A Phys - Quiz 6 info (p. 88-124) Flashcards
What are the differences between invertebrate and vertebrate light reception
- invertebrates have PLC made as teh 2nds messenger from the G-protein (transducin) and that is used to stimulate PIP2 in the membrane which in turn makes IP3 and DAG. These two messengers close the Na+ channel and stop Na+ influx.
PIP2 stands for;
Phosphatidyl 4, 5-bisphosphate
DAG stands for;
Diacylglycerol
IP3 stands for;
Inositol triphosphate
PLC stands for;
Phospholipase C
PDE stands for;
phosphodiesterase
When the invertebrate photoreceptor cell is exposed to light, what happens?
- the cell depolarizes, moving away from the K+ Nernst pot.
- there is increase G(Na) (maximum sodium conductance)
- it is moving towards 0/towards E(Na)
- when light is no longer on, the cell hyperpolarizes (Na+/K+ ATPase) and returns to a negative, resting potential.
When the vertebrate photoreceptor cell is exposed to light, what happens?
- the cell is close to zero and hyperpolarizes towards the K nernst potential
- there is a decrease in G(Na) (maximum sodium conductance
- once the light is off, the potential depolarizes as Na+ influxes.
What is the ERG? What is it used for?
It is an electroretinogram that tracks the electrical activity of the retina in response to light stimulus
What is the a wave in an electroretinogram?
it is hyperpolarization due to inhibition of dark current in photoreceptor cells, it is the first movement and it is downward on a graph; it happens immediately after light is applied.
What is the b wave in an electroretinogram?
it is the depolarization of bipolar cells, it is second wave and is significantly larger than the a wave; it happens directly after the a wave and happens while light is applied.
What is the c wave in an electroretinogram?
it is the interaction between photoreceptor cells and pigmented epithelium; this happens after the light is turned off and it is a signal that these cells are functional (bc they are wrapped around photoreceptor cells)
Across a turtle, toad, rabbit and human, how are the ERGs similar and different?
Similar:
- they all have an a and b wave
- the a and b wave are in the same directions as human waves
Different:
- the toad and turtle have a d wave as well
- there is variability in the amount of volts and milliseconds for each
What is nociception?
the detection of painful/noxious stimuli
Mechanical nociceptors are most _____, and respond to __________ damage such as: _______, crushing, and _______. These are also the _____ to respond
basic; mechanical; cutting; pinching; fastest
Thermal nociceptors respond to _________ extremes, they are enabled by _______ _____ channels that open at certain _______
temperature; TRP cation; temperatures
Polymodal nociceptors are most _____ and respond ______ to all kinds of damaging stimuli; they respond to _____ released from ______ tissues. It takes _____ to work but senses pain over a ______ ______.
complex; equally; chemicals; injured; longer; long period
_____ _____ activates nociceptors
tissue damage
What do damaged cells release?
signaling chemicals, 5-HT, bradykinin, prostaglandins
What do chemicals like 5-HT, bradykinin and prostaglandins open?
cation channels on nociceptor cells and trigger APs down the dorsal root ganglion neuron
How do nociceptors send signals to the brain?
they synapse in the spinal cord with afferent neurons to the brain
What are some characteristics of pain?
- initial sharp twinge of pain via the fast pain pathway
- secondary, diffuse wave of pain shortly after + occurs via the slow pain pathway
What is involved in the fast pain pathway (+ characterize it)
characterization: initial sharpe twinge of pain
Involved:
- mechanical nociceptors
- thermal nociceptors
What is involved in the slow pain pathway (+ characterize it)
characterization: secondary, diffuse wave of pain shortly after painful stimuli
involved:
- triggered by chemicals released by damaged tissue + detected by polymodal nociceptors
- prolonged pain