Somatosensation Flashcards
Exteroception
sense the external world, information about the external world
Proprioception
sense of position and movement, knowing where our body is in space
Interoception
sense of internal world, physiological status, how hungry I am or full, emotions and social kind of thoughts
Somatosensory receptors:
inform us about objects in our external environment through touch and about the position and movement of our body parts
how does external stimulus get to the CNS
Stimulus > Receptor (generator) potential > the receptor make a local potential, which means coding that stimulus, which then leads to AP that fire into the CNS
what is needed to activate Somatosensory receptors
stimulus
Thresholdto activate Somatosensory receptors
easy or hard to activate
somatosensory receptors adaptive response
does it tell you continually that you are holding a glass, or do you have to remember that you are holding the glass
Low threshold mechanoreceptors
discriminative touch (spatial and temporal acuity high)
High threshold mechanoreceptors
ouch
Thermal receptors
warm and cool
Proprioceptors
body and limb position, movement and force
Nocioceptors
noxious mechanical, chemical, thermal (pain receptors)
Polymodal receptors
discomfort, itch, hurt (uncomfortable but not descriptively describing it)
three types of Low threshold mechanoreceptors
RA: rapidly adapting
SA: slowly adapting
PC: Pacinian Corpuscle
RA: rapidly adapting
On and off, responds to the change in the stimulus (no sustained)
SA: slowly adapting
SA receptor responds to steady state of the stimulus
- Holding a glass – continually tells you (sustained)
PC: Pacinian Corpuscle
responds to oscillation of the stimulus, vibration
Low threshold mechanoreceptors in the skininclude
RA type 1 [RAor RAI], Meissner corpuscle
RA type II [RAII], Pacinian corpuscle
SAI, Merkel’s disk
SAII, Ruffini ending (not clearlyknown in humans)
RA type 1 [RAor RAI] other name
Meissner corpuscle
RA type II [RAII], other name
Pacinian corpuscle
SAI, other name
Merkel’s disk
SAII, other name
Ruffini ending (not clearlyknown in humans)
RAI and SAI properties
have very small, well-defined receptive fields: detecthigh acuity of touch; useful for detecting fine detail or texture ofobjects
Receptive field
area of skin that results in a consistent responsefrom the neuron when stimulated with the appropriate stimulus
Small RF are better with what kind of details
Better with discriminative details
RAII properties
have large receptive fields with most sensitive central area and a lesssensitive surround; respond to fine vibrations of skin; useful formanipulating a tool or utensils, detection of fine textures
SAII properties
have large receptive field with directional preferences coded bygroups of receptors; this may be coded by SAIs as well
Does the Density of RAI and SAI increase or decrease as we get to the tip of our fingers
increase at we get to the tip of our fingers
Discriminative touch is based on what properties of receptor fields
on small receptor fields and the density of these receptors
Discriminative active touch
is a process by which humans actively seektactile information; gather information by engaging in the environment
nocioceptorreceptor description
Receptors described as free nerve endings
Peripheral pain afferents are made of what kind of fibers
small fibers, A delta and C fibers
Peripheral pain afferents project to
Neurons in the outer layers ofthe dorsal horn:
marginal zone and substantiagelatinosa
Wide dynamicrange (WDR)neurons in the nucleusproprius.
from the dorsal horn where does the pain stimulus travel
neurons project axonsinto the spinothalamic tract on opposite side of spinalcord and ascend to communicate to neurons in thethalamus and onto the cortex
What do WDR neurons receive
large fiber afferent,mechanoreceptor inputs, inaddition to small fiberafferents
send this information to a third order neuron in the thalamus
Pain afferent receptors fields
have small receptive fields inthe periphery
Pain stimuli lead toneuroplastic changes in pain afferents - what kind of change is seen
heightened sensitivity of peripheral receptorsand dorsal horn neurons
a rapidexpansion of their receptive fields.
Neurons in brainstem nuclei of the midbrainperiaqueductal grey, pons and medulla,nucleus raphe magnus respond to pain fibers by doing what
releasing endogenous opiate
what happens when pains activates the neurons of thenucleus raphe magnus
Descending response to the dorsal horn
Descending projection to the opiateinterneuron(enkephalin) in the substantiagelatinosa of the spinal cord- this blocks or alter the pain response
Modulating the incoming pain information
what is Kinesthesia
the ability to sense the position and location and orientation and movement of the body and its parts.
Without vision
what contributes to Kinesthesia
Muscle proprioceptors, joint receptors, cutaneous receptors,vestibular system
Muscle proprioceptors
muscle sense of moving, tension and effort
two things that contribute to Muscle proprioceptors
Muscle spindles
Golgi Tendon Organs (GTO)
Muscle spindles other name
intrafusal
Muscle spindles location
embedded in skeletal muscle
Parallel with muscle
What does the Muscle spindles tell us
signals change in musclelength, and rate of change in muscle length.
