Pain and Inflammation Flashcards
What is the definition of a transducer? Name a physiological example.
Something that translates energy from the environment into an action potential. Examples are mechanoreceptors, chemoreceptors, thermoreceptors, etc.
In a mechanoreceptor, deformation of the cell membrane opens ___ channels. This change in membrane potential is known as the ________ ________, aka ________ _______.
Na+ channels open, cause a generator potential aka receptor potential.
As stimuli intensity increases, generator potentials increase in a ________ relationship.
logarithmic
How do increasingly large generator potentials affect the action potentials in the coding region of the nerve?
Frequency of the APs increases.
What does the “graded response” refer to?
The fact that various stimuli intensity results in variations of intensity of the corresponding generator potential.
What is the region of the nerve called that lies between the receptor region and the coding region?
The spike-generating region.
Define the following regarding adaptation:
Tonic
Phasic
Accomodation
Tonic: no adaptation; no change in AP frequency.
Phasic: generator potential adapts by decreasing in intensity, so the AP frequency decreases.
Accomodation: coding region membrane threshold slowly increases as a result of repetitive depolarizations and inactivation of Na+ channels. Generator potential does not adapt, though!
Which results in a larger increase in action potential frequency:
1. Light touching on the face vs. a poke in the cheek
or
2. A medium whack with a hammer to the nose vs. a hard whack with a hammer to the nose.
Scenario 1 would result in a larger increase in AP frequency - the relationship is inversely logarithmic.
What are the three sources of pain signals?
Superficial (body surfaces), deep (muscles, joints, connective tissue), visceral (organs)
What is the fancy word for pain receptor?
Nociceptor
Do nociceptors have a higher threshold than other sensory receptors?
Yeah
What are the two nerve fibers involved in conducting superficial pain signals?
A-delta fibers quickly conduct initial pain signals, and the C fibers (slow conducting) mediate delayed pain signals.
-biphasic
Are C fibers myelinated?
Nope
What is hyperalgesia? What is the difference between primary and secondary hyperalgesia?
It is the tendency for inflamed tissues to have a reduced threshold for pain. Primary is local, damaged tissues that are sensitive to pain. Secondary is when the surrounding tissues also become sensitive.
Damaged tissues release inflammatory chemicals like bradykinin, prostaglandins, and substance P. Can these substances stimulate nociceptors?
Yeah
By what mechanism does a gentle massage help reduce superficial pain?
The massage stimulates an inhibitory interneuron to “gate” the transmission of the nociceptive info to the CNS.
How can the higher centers in the brain “gate” pain signals?
Higher centers may send an efferent signal to interrupt the afferent pain signal at the spinal level.
Endorophins, often released during exercise, can bind to ______ receptors in the brain.
opioid
Why are certain visceral pain signals sometimes referred to other parts of the body? What is this phenomena called (fancy term)?
Nociceptive fibers converge with common secondary afferent neurons at the spinal level, so signals from the secondary neuron may be interpreted as originating from a different part of the body - the dermatone. This is called visceral somatic convergence.
When does ectopic nerve disharge occur?
It happens when a nerve is injured (cut).
