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D1 Spring - Physiology > 2/5: Sensory Physiology > Flashcards

2/5: Sensory Physiology Flashcards

1
Q

What does the afferent pathway inter the CNS via?

A

The posterior/dorsal roots

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2
Q

What are labeled lines?

A

Receptors and neurons in the CNS are dedicated to carrying particular sensory information

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3
Q

What are the schematics of sensory (afferent) pathways?

A

Receptor
First order neuron
Second order neuron
Third order neuron
Primary somatosensory cortex (parietal lobe)

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4
Q

What does the second order neuron do?

A

Decussation (crossing over) occurs, though where this occurs within the CNS varies based on the sensory modality

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5
Q

What does the dorsal column medial lemniscal pathway do?

A

Touch, pressure, and proprioception

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6
Q

What does the spinothalamic tract do?

A

Pain, temperature

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7
Q

Input to the nervous system is provided by _______ receptors

A

Sensory

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8
Q

What are the 5 functional types of sensory receptors?

A
  1. Mechanoreceptors
  2. Chemoreceptors
  3. Thermoreceptors
  4. Nociceptors
  5. Photoreceptors
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9
Q

What are mechanoreceptors?

A

compression/stretch
Includes receptors in skin, muscle spindles, hearing, equilibrium, arterial pressure, etc

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10
Q

What are chemoreceptors?

A

Ligands
incldues receptors for taste, smell, arterial oxygen, osmolarity, blood gas, blood glucose, etc

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11
Q

What are thermoreceptors?

A

Cold/warm

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12
Q

What are nociceptors?

A

Damage

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13
Q

What are photoreceptors?

A

Electromagnetic receptors
Light

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14
Q

What is an adequate stimulus?

A

Particular form of energy to which a receptor is most sensitive

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15
Q

What do receptors respond to?

A

Forms of energy, but the threshold for these nonspecific responses is much higher

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16
Q

Sensory receptors are specific for a ___________________

A

Particular energy type (or modality)

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17
Q

Activation of any sensory receptor changes _____________ and produces what is called ____________

A

Membrane potential (transduction); receptor potential (a graded potential)

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18
Q

Describe how the pacinian corpuscle works as a mechanoreceptor?

A

When the surrounding capsule is distressed, the
central nerve fiber is in turn distorted, opening ion channels. The greater the
depression, the more ion channels will open, so a larger GP will be produced which leads to more APs

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19
Q

What does an increase in stimulus strength also increase?

A

The amplitude of receptor potentials, but this is not a direct (linear) relationship

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20
Q

What two things does the intensity (or strength) of stimulus perception determined by?

A
  1. The frequency of action potentials (temporal summation)
    - APs are all or none, a stronger stimulus will NOT generate a larger AP
    - AP frequency (how close together in time the AP’s are)
  2. The total number of receptors activate (Spatial summation)
    - stronger stimulus = more receptors
    - number of receptors activated
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21
Q

A stronger stimulus intensity produces a __________ receptor (graded) potential, _______ action potentials (temporal summation), and causes _______ neurotransmitter release into the synapse

A

Larger; more; more

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22
Q

What are two types of receptor adaptation?

A
  1. Perceptual threshold
  2. Adaptation can occur at the receptor or in the neuron
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23
Q

What is perceptual threshold?

A

If a stimulus of constant strength is maintained on a sensory receptor, the frequency of the action potentials in its sensory nerve declines over time.

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24
Q

What is adaptation?

A

In response to continual,
high impulse sensory stimuli, the response of almost all receptors decreases, but to varying degrees
- second you put a necklace on, you feel it due to adaptation
- jumping into a cold pool

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25
Q

What are the two sepcific types of adaptation receptors?

A

Tonic = slow adapting
- receptors that adapt after they initially respond
- pain receptors are tonic
Phasic = fast adapting

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26
Q

What is receptor adaptation?

A

Decrease in amplitude of receptor potential over time in the presence of a constant stimulus
- corresponding decrease in frequency of APs
- decreases perception of stimulus

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27
Q

What do tonic receptors help differentiate?

A

Stimulus intensity
- slow adapting

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28
Q

What are examples of tonic receptors?

A

Golgi tendon organs, NOCICEPTORS, chemoreceptors, baroreceptors

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29
Q

Phasic receptors help differentiate stimulus ___________

A

Duration

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30
Q

What are examples of phasic receptors?

