Touch and Pain Flashcards
Touch is the sense by which we determine
the characteristics of objects: size, shape, and texture.
How do we touch
through touch receptors in the skin. In hariy skin areas some receptors consist of webs of sensory nerve cell ndings wrapping around the base of hairs
Signals from touch receptors pass via sensory nerves to the spinal cord where they
synapse (make contact) with other nerve cells in which in thurn they send the information to the thalamus
The transmission of this information is highly topographic meaning that
the body is represented in an orderly fashion at levels at different levels of teh nervous system
Large areas of the cortex are devoted to sensations from the
hands and lips, much smaller cortical regions represent less sensitive parts of the bdoy
Different parts of the boyd vary in thier sensitivity to tactile and painful stimuli acrding to
the number and distribution of receptors.
Neurologists measure sensitivity by determinging the patients
two point threshod, the methond involvings touching the skin with calipers at two points. The two point threshold is the distance between the two points that is necessary for the indiviudal to distinguishtwo stimuli from one
The thrshold is lowest where?
On the finger and lips
Until recently, pain was thought to represent a simple message resulting from neurons sending
electrical impulses froma site of injury directly to the brain
What do we now know?
That the process is very complicated
Nerve impulses from sites of injury can persist for how long
hours, days or longer
What can persistantinjury lead to?
Changes in the nervous system that amplify and prolong the pain signla
When the pain signal is proloned, the result is astate of hypersensitivity in which pain persists and can be evoked by
normally innocuous stimuli
Until recently, what was pain thought to be
a simple message from neurons from an electrical thing
What cana persistan tinjury lead to ?
Changes in the nervous system that amplify and prolong pain signal
The sensory fibers that respond to stimuli and that damage ttissue are called what?
nociiceptors
Different nociceptor subsets express molecules that are
responsible to painful, thermal of chemical stimuation
The same molecules can respond to plant derived chamicals fomr
capsaicin, garlic and wasabi
Tissue injury also can cause the elease of chemicals like
prostaglandins, to enhance the sensitivity of receptos to tissue damage nad ultimately can induce more pain sensation
What is allodynia
in which innocuous simuli can produce ain
Where are pain messages transmitted to?
the spinal cord via small, myelinated fibers nad C fibers- very small unmyelinated fibers
The small myelinated pain sensitive nerve fibers evoke what?
The fastest, sharpest pain that is produced
What is C-Fiber pain
dull
In the ascending system, what happnes to impulses,
they are relayed from the spinal cord to several brain structures including the thalamus and cerebral cortex which is involved in the proces by which pain messages become a concious experiences
The experience of pain is not just as
funciton of the magnitude of the injury or even the intensity of impulse activty generated by injury
Pain messages can be suppressd by
systems of neurons that originate within the gray matter in the brainstem.
The descending systems suppress the transmission of pain signals from the dorsal horn of the spinal cord to higher brain centers.
What do some of the descending system sue?
They use naturally ocuring chemicals, the endogenous opioids or endorphins which are funtionally smilar to morphine
