Touch and Pain Flashcards
The largest sense organ in the body is known as…?
Skin
True or False?
Skin is the smallest sense organ in the body
False
Skin is the largest sense organ in the body
On average, what is the area m^2 of human skin?
1.8 m^2
On average, what is the weight in kg of human skin?
5 kg
What are the 2 types of skin?
1) Glabrous
2) Hairy
Where is glabrous skin found on the human body?
Palms of hands and feet
Where is hairy skin found on the human body?
Everywhere but the palms of hands and feet
What type of skin covers everywhere but the palms of hands and feet?
Hairy
What type of skin covers only the palms of hands and feet?
Glabrous
Describe the physiology of skin senses. List 4 steps
1) Stimulus makes contact with the skin
2) Receptors in the skin fire; sends signals
3) Signal travels to the brain via the spinal cord
4) Signal reaches the somatosensory cortex on the opposite side of the body
(e.g. signals from the left side of the body reach the right side of the brain)
Receptors are sensitive to many kinds of energy and give rise to at least 4 senses. What are they?
1) Touch (mechanical stimuli)
2) Pain
3) Body sense (proprioception; where our body is in space)
4) Temperature
Each mechanoreceptor responds to a touch stimulus in a specific area of the skin.
This is known as…?
A region called the receptive field of the receptor
What is a receptive field of the skin receptor?
A region where each mechanoreceptor responds to a touch stimulus in a specific area of the skin
List the 4 primary tactile receptors (mechanoreceptors) of the human skin
1) Merkel (tactile) disc
2) Meissner corpuscle
3) Ruffini corpuscle
4) Pacinian corpuscle
List the 2 primary tactile receptors (mechanoreceptors) of the human skin that are closer to the surface of the skin
1) Merkel (tactile) disc
2) Meissner corpuscle
List the 2 primary tactile receptors (mechanoreceptors) of the human skin that are located deeper in the skin
1) Ruffini corpuscle
2) Pacinian corpuscle
Are the Ruffini corpuscle and Pacinian corpuscle located near the surface of the skin or deeper?
Deeper in the skin
Are the Merkel (tactile) disc and Meissner corpuscle located near the surface of the skin or deeper?
Near the surface of the skin
What is the Merkel (tactile) disc skin receptor sensitive to?
Fine details (e.g. braille or telling apart texture)
What is the Meissner corpuscle skin receptor sensitive to?
Flutter (e.g. object slipping through fingers)
e.g. Picking up a raw egg by holding it with the right amount of pressure to not crush it but also not drop it
What is the Ruffini corpuscle skin receptor sensitive to?
Stretching (e.g. due to picking up something)
What is the Pacinian corpuscle skin receptor sensitive to?
Vibration, fine texture (e.g. using a tool)
e.g. using a pen and feeling the vibrations coming through the pen (fine spacial detail)
Which tactile skin receptor looks like an onion n?
Paccinian corpuscle
Which tactile receptor is mostly found in the fingertips?
Merkel’s disc
Which type of tactile skin receptor responds to fine details (e.g. braille or telling apart texture)?
Merkel’s disc
Which type of tactile skin receptor responds to flutter (e.g. object slipping through fingers)
e.g. Picking up a raw egg by holding it with the right amount of pressure to not crush it but also not drop it?
Meissner corpuscle
Which type of tactile skin receptor responds to stretching (e.g. due to picking up something)
Ruffini corpuscle
Which type of tactile skin receptor responds to vibration, fine texture (e.g. using a tool)
e.g. using a pen and feeling the vibrations coming through the pen (fine spacial detail)
Paccinian corpuscle
Why do we have multiple receptor types?
To detect many types of information (c.f. rods and cones)
True or False?
A single stimulus can only activate a single receptor system
False
A single stimulus can activate many different receptor systems
The area of skin that a particular cell receives information about is known as…?
Receptive field
Which tactile skin receptor has a bigger receptive field than the other?
a. Paccinian corpuscles have bigger RF than Meissner’s corpuscle
b. Merkel’s disc have bigger RF than Paccinian corpuscles
c. Meissner’s corpuscle have bigger RF than Ruffini corpuscle
d. Meissner’s corpuscle have bigger RF than Meissner’s corpuscle
a. Paccinian corpuscles have bigger RF than Meissner’s corpuscle
Describe an experiment investigating the receptive fields of human sensory receptors. Discuss the results as well. List 3 points
1) Microelectrode inserted into the median nerve of the arm
2) It records the action potential from a single sensory axon and maps its RF on the hand after being in contact with a stimulus
3) Results: RF are either relatively small as for the Meissner’s corpuscles or large for Pacinian corpuscles
Paccinian corpuscles have larger receptive fields than Meissner’s corpuscles
Which type of tactile receptor is more likely to be sensitive to fine detail and why?
Meissner’s corpuscles
Because its receptive fields are small
Paccinian corpuscles have larger receptive fields than Meissner’s corpuscles
Which type of tactile receptor is more likely to be sensitive to vibrations and why?
Paccinian corpuscles
Because its receptive fields ar elarger
The ability to recognise that two nearby objects touching the skin are truly two distinct points, not one
This is known as…?
2-Point discrimination
What is 2-point discrimination?
The ability to recognise that two nearby objects touching the skin are truly two distinct points, not one
The smallest separation of 2 separate but adjacent points of stimulation on the skin that just produces two distinct impressions of touch
This is known as…?
2-point threshold
What is the 2-point threshold?
The smallest separation of 2 separate but adjacent points of stimulation on the skin that just produces two distinct impressions of touch
On average, people have the ability to recognise that two nearby objects touching the skin are truly two distinct points with their fingertips at what minimum distance apart?
a. 2cm
b. 2mm
c. 1.5mm
d. 5mm
b. 2mm
On average, people have the ability to recognise that two nearby objects touching the skin are truly two distinct points with their arm at what minimum distance apart?
a. 2cm
b. 5.5cm
c. 3.5cm
d. 7cm
c. 3.5cm
Most people can tell apart 2 objects touching their skin on their fingertips that are 2mm apart
Is this considered really good/sensitive or not very good/not as sensitive?
Really good/sensitive
Most people can tell apart 2 objects touching the skin on their arm that are 3.5cm apart
Is this considered really good/sensitive or not very good/not as sensitive?
Not very good/not as sensitive
Why is the skin on our fingertips better at detecting fine details relative to the skin on the back of our back?
Because there are more receptors per square cm on our fingertips than our arms
We have ……. times more receptors per square cm on your finger tip than on your back
a. 2x
b. 200x
c. 50x
d. 100x
d. 100x
The more receptors present on the skin, the ….. two points from 2 separate objects be discriminated
a. More likely
b. Less likely
a. More likely
According to the amount of cortex in the primary somatosensory dedicated to sensation in the body, which 3 parts of the body are most sensitive to sensations?
1) Lips
2) Hands
3) Face
The “fovea” of the skin is known as…?
The fingertips
(Because there are more receptors in this particular area than the rest of the body, similar to the fovea where there is a large number of cone receptors present)
True or False?
Acuity can change with experience
True
Tactile acuity can change with experience
e.g. Braille readers, musicians
Tactile acuity can change with experience
How?
The more you use your fingertips, the more improved your tactile acuity will be as the brain will allocate more attention towards it
(e.g. playing the violin for many years makes your fingertips more sensitive and you’re able to detect whether you are playing the correct notes just by feeling where on the string your fingers are pressing)