Biomed module 13 obj.8-15

  1. Mechanoreceptors
    • detect movement, such as pressure of clothing on skin, or a finger touching your, muscles being stretched, or pressure waves of air(i.e. sound)
    • Sensory system: somatosensory, proprioception, auditory(hearing), vestibular(hearing)
  2. True or false.
    The movement of small rocks in the inner ear produces the sensation of balance.
  3. Thermoreceptors
    • detects temp. between 4 degrees Celsius and 50 degrees Celsius.
    • below 4 and above 50, tissue is damaged and pain results.

    When we touch dry ice or a hot stove, you don't measure the temperature of it. it just hurts.

    Sensory system: somatosensory
  4. Nociceptors
    • same root as noxious and obnoxious
    • detect harmful or damaging stimuli

    When tissue is damaged a number of chemical factors are released from the damaged cells. These stimulate receptors on what appear histologically as free nerve endings in the skin.  (pain receptors)

    Sensory system: somatosensory
  5. Photoreceptors
    detect photons (particles/waves of light energy)

    Different wavelengths of light correspond to different hues; there is one photo receptor type for each of the primary colors, which is what makes them primary.

    Sensory system: visual (sight)
  6. Chemoreceptors
    Detect chemicals in the internal or external environment.

    examples of these are found in senses of taste (sugar, acid, salt, or other substances dissolved in saliva); of smell; and the oxygen, carbon dioxide, and pH receptors which monitor the bloodstream.

    sensory system: olfactory(smell), gustatory(taste), receptors in blood
  7. Osmoreceptors
    In the hypothalamus, detects the salt levels in blood, and respond by secreting chemicals that regulate water retention or loss

    Sensory system: hypothalamus, endocrine
  8. Generator potential
    the voltage change in a sensory neuron that results from the relevant stimulus being applied to the sensory nerve ending and activation an ion channel
  9. Sensory cells in the skin fit into the category of ______ _______.
    unipolor neurons

    This means they have a dendrite which picks up info, a long axon which starts at the base of the dendritic tree and extends into the CNS, and a cell body shoved off to one side somewhere in between.
  10. The Unipolar Somatosensory Neuron
    • 1. receptor (modified dendrite) in skin
    •   -this is where generator potential is set up

    • 2. Axon from skin to posterior root ganglion
    •   -trigger zone where receptor meets axon

    • 3. Cell body in posterior root ganglion
    •   -also called dorsal root ganglion

    • 4. Axon terminals in CNS
    •   -some travel to brain
    •   -others make synapse in spinal cord
  11. see objective 11, page 601
  12. Adaptation
    • In the somatosensory system, adaptation refers to how the response of receptors changes, even when the stimulus does not
    • Skin receptors are classified as rapidly-adapting or slowly adapting
    • Rapidly-adapting: Meissner, Pacinian
    • Slowly-adapting: Merkel, Ruffini
  13. What are the different skin receptors?
    • Pacinian or lamellated corpuscles (onion-shaped)
    • Ruffini corpuscles 
    • Merkel corpuscles
    • Meissner corpuscles
  14. Rapidly adapting skin receptors
    • Meissner and Pacinian corpuscles 
    • when a stimulus is applied, they fire a quick burst of action potentials and then shut up
    • They are vibration sensors 
  15. Slowly adapting skin receptors
    • Merkel corpuscles and Ruffini endings 
    • these detect light touch
    • They fire an initial burst of action potential when a stimulus is applied, and continue to fire at a low but steady rate for as long as the stimulus is there.
  16. Dermatomal map
    because a single spinal nerve carries info form a defined region of the skin surface a single dorsal (posterior) root in the spinal cord, we can pair regions of the skin surface with dorsal roots.
  17. Dermatomes
    • (Greek, derma- "skin" tomes- "slice")
    • An area of the skin that is innervated by a single spinal nerve
    • The letters and numbers indicate which spinal nerve roots distribute to the area shown
    • Lots of overlap and individual differences
    • Land mark dermatomes:
    • C6/C7: thumb and index finger (six shooter)
    • T4: nipple line
    • T10: umbilicus ("belly button" shape of 0)
    • L1-L5: the legs (Lower extremities)
    • see p.603
  18. Tracts
    bundles of axons, all running from and to the same place, in the CNS
  19. Ascending tracts 
    carry sensory information from the body to the brain, or from the spinal cord to the brain.
  20. What are the two examples of ascending tracts?
    • Posterior columns 
    • Spinothalamic tract
  21. Posterior columns
    • A column is a bunch of tracts running together.
    • carry information about light touch, vibration, and proprioception (body position).
    • found in the posterior(dorsal) part of the spinal cord.
    • Carries info that needs to be conveyed rapidly to the brain 
    • it stays on the same side of the spinal cord as where it entered and then goes directly to the medulla, the lowest part of the brainstem.
    • see pic. p. 604
  22. Spinothalamic Tract
    (Anterolateral system- ALS)
    • A tract is a bundle of axons running together
    • Carries information (pain and Temp) from the spinal cord to the thalamus.
    • Info. is picked up by free nerve endings in the skin, and is carried on spinal nerves and enters the dorsal root.
    • See pic. p.605
  23. The processing of pain and temperature info. in the ________ _____ allows the brain to heavily influence the _________ of pain through axons from the brain that interact with __________ pain signals.
    spinal cord, perception, incoming
  24. True or False.
    In order for information from the skin to reach conscious perception, it has to be relayed through the thalamus.
  25. Thalamic Relay
    1. Sensory Neurons- Spinothalamic axons

    2. Sensory relay neurons- Posterior Column axons

    3. Thalamus- both types of info are relayed through the same part of the thalamus (ventroposterior nucleus)
  26. Primary somatosensory cortex
    • found i Brodmann's areas 3, 1 and 2
    • Also known as the postcentral gyrus of the parietal lobe of the brain, just posterior to the central sulcus.
    • All sensory info. for skin reaches conscious perception if it arrives here.
  27. Sensory Homunculus
    • an orderly map of the body surface in somatosensory cortex
    • same basic pattern as motor homunculus
    • The face is most lateral and the feet (and genitals) are most medial.
  28. Reflex
    • a quick, inborn response to a stimulus that uses just a few neurons to get the job done.
    • see slide on p.607
  29. What does a Reflex arch consist of ?
    • Sensory receptor- picks up information form the environment
    • Sensory neuron- (which may or may not be the same as the receptor) to carry the info. to the CNS.
    • Integrating Center- (i.e. the CNS)
    • Motor neuron- to innervate the effector
    • Effector (generally, skeletal muscle)
  30. True or False.
    Reflexes are hardwired.
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Biomed module 13 obj.8-15
Biomed module 13 obj.8-15