Test 3 - 10/2 Lecture Flashcards
The main difference in myelination status in the fast pain and slow pain pathways is the myelination of the
First order nociceptor
The cell body on the nociceptor is located in the ______
Dorsal root ganglia
Fast pain uses _____ neurotransmitters. Slow pain uses _____, ______ and ______ neurotransmitters.
Glutamate.
Glutamate, substance P, and CGRP.
T/F. All slow pain is stopped before it makes it to the parietal lobe
False. A small amount can make it to the parietal lobe
Where does lateral inhibition take place?
In the cord but also some happens in the periphery
Neurotransmitter release is mediated via what?
AP causes Calcium entry into the presynaptic cell
The second order neuron of the spinothalamic tracts may or may not be ______ regardless of if it synapses with the fast or slow pain primary neuron
myelinated
Are second order neurons myelinated?
Most of them are myelinated
Where does the cell body for the 3rd order neuron sit? what about the rest of the cell?
cell body is just outside dorsal horn and then a penetrating portion goes into dorsal horn for synapse
Describe the myelination of the grey matter in regards to fast pain
Fast pain is all myelinated. Grey matter is typically only cell bodies and non myelinated but a small portion can be myelinated (ex fast pain pathways
Metabotropic glutamate receptors are typically found _____
“more upstairs” more in the brain
Glutamate Ionotropic and metabotropic receptors tend to be ________
excitatory in nature
an opiate Mu receptor is synonymous with
Enkephalin receptors
What type of receptor is an enkephalin receptor
a GPCR with a 7TM spanning domain.
When Enkephalin receptors are activated the action that is carried out by it’s activated alpha sub-unit is _______
opening potassium channels allowing K out of cell; causing hyperpolarization hence the pain control (bc they are more difficult to excite)
How do opiate receptors work?
They increase cell wall permeability to potassium and that inhibits the cells.
Alpha-2 receptors in the pain pathways have what function when activated?
They increase cell wall permeability to potassium and that inhibits the cells.
Alpha 2 activation at the synapse will have what affect?
It will shut down the first order nociceptor and the second order pain transmission neuron
3 examples of alpha 2 agonist from lecture ranked in order of lease selective for alpha 2 to most selective to alpha 2
1- Xylazine
2- Clonidine
3- Precedex (most selective)
Which medication mentioned (Xylazine, clonidine, precedex) works on both alpha 1 and 2?
Xylazine
Zylazine, clonidine and precedex have what affect?
pain suppression and relaxation. Doesn’t work upstairs (no euphoria)
Horse tranquilizer mentioned in class
Xylazine
One way volatile anesthetics cause inhibition in the nervous system is by
Generalized increase in potassium conductance causing pain suppression/hyperpolarization
For our class potassium will always be ______ the cell and that will cause _____
Leaving.
Hyperpolarization
We can expect an increase in cyclooxygenase II in the spinothalamic tract in response to _______
Frequent activation/pain
COX 2 is expressed within our ______
first order and second order pain neurons
An increase in COX II would also cause an increase in
Prostaglandins
Prostaglandins that are produced from an increase in COX 2 will act on ______ receptors located on ______ and cause ______
Prostaglandin.
1st order and 2nd order ascending pain transmission neurons.
Increased sensitivity to painful stimuli.
What do prostaglandins have to do with action potential?
They don’t directly cause an AP but will increase the chances of an AP or repetitive AP
i NOs is ______ and causes ________ in regards to pain.
an inducible form of Nitric Oxide Synthase; an increased sensitivity to pain.
How do we typically think of iNOs? (not in regards to pain)
relax blood vessels and keep BP down and gives us organ perfusion.
3 examples of substances that increase sensitivity to pain without exciting the cells themselves
1- Prostaglandins
2- COX 2
3- i NOs
We may recommend a _______ supplement to someone with chronic pain. Why?
Magnesium; it is thought that it inhibits the NDMA receptors.
What can happen if you take too much mag?
runnnnnnnin to da bathroom
Does Ca as a supplement help with pain? what does Ca help with?
