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Ch 50 sensory & motor mechanisms


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Ch 50 sensory & motor mechanisms

  1. 1. Sensory & Motor Mechanisms<br />Chapter 50<br />
  2. 2. Sensory receptors transduce stimulus energy and transmit signals to the CNS<br />Stimuli = forms of energy<br />Sensation involves converting energy into a change in the membrane potential of sensory receptors<br />Sensations are action potentials that reach the brain via sensory neurons<br />The brain interprets sensations, giving the perception of stimuli<br />
  3. 3. Sensory pathway<br />Fig. 50-2<br />Weakreceptorpotential<br />Action potentials<br />–50<br />Membranepotential (mV)<br />Membranepotential (mV)<br />0<br />–70<br />–70<br />Slight bend:weakstimulus<br />1 2 3 4 5 6 7<br />0<br />Brain perceivesslight bend.<br />Dendrites<br />Time (sec)<br />Stretchreceptor<br />2<br />4<br />1<br />Axon<br />3<br />Brain<br />Muscle<br />Brain perceiveslarge bend.<br />Action potentials<br />Large bend:strongstimulus<br />0<br />Membranepotential (mV)<br />Strong receptorpotential<br />–50<br />Membranepotential (mV)<br />–70<br />Reception<br />1<br />1 2 3 4 5 6 7<br />0<br />–70<br />Time (sec)<br />Transduction<br />Transmission<br />Perception<br />2<br />3<br />4<br />
  4. 4. Sensory Reception<br />Detection of stimulus<br />Sensory receptors<br />Detect heat, light, pressure, chemicals<br />Blood pressure, body position<br />Sensory transduction<br />Conversion of stimulus to change in membrane potential<br />Charge difference in membrane due to ions<br />
  5. 5. Transmission<br />Passage of nerve impulse along axons and across synapses<br />Sensory cells without axons release neurotransmitters at synapses with sensory neurons<br />Larger receptor potentials generate more rapid action potentials<br />Integration of sensory information begins when information is received<br />
  6. 6. Perception<br />Interpretation of sensory system input by brain<br />Ex: colors, smells, sounds, tastes<br />Is there a sound if a tree falls and no one is around to hear it?<br />Action potentials = all or none!!<br />
  7. 7. Modification of stimuli<br />Amplification<br />Strengthening of stimulus energy<br />During transduction<br />Produces many product molecules by one enzyme <br />Adaptation<br />Decrease in responsiveness<br />Allows you to filter stimulus<br />
  8. 8. Types of Sensory Receptors<br />Mechanoreceptors<br />Sense physical deformation<br />Pressure, touch, stretch, motion, sound<br />Chemoreceptors<br />Both general and specific<br />General = total solute concentration<br />Specific = chemicals that attach to specific receptor proteins<br />Electromagnetic receptors<br />Detect electromagnetic radiation<br />Light, electricity, magnetism<br />
  9. 9. Types of Sensory Receptors<br />Thermoreceptors<br />Detect heat and cold<br />Pain receptors<br />Extreme pressure or temperature<br />Nocireceptors<br />Detect noxious conditions<br />
  10. 10. Ex: Hearing & Equilibrium<br />Mechanoreceptors produce receptor potentials <br />settling particles or moving fluid cause deflection of cell surface structures<br />Hairs<br />Different stiffness and lengths<br />Cause vibrations of different frequencies<br />Statocysts<br />Sense gravity & maintain equilibrium<br />Grains of sands <br />Gravity settles sand to bottom stimulates receptor<br />
  11. 11. Hearing in mammals<br />Ear converts energy of pressure waves to nerve impulses<br />Mechanoreceptor = hair cells<br />Signal is amplified before it reaches the hair cell<br />
  12. 12. Hearing in mammals (cont)<br />1. Moving air causes tympanic membrane to vibrate<br />2. 3 bones transmit vibrations to oval window – membrane on cochlea’s surface<br />3. when bone vibrates on oval window, pressure waves created in fluid<br />4. in vestibular canal, pressure causes hairs to vibrate up and down<br />5. mechanoreceptors open or close ion channels in membrane<br />
  13. 13. Fig. 50-8<br />Middleear<br />Outer ear<br />Inner ear<br />Stapes<br />Skullbone<br />Semicircularcanals<br />Incus<br />Malleus<br />Auditory nerveto brain<br />Bone<br />Cochlearduct<br />Auditorynerve<br />Vestibularcanal<br />Tympaniccanal<br />Cochlea<br />Ovalwindow<br />Eustachiantube<br />Pinna<br />Auditorycanal<br />Organ of Corti<br />Roundwindow<br />Tympanicmembrane<br />Tectorialmembrane<br />Hair cells<br />Hair cell bundle froma bullfrog; the longestcilia shown areabout 8 µm (SEM).<br />Axons ofsensory neurons<br />To auditorynerve<br />Basilarmembrane<br />
  14. 14. Sound variables<br />Volume<br />Determined by amplitude of sound wave<br />Larger volume = greater bending of hairs <br />Pitch<br />Determined by sound wave’s frequency<br />High frequency = high pitch<br />
  15. 15. Equilibrium in mammals<br />Inner ear detects movement, position and balance<br />Utricle & Saccule<br />Chambers located behind oval window<br />Sheet of hair cells that go into a gelatinous material<br />Contains otoliths<br />Semicircular canals<br />Connected to utricle<br />Detect turning of the head<br />
  16. 16. Muscle Contraction<br />Skeletal muscle<br />Striated<br />Connected to bones<br />Thick filaments<br />Staggered arrays of myosin<br />Thin filaments<br />2 strands of actin and 2 strands of a regulatory protein coiled<br />
  17. 17. Skeletal muscle<br />Sarcomere<br />Repeating unit<br />Z lines<br />M lines<br />Fig. 50-25b<br />TEM<br />0.5 µm<br />M line<br />Thickfilaments(myosin)<br />Thinfilaments(actin)<br />Z line<br />Z line<br />Sarcomere<br />
  18. 18. Sliding Filament Model <br />Thin and thick filaments slide past each other increasing the overlap of the fibers<br />Head of myosin<br />Binds ATP to provide energy for muscle contraction<br />Tail of myosin<br />Adheres to other tails of myosin to form the thick filament<br />
  19. 19. Muscle fiber contraction<br />Myosin head is bound to ATP (low energy)<br />
  20. 20. Muscle Fiber Contraction<br />Myosin hydrolyzes ATP to ADP now in high E<br />
  21. 21. Muscle Fiber Contraction<br />Myosin head binds<br />to actin = cross-bridge<br />
  22. 22. Muscle Fiber Contraction<br />ADP is <br />released, <br />myosin <br />returns to <br />low E, <br />thin <br />filament<br />slides<br />