Transmission of Sensory Information: From Receptor Flashcards
what are the 3 neuron pathways of the somatosensory system
first order neuron, second order neuron, third order neuron
from receptors (sensory end organs) via primary affect fibers to DRG
first order neuron
where does the DRG then send sensory information
dorsal horn
second order neurons send information from where to where
spinal cord or brain stem to thalamus
a collection of cell bodies that relay information to the parietal lobe
thalamus
third order neurons send information from where to where
thalamus to cerebral cortex and cerebellum
means crossing point
decussation
what are the 2 types of conscious sensation
special sense and somatic senses
what are the two types of subconscious sensation
somatic and visceral
is the changing the form of a stimulus
transduction
what is the order of events that allow use to differentiate between senses
Stimulus at receptor
Generates potential
Threshold met
Action potential is afferent
Message from receptor to DRG
DRG to dorsal horn
Ascends thalamus
Somatosensory cortex
what are the 3 characteristics of sensory receptors
selectivity, adaptation, receptive field
sensory receptors only respond to one sensory stimuli and converts it to an electrical graded potential
selectivity
if the stimulus is maintained the perception of a sensation may fade or even disappear even though the stimulus persists
adaptation
examples of rapid adaptation
pressure, tough, smell
examples of slow adaptation
pain, body position, chemical composition of blood
area of the skin innervated by the primary affect; size of receptor depends on the specific type of receptor
receptive field
what areas of the body have the smallest areas where sensory receptors are most dense
lips and finger tips
what are the 6 ways to classify receptors
structure, source of stimulus, location, sensitivity, rate of adaptation, size of receptive field
what are the two categories of classifying receptors by structure
free/diffuse nerve endings and encapsulated nerve endings
what receptors are free/diffuse nerve endings
temp, tickle, temp, and some pain
what receptors are encapsulated
pacinian corpuscle (pressure
what are the 3 ways receptors can be classified by stimulus and location
exteroceptors, proprioceptors, interoceptors
detect information from the external environment
exteroceptors
examples of exteroceptors
touch, smell, light, sound
where are exteroceptors found
in the skin
detect position sense and muscle tension
proprioceptors
where are proprioceptors found
muscles, tendons, joint capsule
detect changes within the internal environment of the body
interoceptors
examples of interoceptors
pH, BP, thirst, visceral pain
where are interoceptors found
walls of digestive structures, blood vessels, respiratory walls
what are the 4 types of receptors based on the type of stimulus energy
nociceptors, thermoreceptors, mehcanoreceptors, mechanoreceptors
what does nocere mean
to injury
free nerve endings found in skin, muscle, joints, and viscera
nociceptors
where are nociceptors most numerous
skin
small, myelinated and unmyelinated peripheral nerve fibers
nociceptors
what type of stimuli are nociceptors sensitive to
noxious
what type of nerve endings are most numerous in our body and aid in protection
free nerve endings
examples of stimuli for nociceptors
extreme thermal pain (above 45C and below 15C), sharp sensation (mechanical), chemical agents in blood or body fluids or external exposure
responds to heat or cold gradients
thermoreceptors
what type of nerve endings are thermoreceptors
free nerve endings
can thermoreceptors respond to both heat and cold
no, can either respond to hot or cold, never both
where are thermoreceptors found
skin, mucous/serous membranes, deep fascia, joints, connective tissue of organs
if hot/cold stimulus is outside the gradient for thermoreceptors, what receptors kick in to prevent injury
nociceptors
respond to substances released by cells, including damaged cells following an injury or infection
chemoreceptors
are chemoreceptors typically free N endings or encapsulated
encapsulated
examples of chemoreceptors
taste buds, olfactory receptors in olfactory epithelium, aortic and carotid bodies respond to changes in O2 in blood, CO2 receptors in the medulla/aortic/carotid bodies, gut receptors that regulate blood glucose/amino/fatty acids in the stomach and intestines
respond to mechanical deformation by touch (course/crude/light), pressure, stretch, vibration
mechanoreceptors
hairy
non-glaborous skin
hairless
glabrous skin
transmits touch (course/crude/light), pressure, tickle, itch, movement of skin
superficial cutaneous mechanoreceptors
examples of superficial cutaneous mechanoreceptors
Hair follicle endings
Meissner’s corpuscles
Merkel’s disks/merkel cell-neurite complex
Raffini
Pacinine
found in hair/nonglabrous skin
hair follicle endings
what is the stimuli for hair follicle endings
bending of the hair
hair follicle endings are ______ afferent axons and ______ adapating
myelinated AB and rapidly
are encapsulated and are found at superficially at epidermal-dermal junction in glabrous skin areas
meissners corpuscle
meissner’s corpuscles can adapt _____ and have a _____ receptive field
fast and small
stimuli for meissners corpuscle
rapid skin displacement (flutter, quick brushing of skin)
where are meissner’s corpuscles most numerous
finger pads, lips, anterior tongue, toes
example of two point discrimination for meissner’s corpuscles
braille
where are merkel cells founds
epidermis/dermis junctions
are single large myelinated AB afferent axons that may carry more information from more than one complex
merkel cells
are merkel cells founds on glabrous or nonglabrous skin
glabrous
are merkel cells slow or fast adapting
slow
stimuli for merkel cells and example
light, uniform or sustained pressure
Holding a pen
discriminative touch
Merkel cells
able to tell the difference between objects based on texture, shape, and edges of objects
able to recognize something by touch
stereognosis
ability to recognize symbols that are traced on the skin/palm
graphesthesia
where are ruffini endings found
subcutaneous skin in both glabrous and nonglabrous skin
encapsulated and unmeylinated terminal of a myelinated AB afferent
