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Somatosensation Study Guide Flashcards

Lab

1
Q

What is Nociception?

A

pain

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2
Q

What is somatosensation?

A

Tactile + Proprioception
the sense of touch
Occurs when there is a mechanical interaction between your body and another object

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3
Q

What is thermoreception?

A

temperature

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4
Q

What is proprioception?

A

sensory input from your internal body (e.g. stomach)

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5
Q

Hairy skin

A

skin with hair
ex: arms, back

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6
Q

What are the 3 types of cutaneous receptors?

A

-Mechanoreceptors
-Thermoreceptors
-Nociceptive receptors

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7
Q

What are mechanoreceptors?

A

= respond to mechanical stimulation or pressure
•Embedded in the epidermis and dermis
•Consists of a nerve fiber and an expanded ending

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8
Q

What are thermoreceptors?

A

a cutaneous receptor that codes absolute and relative changes in temperature
-reside in dermis and epidermal layers
-differently concentrated in different areas

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9
Q

What are nociceptive receptors?

A

a sensory receptor that responds to painful input, such as extreme heat or pressure

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10
Q

What are the different mechanoreceptors?

A

Meissner Corpuscle (FA I)
Merkel Complexes (SA I)
Pacinian Corpuscle (FAII)
Ruffini Endings (SAII)

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11
Q

Fast-adapting (FA)=

A

motion of objects against skin
responds with action potentials when the stimulus is applied and again when the stimulus is removed

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12
Q

Slow-adapting (SA)=

A

pressure and shape of objects
Remains active as long as the stimulus is applied
(continuous firing)
Total number of action potentials evoked per second is proportional to indention force applied

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13
Q

Type I mechanoreceptor=

A

small receptive field
Located at the dermal-epidermal boundary
Low threshold, small RFs
Meissner Corpuscle: FA type
Merkel Cell: SA type, steady downward pressure
Both respond best to low frequency vibrations

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14
Q

Type II mechanoreceptor=

A

large receptive field
Located deep in the dermis
Higher threshold, Large Res
Pacinian Corpuscle: FA type; fast & sudden pressure, high frequency vibrations
Ruffini Endings: SA type, sustained downward pressure & lateral skin stretch

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15
Q

What type of information does the Meissner Corpuscle (FA I) convey?

A

§ Specialized encapsulated nerve endings
§ Concentrated in thick hairless skin (particular finger pads)
§ Relay light touch and low frequency vibration sensations
§ Sensitive to “skin slip” like when you start to drop the item you are holding
Fast adapting

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16
Q

What type of information does Merkel cell neurite complexes (SA I) convey?

A

§ Oval-shaped mechanoreceptors
§ Abundant in highly sensitive areas like the fingertips
§ Essential for light touch
§ Sensitive to texture or form perception
§ Ex: reading braille

Slow adapting

17
Q

What type of information does Pacinian corpuscles (FA II) convey?

A

§ Larger and fewer in number
§ Very responsive to vibration and pressure
§ Sensitive to fine texture perception and vibration
§ Ex: tell the difference between rough and smooth sandpaper, when an object you are holding and it hits something

Fast adapting

18
Q

What type of information do Ruffini endings (SA II) convey?

A

§ Spindle shaped receptors
§ Found on hairless skin on the fingertips
§ Important for finger position when picking up objects
§ Ex: playing the piano

Slow adapting

19
Q

What is two-point threshold?

A

=the minimum distance at which two stimuli (e.g., two simultaneous touches) are just perceptible as separate

=the smallest separation of two separate but adjacent points of stimulation on the skin that produces two distinct impressions of touch

20
Q

Why do different areas of the body have different two-point thresholds?

A

The glabrous skin of the hand and forehead shows the greatest sensitivity (lowest threshold) for both: At this location, pain acuity is nearly at the level of tactile acuity.
On the hairy skin of the arm, however, pain and touch diverge. For example, the shoulder is more spatially sensitive than the forearm to pain, but the reverse is found for tactile stimulation.

