Physio lab Sensation

1

Subject: Physiology Lab Topic: Sensation Lecturer: Dr. Simbulan Simbulan and class Transcriptionist: Pegasus Editor: None. Read at your own risk Pages: 9

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Hey, guys, this turned out to be pret ty much a copy and paste of the power points presented by the megagroups since everyone pretty much read off their s, with the addition of a few choice words from Dr. Simbulan. Experiment 10 y Information about the internal and external environment activates the CNs via a variety of sensory receptors. y These receptors are transducers that convert various forms of energy in the environment into action potentials in neurons y 4 types of sensory receptors 1. Chemoreceptors  specific ligands 2. Osmoreceptors  concentration of solutes 3. Mechanoreceptors  touch, pressure, vibration, stretch 4. Thermoreceptors  temperature change a. Cold receptors lower than body temperature b. Warm receptors  37  45° C 5. Photoreceptors - light y Classification of sensory system by structural complexity Somatic (general senses) o Touch  Temperature  Nociception  Itch  Proprioception  Special senses o  Vision Hearing  Taste  Smell   Equilibrium y CNS distinguishes 4 stimulus properties Modality of stimulus o Type of receptor  o Location o Intensity Duration o Touch/pressure/position (mechanoreceptors) y They are sensitive to stimuli that distort their cell membranes. They contain mechanically regulated ion channels, which open and close in response to movement. y There are 3 classes: o Tactile Baroreceptors o Proprioceptors o y Tactile receptors

o

o

o

Provide the sensations of touch, pressure, and vibration Fine touch and pressure receptors provide detailed information about a source of stimulation, including the exact location, shape, size, texture, and movement. They also have extremely sensitive and relatively narrow receptive fields. Types of Tactile Receptors:  Free nerve endings: sensitive to touch and pressure  Root hair plexus: made up of free nerve endings to detect hair movement.  Merkels discs: fine touch and pressure neurons located in the lower epidermal layer of the skin  Meissners corpuscles: corpuscles: fine touch and pressure receptors located in the eyelids, lips, fingertips, nipples , and external genitalia Pacinian corpuscles are large receptors  sensitive to deep pressure and to pulsing or high-fre quency vibrations. They are found in the skin, fingers, breasts, external genitalia and some visceral organs as well. Ruffini corpuscles are located in the  dermis of the skin and are sensitive to pressure and distortions of the skin.

Objectives y To understand the different features of sensation y To identify the different type of skin receptors y To understand the concept of sterognosis Procedure Part1 y Tip of needle was lightly pressed against various spots on a 2 sq. cm stamp imprint on the arm y U niform pressure was applied in all trials using a needle inserted through a cork. y Any sensation such as pain, touch, cold, etc. should be recorded. Use the designated legends for the sensation felt. Part 2 y With the subject blindfolded, a cork was placed on the top of the skin of the forearm for 1  2 minutes. y Subject was asked if the initial sensation of touch or pressure was continually unaltered Part 3.1 y A coin was warmed by another group member using his/her hands

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2 y

y

Subject was asked to touch the coin and was asked to describe the shape. The coin was held by the subject for 2 minutes. Subject was asked if the initial sensation of touch and pressure remain unaltered.

Part 3.2 y

y

y

are found in the fingertips. Nerve fibers for touch receptors are ,  and C fibers Itch sensations are through naked nerve endings Discussion of Part 2 Sensation was altered since the skin has already adapted to the pressure of the cork Adaptation: decrease in the frequency of action potentials in an efferent neuron despite the main maintenance of the stimulus at a constant strength. Rapidly adapting vs. slowly adapting receptors y

y

coin was placed on the volar surface of the forearm, antecubital fossa Subject was asked to flex his/her forearm, squeezing the coin lightly (2 minutes) Subject was asked if he/she can describe the shape of the coin accurately and if the initial sensation of touch or pressure remain unaltered. A

y

Results

Part 1 y

y

y y

y

y

Pain receptors: this should should be the most receptors found Cold receptors: this should be the least in number Itch receptors: this is rare in most cases Sense organ for pain, which are free nerve endings are found in all parts of the body (superficial part of the skin) Note: There is individual difference in the recorded sensation felt. Note: Dr. Simbulan made a point of stressing that more than 1 chart should have been presented.

Part 2 y

y

Does the initial sensation of touch or pressure remain unaltered? NO. Initial sensation was touched and was then altered after 2 minutes.

