What is the breakdown of the somatosensory system?Include the three parts
1) Cutaneous senses
- >touch and pain
2) Proprioception
- >sense body position and limb position
3) Kinesthesis
- >movement of body and limbs
What is the heaviest organ of the body?
-the skin
What is the layer of dead skin cells? What layer is below it?
- the layer of dead skin cells is the epidermis
- below it is the dermis
Where are mechanoreceptors found?
-in the dermis and the epidermis
What are Merkel receptors referred to? Do they have a large receptive field?
- slowly adapting fiber
- SA1 fibers
- the nerve fiber fires continuously as long as the stimulus is on
- have a small cutaneous receptive field
-involved with fine details, texture and shape
What are Meissner corpuscle receptor referred to? Do they have large receptive fields?
- fast adapting fibers
- RA1
- the nerve fiber fires only when the stimulus is applied and when it is removed
-involved with handgrip control, and perceived motion across the skin
Describe the Ruffini cylinder
- it is a mechanoreceptor
- > fires to stretching
- a SA2 fiber
- deeper in the skin
- > has a larger receptive field than Merkle and Meissner
Describe the Pacinian corpuscle
- it is a mechanoreceptor
- a RA2 fiber
- deeper in the skin
- responds to biration
- fine texture moving across the fingers
Differentiate th emedial lemniscal pathway and the spinothalamic pathway
- lemniscal pathway has large fibers
- > carry signals related to proprioception and perceiving touch
- spinothalamic pathway carries signals related to pain and temperature
- > smaller fibers
Are there pain receptor in the brain
-no
What is the homunculus
-it shows the areas of the skin that project to areas of the brain
How does using a function more often contribute to its cortical organization
- if a function is used more often
- >that area of the cortex becomes larger
What is the Braille characters used for
- it is used by blind people to read
- consists of a cell made up of one to six dots
- different arrangements represents different letters of the alphabet
- all of this depends on tactile detail perception
How does grating acuity relate to Merkel receptors and Paccinian receptors
-better acuity is associated with less spacing between Merkel receptors
How does the cortex relate to tactile acuity
- there is a relationship between tactile acuity and the cortical homunculus
- > the smaller the receptive field
- > the less the overlap in the cortex
- > so more firing of neurons in the cortex
- eg; fingers have small receptive fields
- > so the neurons in the cortex wouldn’t overlap and would fire separately
- > can’t say the same for the receptive fields of an arm
Why does the Pacinian receptor respond to rapid vibrations but not constant stimulations
- due to the corpuscle fibers
- > they have a series of layers
- > fluid between each layers
- > transmits rapidly repeated pressure like vibrations
- > does not transmit continuous pressure
- therefore, the pacinian responds well
- > at the beginning when a stimulus first fires
- > and when the stimulus ends
-or it responds well to a vibration
What is surface texture
-it is the physical texture of a surface created by peaks and valleys
What provides a more accurate assessment of surface texture? Touch or vision?
-touch
Describe the duplex theory of texture perception
- perception of texture depends on
- > spatial cues
- > temporal cues
What are spatial cues
- provided by large surface elements
- > eg; bumps and grooves
- > felt when the skin moves across surface elements
- > feel different shapes, sizes and distribution of surface elements
What are temporal cues
- fingers moved across textured surface
- > like fine sandpaper
- > perception of fine texture that cannot be detected unless the fingers are moving across the surface
-fine textures sensation was due to the role of vibtation
How does adapting the Pacinian corpuscle receptor affect our ability to tell the difference between two fine textures
- it removes that ability
- Pacinian receptors play a huge role in temporal cues
Contrast active touch with passive touch. What kind of perception do you engage in the active touch.
Active touch
- > touch in which person actively explores an object
- > with fingers and hands
- > you engage in haptic perception
- > experience the objects you are touching
Passive touch
- > when touch stimuli are applied to the skin
- > experience stimulation of the skin
Describe the haptic perceptual system. What parts of the body work together in this system?
-it is when the sensory system, the motor system and the cognitive systems work all together
