INT PHYS EXAM1 studyguide2

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  1. Describe presynaptic modulation (inhibition and
    • axoaxonic
    • may only affect a few postsynaptic cells
    • inhibition is due to decrease of neurotransmitter release from the presynaptic cell by blocking calcium channels
    • facilitation is due to an increase in neurotransmitter by keeping calcium channels open
  2. Describe postsynaptic modulation (inhibition and
    • axosomatic or axodendritic
    • affects all target cells
    • summation of inhibitory vs excitatory signals can result in varying levels of neurotransmitter release
  3. Define Sensory Receptor
    specialized neuronal structures that detect specific types of energy
  4. Name the stimuli that are detected by visceral
    (interoceptor) and somatic senses.
    • Visceral receptors detect stimuli that arise with the body
    • Somatosensory receptors detectsensations associated with receptors in the skin, and proprioception
  5. Define modality
    The energy form of a stimulus is called its modality
  6. Define the law of specific nerve energies
    Sensory receptors are specific for a particular modality.
  7. Define adequate stimulus
    Specific modality to which receptor is most sensitive
  8. Under what circumstances will a receptor respond to an
    “inadequate stimulus”?
    If the strength of an “inadequate stimulus” is high enough, the receptor will respond
  9. List the major groups of receptors and their
    adequate stimuli
    • chemo receptors : smell, taste, blood concentration of O2 and CO2
    • mechano receptors: pressure, stretch eg.baroreceptor
    • photo receptors: light wavelengths
    • thermo receptors: sensations of coldness and warmth
    • noci ceptors: tissue damage interpreted as pain stimulated by intense mechanical, thermal or chemical stimuli
  10. List the 3 structural types of sensory receptors
    • simple
    • complex
    • special senses
  11. Define neural and non-neural receptors
    • neural receptors have free nerve endings (if surrounded by connective tissue or not)
    • non-neural receptors are cells that release NT onto sensory neurons to initiate an AP
  12. Explain how a sensory stimulus is transduced
    into electrical signals
    • convert the energy of the stimulus into changes in membrane potential
    • to cause direct/indirect change in membrane potential must open/close ion channels
    • results in generator potentials or receptor potentials (in non-neural cells)
  13. Define Adaptation
    process in which sensory receptors decrease their response to a stimulus over time.
  14. define Tonic Receptors
    adapt slowly, transmit signals to the CNS as long as the stimulus persists
  15. define Phasic Receptors
    fire when the first stimulus is received, then switch off when the stimulus is at constant intensity
  16. define Labelled Lines
    Specific neural pathways transmitting specific modality information
  17. Define sensory unit and receptive field
    • sensory unit is a single afferent neuron with all its receptor endings
    • the region within which a sensory neuron can detect a stimulus is called the receptive field
  18. Describe a generalized pathway for sensory
    stimulus-receptor-afferent first order neuron-spinal cord or brain stem-second order neuron-thalamus-third order neuron-cortex
  19. Describe the Spinothalamic Tract
    transmits pain/temp stimulus - primary neuron - dorsal horn of spinal cord - secondary neuron crosses over at spinal cord - acends anterolateral column of spinal cord - VPL of thalamus - tertiary neuron - somatosensory cortex
  20. Describe the the Dorsal Column pathways
    transmits touch/pressure stimulus - primary neuron - dorsal horn of spinal cord - secondary neuron crosses over at medulla - VPL of thalamus - tertiary neuron - somatosensory cortex
  21. Describe the various fibers types involved in
    the transmission of somatic sensation
    • A-β : largest, myelinated, fastest, sense pressure/vibration
    • A-δ : small, myelinated, fast, sense very hot/cold, sharp pain
    • C fibers : small, unmyelinated, slow, sense dull pain and moderate temps
  22. To what parts of the CNS are painful stimuli
    • Signals from painful stimuli are transmitted to the cortex(perceived)
    • also to the limbic system and the hypothalamus hence emotional and autonomic reactions occur
  23. Define referred pain and describe the
    physiological cause
    • Caused by multiple primary sensory neurons converging on single ascending tract
    • brain gets confused between signals coming from somatic (skeletal) sources versus those which are visceral.
  24. Describe the Gate Control Theory of Pain
    • somatic signals of non-painful stimuli can inhibit signals of pain at the spinal level
    • inhibitory interneurons can be stimulated by collaterals of A-β fibers associated with pressure and touch to stop transmission of painful stimuli from proceeding
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INT PHYS EXAM1 studyguide2
2011-10-02 23:50:52

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