Flashcards in Neuro Deck (155)
What is the somatosensory system?
Allows us to sense: touch, temperature, propioception, pain
What are teh exteroreceptive sense?
thermoreceptors: warming and cooling
nociceptors: sharp and burning pain
area in the periphery where application of an adequate stimulus causes response
At peripheral terminal stimulus activates receptors and ion channels; generates receptor potential; receptor potential strong enough generates action potentials
Intensity of stimulus is encoded by what?
Each neuron through frate code of frequency
in many neurons through number of neurons firing the spatial summation code
what are the different types of nerve fibers?
Aalpha, Abeta (both are large and mylenaited)
Adelta (thin and myelinated)
C fibers (unmyelinated)
Glaborous skin specializes in what?
Has severl different types of specilalized sensor receptor
Spatial resolution depends on what?
receptive field size and innervation density
What are mechanoreceptors?
mediate tactile/touch sensation, very sensitive to force(low threshold),have myelinated axons, superficial receptors in border between epidermis and dermis
What are merkel disks?
type of mechanoreceptorss: Responsible for fine touch, 2point discrimination, receptive field, multiple small spots, several disks for one axon, slowly adapting response encodes amount of force
What are Meissner's corpuscles?
[mechanoreceptors] Fine touch, 2-point discrimination. Sense abrupt changes in edges. Help adjust grip. Receptive field: single spot. Corpuscle encloses a stack of flattened epithelial cells. Rapidly adapting responses encodes offset of skin indentation.
What are Ruffini Endings?
Sense stretch of skin, help determined shape of grasp objects. Receptive field: large and diffuse. Ruffini ending is encapsulated. Slowl adapting resposne sto stretching skin
What are pacinian corpsucles?
[mechanoreceptors] Respond to high frequency vibration; MOst sensitve mechanoreceptor even distribution throughout skin.
Receptive field: large and diffuse
Fluid filled capsule wrapped around bare nerve endings filters out sustained stimuli
Rapidly adapting response
What are hair follicle receptors?
[mechanoreceptors], respond tot movement of hairs, receptive field is around base of hair. Bare axon wraps around base of hair follicle; rapidly adapting response encodes velocity of hair
Spatial summation code is what?
OVerall picture in brain is due to sum of information provided by different active and silent fibers
Thermoreceptors are what?
Encode skin temp (warming, cooling). Discharge continuously (steady rate) @ normal skin temp
What are cooling receptors?
[thermoreceptor] increase firing when skin is cooled. Free nerve endings with myelinated axons. Small receptive fields; infrequent distribution
What are warming receptors?
increase firing rate when skin is warmed aboved 32 C. Stop firing when skin is cooled. Free nerve endings with unmyelinated axons
What are nociceptors?
Respond to stimuli that damage or threaten to damage tissue; 70% of DRG are nociceptors and provide almost all innervation to tooth pulp and cornea
What is Mechanonociceptors?
[nociceptor] Adelta axon
Respond to intense mechanical force, sometimes intense heat
free nerve ending
small receptive fields
slowly adapting response
mediate fast initial pain, sharp pricking, easy to localize
What are polymodal nociceptors?
Respond to intesne mechancial force, high heat, noxious chemicals
free nerve endings,
small receptive fields
slowly adapting response
mediate slow aching, "burning" pain
What does the DC/ML transmit sensations of?
What are teh components of the DC/ML system?
1st in sensory ganglion
2nd in spinal cord and/or braiinstem
3rd in thalamus
In the DC/ML system waht is the 1st neurons responsibility?
Peripheral process transmits info from mechanoreceptor
cell body i DRG
Central process transmits info via dorsal root and ascends within ipsilateral dorsal colum
terminates in dorsal column nuclei
What is the role of the 2nd Nueron in the DC/ML system?
Cell body in ucleus gracillis or nucleus cuneatus
terminates in ventral posterior lateral nucleus of thalamus
axon decussates to contralat side and ascends in medial lemniscus
What is the role of the 3rd neuron in the DC/ML system?
Cell body in VPL of thalamus
Axons pass through posterior limb of termial capsule
Terminates in SI cortex (postcentral gyrus, primary somatosensory cortex)
What does the faciculus gracilis contain?
Located medially, contains axons from below T7
What does the faciculus cuneatus contain?
Axons from about T7 in DC/ML system and it's located laterally
What is the role of Somatotopy in the 1st neuron of the DC/ML system?
Sacral dermatomes located medially, and each level on the way up located progressively laterally helps perserve info about location and nature of stim