Sensory Physiology and Somatosensation - Fitzakerly

Question 1

Two senses that can be a perception rather than a sensation?

Answer 1

Two examples:
itch
pain

Question 2

Essential step in transduction:

Answer 2

Conformational change in transducer protein

There is not necessarily always a depolarization or opening of an ion channel

Question 3

3 types of energy encoded by human sensory receptors:

Answer 3

Chemical - olfactory
Mechanical - nociception, touch, audition
Electromagnetic - sight

Question 4

What does the term adequate stimulus mean?

Answer 4

It means the right type of stimulus, NOT a big enough stimulus to perceive.

No matter what actually caused the receptors to be stimulated the perception will be of the adequate stimulus

Question 5

Give an example of a change in acuity:

Do it!

Answer 5

Acuity is the ability to localize a stimulus

Following peripheral nerve damage, a physical therapist measures an improvement in a patient’s two point discrimination.

Question 6

Lateral inhibition seeks to enhance what about perception?

Answer 6

Seeks to enhance contrast. The CNS will actually inhibit the edges of the stimulated area in order to to contrast the area in and outside the stimulated field.

Question 7

3 types of pain?

Answer 7

1 - nociceptive (sensation = perception)
2 - inflammatory
3- Neuropathic
(2 and 3 have much more processing involved)
(This makes them much more difficult to treat)

Question 8

You bang your head (again) on a low-hanging pipe in your basement. You rub it and it feels like some of the pain goes away. Is there any physiological basis for this?

Answer 8

Yes. Nociceptive pathway both stimulate the excitatory pathway and inhibit the inhibotry interneuron that would decrease the nociception.

When you stimulate the mechanoreceptors in the surrounding skin, you actually are reactivating the the inhibitory interneurons which will act to decrease the nociceptive stimulus down the line.

Question 9

Which of the following functions is the first to be blocked by low concentrations of a local anaesthetic?
Voluntary muscle movements
Touch/pressure detection
Autonomic system function
Pain

Answer 9

Pain

Question 10

Compare adaptation speed between Meissner’s/Pascinian corpuscles and Merkel/Ruffini recpeors

Answer 10

o Meissner and Pacinian corpuscles, which encode flutter and vibration, adapt rapidly (they’ll respond when something first touches your skin)

o Merkel discs and Ruffini endings, which encode steady pressure and stretch adapt slowly (they’ll continue to respond if something stays in contact with your skin)

Question 11

Basic characteristics of TRP channels? Go!

Answer 11

• Involved in many sensations
• have 6 transmembrane domains
• permeable to cations, NONSELECTIVELY
• The direction and nature of ion flow therefore depends on the concentration gradients for the various ions

Question 12

What are the 3 main fiber types and their modalities and relative speeds?

Answer 12

A-beta = fastest, mechoreception
A-delta = very fast, mechnoreception, cold, fast pain
C = slow, mechanoreceptionm thermoreception, slow pain

Question 13

Use the 3 types of fibers discussed to label an experience of banging you head on a desk due to “Neuro-induced-cabin-fever, (NICF).

1) “I hit my head.”
2) “ Ow!”
3) “My Head aches”

Answer 13

1) “I hit my head.” = mechanoreception carried by Aβ fiber.
2) “ Ow!” = fast pain carried by Aδ fibres
3) “My Head aches just like my heart yearns for summer” = Unmyelinated C-fbers

Question 14

What is adaptation like in phasic receptors?

Answer 14

They adapt very rapidly

Question 15

What is the difference between allodynia and hyperalgesia?

Answer 15

Allodynia = Normal stimulation as percieved as intense pain

Hyperalgesia = Things that would normally only cause slight pain, cause intense pain

Question 16

What is TENS and why is it effective for pain management?

Answer 16

Trans-cutaneous electrical nerve stimulation (TENS) is a treatment for pain that also activates this suppression mechanism by delivering a small current to the skin overlying a nerve.

So basically it uses an electrical stimulation to provide the same kind of relief as rubbing your elbow after you hit it.

That whole gate-theory thing!

Question 17

Explain why the cocktail party effect makes it impossible to hear at party, for people with particular cortical damage to their brain.

Answer 17

Selective attention in a situation like this is dependent upon high order cortical brain regions that alter the sensitivity of sensory processing to preferentially extract the information they want in the midst of many complex stimuli.

Like many voices and noises at a cocktail party

Question 18

What is an adequate stimulus?

Answer 18

If you said “a big enough stimulus” then you my friend are wrong. Take a break and come back later.

AN adequate stimulus is the type of stimulus that the receptor responds to under normal conditions

• The principle of specificity does NOT mean that a receptor cannot respond to any other forms of energy (e.g. photoreceptors responding to intense pressure).
• However, due to segregation of sensory pathways (think of the organization of sensory cortices, with each system in a different physical location, any stimulus is perceived as if it was the adequate stimulus

Question 19

What are the special senses?

Answer 19

Gustation
Audition
Vision
Olfaction
Balance

Question 20

What is stimulus coding?

Answer 20

the cortex is left with the task of assembling all of this information, and deciding why you should care about it

• What: stimulus modality
• How big: stimulus intensity
• When: stimulus duration
• Where: stimulus location

Question 21

What does the labeled line theory have to say about how we perceive our environment?

More importantly… does labeled line theory affirm the premise behind “The Matrix?”

Answer 21

The answer is yes, the matrix could work in one sense because if you are stimulating all the right receptors then the individual will be percieving things as if they corresponded to the adequate stimulus

the brain associates a specific modality (the adequate stimulus) with a signal coming from a specific receptor (e.g., “light” is detected by the photoreceptors, even if the stimulus is pressure on the eye)
further evidence seen in the way the brain is “mapped”

Question 22

Give me the basics of patten theory:

Answer 22

•Premise: some sensory systems (esp. taste and olfaction) integrate information across multiple primary afferents and a few types of afferent endings are multimodal (more than one sensation can be evoked by their activation)

•Conclusions: an ascending pathway can convey sensory information by altering the temporal pattern of action potentials among multiple responding primary afferents
-under this theory, it is the pattern of activation of neural networks that forms the basis of perception

•Evidence: examples are found in the olfactory system & in color perception

Question 23

Define adaptation (In the neuro sense of things)

Answer 23

receptor process by which the response to a constant stimulus declines over time

Question 24

How could you use the idea of adaptation to explain why the smoker who lives underneath my apartment continues to bother me no matter how often I can smell the smoke in my kitchen?

Answer 24

Olfaction is an example of a tonic adapting receptor system. This means that adaptation occurs much slower and the smell will continue to annoy me longer.

Question 25

Define acuity:

Answer 25

the ability to precisely localize a stimulus or the ability to localize a discriminative touch stimulus is called point localization, and it is dependent upon receptive field size, which varies widely throughout the body

3 forms are recognized

1) Spatial acuity: ability to resolve 2 points in space
2) Temporal acuity: ability to distinguish visual events in time
3) Spectral acuity: ability to distinguish differences in the wavelength of the stimuli