1. The Peripheral Nervous System and Reflex Activity: Part A13
The Peripheral Nervous System and Reflex Activity: Part A

2. Peripheral Nervous System (PNS)
What is the peripheral nervous system?
How do we sense stuff?

3. Peripheral Nervous System (PNS)
What is the peripheral nervous system?
Everything except the brain and spinal cord
How do we sense stuff?

4. Peripheral Nervous System (PNS)
What is the peripheral nervous system?
Everything except the brain and spinal cord
How do we sense stuff?
Sensory receptors
Peripheral nerves and associated ganglia
Motor endings

5. Review: what was the difference?
Afferent vs efferent?
Somatic vs autonomic?
Symp vs parasymp?
Central nervous system (CNS)
Peripheral nervous system (PNS)
Sensory (afferent)
division
Motor (efferent) division
Somatic nervous
system
Autonomic nervous
system (ANS)
Sympathetic
division
Parasympathetic
division
Figure 13.1

6. Sensory Receptors Why do we need sensory receptors?
These receptors communicate
graded potentials  trigger nerve impulses
WIDB: sensation vs perception?

7. Sensory Receptors Why do we need sensory receptors?
Responding to changes in environment
These receptors communicate
graded potentials  trigger nerve impulses
WIDB: sensation vs perception?

8. Sensory Receptors Why do we need sensory receptors?
Responding to changes in environment
Why do we need to do this?
These receptors communicate
graded potentials  trigger nerve impulses
WIDB: sensation vs perception?

9. Sensory Receptors Why do we need sensory receptors?
Responding to changes in environment
Why do we need to do this? Homeostasis
These receptors communicate
graded potentials  trigger nerve impulses
WIDB: sensation vs perception?

10. Sensory Receptors Why do we need sensory receptors?
Responding to changes in environment
Why do we need to do this? Homeostasis
These receptors communicate
graded potentials  trigger nerve impulses
WIDB: sensation vs perception?
Sensation sensing (unconscious interpretation)
Perception “sensing the sense” (conscious interpretation)

11. Classification of Receptors
How are the receptors classified?

12. Classification of Receptors
How are the receptors classified?
Stimulus type what you sense
Location where you sense
Structural complexity structure to help sense

13. Classification by Stimulus Type
What are the five types of stimuli we need to sense?

14. Classification by Stimulus Type
What are the five types of stimuli we need to sense?
Touch, vibration
Temperature
Light
Chemicals
Pain

15. Classification by Stimulus Type
What are the five types of classifications that go with these types of stimuli?

16. Classification by Stimulus Type
What are the five types of classifications that go with these types of stimuli?
Mechanoreceptors touch, pressure, vibration, stretch, and itch
Thermoreceptors changes in temperature
Photoreceptors light energy
Chemoreceptors chemicals
Nociceptors pain-causing stimuli
What are some examples of areas or scenarios where these are important?

17. Classification by Location
What are some simplified locations where you think that certain receptors may be needed?

18. Classification by Location
What are some simplified locations where you think that certain receptors may be needed?
Externally
Internally
“Middle”
(Remember this as the orientation)

19. Classification by Location
Exteroceptors
Where are the receptors?
Where are the stimuli?
What will they sense?

20. Classification by Location
Exteroceptors
Where are the receptors? Skin, most special organs
Where are the stimuli?
What will they sense?

21. Classification by Location
Exteroceptors
Where are the receptors? Skin, most special organs
Where are the stimuli? Outside of body
What will they sense?

22. Classification by Location
Exteroceptors
Where are the receptors? Skin, most special organs
Where are the stimuli? Outside of body
What will they sense? touch, pain, temp

23. Classification by Location
Exteroceptors
Where are the receptors? Skin, most special organs
Where are the stimuli? Outside of body
What will they sense? touch, pain, temp
Remember: what are the different forms of touch?

24. Classification by Location
Exteroceptors
Where are the receptors? Skin, most special organs
Where are the stimuli? Outside of body
What will they sense? touch, pain, temp
Remember: what are the different forms of touch?
Light
Pressure
Vibration
Deep

25. Classification by Location
Interoceptors (visceroceptors)
Where are the receptors?
Where are the stimuli?
What will they sense?

26. Classification by Location
Interoceptors (visceroceptors)
Where are the receptors? Visceral organs, BV
Where are the stimuli?
What will they sense?

27. Classification by Location
Interoceptors (visceroceptors)
Where are the receptors? Visceral organs, BV
Where are the stimuli? Internally
What will they sense?

28. Classification by Location
Interoceptors (visceroceptors)
Where are the receptors? Visceral organs, BV
Where are the stimuli? Internally
What will they sense? Chemical, temp, stretch

29. Classification by Location
Interoceptors (visceroceptors)
Where are the receptors? Visceral organs, BV
Where are the stimuli? Internally
What will they sense? Chemical, temp, stretch
What are some examples of when this would be important?

