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Physiology II > Somatic Sensation > Flashcards

Somatic Sensation Flashcards

1
Q

This process occurs in response to a sustained stimulus and results in a neuron showing a decreased firing rate over time

A

Adaptation

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2
Q

What are the two types of adaptation a neuron may experience?

A

Fast and slow

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3
Q

What are some characteristics of slow adaptation?

A
  • It provides continuous information (tonic)
  • It is relatively non-adapting
  • Helps the cell respond to a sustained stimulus
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4
Q

What are some examples of neurons that undergo slow adaptation?

A
  • Joint capsule
  • Muscle spindle
  • Merkel’s discs
  • Ruffini end organs
  • Nociceptors
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5
Q

What are some characteristics of fast adaptation?

A
  • Rapid or phasic
  • Reacts strongly when a change is taking place
  • Responds to vibration
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6
Q

What are some examples of neurons that undergo fast adaptation?

A
  • Hair receptors (30-40Hz)
  • Pacinian corpuscles (250Hz)
  • Meissner’s corpuscles (30-40Hz)
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7
Q

Membrane adaptation is thought to be due to entry of what ion during action potentials?

A

Calcium

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8
Q

Which spinal joints are the most heavily innervated?

A

Cervical joints

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9
Q

What are the four types of sensory receptors of the spinal joints?

A

Type I, II, III, IV

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10
Q

Of the four spinal joint sensory receptors, which are the largest? Smallest?

A

Type I are the largest, while Type IV are the smallest

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11
Q

Of the four spinal joint sensory receptors, which are myelinated? Unmyelinated?

A

Type I-III are myelinated, while Type IV are unmyelinated

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12
Q

This type of mechanoreceptor is found on the outer layers of the joint capsule and fires at a degree proportional to the joint movement. They are low threshold, slow adapting, and have a tonic effect on lower motor neuron pools.

A

Type I mechanoreceptors

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13
Q

This type of mechanoreceptor is found in the deeper layers of the joint capsule and functions in joint movement monitoring. They are low threshold, rapidly adapting, and have a phasic effect on lower motor neuron pools.

A

Type II mechanoreceptors

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14
Q

This type of mechanoreceptor has recently been found in spinal joints and is the joint version of a Golgi tendon organ. They have a very high threshold and are slow adapting.

A

Type III mechanoreceptors

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15
Q

This type of receptor is a nociceptor and are completely inactive in a physiologically normal joint. They have a very high threshold and activate with joint narrowing, increased capsule pressure, or chemical irritation.

A

Type IV receptors

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16
Q

What does information transmitted to the brain from mechanoreceptors in fingers allow us to do?

A
  • Feel the shape and texture of objects
  • Play musical instruments
  • Type on computer keyboards
  • Palpate and perform adjustments
  • Perform a multitude of tasks using our hands
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17
Q

Tactile information from mechanoreceptors is ____ by receptors and must be integrated by the ____.

A

Fragmented; brain

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18
Q

What is one of the most important complex functions of the somatosensory system?

A

The ability to recognize objects placed in the hand on the basis of touch alone.

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19
Q

This is the ability to perceive form through touch.

A

Stereognosis

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20
Q

What does stereognosis test?

A
  • The ability of the dorsal column-medial lemniscal system to transmit sensations from the hand
  • The ability of cognitive processes in the brain where integration occurs.
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21
Q

What are the categories of sensory modalities?

A

Pressure receptors, cold receptors, warmth receptors, and nociceptors

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22
Q

Which sensory modalities compose our perception of wetness? Ticklishness? Itching?

A
  • Wetness: stimulation of pressure and temperature
  • Ticklishness: gentle stimulation of pressure receptors
  • Itching: gentle stimulation of nociceptors
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23
Q

When fine textures are stroked on the fingerpad skin, the fingerprint ridges ____ and cause ____ ____ to respond enabling the detection of microtexture.

A

Vibrate; Pacinian corpuscles

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24
Q

When perceiving shape, the depth of indentation and change in curvature of the skin surface are encoded by discharge rates of what types of fibers?

A

Slow adapting afferent fibers

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25
Q

When perceiving shape, the velocity and rate of change in skin surface curvature are encoded by discharge rates of what types of fibers?

A

Slow adapting and rapidly adapting afferent fibers

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26
Q

What are the rapidly adapting cutaneous mechanoreceptors?

A

Meissner’s corpuscles, hair follicle receptors, and Pacinian corpuscles

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27
Q

Where are Meissner’s corpuscles typically found?

A

They are typically found in glabrous (non hairy) skin and concentrated in the fingertips

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28
Q

Where are hair follicle receptors typically found?

A

Hairy skin

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29
Q

Where are Pacinian corpuscles typically found?

A

Subcutaneous tissue

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30
Q

What are the slowly adapting cutaneous mechanoreceptors?

