Exam 3 - Lecture 3 Flashcards
Why don’t arteries collapse?
Arteries have a high internal pressure and it would take a massive amount of ICP to collapse those.
Are 2nd order neurons in slow pain myelinated or not myelinated?
may or may not be myelinated
Are 2nd order neurons in fast pain myelinated or not myelinated?
Almost always myelinated
Tips of nociceptors are sensitive to 2 things
damage and chemicals (multiple as stated before)
Cell body of nociceptor is in:
dorsal root ganglia
What pathway is right next to nociceptor?
DCML pressure sensor considered a neighboring pathway
Nociceptors can connect to which lamina?
Fast: Lamina I
Slow: II, III, V
Where does lateral inhibition happen?
In dorsal horn or in periphery
Metabotropic receptors in ascending pain pathway are typically found where?
In the brain
Are ionotropic and metabotropic receptors in pain pathway excitatory or inhibitory?
Excitatory
In DIC, the 3rd order neuron secretes enkephalins and they bind to receptors in what areas?
periphery right outside cord and in the lamina
Enkephalin receptors are what type of receptors? what are they also called?
GPCRs; Opiate receptors
Enkephalin Receptors are functionally linked to:
Potassium channels
When opiates hit enkephalin receptors, it allows __________ to open. Results in what?
Potassium channels; to open and leave cell, making the cell more negative/difficult to excited.
There are opiate receptors on what part?
Both pre and post synaptic of pain pathway
What other receptors are on synapse in pain pathway?
Alpha-2 receptors
What do alpha-2 receptors do when an agonist binds to them?
Open up potassium channels.
What receptors do alpha-2 agonist drugs affect and where?
Both pre and post synapse/at 1st order nociceptor and 2nd order transmission neuron.
Opiate receptors and alpha-2 receptors both increase:
Cell wall permeability to potassium, not sure if theyre the same K+ channels or not.
Alpha-2 Agonists mentioned in lecture in order of specificity weakest to strongest
Xylazine, Clonidine, Precedex
What alpha-2 agonist mentioned also ends up being an alpha-1 agonist?
Xylazine
Why are alpha-2 agonist useful?
Just pain suppression/relaxation of CNS without getting high upstairs
Alpha-2 receptors are located where
all over CNS, but our focus is at the ascending pain pathway.
What drug do people abuse papa talked about? And what does the media call it?
Xylazine; horse tranquilizer
Volatile anesthetics effect on pain pathway
Suppress activity throughout nervous system, increase potassium conductance at pain synapse.
Potassium will always be _______ in this class.
Leaving the cell.
Cox-2 is expressed in:
1st and 2nd order pain neurons
More pain we have, the more ___ expressed.
Cox-2
COX-2 produces _________ which interact with __________. Which neurons?
Prostaglandins; prostaglandins receptors; 1st and 2nd order transmission neurons (ascending)
How do prostaglandins increase pain?
Increase sensitivity to painful things/amount of action potentials sent up ascending pain pathway.
Doesnt actually fire AP itself.
iNOS and what does it do
Nitric oxide synthase; increases painful stimuli sensitivity in the synapse
What supplement can help with chronic pain? Possible negative side effect?
Magnesium via blocking NDMA-r, but can cause upset stomach.
Do calcium levels impact pain like mag?
No.
4 spinal reflex pathways
Stretch, tendon, withdrawal, crossed extensor reflex
Which 2 spinal reflex pathways are responses to pain?
Withdrawal and Crossed extensor reflexes
Which 2 spinal reflex pathways are stretch sensors for muscles?
Stretch and tendon reflexes
Where are reflex sensors located?
Out in periphery, may involve pain sensors and tension receptors.
Where are tension receptors found?
Imbedded in skeletal muscles and/or tendons that can sense tension.
Reflexes must have ____ components. What are they?
2; sensory and motor
How do sensory and motor neurons talk to each other in reflexes?
Direct synapses in the grey matter of spinal cord.
Or via interneurons, can either be excitatory or inhibitory.
A “bridge” between motor and sensory neurons in reflexes
Interneurons
We may use _______ interneurons depending on complexity of reflex.
1 or multiple.
Afferent information
periphery to CNS (Sensory)
Efferent information
CNS to periphery (Motor)
In order for reflexes to occur on both sides of the body, the cross-over of communication happens via
Interneurons in the spinal cord, there are no direct pathways.
Stretch reflex is the most ______ reflex.
Simple
Stretch reflex’s purpose is to
Keep muscles at a constant length, for support/weight bearing.
i.e. leg muscles
Which reflex’s purpose is to keep posture constant? (hand on forehead example)
Stretch reflex
If youre pushed on your forehead, which muscle does the stretch muscle activate?
Quadriceps; they contract and shorten to original length to prevent stretch of the muscles to lean back.
Do we usually need interneurons for stretch reflex?
No, just achieved using single sensory neurons, no inhibitory neurons needed.
When would interneurons be needed for stretch reflex?
If we needed reflex relaxation of antagonistic muscle set (if quads are activated, this example would be hamstrings).
If the stretch reflex activates the quads to contract to keep us up straight, and we needed the hamstring muscles to relax as well, this would be what type of response of the hamstrings?
inhibitory
Does the stretch reflex cross the cord?
No the loop is in the same side of body.
Where is the stretch reflex found?
Inside the muscle itself
Springs that detect tension in muscles are called?
Spindles
Stretch receptors are also called
muscle spindles
Stretch reflex #1 in his example
Quads contracting
Stretch reflex #2 in his example
Hamstrings relaxing
How do you test for complete circuit of stretch reflex? What happens?
Tap on ligament underneath patella. Contracts the quadricep muscle, foot twitches forward.
