Warm-Up

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Warm-Up

• What is the function of
• Cone cells?
• Rod cells?
• The perceived pitch of a sound is dependent on ?
• What is the difference between perception and
  sensation?

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Warm-Up

• What is the function of
• Cone cells? Color
• Rod cells? Light
• The perceived pitch of a sound is dependent on ?
• wavelength (?)
• What is the difference between perception and
  sensation?

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Sensory and Motor Mechanisms

• Chapter 50
• Campbell Biology 9th Edition

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You must know

• The location and function of several types of
  sensory receptors
• How skeletal muscles contract
• Cellular events that lead to muscle contraction

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Sensory Receptors

• Mechanoreceptors physical stimuli pressure,
  touch, stretch, motion, sound
• Thermoreceptors detect heat/cold
• Chemoreceptors transmit solute conc. info
  taste (gustatory), smell (olfactory)
• Electromagnetic receptors detect EM energy
  light (photoreceptors), electricity, magnetism
• Pain receptors respond to excess heat, pressure,
  chemicals

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Chemoreceptors antennae of male silkworm moth
have hairs sensitive to sex phermones released by
the female
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• Reception receptor detects a stimulus
• Sensation action potentials reach brain via
  sensory neurons
• Perception information processed in brain

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Structure of the Human Ear
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Equilibrium in the inner ear Semicircular canals
(fluid-filled chambers) detect head movements
through hairs of receptor cells
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Structure of the Vertebrate Eye(also some
invertebrates)
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Vision

• Compound eyes several thousand ommatidia (light
  detectors) with its own lens insects
  crustaceans
• Vertebrates
• Rods sense light
• Cones color vision
• Rhodopsin light-absorbing pigment that triggers
  signal transduction pathway that leads to sight

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Types of Skeletons

• Hydrostatic fluid held under pressure in closed
  body compartment
• Hydra, nematodes, annelids
• Exoskeletons hard encasements on surface of
  animal
• Insects, mollusks, crustaceans
• Endoskeleton hard supporting elements buried
  within soft tissues
• Human bony skeleton

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• Muscles always contract
• Muscles work in antagonistic pairs to move parts
  of body

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Skeletal Muscle Structure

• Attached to bones by tendons
• Types of muscle
• smooth (internal organs)
• cardiac (heart)
• Skeletal (striated)
• 1 long fiber single muscle cell
• Each muscle fiber bundle of myofibrils,
  composed of
• Actin thin filaments
• Myosin thick filaments

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Sarcomere basic contractile unit of the muscle

• Z lines border
• I band thin actin filaments
• A band thick myosin filaments

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Muscle Contraction

• Sarcomere relaxed actin myosin overlap
• Contracting
• Muscle fiber stimulated by motor neuron
• Length of sarcomere is reduced
• Actin slides over myosin
• Fully contracted actin myosin completely
  overlap
• Sliding-filament model thick thin filaments
  slide past each other to increase overlap
• (Note Filaments do NOT shorten!)

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Muscle fibers only contract when stimulated by a
motor neuron
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Depolarization of muscle cell releases Ca2 ions
? binds to troponin ? expose myosin sites on
actin
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Hydrolysis of ATP by myosin ? cross-bridge formed
? thin filament pulled toward center of sarcomere
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• Speed of muscle contraction
• Fast fibers brief, rapid, powerful contractions
• Slow fibers sustain long contractions (posture)

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Problems

• ALS (Lou Gehrigs disease) degeneration of motor
  neurons, muscle fibers atrophy
• Botulism block release of acetylcholine,
  paralyzes muscles
• Myasthenia gravis autoimmune disorder, produce
  antibodies to acetylcholine
• Calcium deficiency muscle spasms and cramps
• Rigor mortis (after death) no ATP to break
  actin/myosin bonds sustained muscle contraction
  until breakdown (decomposition)