Final: Chapter 15 Flashcards
What happened to Ian Waterman?
As a result of an autoimmune reaction that destroyed most of the neurons that transmitted signals from his skin, joints, tendons, and muscles to his brain, he lost the ability to feel skin sensations, so he couldn’t feel his body when lying in bed.
What are the parts of the somatosensory system?
- cutaneous senses
- proprioception
- kinesthesis
responsible for perceptions such as touch and pain that are usually caused by stimulation of the skin
Cutaneous senses
the ability to sense the position of the body and limbs
Proprioception
the ability to sense the movement of the body and limbs
Kinesthesis
What is the heaviest organ in the human body?
Skin
What is on the surface of the skin?
A layer of tough dead skin cells
Layer of dead cells is part of the outer layer of skin
Epidermis
What is the layer under the epidermis?
the Dermis
Receptors within the skin that respond to mechanical stimulation, such as pressure, stretching, and vibration
mechanoreceptors
Where are mechanoreceptors located?
epidermis and dermis
What are the four types of mechanoreceptors?
merkels disks, meissners corpuscles, ruffini endings, Pacinian corpuscles
What two mechanoreceptors are located close to the surface of the skin, near the epidermis?
Merkel receptor and the Meissner corpuscles
Why do Merkel receptors and the Meissner corpuscles have small receptive fields?
Because they are located close to the surface
The area of skin which, when stimulated, influences the firing of the neuron
Cutaneous receptive field
What type of fiber is merkel receptors? why?
Slowly adapting (SA1) fiber; because the nerve fiber associated with the slowly adapting Merkel receptor fires continuously as long as the stimulus is on
What type of fiber is Meissner corpuscles? why?
Rapidly adapting (RA1) fiber; because the nerve fiber associated with the rapidly adapting meissner corpuscle fires only when the stimulus is first applied and when it is removed.
What type of fiber is Ruffini cylinders?
slowly adapting (SA2) fiber; which responds continuously to stimulation
What type of fiber is Pacinian corpuscles?
rapidly adapting (RA2) fiber; which responds when the stimulus is applied or removed
Why do Ruffini cylinders and Pacinian corpuscles have larger receptive fields?
they are both located deep in the skin
Where are cutaneous receptors in the skin located?
They are distributed over the whole body
Through what structure does the spinal cord receive signals?
through a bundle of fibers called the dorsal root
What happens after the signals enter the spinal cord?
Nerve fibers transmit them to the brain along two major pathways: the medial lemniscal pathway and the spinothalamic pathway
Has large fibers that carry signals related to sensing the positions of the limbs (proprioception) and perceiving touch.
medial lemniscal pathway
What do large fibers in the medial lemniscal pathway help with?
They transmit signals at high speeds, which is important for and reacting to touch.
Consists of smaller fibers that transmit signals related to temperature and pain
spinothalamic pathway
Describe Ian Waterman in the sense of pathways
He lost the ability to feel touch and to sense the positions of his limbs (lemniscal pathway), but he was still able to sense pain and temperature (spinothalamic pathway)
Is the signals in the spinal cord pathways contralateral or ipsilateral?
Contralateral: signals in the spinal cord have crossed over to the opposite side of the body, signals originating from the left side of the body reach the thalamus in the right hemisphere of the brain, and signals from the right side of the right side of the body reach the left hemisphere.
What are the two areas that receive signals from the thalamus?
primary somatosensory cortex (S1) in the parietal lobe and the secondary somatosensory cortex (S2)
suggested that the seizures reflected the spread of neural activity across maps in the motor area of the brain
The Jacksonian march
Shows that adjacent areas of the skin project to adjacent areas in the brain, and that some areas on the skin are represented by a disproportionately large area of the brain
Homunculus
Exploring objects with the hand
Haptics
The capacity to detect details of stimuli presented to the skin
Tactile acuity
The minimum separation between two points on the skin that when stimulated, is perceived as 2 points
two-point threshold
measured by pressing a grooved stimulus like the one onto the skin and asking the person to indicate the orientation of the grating.