Part 3.1 y

y

Does the initial sensation of touch or pressure remain unaltered? YES Initial sensation felt was touch and the subject could describe clearly the shape of the coin. After 2 minutes, it remained unaltered

Part 3.2 Was the subject able to describe the shape of the coin accurately? Does the initial sensation of touch or pressure remain unaltered? Initial sensation felt was touch and deteriorated after 2 minutes. The subject wasnt able to describe the shape of the coin. Discussion Pain receptors: This should be the most receptors found Cold receptors: This should be the least in number Itch receptor: This is rare in most cases Note: There is individual differences in the recorded sensation felt. Sense organ for pain, which are free nerve endings are found in all parts of the body (superficial part of the skin) Receptors for touch are: Meissners corpuscle, Pacinian corpuscle, and Merkels d Mostly y

y

y

y

y y

y

y

Discussion

of part 3.1 The unaltered state of sensation is due to slow adapting receptors. The fingertips contain large numbers of expanded deep tactile receptors. One type of which is Merkels disc. Discussion of part 3.2 The deterioration of sensation is due to the rapid adapting receptor in this area of the forearm. When a continuous sensory stimulus is applied, the receptor responds at a very high impulse rate at first, then at a progressive slower rate until finally many of them no longer respond at all. This accounts why the subject wasnt able to to describe the shape of the coin while placed at volar area of the forearm. Stereognosis Ability to identify an object by handling them without looking at them. Normal person can readily identify objects such as keys and coins of various denominations. This ability depends upon relatively intact touch and pressure sensations. U ses dorsal column  medial m edial lemniscus pathway (posterior column - medial lemniscus pathway) Conclusion 1. Variance in the frequency of each receptor Many nociceptors activated, compared to o cold and itch receptors y

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3 2. Duration of stimulus presentation (constant intensity) is inversely proportional to the activation frequency of a receptor, depending on type of receptor. Adaptation occurs. 3. Number of receptors is directly proportional to duration of sensation, depending on type of receptor. Also, some types of receptors are more o numerous in certain parts of the body than others. Recommendation: 1. To get a more precise result in testing differences in sensations such as pain, cold, touch, and tickle, we suggest the use of an improvised tool which will produce uniform pressure rather than doing it manually. 2. In testing sensation of touch and pressure, we suggest use of a standard object such as calibrated weight set or anything with specific size and weight to determine which initial weight does the subject feel the sensation of touch and pressure. 3. The procedure should be performed on a subject unaware of the experiment. Experiment XI: Relative touch sensitivity Introduction y The tactile sense of modality is a very important component of the multimodal system of our body. The tactile modality can be used as an additional, independent input modality to give information to the user or can also be used t o confirm or increase the information brought about by other sensory modalities like the eyes and the ears (Myles and Binseel, 2007). Another important feature of the tactile modality i s the discriminative touch, which is used for knowing the location of the stimulus induced enough for the brain to pinpoint where the stimulus was Results Group 6 ASCENDING TEST

SITES

X

X

X

X

1

2

3

FINGERTIPS

2

3

3

PALM

1

1

FOREARM

1

BACK

DESCENDING TEST X

X

X

X

1

2

3

MEAN

2.7

2

3

3

2.7

1

1

1

1

1

1

1

1

1

1

1

1

1

1

3

2

2

1

3

2

2

SCAPULAR REGION

1

2

1

1.3

1

2

1

1.3

KNEECAP REGION

2

2

2

2

2

2

2

2

OF THE NECK

Group

MEAN

7 ASCENDING TEST

SITES

X

X

X

X

1

2

3

FINGERTIPS

2

3

2

PALM

2

1

FOREARM

1

BACK

OF THE NECK

DESCENDING TEST X

X

X

X

1

2

3

MEAN

2.3

1

1

1

1

1

1.3

1

1

1

1

1

1

1

1

1

1

1

1

1

2

1.3

1

1

2

1.3

SCAPULAR REGION

3

2

1

2

2

1

1

1.3

KNEECAP REGION

1

1

1

1

1

1

1

1

Group

MEAN

8 ASCENDING TEST

SITES

X

X

X

X

DESCENDING TEST X

X

X

X

stimulated. This feature of the tactile modality allows the human body to adapt to different kinds of environment and also able to avoid dangerous stimuli that can be detected and subsequently avoided by the individual. i ndividual. And lastly, pain stimulus is the one that warns an individual to avoid doing the particular stimulus to avoid tissue destruction/deformation. Objectives Determine relative sensitivity of selected areas of the skin State the roles that touch plays and describe its qualities Distinguish between touch and touch acuity Discuss the effects of various surface textures on the perception of touch. Materials Von Frey-type aesthesiometer Blindfold Methods Subject was covered with blindfold. The bristle of the aesthesiometer to 6 areas of the skin in the following manner: Press bristle #1 against the skin until it o flexes slightly and maintain this slight flex. o Ask if subject can feel the bristle. o If subject feels nothing, apply bristle #2 and so on until subject reports feeling the bristle. o Apply next larger bristle and then repeat the above procedure in the reverse direction until the subject reports he can no longer feel the bristle. Record the number of first and last bristle felt each time. This should be repeated 3 times for each bristle at the site of fingertips, palm, forearm, back of neck, scapular region, kneecap. y

