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)
What are the 2 types of touch?
1) Active
2) Passive
What is active touch?
Active exploration of the environment
What is passive touch?
The body is stationary but you feel the touch
Active exploration of the environment
This is known as…?
a. Active touch
b. Passive touch
a. Active touch
The body is stationary but you feel the touch
This is known as…?
a. Active touch
b. Passive touch
b. Passive touch
Rubbing the object with your fingertips to feel the texture of a bedsheet is known as…?
a. Active touch
b. Passive touch
a. Active touch
When the whiskers of a cat touch your arm is known as…?
a. Active touch
b. Passive touch
b. Passive touch
What are the 3 advantages of active touch?
1) More parts of the body contact with the object
2) You can search for the most diagnostic parts of objects to feel
3) Kinesthetic senses (the ability to sense the position and movement of our limbs and trunk) are also engaged
What are the 2 types of texture cues available for us to perceive texture?
1) Spatial cues
2) Temporal cues
When perceiving texture, what spatial cues might we experience?m
Bumps and grooves, when the finger is stationery or moving
Bumps and grooves, when the finger is stationery or moving
What type of texture cue is this?
Spatial cues
When perceiving texture, what temporal cues might we experience?
How fast the information about the object changes as you move your finger across the object
How can we perceive texture?
Via a tool
What affects the performance of paccinican corpuscles?
Adaptation to high frequencies
What is the double dissociation seen in patients with tactile sensory impairment?
Tactile agnosia vs Tactile extinction without problems in object recognition
What is tactile agnosia?
When patients cannot identify objects by touch, but has no problems with spatial processing
Simply = Tactile agnosia refers to the inability to recognize objects by touch but they can name objects visually and process spatial info
e.g. When holding a pen, they can’t identify the object by touch but they can give a lot of spatial details about the pen such as it is long, it has a clicky button at the end, etc.
What is Tactile extinction without problems in object recognition?
When patients can easily identify objects by touch but have problems with spatial processing
Simply = The ability to recognize objects by touch but the inability to name objects visually and process spatial info
e.g. When holding a pen, they can easily identify the object by touch but they can’t give a lot of spatial details about the pen such as it is long, it has a clicky button at the end, etc.
When patients cannot identify objects by touch, but has no problems with spatial processing
Simply = Tactile agnosia refers to the inability to recognize objects by touch but they can name objects visually and process spatial info
e.g. When holding a pen, they can’t identify the object by touch but they can give a lot of spatial details about the pen such as it is long, it has a clicky button at the end, etc.
This is known as…?
Tactile agnosia
When patients can easily identify objects by touch but have problems with spatial processing
Simply = The ability to recognize objects by touch but the inability to name objects visually and process spatial info
e.g. When holding a pen, they can easily identify the object by touch but they can’t give a lot of spatial details about the pen such as it is long, it has a clicky button at the end, etc.
This is known as…?
Tactile extinction without problems in object recognition
In a brain scanning study involving healthy participants, when asked what the object presented to them was, which part of the brain was most active?
Name 2
1) Primary somatosensory cortex
2) Secondary somatosensory cortex
In a brain scanning study involving healthy participants, when asked where the object presented to them was, which part of the brain was most active?
Superior parietal areas
The superior parietal areas of the brain are most active when Ps had to name ….. the object presented to them was
a. Where
b. What
a. Where
The primary and secondary somatosensory cortex of the brain is most active when Ps had to name ….. the object presented to them was
a. Where
b. What
b. What
What are the 2 top-down influences of touch?
- Emotional effect
- Expectation and surprise
True or False?
We must update as we move our body position around in space
True
The emotional effect is a top-down influence on touch
What is the emotional effect?
When the same skin sensation may be pleasurable or unpleasant depending on the context
e.g. Holding a hairy tarantula; it may feel soft and pleasant but because of the visual appearance and knowledge of how dangerous tarantulas can be, holding the tarantula may not be a pleasant experience overall
When the same skin sensation may be pleasurable or unpleasant depending on the context
e.g. Holding a hairy tarantula; may feel soft and pleasant but because of the visual appearance and knowledge of how dangerous tarantulas can be, holding the tarantula may not be a pleasant experience overall
This is known as…?
Emotional effect
What is Aristotle’s illusion?
A tactile illusion that is created when the eyes are closed, two fingers of one hand are crossed, and a small object such as a pen is pressed into the cleft between the tips of the crossed fingers.
The sensation is that of touching two objects rather than one.
A tactile illusion that is created when the eyes are closed, two fingers of one hand are crossed, and a small object such as a pen is pressed into the cleft between the tips of the crossed fingers.
The sensation is that of touching two objects rather than one.
This is known as…?
Aristotle’s illusion
Describe the cutaneous rabbit tactile illusion
1) Ps are given two taps close to the wrist and two other taps closer to the elbow. The taps are given simultaneously
2) Ps perceive the 4 taps as equally spaced out when in actuality, they are not (they were widely separated taps)
3) It gives the illusion of rabbits jumping in sequence on their arm
1) Ps are given two taps close to the wrist and two other taps closer to the elbow. The taps are given simultaneously
2) Ps perceive the 4 taps as equally spaced out when in actuality, they are not (they were widely separated taps)
3) It gives the illusion of rabbits jumping in sequence on their arm
This is known as…?