The muscle spindle looks for
Tension changes in skeletal muscle.
Goal of Tendon reflex
Protective nature, there are stretch sensors in tendons of skeletal muscles that sense large amounts of tension within tendon and cease contraction to prevent tendon tears. Has a “reflex relaxation”
Tendon reflex #1
Cease contraction under heavy load to prevent tendon tears
Tendon reflex #2
Contract antagonistic muscles to speed retraction from load source.
What prevents muscles from being pulled out of their insertion points?
Tendon reflex
Tendon reflex tends to not be engaged in situations such as
Lifting a car off of a child, dont know how it works.
tendon reflex sensory information enters back of cord and comes in contact with
2 sets of interneurons consisting of 1 set being excitatory and one is inhibitory.I
Inhibitory interneuron in tendon reflex is in charge of
Inhibiting activity of motor neuron that attaches to effector muscle group (the one attached to tendon)
Excitatory interneuron in tendon reflex causes
Reflex activation of antagonistic muscle set.
e.g. obscene tension on quad, causes inhibition/relaxation of quad and excitation/contraction of hamstring.
Tendon reflex uses ____ sets of interneurons
2
Tendon reflex is used by both sides of cord or just same side of cord?
Same side
Flexor reflex aka
Withdrawal reflex
Goal of flexor reflex
Involves pain sensors, we usually want to withdraw limbs from painful stimuli to prevent injury.
Does the flexor reflex use both sides of cord or just one side?
Usually just one side.
If you slam your foot into the wall, the effector muscle would be?
Hamstring to pull it back. May include relaxing the quadriceps.
If we can pull away from pain using effector muscles, we could pull away even faster using the _________
relaxing muscles too
Typically, the flexor reflex involves more muscles/levels of cord than ____________ because of ________.
Tendon and stretch reflex; pain
Flexor reflex involves how many levels of the cord, typically?
2 vertebra levels up, 2 vertebra levels down.
5 total ;)
how does flexor reflex travel up and down the cord to involve more muscles?
Ascending and descending interneurons.
Where are ascending/descending interneuron cell bodies located? What’s the area called?
An area just posterior to dorsal grey matter, inside the white matter of cord, called the Tract of Lissaur
Where is the tract of lissaur?
In the white matter just posterior to dorsal horn at the tip.
The more _________ of spinal cord involved, the better the reflex
levels
Crossed extensor reflex is called that why?
Involves both sides of the cord
Which reflex is most complicated?
Crossed extensor reflex
Crossed extensor reflex goal
Used when incurring pain during a complex motion
i.e. stubbing your toe midstride, you need to transfer your weight to the non-weight bearing leg while you retract the leg incurring pain, stabilizing your body weight.
Does crossed extensor reflex involve multiple levels of the cord?
Yes, cause it involves pain.
Communication between one side of cord to other causes
one muscle group to contract and one muscle group to relax, via interneurons.
If you hit your right leg while walking, what happens to muscle groups in each leg?
Plant left leg and stabilize by contracting extensor muscles (quads) in left leg, relaxation of hamstring (flexor).
Right side of body will withdraw effective limb, contracting hamstring muscle (flexor muscle group) and antagonistic relaxation of quads in right leg.
Which reflex would use the most interneurons?
Crossed extensor reflex
Extensor muscles
Quads
Flexor muscles
Hamstrings
How do you inhibit reflexs?
Strong drugs that affect nervous system i.e. spinal block. inhibit pain but also inhibit spinal reflexes, can test reflexes to get an idea how good your block is.
Adult NMJ will have _________ of nACHr
Mature/adult versions
Should we see mature nACHr outside the NMJ?
No, only at NMJ.
Mature nACHr channels have _____ domains.
Five.
Alpha1, Beta1, Delta, Alpha, Epsilon
Clockwise order of mature nACHr starting at 11o clock
a1, b1, delta, alpha (6 o clock), epsilon (9o clock)
Mature nACHr can be thought of _____ conductance channels
High aka how permeable is the cell wall to things moving in and out
When mature nACHr are open, the speed is
very high and thats why its called a high conductance channel
Mature nACHr stay open for a ________
Very short period of time.
What is the different subunit for immature vs mature nACHr?
The epsilone is replaced by a gamma subunit
Newborns will have _______ at the NMJ.
Immature nACHr.
Immature nACHr are also found
outside the NMJ across the skeletal muscle where they arent supposed to be.
Immature nACHr are also called
Fetal
When immature nACHr are open, they have a ________ conductance
Slower
The depth of projection when immature nACHr open is _____ than mature.
Shallower, not as deep.
Which nACHr stay open for a longer period of time?
Immature.
Where are the 2 main nACHr found?
exclusively in skeletal muscle
alpha7 ACHr all subunits are
a7
Where are alpha7 ACHr found?
In the CNS
alpha7 has how many subunits?
Five, all alpha7
Succynlcholine has a greater effect on the
immature nACHr, since they already stay open a long time. will stay open longer.
What happens when brain tells a muscle to contract but muscle doesnt respond?
Brain doesnt get feedback of muscle movement, CNS figures something is wrong, response will be to try fix it by increasing (expressing) amount of nACHr at NMJ.
What type of nACHr are created when brain thinks muscle isnt responding? would this help with MG?
They express/turn on fetal nACHr which are poorly placed and less efficient, populated across entire muscle.
Yah, a little bit. but not for much else issues.
If there are alot of fetal receptors and you give them sux after theyve had a history of stroke/ bad muscles what can happen? What arrhythmia as a result?
Severe hyperkalemia -> vfib
Another name for enkephalin opiate receptors
Mu-receptors