y

y y

y y

y y

y





4

FINGERTIPS

5

5

5

5

4

4

4

4

PALM

4

4

4

4

3

3

3

3

FOREARM

1

1

1

1

1

1

1

1

BACK

1

1

1

1

1

1

1

1

SCAPULAR REGION

1

1

1

1

1

1

1

1

KNEECAP REGION

1

1

1

1

1

1

1

1

OF THE NECK

Group

9 ASCENDING TEST

SITES

X

X

X

X 3

X

1

2

FINGERTIPS

2

1

4

2

PALM

1

3

3

FOREARM

2

3

BACK

DESCENDING TEST

MEAN

X

1

X

X

2

3

3

3

3

MEAN

3

2

1

3

2

2

1

2

1

1

1

1

OF THE NECK

3

4

3

3

3

3

3

3

SCAPULAR REGION

2

3

2

2

2

2

2

2

KNEECAP REGION

3

3

2

3

2

4

4

3

Group 10 ASCENDING TEST

SITES

X

X

1

X 2

DESCENDING TEST

X 3

X MEAN

X

1

2

X 3

X MEAN

FINGERTIPS

5

5

4

4.7

5

2

2

3

PALM

2

2

4

2.7

3

2

2

2.3

FOREARM

1

1

1

1

1

1

1

1

BACK

OF THE NECK

1

1

1

1

1

1

1

1

SCAPULAR REGION

4

2

3

3

2

1

3

2

KNEECAP REGION

3

3

3

3

6

5

3

4.7

Total

mean of groups 6  10 ASCENDING TEST

SITES

G6

FINGERTIPS

G7

G8

X

X

X

X

X

2.7 1

2.3 1.3

5

4.7

4

2 2

FOREARM

1

1

1

BACK

2

1.3

SCAPULAR REGION

1.3

KNEECAP REGION

2

PALM

THE

OF NECK

G9

DESCENDING TEST G10

TX

G6

G7

G8

G9

G10

TX

X

X

X

X

X

2.7 1

1 1

4

2.7

3.34 2.2

3

3 2

3 2.3

2.74 1.86

2

1

1.2

1

1

1

1

1

1

1

3

1

1.66

2

1.3

1

3

1

1.66

2

1

2

3

1. 86

1.3

1.3

1

2

2

1.52

1

1

3

3

2

2

1

1

3

4.7

2.34

Discussion y

y

areas of the skin are most sensitive and which are least sensitive? The receptors in our skin are not distributed o in a uniform way around our bodies. Theoretically, our fingers and lips are the most sensitive parts of our body since more receptors are found in these areas. However, this was not evident in the experiment performed by the five groups. Note, according to Dr. Simbulan: the finer o strands may be bent after all these years making it difficult to get accurate results. What biological signif icance can you associate with the relative sensitivity of diff erent erent areas of the skin? The nerve endings in the skin can detect o pressure, pain, and temperature. o The ability to sense pain is a warning device. It warns us to quickly pull our hand away from a hot stove, or not to grab hold of the wrong end of a pair of scissors. o The ability to sense temperature is also a safety feature.

reminds us to bundle up when we go out in winter weather, and to stop and cool off after exercising. Your sense of touch allows you to tell the o difference between rough and smooth, soft and hard, and wet and dry. o Touch is the most important of all the senses; without it, animals would not be able to recognize pain which would greatly decrease their chances for survival. How is the diff erenti erential touch sensitivit y of various parts of the skin associated with behaviour? o Touch sensitivity varies in different body regions because of differential density of distribution of the specific nerve endings. o Areas such as the fingertips and lips (glabrous skin) are richly endowed with nerve endings and are very sensitive. o Hairy skin has fewer endings and different kinds, and so produces a different sensory experience Skin of the trunk and back, with a low o density of touch receptors, is less sensitive to touch than skin elsewhere. o