Grating acuity
measured by determining the narrowest spacing for which orientation can be accurately judged. can also be measured by pushing raised patterns such as letters onto the skin and determining the smallest-sized pattern or letter that can be identified
Acuity
TRUE OR FALSE: the firing of the Merkel receptor’s fibers signals details
TRUE
What part of the body is the most sensitive to details?
fingertips
What type of receptive fields do cortical neurons that represent part of the body with better acuity have?
smaller receptive fields
Which mechanoreceptor is primarily responsible for sensing vibration?
Pacinian corpuscles
The physical texture of a surface is created by peaks and valleys.
Surface texture
states that our perception of texture depends on both spatial cues and temporal cues
The duplex theory of texture perception
Provided by relatively large surface elements, such as bumps and grooves. that can be felt both when the skin moves across the surface elements and when it is pressed onto the elements.
Spatial cues
What texture cue is Braille an example of?
spatial cue
Occur when the skin moves across a textured surface like fine sandpaper; they are responsible for our perception of fine texture that cannot be detected unless the fingers are moving across the surface
Temporal cues
provides information in the form of vibrations that occur as a result of the movement over the surface.
Temporal cues
When testing responses of the somatosensory cortex of monkeys, what did the patterns show?
- different textures caused different firing patterns in an individual neuron
- different neurons responded differently to the same texture
Where do cortical neurons that fire best to coarse textures receive input from?
SA1 neurons in the skin (Merkel receptors)
Where do neurons that fire best to fine textures receive input from?
PC receptors (Pacinian corpuscles)
touch in which a person actively explores an object, usually with fingers and hands
active touch
occurs when touch stimuli are applied to the skin, as when two points are pushed onto the skin to determine the two-point threshold
passive touch
perception in which 3-D objects are explored with the fingers and hand
Haptic perception
involved in detecting cutaneous sensations such as touch, temperature, and texture and the movements and positions of your fingers and hands
Sensory system
Involved in moving your fingers and hands
Motor system
involved in thinking about the information provided by the sensory and motor systems
Cognitive system
you experience stimulation of the skin
Passive touch
You experience the objects you are touching
Active touch
What do people mainly use to judge texture?
they use lateral motion and contour
What do people mainly use to judge exact shape?
they use enclosure and contour
What are the 4 types of exploratory procedures?
- lateral motion
- pressure
- enclosure
- contour following
a change in direction from a previous position, and can occur in any plane
lateral motion
continuous physical force exerted on or against an object by something in contact with it.
pressure
an area surrounded by a fence or other structure
enclosure
when you trace the contour of something
contour following
The tactile area of the thalamus; have center-surround receptive fields that are similar to the center-surroud receptive fields in the lateral geniculate nucleus
Ventral posterior nucleus
when one person is touching another person
Interpersonal touching or social touch
Involves inserting a metal electrode with a very fine tip just under the skin
Microneurography
CT afferents and their central projections are responsible for social touch
Social touch hypothesis
Sensing details, texture, vibration, and objects
Discriminative functions of touch
Sensing pleasure and therefore often eliciting positive emotions. The CT system is the basis.
The affective function of touch
What are CT afferents specialized for?
slow stroking
When does the perception of touch happen?
it doesn’t happen until the signals from the CT afferents reach the brain
What connections does slow stoking make?
connections between the back of the insula and the front of the insula
which part of the insula receives sensory information?
the back
which part of the insula is connected to emotional areas of the brain?
the front
What can influence the effects of slow stroking?
- location and rate of stoking
- knowledge of who is doing the stroking can determine whether the stoking is perceived as pleasant or unpleasant
The fact that people’s thoughts about who is touching them can influence their perception of pleasantness is an example of how ___________________ can influence the perception of social touch.
top-down processing
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
Pain
caused by damage to tissue or inflammation of joints or by tumor cells.
