Somatosensation 1 Flashcards
Descartes
Pain scientist - I think therefore I am
Thought humans had immaterial souls - thinking thing = immaterial soul
Sceptical about sensations but exceptions = senses coming from body = passions of the soul
Do not perceive injury through reason, we directly feel it, passions of soul - suffering forces themselves on us
Ex = fire, particles interact with animal spirits in our nerves, pull strings that constitutive nerves —> inform immature souls of the fire, rings bell in brain pineal hand - interfaces between body and soul
Absence of tactile sensation and proproception
Losing touch = very bad
Bc viral infection = causes this
Cannot touch - no feedback from limbs ad no propriocetopn - cannot feel, pain and temp remained tho
Most of the time do not perceive these but very important for movement
Patient= virtually hanicapped - cannot move effectively
Describe somatosensory cortex
Motor cortex, sensory cortex
Communicate a lot
Proprioception
Sense of body position
Is based on ability to perceive position of joints
Also includes vestibular sensations - sense of balance, equilibrium
Kinesthesia
Reception of movement
Does not include balance
Substantantially the same receptors as proprioception
Name and describe the 2 types of receptors
Muscle spindle = kinesthetic/proprioceptive nerve fibres attached to muscular fibres,stretch receptors
Golgi tendon organ= in tendons, perceive pull on tendons
Describe tactile perception
Touch
Perception of objects that come into contact with skin
Type of exteroceptive sense - perception of external world like vision or hearing
Associated with Sophisticated fibres associated with weird kinds of apparatus at dendritic ends = markels receptors, pacinian corpuscle, Ruffini corpuscle, meissners corpuscle = help tactile finders perceive diff aspects/dimensions
Describe thermoalgesia
Temp and pain - same system perceiving them
Interoception = perception of internal state of body - such as hunger, thirst, pee
Isnide body
Tells you state of own body
Free nerve endings on dendritic ends
Describe somesthetic nerve fibres
A alpha = faster and huge since heavy myelinated, proprioception
A delta (myelinated) - fast tissue damage pain fibres
Small unmyelinated c = pain fibres, slower tissue damage
What is tactile perception characterized by
Size of respective field = large or small
Adaptation rate = slow or fast, if fast adapting and fire constantly = then adapt = stop fitting if sensation continues,more interested in change of stimulus
Sa I
Merkel
Small receptive field
Slow adapting
Fine grain patterns of tactile perception, pattens and forms
Sa ii
Ruffini
Only in hands, larger receptive fields
But slow adapting
Good at percieving skin deformation- shape of hand for grabbing
Fa I
Mesissner
Fast adapting
Good for holding grip
Perceive vibrations of skin - low freq like if object slipping out of hand
Fa ii
Pacini
More sensitive to high freq vibrations
Like cheers, pencil writing, interacting with tools
Describe opening door
Feel shape of key in pocket = Sa I (fine detailS)
Shaping fingers to grasp key = Sa ii (configuration of hand)
Insert key into lock, strengthen grip to prevent key from slipping = Fa I (grab)
When key reaches end of hole = Fa ii (interacting with objects)
Describe tactile perception - deramtomes
All touch fibres eventually group together into a nerve that enters spinal cord between each spinal disc
Each area of skin innevated by specific nerve - dermatom e
Describe dorsal column pathway
Enters spinal cord then stays on same side
Cuneate and gracile nucleus = 1st relay
Axons cross over to Ventral posterior nucleus of thalamus - 2nd relay
Then to somatosenory cortex posterior to central sulcus
Describe primary somatosensory cortex
Somatotopic organization = corresponding points
More touch receptors on face and hands - homunculus
Describe 2 point discrimination trheshold
2 pins - distance varies and ask if feel 2 or 1 pins
If receptive field large = cannot perceive 2 pins - large distance required = larger number = poor discrimination
In hands = smaller receptive fields so 2 pins will be in diff fields
what is pain
What causes pain
Hard to define pain
Subjected
What are we perceiving???
Define pain
Unpleasnet sensory and emotional experience associated with or remsbling that associated with actual or potential tissue damage
Injury + intensity
Define nociception
Neural process of encoding nociceptive stimuli - encoding stimuli
Describe nociceptive stimulus
Actual or potentially tissue damaging event transduced adn encoded by nociceptors= whatever causes nociception
Ideas about pain - intensity theory
Says a pain = excessive sensory stimulation = if v high intensity
No special system for perciving pain, noxious stimuli = more painful