Cutaneous rabbit tactile illusion
The cutaneous rabbit tactile illusion led to activities in which regions of the brain?
Primary somatosensory cortex as if P2 had really been stimulated
Why can’t you tickle yourself?
Because you can predict the consequences of one’s own action and removes the element of surprise
In an experiment involving a tickling machine with foam that touches the Ps hand, the Ps found the machine more ticklish when…?
a. The Ps tickle themselves with the machine
b. The experimenter tickles the Ps with the machine
b. The experimenter tickles the Ps with the machine
True or False?
The same touch from the tickling machine was rated as less ticklish when it was produced by the experimenter rather than the participants themselves
False
The same touch from the tickling machine was rated as more ticklish when it was produced by the experimenter rather than the participants themselves
The same touch from the tickling machine was rated as more ticklish when it was produced by the experimenter rather than the participants themselves
Why?
Because the Ps could not predict when the tickling would happen (element of surprise involved)
What is the old view of pain?
Pain is the overstimulation of any system
Pain is the overstimulation of any system
Is this an old or new view of pain?
Old
What are the receptors for pain?
Nocieceptor
What are Nocieceptor?
Receptors for pain
What are the 2 types of pain?
1) A delta fibres – fast pain (sharp)
2) C fibres – slow pain (dull)
What type of pain is carried by A delta fibres?
Fast pain (sharp)
What type of pain is carried by C fibres?
Slow pain (dull)
Fast pain (sharp) is carried by what type of fibre?
A delta fibres
Slow pain (dull) is carried by what type of fibre?
C fibres
Pin pricks, pinches and extreme temperatures are examples of what type of pain
Fast pain (sharp)
Give 3 examples of fast pain (sharp)
1) Pin pricks
2) Pinches
3) Extreme temperatures
True or False?
Mild stimulation can be pleasurable
True
True or False?
The same stimulus can activate both the fast pain and slow pain systems
True
What does pain help us do?
Protect the body from actual injury
It acts as a warning for your body to stop doing a particular action
Pain is more than a receptor activity
What else can it do? List 3 things
1) Pain can be affected by a person’s mental state
2) Pain can occur in the absence of stimulation
3) Pain can be affected by attention
True or False?
Pain cannot be affected by a person’s mental state
False
Pain can be affected by a person’s mental state
e.g. battlefield analgesia
True or False?
Pain cannot occur in the absence of stimulation
False
Pain can occur in the absence of stimulation
e.g. phantom limb pain
True or False?
Pain cannot be affected by attention
False
Pain can be affected by attention
What does the spinal cord do when the body experiences pain?
It influences the degree to which painful information reaches the brain
What influences the degree to which painful information reaches the brain?
The spinal cord
What are the 2 ways pain can be reduced?
1) Non-painful tactile inputs (massage, rubbing)
2) Top-down input (expectations etc.)
Give 2 examples of non-painful tactile inputs
- Massage
- Rubbing
Give an example of top-down input
Expectation
What is a phantom limb?
After a limb is amputated, the patient may feel like the limb is still in place
After a limb is amputated, the patient may feel like the limb is still in place
This is known as…?
Phantom limbs
What is phantom limb pain?
When the patient experiences limb pain despite the limb being amputated and no external stimulus is present
When the patient experiences limb pain despite the limb being amputated and no external stimulus is present
This is known as…?
Phantom limb pain
Many patients “feel” phantom arms/hands when touched on….?
a. The leg
b. The finger
c. The shoulder
d. The face
d. The face
Why do patients experience having a phantom hand?
The missing hand is still represented in the brain after a long time since they’ve lost the limb
What is proprioception?
Where your body is in space
Simply = The sense that lets us perceive the location, movement, and action of parts of the body
Where your body is in space
Simply = The sense that lets us perceive the location, movement, and action of parts of the body
This is known as…?
Proprioception
How do we experience proprioception? List 3 ways
1) Signals from muscles
2) Using other modalities (vestibular system, tactile receptors, etc)
3) Kinesthesis
The movement of the limbs in space is known as…?
Kinesthesis
Who was the patient who lost most proprioception, kinesthesis and touch due to a viral infection at 19?
IW
IW lost most proprioception, kinesthesis and touch due to viral infection.
What can he do and not do?
1) He can move his body
2) But he can’t feel tactile sensations when moving around
e.g. He can walk in a straight line but he has to look down to see where he is going because he can’t feel the sensation of walking on the road from this feet
What did IW do to compensate for his lack of tactile sensation?
He only used visual information to help him move around in the world
True or False?
IW could easily move around in the dark
False
IW was unable to move at all in the dark
What led to IW’s condition and what fibres did he lose?
- Viral infection
- Lost fast myelinated fibres and retained slow C fibres
What is the name of the new receptor discovered in 2002?
CT (C Tactile) fibres
How are CT (C Tactile) fibres elicited?
By stroking the arm with a soft paintbrush
Patients like Iam Waterman (IW) have lost all other senses of touch but they can still feel…?
List 3 sensations
1) Pain
2) Temperature
3) Enjoy being cuddled