A

Merkel’s discs and Ruffini end organs

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31
Q

What do Merkel’s discs sense?

A

Curvature of an object’s surface

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32
Q

How are Ruffini end organs activated?

A

By stretching the skin. This can occur even at some distance away from the receptor

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33
Q

These receptors are rapidly adapting (vibratory sensation) and are superficial (small receptive field).

A

Meissner’s corpuscles

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34
Q

These receptors are rapidly adapting (vibratory sensation) and are deep (large receptive field).

A

Pacinian corpuscle

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35
Q

These receptors are slowly adapting (sustained pressure) and are superficial (small receptive field).

A

Merkel’s discs

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36
Q

These receptors are slowly adapting (sustained pressure) and are deep (large receptive field).

A

Ruffini’s end-organ

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37
Q

This area of the brain receives projections from the thalamus, has a somatotopic organization, and each central neuron has a receptive field.

A

Somatosensory cortex

38
Q

This term is used to describe the process by which a 1st order neuron synapses and subsequently excites 2nd order neurons as well as interneurons. This results in surrounding inhibition and the enhancing of edges.

A

Lateral inhibition

39
Q

Does lateral inhibition improve acuity?

A

No

40
Q

What are the two major pathways of the somatosensory cortex?

A

Dorsal column-medial lemniscal system (Epicritic) and the anterolateral system (Protopathic)

41
Q

This somatosensory pathway contains 1st order neurons that synapse in the brain stem and deals with most aspects of touch and proprioception.

A

Dorsal column-medial lemniscal system (Epicritic)

42
Q

This somatosensory pathway contains 1st order neurons that synapse in the dorsal horn of the spinal cord and deals with sensations of crude touch, nociception, temperature, tickle, itch, and sexual sensations.

A

Anterolateral system (Protopathic)

43
Q

What do 2nd order neurons do in both somatosensory pathways?

A

They cross to the other side and ascend, synapsing in the thalamus

44
Q

Does the dorsal column-medial lemniscal system (Epicritic) contain ipsiliateral or contralateral fibers?

A

Ipsilateral

45
Q

Does the anterolateral system (Protopathic) contain ipsiliateral or contralateral fibers?

A

Contralateral

46
Q

This type of pathway is old (phlogenetically), synapses in the cord, contralateral in the cord, has small fibers, initiates actions, and is involved with pain, temperature, tickle, itch, and sexual sensations.

A

Protopathic

47
Q

This type of pathway is new (phlogenetically), synapses in the brain stem, ipsilateral in the cord, has large fibers, modifies actions, and is involved with fine touch/proprioception.

A

Epicritic

48
Q

Most nerve cells are responsive to how many modalities?

A

Only one

49
Q

Which receptors provide input to Brodmann area 3a?

A

Muscle stretch receptors (spindles)

50
Q

Which receptors provide input to Brodmann area 3b?

A

Cutaneous receptors

51
Q

Which receptors provide input to Brodmann area 2?

A

Deep pressure receptors

52
Q

Which receptors provide input to Brodmann area 1?

A

Rapidly adapting cutaneous receptors

53
Q

What are the three different types of neurons in Broadmann areas 1 and 2 that have complex feature detection capabilities?

A
  • Motion sensitive neurons
  • Direction-sensitive neurons
  • Orientation-sensitive neurons
54
Q

This type of neuron within Brodmann areas 1 and 2 responds well to movement in all directions but not selectively to movement in any one direction.

A

Motion sensitive neurons

55
Q

This type of neuron within Brodmann areas 1 and 2 responds much better to movement in one direction than in another.

A

Direction-sensitive neurons

56
Q

This type of neuron within Brodmann areas 1 and 2 responds best to movement along a specific axis.

A

Orientation-sensitive neurons

57
Q

This Brodmann area integrates tactile information from mechanoreceptors in skin with proprioceptive inputs from underlying muscles and joints.

A

Brodmann area 5

58
Q

This Brodmann area receives visual, tactile, and proprioceptive inputs. It integrates stereognostic and visual information.

A

Brodmann area 7

59
Q

What are some of the main functions of the posterior parietal cortex (Brodmann area 5 and 7)?

A
  • Projects to motor areas of the frontal lobe

- Sensory initiation and guidance of movement

60
Q

This area of the brain is located in the superior bank of the lateral fissure and projects to the insular cortex, which innervates regions of the temporal lobe believed to be important in tactile memory. Projections from the primary somatic sensory cortex are required for function of this area.

A

Secondary somatic sensory cortex (S-II)

61
Q

These types of receptors are sensitive to temperature of the skin. They are slow adapting, discharge spontaneously under normal conditions, and discharge phasically when skin temperature is changing rapidly.

A

Thermoreceptors (two types: cold and warmth)

62
Q

At extreme skin temperatures thermoreceptors become inactive and these types of receptors become active.

A

Nociceptors (pain)

63
Q

What types of stimuli can activate nociceptors?