What

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It





5

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y

y

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Touch

receptors branch out at their ends, and a single neuron may receive input from a region of the skin several centimeters in diameter, called its receptor field. Receptor fields in the lips may be as small o as 2 to 3 millimeters (.78 to .118 inches) o The rest of the body have around 4 to 7 centimeters (1.5 to 2.7 inches). How well people get along with each other depends partly on the amount of physical contact they have and what form it takes. Touching is often a sign of affection. o Research has shown that touch has o tremendous psychological ramifications in areas like child development, persuasion, healing, and reducing anxiety and tension. Touch has a tremendous impact on most animals' physical and psychological well being Touch greatly influences how we develop o physically and respond to the world mentally. For example, premature babies that  receive regular massages will gain weight more rapidly and develop faster mentally than those who do not receive the same attention. Touching of premature babies can also  stimulate growth hormones (such as the hormone needed to absorb food) that occur naturally in healthy babies. o Touch serves as a type of reassurance to infants that they are loved and safe, which translates into emotional well being. o In general, babies who are held and touched more tend to develop better alertness and cognitive abilities over the long run Touch continues to have a great psychological impact throughout peoples' lives. o Even adults who are hospitalized or sick at home seem to have less anxiety and tension headaches when they are regularly touched or caressed by caretakers or loved ones. Touch also has a healing power. Researchers have found that touch reduces o arrhythmias. o Another study showed that baby rats who are touched often during infancy develop more receptors to control the production of biochemicals called glucocorticoids, which are known as stress chemicals because of their ability to cause muscle shrinkage, high blood pressure, elevated cholesterol, and more. Touch is a powerful persuasive force. Touch can have a big impact in marketing o and sales. Salespeople often use touch to

establish a camaraderie and friendship that can result in better sales. o In general, people are more likely to respond positively to a request if it is accompanied by a slight touch on the arm or hand. Sensations are mediated through the actions of receptors. For a certain sensation to be felt there must be a specific receptor for it Different areas of the body have different concentrations of specific receptors. Areas with a higher concentration of a particular receptor are more sensitive to the particular sensation mediated by that receptor. The fingertips, scapular regions and knee cap regions are the areas of the body more sensitive to touch. Increased sensitivity of certain areas of the skin serves a particular biologic purpose. For the fingertips, and increased sensitivity most probably is associated to the fact that these body parts are the once most often used when an individual explores his/her surrounding. While for the scapular regions and the knee regions, an increased sensitivity probably serves a protective purpose, allowing an individual to sense and react immediately to the presence of an object in these general areas. Recommendations Since this experiment is based on the subject actually confirming that touch is felt, an observable change, for example a twitching of the surrounding area, that occurs as a result of the stimulation actually being felt will make this experiment more objective and hence less susceptible to human errors of judgment. y

y

y

y

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Diff erenti erential

Temperature Sensation Introduction Perception of cold and hot is one of lifes essential function because our body needs to maintain a certain body temp for the enzymes to function properly. Important components for TEMPERATURE SENSATION Appropriate stimuli: physiologic range of o temperature (approx 10-42 C) Sensory receptors (thermo-sensitive) o Peripheral fibers (type A-delta VS. type C) o First-order neuron: DORSAL ROOT o GANGLION Pathway: Anterolateral system (together o with fibers that carry pain sensations) TWO CATEGORIES of temperature-related sensation: o Temperature sensation o Thermal comfort °





6

Method

of Experiment

o

3 parts: y

y

y

Part one: o Cool temperature cylinder to about 5° C Press the back end of the cylinder against o the subjects forehead (5 seconds) Record sensation felt o In place  After removal  Part two: o Place one hand in cool water (10° C) and the other in lukewarm water o When the subject reports that the hand in cold feels warmer, place that hand in lukewarm water. Record sensation felt o Part three: Cool one comb in cold waterRemove, dry, o and place one comb on the boardLay forearm across the comb and note sensation o Warm one comb in warm waterRemove, dry, and place one comb on the board Lay forearm across the comb and note sensation Cool one comb in cold water and warm one o comb in warm waterRemove, dry, and place 2 combs on the boardLay forearm across the comb and note sensation Cool one comb in cold waterRemove, dry, o and place one comb on the boardLay finger across the comb and note sensation Warm one comb in warm waterRemove, o dry, and place one comb on the board Lay

Cool one comb in cold water and warm one comb in warm waterRemove, dry, and place 2 combs on the boardLay finger across the comb and note sensation

Results

Part 1 SENSATION

GROUP

WHILE

THE CYLINDER WAS IN PLACE

LOCATION OF SENSATION OF TEMPERATURE FELT

AFTER THE REMOVAL OF THE CYLINDER

SINGLE SPOT ON FOREHEAD

Group 11

cold

cold in circular spot

yes

Group 12

cold


yes

cold


yes

Group 13

Part one comparison

Part two







7

HAND

HAND

PLACED

GROUP

ON COLD WATER

PLACED

ON LUKEWARM WATER

TRANSFER OF HAND FROM COLD WATER TO LUKEWARM WATER

Group 11

cold  numbness  water becomes warmer

warm  normal temperature

warm  normal temperature

Group 12

cold

cold

normal

warm

hand soaked in cold water becomes warmer compared to hand already in the lukewarm

