Bio 224 Theme 10

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Bio 224 Theme 10
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2013-10-11 20:09:40
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Bio 224 Theme 10
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  1. 7 senses
    • •Sight,
    • •Hearing,
    • •Touch,
    • •Taste,
    • •Smell,
    • •Balance
    • •The ability to sense temperature and pain
  2. stimulus
    any agent detectable by an organism—such as light, vibration, and so on.
  3. transduction:
    the conversion of one form of energy—an external stimulus—into electrical energy that can be interpreted by a nervous system.
  4. Ion Channels fall into two broad types
    –Leak channels

    –Gated channels, open and/or close in response specific stimuli
  5. 4 types of gated channels
    • (1) mechanically gated,
    • (2) chemically gated,
    • (3) voltage-gated, and
    • (4) thermally gated channels.
  6. Mechanically gated channels
    • •Sensitive to stretch,
    • -they may have served as osmotic stress sensors in prokaryotes, opening when a cell was deformed by changes in cell volume;
  7. Chemically gated channels
    • •Sense chemicals in the environment
    • -Involves chemoreceptor proteins rather than, or in addition to, gated channels
    • -necessary for chemotaxis
  8. mechanism of chemotaxis
    • •Binding of the molecules to surface-membrane receptor proteins  transduce the signal to the cell interior to alter flagellar motions;
    • –Primitive mechanism of cell to cell communication during evolution of multicellularity;
  9. –Starvation induces the single-celled amoeba to secrete ___ into the environment;
    • cAMP
    • -Primitive mechanism of cell to cell communication during evolution of multicellularity
  10. How does binding external cAMP effect cell behavior?
    -Leads the amoebas to aggregate into large-bodied slugs (move to food, or reproduce to spread spores to new habitat)

    -cAMP receptor protein triggers a G-protein
  11. Voltage-gated channels
    -essential to long-range signaling involved in both sensory input and effector control
  12. Voltage-gated K+ channels are also found in the plasma membranes of __ cells
    yeast
  13. Voltage gated ___ channels are found only in animals and a few protists;
    Na+
  14. Thermally gated channels
    Widespread in animals, including in some animal-like protists like Paramecium
  15. •Paramecium,
    • a protozoa with swimming cilia;
    • –Considered free-swimming sensory cells with most of the sensory capabilities of animals;
  16. Paramecium is a living proof that the machinery associated with the function of ___ ___ arose long before the evolution of ___ ___
    • sensory neurons 
    • nervous systems
  17. Paramecium Respond to what environmental stimuli?(5)
    • Thermal, mechanical, chemical, photic, and ionic
    • –through changes in their membrane potentials;
  18. How do Paramecium respond to stimuli?
    by changing either their cell shape or the pattern of ciliary beating
  19. What types of gated channels do paramecium have?
    • all 4
    • voltage
    • chemical
    • mechanical
    • thermally
  20. Paramecium have ___ ___ that react to chemicals that affect membrane potential via second messenger
    Receptor proteins
  21. TRP-Nl
    • A TRP protein found in fruit flies
    • -mechanically gated Ca2+ channel.
  22. TRP
    • transient receptor-potential
    • -a family of proteins involved in sensory transduction in eukaryotes from yeast to mammals
  23. What stimuli do TRP proteins respond to?
    • heat, cold, intense heat, mechanical, mustard oil, ethanol, etc…. 
    • signals such as ATP, acetyl-choline… in channels
  24. –Mechanoreceptors:
    • transduce
    • mechanical energy
  25. –Thermoreceptors:
    respond to cold and heat
  26. –Nociceptors,
    • pain receptors:
    • •respond to extreme heat, cold, and pressure, as well as to certain molecules such as acids;
  27. –Electromagnetic receptors
    :•Detect radiation within a wide range of the electromagnetic spectrum; ex pigeons
  28. –Photoreceptors:
    •respond to visible light energy
  29. –Chemoreceptors:
    respond to specific chemicals
  30. Interoreceptors
    sense mechanical changes  at numerous sites, mainly in association with blood vessels and gutfluids;
  31. •Exteroreceptors
    • detect external stimuli:
    • –light, chemicals (taste, smell), touch, temperature, electromagnetic fields, and sound
    • -also known as somesthetic
  32. Proprioceptors
    located mainly in the muscles, tendons, and joints, and also in the inner ear. Can detect position in the environment
  33. Two different types of receptor cells.
    • specialized afferent neuron endings
    • seperate cell receptor
  34. signaling process for specialized afferent neuron endings
    3 steps
    • 1. stimulus opens stimulus-sensitive channels, permitting net Na+ entry that produces receptor potential.     
    • 2.Local current flow between depolarized receptor ending and adjacent region opens voltage-gated Na+ channels.     
    • 3.Na+ entry initiates action potential in afferent fiber that self-propagates to CNS. 
    • -no neurotransmitter necessary
  35. signaling process for seperate cell receptor
    6 steps
    1. stimulus opens stimulus-sensitive channels, permitting net Na+ entry that produces receptor potential.     