A

Pacinian corpuscles, vestibular receptors in inner ear, TEMP RECEPTORS

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31
Q

What does a precise modality activate?

A

Specific receptors and postsynaptic cells
- This information continues on a predicted pathway such that particular kinds
of information are conveyed via specific nerve fibers to specific regions of the CNS that are programmed for perception of that modality

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32
Q

What does the homunculus correlate to?

A

The anatomical regions of the CNS with where interpretation and awareness of sensations are perceived

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33
Q

Where are the two first order neuron locations?

A

Dorsal column pathway
Spinaothalamic tract

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34
Q

Where does the second order neuron occur?

A

In the dorsal column it crosses into the lower medulla
In the spinothalamic tract is crosses over immediately in the upper limb

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35
Q

Where does the third order neuron occur?

A

In thalamus for both pathways

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36
Q

What is a receptive field?

A

Region where a single fiber’s afferent receptors (primarily on dendrites) are located

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37
Q

The overlap between receptive fields of adjacent neurons improves what?

A

Localization ability - two point discrimination

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38
Q

What is acuity?

A

The precision with which a stimulus is perceived

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39
Q

What enhances acuity?

A

The process of lateral inhibition

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40
Q

What improves discrimination?

A

Lateral inhibition

41
Q

What can sensory stimulation of a single point on the skin elicit?

A

Excitation in one tract of post-synaptic cells while simultaneously inhibiting lateral neurons

42
Q

Where does lateral inhibition occur?

A

In the CNS

43
Q

Why is lateral inhibition advantageous?

A

It diminishes lateral spread of an excitatory signal and increases degree of contrasts in the sensory pattern perceived in the cortex

44
Q

What 3 synapses does lateral inhibition occur at?

A
  1. Medulla
  2. Thalamus
  3. Cerebral cortex
45
Q

Nerve fibers that have _______ diameter axons and/or that are ________ have faster conduction velocities

A

Large; myelinated

46
Q

What fibers are fast fibers?

A

A fibers

47
Q

What fibers are slow fibers?

A

C fibers

48
Q

Which do you perceive first - a temperature or a vibration (mechanical) sensation? Why?

A

Vibration mechanical because it is an A beta fiber that is faster

49
Q

What are examples of slow pain?

A

Crude touch and pressure
Tickle
Aching pain
Warmth

50
Q

What fiber is temperature?

A

A delta & C fibers

51
Q

What do mechanoreceptors include?

A

Tactile and position sensations that are stimulated by mechanical displacement of somet issues in the body

52
Q

What are the three examples of tactile sensations?

A
  1. Touch sensations from
    stimulation of tactile receptors
    in the skin or tissues beneath
    the skin.
  2. Pressure sensations from
    deformation of deeper tissues.
  3. Vibration sensations from
    rapidly repetitive sensory
    signals
53
Q

What are two examples of position sensations?

A
  1. Static position sense is
    conscious perception of
    orientation of different parts of the body with respect to one another.
  2. Rate of movement sense is also called kinesthesia or
    dynamic proprioception
54
Q

What are examples of mechanoreceptors?

A

Free nerve endings
Pacinian corpuscle
Meissner’s corpuscle
Merkel’s disks
Ruffini endings
Hair end-organs

55
Q

What do free nerve endings detect?

A

Touch and pressure (temp and pain)W

56
Q

Where are free nerve endings?

A

Skin, cornea, dental pulp, GI tract

57
Q

What kind of adaptation are free nerve endings?

A

Slow adaptation/tonic

58
Q

What do pacinian corpuscles detect?

A

Deep pressure, vibration

59
Q

Where are pacinian corpuscles?

A

Subcutaneous tissue, viscera, joints

60
Q

What kind of adaptation are pacinian corpuscles?

A

Rapid adaptation/phasic

61
Q

What do meissner’s/tactile corpuscles detect?

A

Light touch, pressure, vibtation

62
Q

Where are meissner’s/tactile corpuscles found on?

A

Glabrous skin (hairless - palms, inside of forearm)
LOCALIZATION

63
Q

What kind of adaptation are meissner’s/tactile corpuscles?

A

Rapid adaptation/phasic

64
Q

The density of meissner’s corpuscles in skin can be determined by?