Muscle receptor of motion, force, and effort
Each muscle spindle has three elements
Intrafusal muscle fibers
Sensory [afferent] fibers
Motor axons
Intrafusal muscle fibers in muscle spindles
contractile fibers in the spindle itself
two types of Intrafusal muscle fibers in muscle spindles
Central equatorial
Polar ends
what kind of tissue is the Central equatorial region
non-contractile region
what kind of tissue is the Polar ends
contractile region, connected to extrafusal muscle
Sensory [afferent] fibers of muscle spindle are connected to what region
connected to the non-contractile central regions (central)
All of the sensory info comes from the central region
Motor axons going to the muscle spindle connect where
to the polar contractile regions (both ends) ofintrafusal muscle fibers.
– things coming back to the spindles
Different types of fibers within one muscle spindle
Nuclear chain
Nuclear bag
two kinds of Nuclear bag
Static nuclear bag
Dynamic nuclear bag
Static nuclear bag properties
static length of muscle
how long I am right now
Dynamic nuclear bag responds to what
rate of change/velocity of muscle lengthening, will recognize a stretch
Nuclear chain properties
nuclei are arranged in a row/chain
responds to static length of muscle
Nuclear bag propties
nuclei are in the middle of the fiber
Sensory/afferent fibers going to the muslce spindle
Primary: Ia afferent (large axon) connects to center/equatorial regions all 3 fibers;
Secondary: type II afferents (medium axon) connected to region adjacent to center;only connects to static nuclear bag and nuclear chain
Primaryand secondary afferent fibers endings signal what from the muscle spindle
steadystatelength of muscle - the length of the muscle
Primaryending 1a: very sensitive to what (muscle spindles)
velocityof stretch
The rate of change in length
Quickstretch of muscle - theIaafferent signals theabruptchange, enables quickcorrectiveactions (the change is occurring quickly)
alpha-gamma co-activation
The process of simultaneous activation of alpha and gamma motor neurons in a voluntary,
Is critical to keep the spindle sensitive and ready to sense stretch
If the above did not occur, the spindle would collapse in an actively contracting muscle
what do Alpha motor neurons do
send efferent axons to contract extrafusal muscle fiber
What do gamma motor neurons do
in a voluntary contracting muscle, gamma motor neurons are activated to contract intrafusal muscle fibers.
two types of gamma efferent
Dynamic gamma motor neurons
Staticgamma motor neurons
Staticgamma motor neurons
Staticgamma motor neuronsinnervate Static Nuclear Bag fibers and Nuclear chain fibers.
Dynamic gamma motor neurons
Dynamic gamma motor neuronsinnervate intrafusal fibers of the Dynamic Nuclear Bag fibers
H-reflex
The electrical equivalent to a monosynaptic reflex
the H reflex can be altered by what
the state of the ventral horn
Reduced from standing to walking to running: if I am standing on one leg my natural response would not be a kick because that is unstable
what happens toe GTO when the muscle is in stretch
leads to squeeze of the GTO when the muscle is stretch
GTO location
in the tendon at musculotendinous junction
in series with the muscle
what does GTO tell you
Tell you the force of contraction
Golgi tendon organ provides a continuous indication of theforce of contraction and changes in force.
GTO is innervated byafferents called
Group (type) Ib fibers
Group (type) Ib fibers location
have specialized endings thatweave in between the collagen fibers
Group (type) Ib fibers signalling
Contraction of muscle pulls on tendon that stretches thetendon organ and compresses theIbafferentendings
Ib inhibits the motor neuron that activate this muscle – tries to protect you from overusing the muscle
Two major ascending sensorysystems to conscious perception
spinothalamic/anterolateral column
Dorsal column
Two major ascending sensorysystems carry what kind of infomation
Have unique information
Spino/AL carries what info
pain and temp (touch)
Dorsal column carries what info
jt position,vibration and discriminative touch information(touch)
dorsal column pathway
First neuron in the DRG medulla (crossed in the brainstem) thalamus somatosensory cortex
Spino/AL pathway
DRG crosses the spinal cord thalamus cortex
unconscious tracts
Ventral spinocerebellar tract,VCST
Dorsal spinocerebellar tract,DCST
Ventral spinocerebellar tract,VCST
role in ‘motor copy’, information about ventral horn activity, e.g., motor commands sent to the muscles.
Enables adjustments to motor plan while moving …
Dorsal spinocerebellar tract,DCST
large fiber afferent information contributes to unconscious perception of movement, position and effort and terminates in cerebellum
Dermatome
area of the skin andsubcutaneous tissues that is served by asingle spinal nerve root
Corticothalamocorticalloop
mechanism of directing attention to some things andnot others; a binding of neurons in the loop attended to
Anterior cingulate role
the final decision making in the cortex, deciding if you are going to wait or move (final decision to move)
The insular cortex
has a lot to do with self awareness, understanding your internal phys and social and emotional states
Anterior insular cortex and anterior cingulate keep a record of what
keep a record of your life
If there was a time in your life that were emotional – these times will get magnified in the AI and AC
This is a reason for the memory that make is feel good
