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Chapter 49 - PowerPoint PPT Presentation

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Sensory and Motor Mechanisms. Chapter 49. Muscles. Skeletal Muscle – attached to bones and is responsible for movement Cardiac Muscle – heart Do not need motor neurons to produce action potentials Ion channels cause rhythmic depolarizations Cannot reach tetanus Smooth Muscle

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  • Skeletal Muscle – attached to bones and is responsible for movement
  • Cardiac Muscle – heart
    • Do not need motor neurons to produce action potentials
    • Ion channels cause rhythmic depolarizations
    • Cannot reach tetanus
  • Smooth Muscle
    • Contract only when stimulated by neurons of ANS
muscle hierarchy
Muscle Hierarchy
  • Muscle
  • Bundle of muscle fibers
  • Single muscle fiber
  • Myofibril
  • Myofilament
    • Thin filament
    • Thick filament
  • The basic contractile unit of the muscle
    • Thin filament – 2 strands of actin (passive, attached to Z line) & 1 strand of regulatory protein coiled around one another
    • Thick filament – staggered arrays of myosin (active, does the work) molecules
    • Z Line – border of sarcomere – thin filaments run between Z line
motor unit
Motor Unit
  • Consists of a single motor neuron and all the muscle fibers it controls
    • When a motor neuron produces an action potential, all the muscle fibers in its motor unit contract as a group
    • The strength of the contraction depends on how many muscle fibers the motor neuron controls.
    • Nervous system regulates strength of contraction in whole muscle by determining how many motor units are activated
    • The force developed by a muscle progressively increases as more and more of the motor units are activated – this is called Recruitment
neuromuscular junction
Neuromuscular Junction
  • Chemical synapse is the same as ch. 48 using Acetylcholine as neurotransmitter.
  • Action potential triggers Ca++ release from sarcoplasmic reticulum
  • Ca++ bind to troponin; troponin changes shape, removing blocking action of tropomyosin; myosin binding sites are exposed
sliding filament theory
Sliding Filament Theory
  • The neuron stimulate the sarcolemma
  • An Action Potential travels down the sarcolemma and T-tubules
  • Sarcoplasmic Reticulum releases calcium ions into the cytoplasm
  • Calcium uncovers myosin-binding sites on actin
  • Myosin heads attach to actin, bend and release, pulling the actin. ATP is used.

the senses
The Senses
  • Sense organs are the windows to the brain.
  • Sense receptors
    • Interoceptors – respond to internal stimuli -bodyposition, chemicals, blood pressure
    • Exteroreceptors – respond to external stimuli -light, pressure, chemicals, heat
  • Integration – processing information
    • Some of this is often done at the receptor
    • Sensory adaptation – decrease in response due to continued stimulation
types of sensory receptors
Types of sensory receptors
  • Mechanoreceptors – pulled or stretched
    • Touch receptors in the skin
    • Arteries detect blood pressure change
    • Lungs respond to degree of lung inflation
    • Proprioceptors – posture and balance
    • Inner ear – sensitive to waves of fluid which establishes equilibrium
types of sensory receptors1
Types of sensory receptors
  • Pain Receptors – respond to excess heat, pressure, or chemicals
    • Histamines, prostaglandins
    • Prostaglandins lower threshold of pain receptors
      • Aspirin & ibuprofen inhibit prostaglandins
  • Thermoreceptors – respond to heat or cold
    • Regulate body temperature
  • Chemoreceptors – monitor osmotic concentration, pH, specific chemicals
    • Taste & smell
types of sensory receptors2
Types of sensory receptors
  • Electromagnetic receptors – light, electricity, magnetism, photoreceptors (sight)
    • Photoreceptors – respond to light energy
  • Types of eyes
    • Simple eye cup – light intensity & direction
    • Compound eye – 1000 or more ommatidia, each with its own lens
      • Gives mosaic image able to detect very slight movement
      • Insects, some arthropods
    • Single lens eye – focuses image on retina
      • Spider, mollusk, polychaete, vertebrates
contralateral processing
Contralateral Processing
  • Nerve fibers bringing info from right half of visual field converge at optic chiasma & pass to left side of brain. Vice versa for left half of vision.
  • Image is inverted & reversed, brain corrects image for us to correctly perceive what is in whole visual field
  • Stimuli of color, form, & motion sent to other parts of the brain
  • Cerebral cortex rebuilds all parts to give us complete understanding of what we are seeing.
types of skeletons
Types of skeletons
  • Hydrostatic skeleton – fluid held under pressure in a closed body compartment
    • Cnidarians, flatworms, nematodes, annelids
    • Adv – aquatic environment; cushion internal organs
    • Disadv – cannot support terrestrial activities
  • Exoskeletons – hard encasement deposited on the surface of an animal
    • Molluscs, arthropods, insects
    • Adv – protection, strength, flexibility
    • Disadv – cannot grow, has to be shed, heavy
  • Endoskeleton – hard supporting elements
    • Chordates (mammals)
    • Adv – internal structure, support, shape
    • Disadv – offers no external protection
  • Ball & socket – rotation of arms & legs
    • Humerus & shoulder
    • Femur & hip
  • Hinge joint – single plane movement
    • Elbow
    • Knee
  • Pivot joint – rotation
    • Forearm
    • Head on neck