A

Two-point discrimination tests
- the number of tactile corpuscles in skin normally declines during adult life

65
Q

What do merkel’s disks detect?

A

Localize continuous pressure and sensing an object’s texture

66
Q

What skin are merkel’s disks on?

A

All skin

67
Q

What kind of adaptation do merkel’s disks have?

A

Slow adaptation/tonic

68
Q

What are ruffini’s endings sensitive to?

A

Stretch or indentation; proprioception

69
Q

Where are ruffini’s endings found?

A

Deep layers of skin, joints, surrounding tooth roots

70
Q

What kind of adaptation do ruffini’s endings have?

A

Slow adaptation/tonic

71
Q

What receptors are periodontal mechanoreceptors in the periodontal ligament?

A

Ruffini like receptors

72
Q

What are hair end-organs sensitive to?

A

Hair movement

73
Q

Where are hair end-organs found?

A

Base of hair follicle

74
Q

What kind of adaptation are hair end-organs?

A

Rapid adaptation/phasic

75
Q

What kind of receptors have smallest receptive fields so most precise localization?

A

Meissner’s corpuscle
Merkel cells

76
Q

Memorize where each somatic receptor is located, size, their receptive fields, and their adaptation type

A
77
Q

What is the medial lemniscus?

A

An ascending bundle of heavily myelinated axons that cross over in the medulla

78
Q

Where does the ascending sensory tract ascend?

A

The spinal cord on the same side as the stimulus

79
Q

Where does the second order neuron cross over?

A

In the medulla oblongata

80
Q

What does the spinothalamic/anterolateral pathway detect?

A

Pain, thermoreceptors, crude tactile, tickle, itch and sexual sensations

81
Q

What does the spinothalamic/anterolateral pathway transmit?

A

A broad spectrum of sensory modalities

82
Q

Where does the second order neuron cross over?

A

crosses over in the spinal cord and ascends in either the anterior or lateral spinothalamic tract on the opposite side of the spinal cord from where the stimulus occurred

83
Q

With a UNILATERAL
lesion of the spinal cord, one would expect to lose
_____ lateral touch/pressure & _____ lateral pain/temperature sensations below the injury level

A

Ipsi (same side); contra (opposite sides)

84
Q

What areas are poscentral gyrus?

A

Areas 1-3

85
Q

What areas are sensory association areas?

A

Areas 5 and 7

86
Q

What does damage to the somatosensory association area result in?

A

the inability to recognize complex objects and forms felt on the opposite side of the body. Also loses sense of form of their own body on the opposite side; mainly oblivious to the opposite side of the body

87
Q

What is proprioception?

A

Awareness of the body’s position in space

88
Q

What are the two types of proprioception?

A

Static vs dynamic

89
Q

What are the receptor types of proprioception?

A
  1. Photoreceptors
  2. Touch and pressure receptors in skin, joints, ligaments (ex: periodontal ligament)
  3. Skeletal muscle receptors (unconscious proprioception)
    a. muscle spindles
    b. golgi tendon organs
  4. Vestibular receptors
90
Q

What are the two types of somatosensory mechanoreceptors in the mouth/face?

A

A. extensive innervation
B. Cutaneous and mucosal receptors

91
Q

What are extensive innervation?

A
  1. Incredibly high sensitivity to stimuli
  2. Relatively large region of the cortex receives
    information (Sensory Homunculus)
92
Q

What are cutaneous and mucosal receptors?

A
  1. Meissner, Merkel, Ruffini, and free nerve endings
    a. No Pacinian Corpuscles
  2. Also send proprioceptive information
  3. Mechanoreceptors can convey taste perception
93
Q

Where are periodontal mechanoreceptors?

A

In the periodontal ligament

94
Q

What are periodontal mechanoreceptors made of?

A

Mostly complex Ruffini-like receptors; also free
nerve endings. Axons are large & myelinated.

95
Q

Describe the adaptation of periodontal mechanoreceptors?

A

Adaptation is both slow and fast

96
Q

What do the location of receptors allow for?

A

respond to any forces applied to the crown of the teeth (when biting and chewing)

97
Q

What does a brisk tap on the tooth do?

A

inhibits jaw closing muscles (ex. jaw opens to prevent damage)

98
Q

What does the weak tap on the tooth do?

A

activates jaw closing muscles (ex. to hold onto food and adjust chewing force)

D1 Spring - Physiology (17 decks)

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