+ remains in cytosol longer • long distance runner • “dark” meat = more blood vessels • Fast twitch muscle fibers • contract quickly, but get tired rapidly • store more glycogen for anaerobic respiration • sprinter • “white” meat

  29. Muscle limits • Muscle fatigue • lack of sugar • lack of ATP to restore Ca2+ gradient • low O2 • lactic acid drops pH which interferes with protein function • synaptic fatigue • loss of acetylcholine • Muscle cramps • build up of lactic acid • ATP depletion • ion imbalance • massage or stretching increases circulation

  30. Diseases of Muscle tissue • ALS • amyotrophic lateral sclerosis • Lou Gehrig’s disease • motor neurons degenerate • Myasthenia gravis • auto-immune • antibodies to acetylcholine receptors Stephen Hawking

  31. Botox • Bacteria Clostridiumbotulinum toxin • blocks release of acetylcholine • botulism can be fatal muscle

  32. Rigor mortis • So why are dead people “stiffs”? • no life, no breathing • no breathing, no O2 • no O2, no aerobic respiration • no aerobic respiration, no ATP • no ATP, no Ca2+ pumps • Ca2+ stays in muscle cytoplasm • muscle fibers continually contract • tetany or rigor mortis • eventually tissues breakdown& relax • measure of time of death

  33. Overview of information processing by nervous systems Sensory input Integration Sensor Motor output Effector Peripheral nervoussystem (PNS) Central nervoussystem (CNS)

  34.  A bat using sonar to locate its prey

  35. Sensory reception: two mechanisms Strongmuscle stretch Weakmuscle stretch Muscle Dendrites –50 Receptor potential –50 –70 –70 Stretchreceptor Membranepotential (mV) Action potentials 0 0 Axon –70 –70 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 Time (sec) Time (sec) (a) Crayfish stretch receptors have dendrites embedded in abdominal muscles. When the abdomen bends, muscles and dendrites stretch, producing a receptor potential in the stretch receptor. The receptor potential triggers action potentials in the axon of the stretch receptor. A stronger stretch produces a larger receptor potential and higher frequency of action potentials. No fluidmovement Fluid moving inone direction Fluid moving in other direction “Hairs” ofhair cell Moreneuro-trans-mitter Lessneuro-trans-mitter Neuro-trans-mitter at synapse Receptor potential –50 –50 –50 Axon –70 –70 –70 Membranepotential (mV) Membranepotential (mV) Action potentials Membranepotential (mV) 0 0 0 –70 –70 –70 0 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 0 0 Time (sec) Time (sec) Time (sec) (b) Vertebrate hair cells have specialized cilia or microvilli (“hairs”) that bend when sur-rounding fluid moves. Each hair cell releases an excitatory neurotransmitter at a synapse with a sensory neuron, which conducts action potentials to the CNS. Bending in one direction depolarizes the hair cell, causing it to release more neurotransmitter and increasing frequency of action potentials in the sensory neuron. Bending in the other direction has the opposite effects. Thus, hair cells respond to the direction of motion as well as to its strength and speed.

  36. Sensory receptors in human skin Cold Light touch Pain Hair Heat Epidermis Dermis Nerve Hair movement Strong pressure Connective tissue

  37. The Structure of the Human Ear 1 2 Overview of ear structure The middle ear and inner ear Incus Semicircularcanals Skullbones Stapes Middleear Outer ear Inner ear Malleus Auditory nerve,to brain Pinna Tympanicmembrane Cochlea Eustachian tube Auditory canal Ovalwindow Eustachian tube Tympanicmembrane Tectorialmembrane Hair cells Roundwindow Cochlear duct Bone Vestibular canal Auditory nerve Axons of sensory neurons Basilarmembrane To auditorynerve Tympanic canal Organ of Corti 4 3 The organ of Corti The cochlea

  38. Transduction in the cochlea Cochlea Stapes Axons ofsensoryneurons Oval window Vestibularcanal Perilymph Apex Base Roundwindow Tympaniccanal Basilar membrane

  39. How the cochlea distinguishes pitch Cochlea(uncoiled) Apex(wide and flexible) Basilarmembrane 500 Hz(low pitch) 1 kHz 2 kHz 4 kHz 8 kHz 16 kHz(high pitch) Frequency producing maximum vibration Base(narrow and stiff)

  40. Organs of equilibrium in the inner ear Each canal has at its base a swelling called an ampulla, containing a cluster of hair cells. The semicircular canals, arranged in three spatial planes, detect angular movements of the head. When the head changes its rateof rotation, inertia prevents endolymph in the semicircular canals from moving with the head, so the endolymph presses against the cupula, bending the hairs. Flowof endolymph Flowof endolymph Vestibular nerve Cupula Hairs Haircell Nervefibers Vestibule Utricle Body movement Saccule The hairs of the hair cells project into a gelatinous cap called the cupula. The utricle and saccule tell the brain which way is up and inform it of the body’s position or linear acceleration. Bending of the hairs increases the frequency of action potentials in sensory neurons in direct proportion to the amount of rotational acceleration.