30. Classification by Location
Interoceptors (visceroceptors)
Where are the receptors? Visceral organs, BV
Where are the stimuli? Internally
What will they sense? Chemical, temp, stretch
What are some examples of when this would be important?
Blood concentrations
Monitoring HCl production in stomach
Find some others while you study!*

31. Classification by Location
Proprioceptors
Where are the receptors?
Where are the stimuli?
What will they sense?

32. Classification by Location
Proprioceptors
Where are the receptors? Skeletal muscles tissues
Where are the stimuli?
What will they sense?

33. Classification by Location
Proprioceptors
Where are the receptors? Skeletal muscles tissues
Where are the stimuli? Skeletal system
What will they sense?

34. Classification by Location
Proprioceptors
Where are the receptors? Skeletal muscles tissues
Where are the stimuli? Skeletal system
What will they sense? Orientation, stretch

35. Classification by Structural Complexity
What are the classifications based on complexity?

36. Classification by Structural Complexity
What are the classifications based on complexity?
Complex
Simple

37. Classification by Structural Complexity
What are the classifications based on complexity?
Complex special; specific
Simple not so special; specific

38. Classification by Structural Complexity
Complex receptors
Function: special sense
Vision, hearing, equilibrium, smell, and taste
Simple receptors
Function: general senses
Tactile, temp, pain, and muscle sense
Structure: unencapsulated or encapsulated
When have we talked about these before?

39. Unencapsulated Dendritic Endings
Thermoreceptors
Cold receptors (10–40ºC); in superficial dermis
Heat receptors (32–48ºC); in deeper dermis
Interesting thought: why do you think that the cold receptors are superficial and that heat receptors are deeper?
Also, why would these need to be unencapsulated?

40. Unencapsulated Dendritic Endings
Nociceptors
Respond to:
Pinching
Chemicals from damaged tissue
Temperatures outside the range of thermoreceptors
Capsaicin
Why would these need to be unencapsulated?

41. Unencapsulated Dendritic Endings
Light touch receptors
Tactile (Merkel) discs
Where are these?
Hair follicle receptors
Why would these need to be unencapsulated?

42. Table 13.1

43. Encapsulated Dendritic Endings
Mechanoreceptors
Meissner’s (tactile) corp. discriminative touch*
Pacinian (lamellated) corp. deep and vibration*
Ruffini endings deep (cont.) pressure*
Muscle spindles muscle stretch^
Golgi tendon organs stretch in tendons^
Joint kinesthetic receptors stretch in articular capsules^
*All of these are specific receptors which can be found in the skin
^All of these can be found in musculoskeletal systems

44. Table 13.1

45. From Sensation to Perception
Remember: what is the difference between sensation and perception?
Sensation
Perception

46. From Sensation to Perception
Remember: what is the difference between sensation and perception?
Sensation awareness of changes
Perception conscious interpretation of stimuli

47. Sensory Integration All the input comes from various receptors
Exteroceptors
Proprioceptors
Interoceptors
Where is the input relayed?

48. Sensory Integration All the input comes from various receptors
Exteroceptors
Proprioceptors
Interoceptors
Where is the input relayed?
CNS, the brain
However, it is processed along the way!

49. Sensory Integration We have different levels of integration
Receptor level sensor receptors
Circuit level ascending pathways
Perceptual level circuits in the cerebral cortex
What is an analogy for these different levels of integration?

50. Remember that this is a very simplified explanation of this concept.1 2 3
Receptor level
(sensory reception
and transmission
to CNS)
Circuit level
(processing in
ascending pathways)
Spinal
cord
Cerebellum
Reticular
formation
Pons
Muscle
spindle
Joint
kinesthetic
receptor
Free nerve
endings (pain,
cold, warmth)
Medulla
Perceptual level (processing in
cortical sensory centers)
Motor
cortex
Somatosensory
Thalamus
Figure 13.2
Remember that this is a very simplified explanation of this concept.

51. Processing at the Receptor Level
What is transduction?
The process by which a stimulus energy is converted into a graded potential.
This potential is called a receptor potential

52. Adaptation of Sensory Receptors
What is adaptation in terms of stimuli?

53. Adaptation of Sensory Receptors
What is adaptation in terms of stimuli?
Adaptation is a change in sensitivity in the presence of a constant stimulus
Receptor membranes become less responsive
Receptor potentials decline in frequency or stop
What are some examples where our sensory receptors might need to adapt to a situation?