Inflammatory pain
is caused by lesions or other damage to the nervous system
Neuropathic pain
pain caused by activation of receptors in the skin called nociceptors
Nociceptive pain
specialized to respond to tissue damage or potential damages
nociceptors
Pain occurs when nociceptor receptors in the skin are stimulated and send their signals directly from the skin to the brain
Direct pathway model of pain
People who have had a limb amputated continue to experience the limb
Phantom limbs
What is one idea about what causes pain in the phantom limb?
Signals are sent from the part of the limb that remains after amputation.
The idea that pain signals enter the spinal cord from the body and are then transmitted from the spinal cord to the brain
- there are additional pathways that influence the signals sent from the spinal cord to the brain.
- signals from these additional pathways can act to open or close a gate, located in the spinal cord, which determines the strength of the signal leaving the spinal cord.
Gate control model
Consists of cells in the dorsal horn of the spinal cord
Gate control system
Fibers activate a circuit consisting entirely of excitatory synapses, and therefore send excitatory signals to the transmission cells.
Nociceptors
What increases firing rate of transmission cells?
excitatory signals from the (+) neurons in the dorsal horn “open the gate”
What does the increased activity in transmission cells result in?
more pain
Fibers carry information about non painful tactile stimulation
Mechanoreceptors
What happens when activity in the mechanoreceptors reaches the (-) neurons in the dorsal horn?
inhibitory signals sent to the transmission cells “close the gate” and decrease the firing of the transmission cells
What does the decrease in firing of transmission cells cause?
decreases the intensity of pain
What decreases cell activity of transmission cells and a decrease in pain?
activity that is coming down from the brain closes the gate
These fibers, which contains info related to cognitive functions such as expectation, attention, and distraction, carry signals down from the cortex
Central control
what is the perception of pain determined by?
a balance between input from nociceptors in the skin and non-nociceptive activity from the skin and the brain
A pill that they believe contains painkillers but that, in fact, contains no active ingredients
Placebo
The patient believes that the substance is an effective therapy
Placebo effect
negative placebo effect
nocebo effect
What is the placebo effect associated with?
increases in network of areas associated with pain perception, and the nocebo effect was associated with increases in activity in the hippocampus
Positive emotions are associated with?
Decreased pain
what does listening to pleasant music do for pain?
decrease both the intensity and the unpleasantness of pain
An unpleasant sensory and emotional experience is a reference to both sensory and emotional experience. What does this reflect?
multimodal nature of pain
When people describe their pain with words like throbbing, prickly, hot, or dull
Sensory component of pain
When they use words like torturing, annoying, frightful, or sickening to describe their pain.
Affective (or emotional) component of pain
What drugs have been used to reduce pain and induce feelings of euphoria?
Opiate drugs such as opium and heroin
What drug can you inject into a person overdosing on heroin? why does it work?
Naloxone; because naloxone’s structure is similar to heroin’s, it attaches to the same receptor sites, thereby preventing from binding to those receptors.
Neurotransmitters were discovered that act on the same receptors that are activated by opium and heroin. They are produced in the brain and released in response to pain or stress, or during pleasurable activities.
Endorphins
How can pain be decreased?
by stimulating sites in the brain that release endorphins
Why does the pain reduction effect of placebos occur?
Because placebos cause the release of endorphins
What does hand holding cause?
synchronized brain waves, which is translated into reduced pain
The ability to share and vicariously experience someone else’s feeling
Empathy
two main areas activated that are both associated with the affective component of pain
Anterior cingulate cortex (ACC) and the anterior insula (AI)
pain caused by social interactions
social pain
a condition which caused the fingers on his right hand to curl into his palm
Hand dystonia
the process by which the brain’s neural circuits are reorganized and created based on life experiences.
Experience-dependent plasticity
How do 9-month-olds respond to movement?
Movement of a brush along their arm with a decrease in heart rate if the brush is moved across the arm at 3 cm per second, which is in the range that activates CT afferents.
What happens when these premature infants are massaged?
they have more weight gain, better cognitive development, better motor skills, and better sleep than premature infants who are not massaged.