    2.This local depolarization opens voltage-gated Ca2+ channels.     

    3.Ca2+ entry triggers exocytosis of neurotransmitter.     

    4.  Neurotransmitter binding opens chemically gated receptor-channels at afferent ending, permitting net Na+ entry.     

    5.  Resultant depolarization opens voltage-gated Na+ channels in adjacent region.    

    6.  Na+ entry initiates action potential in afferent fiber that self-propagates to CNS.
  36. afferent neurons differ from interneurons and efferent neurons how
    (physiologically)
    • -the sit of initiation of action potential occurs after a sensory receptor and before the cell body (cell body is external to path of propagation)
    • - in others cell body is first
  37. Tonic receptor
    Tonic sensory input adapts slowly to a stimulus and continues to produce action potentials over the duration of the stimulus
  38. Phasic receptor
    fast-adapting receptors, active for a short period of time whenever there is a change in the conditions
  39. amount of neurotransmitter released is directly dependent of what?
    Frequency of action potentials which is dependent on

    magnitude of receptor potential which is dependent on

    stimulus strength
  40. Skin Receptors
    3
    • Meissner’s corpuscles
    • Pacinian corpuscles
    • Ruffini corpuscles
  41. •Meissner’s corpuscles
    –sense touch and light pressure–lie just beneath skin surface
  42. Ruffini corpuscles
    senses deep pressure and skin distortion
  43. The Pacinian corpuscle
    • •Consists of concentric layers of connective tissue
    • -detects deep pressure and vibration
  44. Bristle Mechanoreceptor in Drosophila
    consists of:
    • a bristle and three cells:
    • a socket cell, a sheath cell, and a neuron;
  45. Bristle Mechanoreceptor inDrosophila
    how does it operate?
    –When the bristle moves, it distorts the membrane of the neuron’s dendrites, opening up mechanogated channels depolarizing it
  46. Vertebrate skin mechanoreceptors include free nerve endings that:
    wrap around the base of the hair shaft
  47. Lateral inhibition
    • The most intensely activated receptor pathway halts transmission of impulses in the less intensely stimulated pathways through lateral inhibition.
    • -this accomplished with inhibitory interneurons
  48. Stretch Receptors
    • •Commonly found in the walls of organs that can be distended
    • -Stretching deforms them and they depolarize
  49. Specialized Epithelial Cells
    Work as mechanoreceptors that release a chemical neurotransmitter when stimulated
  50. The lateral line system consists of a row of ____ set in pits and canals along each sideof the body;
    neuromasts
  51. neuromasts
    • a mechanoreceptive organ which allows the sensing of mechanical changes in water through a cupula similar to that found in the ear
    • -cupula contains kinocilium and stereo cilia attached to hair cells
  52. tip link in sound transduction
    connection between tips of hairs attached to half of a channel that pulls channels open when hairs spread apart allowing K+ in to depolarized cel and open voltage gated Ca++ channels

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