54. Adaptation of Sensory Receptors
WIDB: the types of adaptation?
Phasic
Tonic

55. Adaptation of Sensory Receptors
WIDB: the types of adaptation?
Phasic fast-adapting receptors
Signal the beginning or end of a stimulus
Examples: receptors for pressure, touch, and smell
Tonic

56. Adaptation of Sensory Receptors
WIDB: the types of adaptation?
Phasic fast-adapting receptors
Signal the beginning or end of a stimulus
Examples: receptors for pressure, touch, and smell
Tonic slow-adapting receptors
Can be slow or not at all
Examples: nociceptors and most proprioceptors
Why might you need both?

57. Processing at the Circuit Level
Pathways of three neurons conduct sensory impulses upward to the appropriate brain regions
First-order neurons
Second-order neurons
Third-order neurons

58. Processing at the Circuit Level
Pathways of three neurons conduct sensory impulses upward to the appropriate brain regions
First-order neurons
Signals from receptor level  second-order neurons
Second-order neurons
Third-order neurons

59. Processing at the Circuit Level
Pathways of three neurons conduct sensory impulses upward to the appropriate brain regions
First-order neurons
Signals from receptor level  second-order neurons
Second-order neurons
Found in CNS: thalamus or cerebellum
Third-order neurons

60. Processing at the Circuit Level
Pathways of three neurons conduct sensory impulses upward to the appropriate brain regions
First-order neurons
Signals from receptor level  second-order neurons
Second-order neurons
Found in CNS: thalamus or cerebellum
Third-order neurons
Impulse from thalamus  somatosensory cortex
Perceptual level
Remember: what does the somatosensory cortex do?

61. Processing at the Perceptual Level
Perception of stimuli depends on the location of the target neurons in the sensory cortex
Aspects of sensory perception:
Perceptual detection detect a stimulus
Requires summation of impulses
Magnitude estimation intensity
Coded in frequency of impulses
Spatial discrimination site or pattern
Two-point discrimination test

62. Main Aspects of Sensory Perception
Feature abstraction complex aspects
Understanding several stimulus properties
Quality discrimination submodalities
Categories of sensation
Pattern recognition familiar/sig. patterns
What could be an example of this????

63. Perception of Pain
Why do we feel pain?

64. Perception of Pain Why do we feel pain? Stimuli include
Warns of actual or impending tissue damage
Stimuli include
extreme pressure and temperature
Compounds: histamine, K+, ATP, acids, and bradykinin
Impulses travel on fibers that release neurotransmitters
Examples: glutamate and substance P
Some pain impulses are blocked by inhibitory endogenous opioids

65. Structure of a Nerve
What is the structure of a nerve?

66. Structure of a Nerve What is the structure of a nerve?
Cordlike organ of the PNS
Bundle of myelinated and unmyelinated peripheral axons enclosed by connective tissue

67. Structure of a Nerve Connective tissue coverings include: Endoneurium
Perineurium
Epineurium

68. Structure of a Nerve Connective tissue coverings include: Endoneurium
loose connective tissue
encloses axons and their myelin sheaths
Perineurium
coarse connective tissue
bundles fibers into fascicles
Epineurium
tough fibrous sheath around a nerve

69. Axon Myelin sheath Endoneurium Perineurium Epineurium Fascicle Blood
vessels
(b)
Figure 13.3b

70. Classification of Nerves
Most nerves are mixtures of afferent and efferent fibers and somatic and autonomic (visceral) fibers
Pure sensory (afferent) or motor (efferent) nerves are rare
Types of fibers in mixed nerves:
Somatic afferent and somatic efferent
Visceral afferent and visceral efferent
Peripheral nerves classified as cranial or spinal nerves

71. Ganglia Contain neuron cell bodies associated with nerves
Dorsal root ganglia (sensory, somatic) (Chapter 12)
Autonomic ganglia (motor, visceral) (Chapter 14)

72. Regeneration of Nerve Fibers
Mature neurons are amitotic
What does this mean?
Damaged soma can regenerate new axon
Involves coordinated activity among:
Macrophages
Schwann cells
Form regeneration tube and secrete growth factors
Axons—regenerate damaged part
Oligodendrocytes have growth-inhibiting proteins
Prevent CNS fiber regeneration

73. Endoneurium Schwann cells The axon becomes fragmented at1
The axon
becomes
fragmented at
the injury site.
Droplets
of myelin
Fragmented
axon
Site of nerve damage
Figure 13.4 (1 of 4)

74. Macrophages clean out the dead axon distal to the injury. Schwann cell2
Schwann cell
Macrophage
Figure 13.4 (2 of 4)

75. Aligning Schwann cells form regeneration tube Axon sprouts,
or filaments,
grow through a
regeneration tube
formed by
Schwann cells. 3
Fine axon sprouts
or filaments
Figure 13.4 (3 of 4)

76. The axon Schwann cell Site of new regenerates and myelin sheath
a new myelin
sheath forms.
Schwann cell
Site of new
myelin sheath
formation 4
Single enlarging
axon filament
Figure 13.4 (4 of 4)