Group 13

cold

5 4

3 2 1

group 11

0

group 12

Discussion y

group 13 y

Part three A) FORE ARM GROUP

BOTH

COOL COMB

WARM

COMB

WARM AND COLD COMB

cold

warm

cold

Group 12

cold

slightly cold

Group 13

subject unable to distinguish the temperature

Group 11

B)

GROUP

Group 11

y

y

cold

Stimulation of receptorTransduction of the stimulusGeneration of impulse Integration of sensory input TRP (Transient Receptor Protein) family: responsible for distinct sensitivities to temperature sensation. TRPA1 and TRPMa: activated at lower o temperatures (10 - 26° C) TRPB3 and TRPB4: normal temperatures o (27 - 38° C) One group is activated at 38  48° C. o o There is some overlap between the groups. Cold is generally perceived in a wider range than heat. Graded potential: potential: would initiate action potential along fiber. Vary in amplitude depending on intensity of stimulus.

FINGERS BOTH

COOL COMB

cold

WARM

WARM

COMB

AND COLD COMB

warm

cold sensation on the thumb up to the

Conclusion





8 Recommendation

Variability of the result due to:

1.

o y

Location

of the subject where experiment took place and (ie, one subject was in front of the air conditioner and was cold before the experiment started) 2. the materials used Exercise XIII: Two  Point Touch Threshold Introduction y Touch experiences are triggered by mechanical disturbance of the skin produced by physical contact with an object. The human skin contains mechanoreceptors, or receptors that are sensitive to mechanical pressure or deformation of the skin. y However, the concentration of mechanoreceptors within the skin is not uniform. Rather, the highly sensitive areas of skin, such as the lips and fingertips, contain densely packed mechanoreceptors, while insensitive areas, such as the abdomen and back, contain lower concentrations of mechanoreceptors. y More sensitive areas of the skin also project to a larger proportion of the somatosensory cortex than less sensitive areas. Thus, the area of the brain which receives touch sensations is proportional to the actual sensitivity of the skin area. y Cutaneous mechanoreceptors can be categorized by their morphology, the kind of sensation they perceive and rate of adaptation. Ruffinis end organ detects tension deep in the skin. It is a slowly adapting type II mechanoreceptor and has a large receptive field. y Meissners corpuscle detects changes in texture. It is a rapidly adapting type I mechanoreceptor and has a small receptive field. Pacinian corpuscle detects rapid vibrations. It is a rapidly adapting type II mechanoreceptor. y Merkels disc detects sustained touch and pressure. It is a slowly adapting type I mechanoreceptor. Mechanorecepting free nerve endings detects touch, pressure and stretch. Hair follicle receptors located in hair follicles sense position changes of hairs. Testing of these mechanoreceptors are used by neurologists in the assessment of nervous

Blindfold

Procedure Blindfold subject o o Test for the two  point threshold on the six areas of different sensitivity as suggested by the table given below:

with descending series. Setting the points of the aesthesiometer at o about 1 mm wider than the expected threshold, apply aesthesiometer gently to skin. Ask subject if he feels one or two points. If o he replies- two, then reduce the point-topoint distance by 1 mm and repeat. Continue this descending series until o subject reports feeling only one point. The two point threshold for the descending series is a distance just above this; increase the distance by about 0.05 mm until the subject feels two points again. o This should be repeated three times. Tabulate your results. Do the ascending series. Then, beginning at o 1mm below a setting at which subject reports feeling only one point, begin an ascending series for each of the six areas of the body previously tested. Report the minimum distance at which the o subject reports two points. This should be repeated 3 times. Tabulate your result. Ascending and descending series is also o known as method of limits. Results and Discussions Group 14 o

Group

15

Begin





9

Group 17

Groups 14

 17 Average

Conclusions y Two-point touch threshold differences may be due to the varying densities of r eceptors on the bodys surfaces. y The denser the receptive field is, the more sensitive the stimulated area will be (see the images directly above) y This test is performed to evaluate the dorsal column/medial lemniscal pathway. Recommendations y Make sure that when placing the points of the caliper, there is even pressure of both points y Make sure that when doing the three repetitions of a certain section, the points are placed in the same place and not moved around the certain area. End of T of Transcription





Physio lab Sensation

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