Two-point threshold is low (that is, the ability to discern two very close points as separate is high) only when the density of receptors is relatively high, the receptive fields are small, and cortical convergence does not occur.
Tactile spatial acuity thresholds are mediated by the SA I (and possibly FA I) tactile receptors, which have relatively small receptive fields and high receptor densities

21
Q

What is the relative distribution of cold and warm receptors?

A

The body has 30x more cold fibers than warm fibers
Most objects in our world are cooler than the normal skin temperature (30-36C or 86-97F)

22
Q

What type of pain fibers do we have?

A

-myelinated A-delta fibers
-unmyelinated C fibers

23
Q

Are our pain fibers myelinated or not?

A

Both
The myelinated A-delta fibers respond primarily to strong pressure or heat
The unmyelinated C fibers respond to intense stimulation of various sorts: pressure, heat or cold, or noxious chemicals.

24
Q

What happens to the sensitivity of thermoreceptors when there is a prolonged increase or decrease in temperature?

A

When the body is exposed to a temperature for a long period of time, the skin becomes less sensitive and changes its perception
For particular locations of the skin, certain temperatures are perceived as neutral
Increasing the temperature is perceived as warm, but it eventually adapts and is perceived as “neutral”
If the temperature of this same location is dropped, even back to the previous “neutral” temperature, it will be perceived as cold

25
Q

What type information is sent by the spinothalamic pathway?

A

Temperature and pain
Transmits information from thermoreceptors and nociceptors
Smaller diameter axons
Slower

26
Q

In the spinothalamic pathway, does the information ascend ipsilaterally or contralaterally from the side of stimulation and where does it cross?

A

Fibers from the body enter the spinal cord at the dorsal horn and cross the spinal cord to their first synapse immediately.
The information then ascends contralaterally (opposite side) via the spinothalamic tract to the ventral posterior nucleus of the thalamus.

27
Q

What information is sent via the dorsal column-medial lemniscus pathway?

A

Transmit touch, vibration, and proprioception
Wider dimeter axons, fewer synapses= faster

28
Q

In the dorsal column-medial lemniscus pathway, does the information ascend ipsilaterally or contralaterally from the side of stimulation and where does it cross?

A

Fibers from the body enter the spinal cord at the dorsal horn and travel up the spinal cord ipsilaterally (same side) via the Dorsal Column
At the medial lemniscus, the information crosses to the contralateral side of the body and then is sent to the ventral posterior nucleus of the thalamus

29
Q

What are dermatomes and what do they represent?

A

= area of the skin innervated by a particular portion of the spinal cord

30
Q

What does the “homunculus” represent in its topographical ​depiction of the cortex?

A

The somatosensory system is organized into a spatial map (somatopically) where each map has been called a sensory homunculus
= maplike representation of regions of the body in the brain

31
Q

Glabrous=

A

skin without hair
ex: lips, fingertips

32
Q

Epidermis=

A

the outer layer of two major layers of skin

33
Q

Dermis=

A

the inner of two major layers of skin, consisting of nutritive and connective tissues, within which lie the mechanoreceptors.

34
Q

How are mechanoreceptors classified?

A

-size of the receptive field
-rate of adaption

35
Q

How are thermoreceptors classified?

A

by temperature based fibers
-Cold fibers
-Warmth fibers

36
Q

How are nociceptive receptors classified?

A

lack specialized endings and can be divided into two types by their nerve fibers
-Unmyelinated A-delta fibers
-Myelinated C fibers

37
Q

What do the myelinated A-delta fibers convey?

A

respond primarily to strong pressure or heat
First signal (finish writing this part with class notes Ch. 13)

38
Q

What do unmyelinated C fibers convey?

A

respond to intense stimulation of various sorts: pressure, heat or cold, or noxious chemicals
Finish with school notes later

Flashcards (12 decks)

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