somatosensory Flashcards
chapter 13
the body senses
- touch
- thermoception
- nociception
- proprioception / kinaesthesis
tactile perception
perception that results fro, the mechanical deformation of the skin
how are tactile receptors classified
- the type of stimulation they respond to
- the size of their rf
- speed of adaptation
where are the tactile receptors located
in the dermis and epidermis
- epidermis: the most surface layer
mechanoreceptors
respond to mechanical stimulation like pressure vibration and movement
4 types of mechanoreceptors
- SAI (markelle)
- SAII
- FAI (Meissner)
- FAII (Pacinian)
Type 1 vs type 2 receptors
type one have smaller receptive fields which give them higher acuity/spatial resolution
- type 1 are usually closer to the surface
slow adapting vs fast adapting receptors
- slow adapting will fire continously as they are stimulated
- fast will fire when they start and end
- fast has better temporal
SAI
- markelle cells
- dense in the dermis
- high spatial acuity and low temporal variation
- respond to indentation, curves and textures
- used to perceive pattern , texture and shape
SA II
- big receptive fields
- low temporal
- low spatial
- respond to stretch and hand conformation
FA I
- small rf
- dense in the upper dermis
- high spatial resolution
- high temporal resolution
-respond to motion and low frequency - used for slip and maintaining grip control
FA II
- large rf
- sparse density in the lower dermis
- low spatial
- high temporal
- high frequency vibrations
- used for perceiving fine textures through vibrations
C-Tactile mechanoreceptors
receptors that are only present in hairy skin which respond to slow, gently pleasnt touch
two point discrimination
psychophysics test to asses the spatial resolution (to point theshold) of the skin
- how far a part do two points have to be for us to feel them as 2
temporal resolution of touch
we can discriminate touches that are about 5ms apart
Braille
SA I are used for this
FA I are kinda good at it too
mechanoreceptors in grip control
FA I is very useful in load phase when it is gripping an object to lift it. FA II detect the additional forces after its lifted.
thermoception
sense of temperature
themoreceptors
we have separate hot ad cold fibers.
they respond when temperature goes below or above baseline
- within the range of 17-43 c
nociception
pain thet arises from potential or actual tissue damage due to physical trauma
2 types of nociceptors
- c-fibers
- A-delta
- 2 kind of fibers makes pain come in 2 waves
C-fibers
unmeylinated pain receptors that cause a slower reaction
a-delta fibers
lightly myelinated fibers that have faster responses
other types of pain
- hyperaglesia: inflammatory
- neuropathic
proprioception
sense of where things are relative to each other in the boy
types of proprioceptive organs
- muscle spindles
- golgi tendons
- joint receptors
muscle spindles
- they sense lenght and change of lenght of the muscle and isometric force in afferent nerves
types of muscle spindles
type 1: for dynamic muscles
type 2: for stati lenght
golgi tendon organs
proprioceptor receptor that sense muscle tension
- so our muscle know what its force output is
joint receptors
used for telling joint when they are reaching their maximum limits in range of motion
dermatones
areas of skin that are innervated by different levels of the spinal cord
spinal cord composition
- grey matter (ell bodies) is on the inside and the whte matter is on the outside.
- ventral side has motor neurons
- dorsal has sensory
path into the spinal cord
sensory afferent neurons enter though the dorsal root, passing through the dorsal root ganglion
pathways of senory signal to the brain
- dorsal column-medial lemniscal pathway
- spinothalamic pathway
DCML pathway
tactile and proprioception signals travel out of the spine and make their first synapse in the medulla where they cross contrallaterally to the VP in the thalamus then to S1
spinothalamic pathway
signals from pain and thermal receptors synapse in the spinal cord and cross there to the medulla then the thalamus to the S1
Primary somatosensory cortex
Subregion of the somatosensory cortex which is the first to receive somatosensory signals (in the central gyrus of the parietal lobe)
somatotopic map
a mapping of the body surface onto the somatosensory cortex, whereby adjacent locations on the cortex receive signals from adjacent locations on the body
- not proportional
homunculus
a representation of the body if the area of skin was proportional to the size of the cortex that represents that body part
Secondary somatosensory cortex
subregion of the somatosensory region which receives signals from area s1
areas of the S1
3a
3b
1
2
Area 3a
receives proprioceptive signals and discriminative nociceptive signals
area 3b
receives tactile signals and discriminative nociceptive signals
Area 1
receives tactile information
Area 2
recieves proprioceptive signals
pathways after S1
after s1 the tactile and proprioceptive information split into dorsal and ventral pathways
dorsal pathway of touch
the where pathway that carries tactile information in planing action.
goes throuhg posterior parietal cortex to premotor cortex
ventral pathway of touch
the what pathway that carries proprioceptive and tactile signals to help indentifiy object shape and qualities.
- s1 –> s2 –> hippocampus –> prefrontal cortex
haptic perception
actively using touch to perceive and identify object by their 3d structure and other material propertie
- uses the other somatosensory sense too