A
  • Mechanical stimuli
  • Thermal stimuli
  • Chemical stimuli
64
Q

This term is used to describe the reception of signals in the CNS evoked by stimulation of specialized sensory receptors that provide information about tissue damage.

A

Nociception

65
Q

This term is used to describe the perception of adverse or unpleasant sensation that originates from a specific region of the body.

A

Pain

66
Q

These are the least differentiated of all sensory receptors and can be sensitized by tissue damage.

A

Nociceptors

67
Q

This nociceptive pathway contains A delta fibers, utilizes glutamate, deals with mechanical/thermal stimuli, has good localization, and is associated with sharp or pricking pain.

A

Fast nociceptive pathway

68
Q

This nociceptive pathway contains C fibers, utilizes substance P and glutamate, deals with polymodal/chemical stimuli, has poor localization, and is associated with dull, burning, or aching pain.

A

Slow nociceptive pathway

69
Q

Where does the fast nociceptive pathway terminate?

A

In the ventrobasal complex of the thalamus

70
Q

Where does the slow nociceptive pathway terminate?

A

It has a diffuse termination to the reticular formation, tectal areas of the mesencephalon, and the periaqueductal grey

71
Q

These fibers are part of the slow nociceptive pathway adn secrete both substance P and glutamate. They synapse primarily in substantia gelatinosa (lamina II and III of the spinal cord)

A

C-fibers

72
Q

Between glutamate and substance P, this secretion’s effects are transient and short acting.

A

Glutamate

73
Q

Between glutamate and substance P, this secretion is release more slowly and concentrations build over time. It is responsible for slow pain.

A

Substance P (substance powder)

74
Q

What are some examples of nociceptive pathways?

A
  • Spinothalamic-major (fast and slow)
  • Spinoreticular
  • Spinomesencephalic
  • Spinocervical (mostly tactile)
  • Dorsal columns (mostly tactile)
75
Q

What are the cardinal signs of inflammation?

A

Rubor: redness
Calor: heat
Tumor: swelling
Dolar: pain

76
Q

What are the two types of pain control mechanisms?

A

Peripheral and Central

77
Q

What is gating theory?

A

It involves inhibitory interneurons in the cord impacting nociception projection neurons

78
Q

Where are endogenous opioids located and what do they do?

A
  • Periaqueductal grey has enkephalin projections to Raphe
  • Raphe nucleus has serotonin projections to the cord
  • Inhibitory interneurons in the cord release enkephalins, which can cause pre-synaptic inhibition of incoming C and A delta fibers as well as 2nd order projection neurons
79
Q

Where are cannabinoid receptors found?

A

In the brain (CB1)

80
Q

Where are endogenous cannabinoids produced? What are some examples?

A
  • They are produced in the brain

- Examples: anandamide, 2-arachidonoylglycerol (2-AG)

81
Q

What substance contributes to a “runner’s high” during exercise?

A

2-arachidonoylglycerol (2-AG)

82
Q

What are some intracranial origins of headaches?

A
  • Meningitis: inflammation of the meninges
  • Migraine: vasoconstriction/vasodilation
  • Irritation of the meninges: abuse of alcohol or constipation
83
Q

What are some extracranial origins of headaches?

A
  • Muscle spasm
  • Irritation of nasal passages and/or sinuses
  • Eye disorders
  • Cervical joint dysfunction
  • Traction of dura
84
Q

What is the relationship between the cervical spine and headaches?

A
  • CN V has sensory innervation of most of the head and face
  • CN V nucleus of termination extends to C2
  • C2 afferents synapse both in the dorsal horn and CN V nuclei
  • Overlap between CN V and C2 can cause headache associated with cervical dysfunction.
85
Q

This term is used to describe the phenomenon of increasing signal strength transmitted by multiple fibers.

A

Spatial summation

86
Q

This term is used to describe the phenomenon of increasing signal strength due to an increased firing rate of a single fiber.

A

Temporal summation

87
Q

This term is used to describe a neuronal circuit causing both excitation and inhibition.

A

Reciprocal inhibition

88
Q

This term is used to describe a postsynaptic potential that lasts for milliseconds and can continue to excite a neuron.

A

Synaptic afterdischarge

89
Q

This is a type of circuit in which positive feedback due to collateral fibers restimulates itself or neighboring neurons in the same circuit.

A

Reverberatory circuit

90
Q

What are some characteristics of a self excitatory system (continuous signal output)?

A
  • Less negative membrane potential

- Leaky membrane to Na+/Ca++

91
Q

What causes rhythmical signal output?

A

Reverberating circuits

92
Q

What are some mechanisms within the nervous system that maintain the stability of neuronal circuits?

A
  • Inhibitory circuits
  • Fatigue of synapses
  • Decreasing resting membrane potential
  • Long-term changes by down regulation of receptors

Physiology II (4 decks)

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