nlab cutaneous receptors and pain Flashcards
what are sensory neurons
afferent neuron that converts stimulus via their receptors into AP or graded potentials called signal transduction
what are sensory receptors
specialized epidermal cells that can be found in both external and internal organs
how are receptors categorized
based on cell type cell type and pos and the stimuli they detect
explain differential sensitivity
each type of receptor is highly sensitive to one stimulus it is for and unresponsive to other types
what do mechanoreceptors detect
touch and pressure
mechanical compression/stretching of receptor or tissues adjacent to receptor
what do thermoceptors detect
sensation of warmth and cold
what do nociceptors detect
harmful stimuli such as pain, extreme heat and cold; physical or chemical damage in tissues
what do chemoreceptors detect
change in the chemical composition of the environment based on where they are located
taste in the mouth, smell in the nose, oxygen level in the arterial blood, osmolality of the body fluids, carbon dioxide concentration
what do photoreceptors detect
n rods and cones in the retina that respond to light (electromagnetic)
significance of fast adapting receptors
emergency purposes (e.g. pain); for discrimination
significance of slow adapting receptors
for pressure - higher force for us to feel
give a fast adapting receptor and its role
Meissner’s (play an important role in discriminative touch (e.g., recognition of texture) and movement of objects over skin) → ball
should feel the texture even if we close our eye
give a slow adapting receptor and its role
Merkel’s (for pressure)
what is the labeled line principle
specificity of nerve fiber sensitivity to a single modality of sensation
what are the 2 main pathways of spinal cord for transmitting senses to CNS
Anterolateral Spinothalamic Tract and Posterior (Dorsal) Column-Medial Lemniscal
senses transmitted in the Anterolateral Spinothalamic Tract
superficial sensations
senses transmitted in the DCML
deep sensations
discuss the path of the Anterolateral Spinothalamic Tract
free nerve endings will be activated pag may pain or thermal stimuli the sends to
DRG - 1st order c lissauer’s tract; then sa SC entering dorsal horn of gray matter
then synapses c SG - 2nd order; gives axons that decussates and ascend in white matter; for LST - lateral part tas AST - anterior white collumn
synapses with VPL nucleus of thalamus - 3rd order
then gives final projection toward the somatosensory cortex tas dun ma interpret
what is transmitted in the lateral spinothalamic tract
non-discriminative superficial sensations such as pain and temperature
FAST PAIN
what is transmitted in the anterior spinothalamic tract
Light or crude touch and pressure.
SLOW PAIN
what sensations in the DCML
discriminative touch, vibration, conscious proprioception, kinesthesia and cortical sensations.
discuss the path of the DCML
sensations synapse sa DRG - 1st order; then enter SC and ipsilaterally ascends on dorsal aspect; can pass lateral or medial sides
then synapses with 2nd order neurons nucleus cuneatus (upper ex), nucleus gracilis (lower ex) then decussates and ascend toward pons/midbrain
synapse c 3rd order VPL of thalamus (UE and LE) tas VPMed (face) and ends sa broadmann’s area 312
speed of spinothalamic
few meters per second up to 40 m/sec
speed of DCML
30 to 110 m/sec
what is the significance of postcentral gyrus
ensations felt by different body parts are delivered to the primary somatosensory cortex in the postcentral gyrus of the parietal lobe
significance of sensory homunculus
dramatical representation of the relative sizes of the cortical receiving areas; represents the sensations of the primary somatosensory cortex
anterior half of the parietal lobe is concerned with
reception and interpretation of somatosensory signals
posterior half of the parietal lobe provides
higher levels of interpretation.
what terminates in the occipital lobe
visual signals
what terminates in the temporal lobe
auditory signals
significance of motor cortex
to control muscle contractions and body movements in response to somatosensory signals
order of sensitivity of motor cortex
Lips > Face > Thumb > Trunk → where lips has the highest sensitivity and trunk has the lowest sensitivity
order of body parts in motor cortex from medial to lateral
genitals - foot - LE - trunk - neck and head - UE - hands - face - tounge
large parts of motor cortex
Hands, foot, tongue & lips - Rich in innervation & sensitive parts
small parts of motor cortex
Trunk and back - Sensations in this area are not as large as compared to the hands and mouth
significance of somatosensory area 1
Somatosensory area I is so much more extensive and so much more important - “Somatosensory cortex” almost always means area I
high degree of localization of the different parts of the body
significance of somatosensory area 2
signals enter this area from the brain stem, transmitted upward from both sides of the body
connect SSA 1 and SSA 2
projections from SSA1 are required for function of somatosensory area II
removal of parts of SSA2 has no apparent effect on the response of neurons in somatosensory area I
what is astereognosis
inability to identify objects through feel only - (Somatosensory Area 1 affectation)
what is abaragnosis
inability to detect weight of an object
what stimuli can elicit pain
mechanical, thermal, and chemical stimuli via nociceptors
explain how mechanical stimuli causes pain
FAST PAIN
over-stretch of muscle fibers/over-rotation of joints
Nodules and taut bands (d/t lactic acid)
muscle spasm - tissue ischemia
explain how thermal stimuli causes pain
FAST PAIN
through excessive heat > 45°C or cold that can cause burns
explain how chemical stimuli causes pain
SLOW PAIN
Tissue Injury → bradykinin (most responsible for pain sensation) & prostaglandin → stimulate nociceptors ↑ pain
fibers for fast vs slow pain
fast - A delta
slow - C fibers
pathway for fast vs slow pain
fast - neospinothalamic pathway or lateral ST
slow - Paleospinothalamic Pathway/Anterior ST
NT for fast vs slow pain
fast - Glutamate
slow - substance P and glutamate
type of pain for fast vs slow pain
fast - Discriminative pain or localized pain
slow - Emotional or motivational aspect of pain
discuss brown sequard syndrome
functional hemisection of the spinal cord
leads to ipsilateral loss of discriminative touch, vibration, proprioception and weakness and spasticity of muscles below the level of the lesion
leads to contralateral loss of pain and temperature sensation beginning one or two segments below the lesion
significance of lissauer’s tracts
baril sa SC, sira WHOLE L2, no sensation on L2 but at the L1,3,4,5, can still feel the superficial sensation since the lissauer’s tract allows it
2 levels above and below
why does rubbing skin near painful areas relieve pain - gate control theory
Detected by the pacinian corpuscles found immediately beneath the skin, which are sensitive to deep pressure and fast vibration
non-nociceptive large diameter fibers like the Aβ fibers are activated through pressure like in the given situation, the substantia gelatinosa is activated and its inhibitory nature will close the neurological gate, blocking the pain signals from reaching the thalamus, significantly reducing the pain
discuss analgesia system
capability of the brain itself to suppress input of pain signals to the nervous system by activating a pain control system
3 major components of the analgesia system
(1) Periaqueductal gray and periventricular areas
(2) the Raphe magnus nucleus
(3) nuc reticularis paragigantocellularis
relate ES to the analgesia system
Electrical stimulation either in the periaqueductal gray area or in the raphe magnus nucleus can suppress many strong pain signals entering by way of the dorsal spinal roots
discuss the opioid system pathway
binding ng opioids like enkephalin and endorphins to receptors leads to a decrease in Ca2+ influx, resulting in a decrease in release of glutamate and substance P
reduced transmission from nociceptive afferents
