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Somatosensory System
The touch sensory system
Somatosensory Cortex
Where sensory information is processed; located in the parietal lobe.
S1/Primary somatosensory cortex
Interprets sensory information
Central Sulcus
seperates frontal lobe from the parietal lobe
Receptor Cells
Convcert energy to neural activity/action potential
Stimuli
a physical event triggering a sensory response
Modality
Different types of sensations that the somatosensory system detects and processes.
Labelled lines
action potentials for each sense carried in different nerve tracts; allows for the brain to distinguish and process different physical stimuli.
receptor potential
receptor cells that responded to local stimuliby causing a local change in its electric potential.
Sensory Transduction
The entire process by which the resonse to stimuli is converted to electrical signal & transmitted to the CNS.
Meissner’s (tactile) corpuscle
object form
pacinian (lamellated) corpuscle
vibration/pressure (texture)
Ruffinl corpuscle
stretching of skin
merkel’s disc
object form
free nerve ending
pain, heat, itch, cold
Dorsal Column System/Pathway
sensory pathway within the CNS; carried information about touch sensation
ascending tract
neural pathway carrying information up to the brain.
plasticity
ability of sensory regions to change (due to experience/injury)
What is the bodies response to pain?
we act to minimize risk to our bodies or we socially communicate our pain (groan, etc).
Nociceptors
neurons detecting temperature, mechanical (pinch, pressure) and chemical insults.
Where are nociceptors located?
Skin, cornea, joints, some free nerve endings, muscles, and internal organs - NOT in the brain.
Nerve Fiber
Elongated extensions of the neurons of nociceptors.
Whats the role of nociceptors?
they send and receive sensory information, control movement, and regulate bodily functions.
Nerve
a bundle of nerve fibers
What are the two types of nerve fibers of nociceptors?
A fibers and C fibers.
A Fiber
myelinated & action potential travels rapidly
C Fiber
NOT myelinated & action potential travels slower
What are the nociceptor cell types?
Vanilloid receptor 1 & TRPM3 receptors
Vanilloid receptor 1
Located: on unmyelinated C fibers
Job: detect rising temperature (by eating capsaicin) & to dull pain following burning.
TRPM3 Receptors
Located: on A delta fibers
Job: detects higher temperatures than the vanilloid & the initial sharp pain following a burn.
What happens when a tissue is injured?
There is a release of serotonin, histamine, and Substance P locally. These stimulate the nociceptors and tell them something is wrong. In response there is local inflammation & then finally the information is transmitted to the brain via spinothalamic or anterolateral pathway.
What are the neurotransmitters that are released in the spinal cord & periphery?
Substance P & Glutamate
Spinothalamic Pathway
the ascending tract carrying information about pain to the brain.
Anterolateral Pathway
what is the order of the Spinothalamic Pathway?
spinal cord → medulla → pons → midbrain (periaqueductal gray) → thalamus → Primary Somatosensory cortex (S1) → cingulate cortex.
Cingulate cortex
Part of the limbic system & focuses on emotional pain.
What are the similarities between the spinothalamic pathway and DCP?
They are both sensory tracks, ascending tracts, and both cross over.
What are the differences between the spinothalamic pathway and DCP?
DCP: carries the sensation of touch, goes to the brain & crosses over in medulla
What are the types of pain?
Short term pain, long term/chronic pain, and neuropathic pain
what is our bodies response to short term pain?
withdrawal from the source (reflex) to prevent further tissue damage; biologically useful
what is longzsxa