  41. Structure of the vertebrate eye Sclera Choroid Retina Ciliary body Fovea (centerof visual field) Suspensoryligament Cornea Iris Opticnerve Pupil Aqueoushumor Lens Vitreous humor Central artery and vein of the retina Optic disk(blind spot)

  42. Focusing in the mammalian eye Front view of lensand ciliary muscle Ciliary muscles contract, pulling border of choroid toward lens Lens (rounder) Choroid Retina Suspensory ligaments relax Ciliarymuscle Lens becomes thicker and rounder, focusing on near objects Suspensoryligaments (a) Near vision (accommodation) Ciliary muscles relax, and border of choroid moves away from lens Lens (flatter) Suspensory ligaments pull against lens Lens becomes flatter, focusing on distant objects (b) Distance vision

  43. Cellular organization of the vertebrate retina Retina Optic nerve Tobrain Retina Photoreceptors Neurons Rod Cone Amacrinecell Horizontalcell Opticnervefibers Ganglioncell Bipolarcell Pigmentedepithelium

  44. Rod structure and light absorption Rod Outersegment H H O C H CH3 C C H3C H CH3 C H2C C H H H2C C C C C Disks C C C C H H H CH3 CH3 cis isomer Insideof disk Cell body Enzymes Light Synapticterminal H H CH3 C CH3 H H H2C C H H H2C C C C C C O C C C C C C H CH3 CH3 H CH3 CH3 Cytosol trans isomer Retinal Rhodopsin Opsin (b) Retinal exists as two isomers. Absorption of light converts the cis isomer to the trans isomer, which causes opsin to change its conformation (shape). After a few minutes, retinal detaches from opsin. In the dark, enzymes convert retinal back to its cis form, which recombines with opsin to form rhodopsin. (a) Rods contain the visual pigment rhodopsin, which is embedded in a stack of membranous disks in the rod’s outer segment. Rhodopsin consists of the light-absorbing molecule retinal bonded to opsin, a protein. Opsin has seven  helices that span the disk membrane.

  45. Neural pathways for vision Right visual field Left visual field Left eye Right eye Optic nerve Optic chiasm Lateralgeniculatenucleus Primaryvisual cortex

  46. Smell in humans Brain Action potentials Odorant Olfactory bulb Nasal cavity Bone Epithelial cell Odorantreceptors Chemoreceptor Plasmamembrane Cilia Odorant Mucus

  47.  Chemoreceptors in an insect 0.1 mm

  48. Sensory transduction by a sweetness receptor Taste pore Sugar molecule Taste bud Sensoryreceptorcells Sensoryneuron Tongue 1 A sugar molecule binds to a receptor protein on the sensory receptor cell. Sugar Adenylyl cyclase G protein Sugarreceptor 2Binding initiates a signal transduction pathway involving cyclic AMP and protein kinase A. ATP cAMP 3Activated protein kinase A closes K+ channels in the membrane. Proteinkinase A SENSORYRECEPTORCELL 4 The decrease in the membrane’s permeability to K+ depolarizes the membrane. K+ Synapticvesicle 5 Depolarization opens voltage-gated calcium ion (Ca2+) channels, and Ca2+ diffuses into the receptor cell. —Ca2+ 6 The increased Ca2+ concentration causes synaptic vesicles to release neurotransmitter. Neurotransmitter Sensory neuron

  49. Specialized electromagnetic receptors Eye Infraredreceptor (a) This rattlesnake and other pit vipers have a pair of infrared receptors,one between each eye and nostril. The organs are sensitive enoughto detect the infrared radiation emitted by a warm mouse a meter away. The snake moves its head from side to side until the radiation is detected equally by the two receptors, indicating that the mouse is straight ahead. (b) Some migrating animals, such as these beluga whales, apparentlysense Earth’s magnetic field and use the information, along with other cues, for orientation.

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