raffini endings
are raffini endings slow or fast adapting
slow
stimuli for raffini endings
stretch receptor for collagenous stretching (skin and joint capsules) — respond to skin drag
most deep and most distributed subcutaneous mechanoreceptor
pacinian corpuscles
egg-shaped, concentric layers of connective tissue with extracellular fluid in the spaces between
pacinian corpuscles
where are pacinian corpuscles found
hands, feet, aponeuroses and tendon sheaths of skeletal muscles, fascial planes, periosteum, around ligaments, interosseous membrane, in muscles
each one has its own heavily myelinated peripheral N fibers
pacinian corpuscles
are pacinian corpuscles slow or fast adapting
fast
stimuli for pacinian corpuscles
onset and removal of pressure, vibration, tickle
primarily concerned with posture, position sense, proprioceptions, muscle one, speed and direction of movement
proprioceptors
where are proprioceptors located
muscles, tendons, joints
examples of proprioceptors
muscle spindles, golgi tendon organs, golgi type endings
what two components make up position sense
kinesthesia and proprioception
awareness of body/limbs in space during movement (rate and direction)
kinesthesia
awareness of static body/limbs in space
proprioception
sensory organ embedded in skeletal muscle
muscle spindle
are muscle spindles free nerve endings or encapsulated
encapsulated
what is the function of muscle spindles
provide info about the present length of muscle and the rate of change in length when a muscle is stretched
do muscle spindles contribute to bone movements
no
fire the entire time the muscle is being stretched
tonic stretch receptors
adapt to a constant stimulus and stop responding; respond briefly to a quick stretch
phasic stretch receptors
muscle spindles are _____ shaped, meaning they are tapered at the ends
fusiform
are specialized fibers inside the muscle spindle
intrafusal
are ordinary striated muscle fibers outside the muscle spindle
extrafusal
the ends of intrafusal fibers are connected to what
extrafusal fibers
intrafusal fibers can only contract where
at their ends
large, sack like, filled with nuclei in the center
nuclear bag fibers
single row or chain of nuclei, attach at either end of nuclear bag fibers
nuclear chain fibers
what are the two types of sensory axons that attach to muscle spindles
annulospiral endings and flower spray endings
annulospiral endings are primary sensory endings of type ____ afferents
Ia
wrap around the central region of the nuclear bad and nuclear chain
annulospiral ending
what type of stimuli do annulospiral endings respond to
tonic and phasic
flower spray endings are secondary sensory ending of type ___ afferents
II
end mainly on nuclear chain fibers adjacent to primary endings
flower spray endings
what type of stimuli do flower spray endings respond to
tonic only
as extrafusal fibers are stretched, ends of intrafusal fibers are stretched and primary and secondary afferents send information to the ____ to adjust muscle tone to fit the task
CNS
small myelinated axons that signals contraction of intrafusal fibers
gamma motor efferents
what are gamma motor efferents under the control of
CNS (cell bodies in ventral horn of spinal cord)
relays tension in tendons
golgi tendon organs
encapsulated receptors found in tendons near the musculotendinous junctions
golgi tendon organs
respond to very slight changes in tension to both active muscle contraction and passive stretch
golgi tendon organs
golgi tendon organs send sensory information to the spinal cord by type ____ afferents
Ib
what provides the CNS with sensory information to allow normal muscle tone/muscle length tension relationship to be maintained
muscle spindles and golgi tendon organs
when a muscle contracts, what happens at muscle spindles and GTO
Spindles not stretched, do not fire
GTO fire under tension
what happens at muscle spindle and GTO when muscle is stretched
Spindles are stretched, increased sensory info to spinal cord
GTO under tension so also send sensory info
if muscle tension is too great or muscle is overstretched, the CNS will send inhibitory message to the ______ to tell muscle to relax
alpha motor neuron
respond to mechanical deformation of the capsule and ligaments
joint receptors
what type of endings in joint capsules signal extremes of joint ROM (type II afferents)
ruffini
what endings in joint capsules respond to movement
paciniform
are similar to GTO’s and respond to tension of ligaments in joint capsules
ligament receptors
what is the end destination for sensory information in the brain
parietal lobe
where are somatic afferent receptors found
skin, joints, muscles
examples of somatic afferents
pain, temp, light touch, discriminative touch, pressure, vibration, tickle, itch, sexual
where are visceral afferent receptors found
glands, organs, vessel walls, membranes
examples of visceral afferent information
pain, stretch, pressure, chemical changes
how are somatic afferents classified
by axon diameter and conductance velocity
are large axons that carry information from muscles, tendons and joints
large afferent axons
myelinated, largest and fastest axons; come from muscle spindles and stimulated by muscle stretch
Ia/Aa somatic afferents
myelinated, large and fast axons; carries sensory information from GTO’s, ligament receptors, and Ruffini endings; stimulated by tendon or ligament tension
Ib somatic afferents
carries information from joint capsules, muscle spindles, cutaneous touch, stretch, and pressure receptors
medium sized afferents
myelinated, medium sized; carries information from muscle spindles, meissners and pacinian corpuscles, ruffini and hair follicle endings
II/AB sized afferents
what stimulated II/AB medium afferents
stimulated by muscle stretch, joint movement, touch, pressure, skin stretch and vibration
carries information from MSK systems and skin about crude touch, pain and temp
small diameter afferents
what are examples of small diameter afferents
Adelta and C
myelinated, small and fast; carry sensory from hair follicles and free nerve endings; pain, cold temp, crude touch
Adelta afferents
unmyelinated, small and slow; carries motor into to glands, smooth mm; slow, burning, throbbing, aching pain, warm temp, smell, itch, tickle
C afferents