No. Ca does help settle down nervous system but increased extracellular calcium doesn’t help with pain
List the 4 spinal reflex pathways
1- Stretch Reflex
2- Tendon Reflex
3- Withdrawal Reflex
4- Crossed Extensor Reflex
2 Reflexes that are a response to pain
1- Withdrawal Reflex
2- Crossed Extensor Reflex
2 reflexes that are tension/stretch reflexes
Stretch reflex
Tendon reflex
A spinal cord reflex can be elicited by _____ or _______
pain or tension receptors in our skeletal muscles/tendons
How does direct communication work with sensory and motor neurons?
If there is a strong enough signal the Sensory neuron will go into dorsal horn and up to the anterior horn and the neurotransmitter release can activate the motor neuron
What are the two ways the sensory and motor neurons can talk?
Direct communication
via intermediary (aka interneurons)
Are interneurons inhibitory or excitatory?
both excitatory and inhibitory
Describe interneurons for more complicated reflexes vs simple reflex
For a simple we may just have one interneuron.
For more complex there might be multiple interneurons.
Afferent
Towards CNS
Efferent
Away from CNS
Most common efferent pathway for us?
Motor output
If a reflex involves both sides of the body how does the information cross over?
Via interneurons
A spinal reflex usually consists of _______ neurons
2-3.
Sensory
Motor
Sometimes interneuron
Goal of stretch reflex
Keep muscles at a constant length; for support
The weight bearing leg muscles typically utilize what reflex?
Stretch reflex
What reflex do we use to keep our posture constant?
Stretch reflex
If someone is standing upright and someone pushes forehead backwards what will happen with and without a reflex. What reflex is this?
Stretch reflex
Without: We would fall backwards
With: The quad muscles would get stretched out and this would cause the stretch reflex to initiate contraction of the quads to keep us upright
How to sensory and motor neurons communicate for the stretch reflex?
Direct communication
How do inhibitory interneurons in the stretch reflex work? (use example of someone pushing forhead backwards)
Allow for reflex relaxation of the antagonistic muscle cell.
Ex above. Hamstring muscle is the antagonistic muscle and would relax as quad is contracted to help keep us in the same posture
the stretch reflex is used on (side (s) of the cord)
the same side that the stretch is being sensed on
The sensor utilized by the stretch reflex is a _______
Muscle Spindle
How can you check for the stretch reflex? Why does this work?
tapping on the ligament below the patella; tapping on the ligament will pull the patella down which is attached to the quad tendons and that will cause the quad to stretch activating the reflex and causing foot to go outward
The quadricep muscle is an _____ muscle
Extensor
The muscle spindle looks for ______ (in regards to the stretch reflex)
tension changes in our skeletal muscles
Goal of tendon reflex
It is protective in nature. Not allowing for damage to tendon insertion site under a heavy load.
Where are the stretch sensors for the tendon reflex?
Imbedded in the collagen and fibrous tissues that make up the tendon
The tendon reflex is activated by
stretch sensors when they sense a massive amount of tension on the muscle/tendon
Is the tendon reflex activated often?
No, only with massive amounts of tension
The response elicited by the tendon reflex is
Causing relaxation of the muscles that are attached to the tendon that is experiencing the tension
How is the tendon reflex protective?
This reflex prevents us from ripping our skeletal muscles out of their insertion points.
A guy jumps out of a tree and lands on his feet. He breaks lots of bones but the muscles dont break. Why?
The tendon reflex prevents them from being pulled out of the insertion point.
Example of a work around for the tendon reflex
Lifting a 5000lb car off of a kid
The tendon reflex has effects on what muscle?
The muscle that has the tension as well as the antagonistic muscle
Does the tendon reflex involve one or both sides of cord?
One
How are interneurons used in the tendon reflex?
2 sets, 1 set excitatory and 1 set inhibitory.
Inhibitory set causes relaxation of the muscle experiencing tension
excitatory set causes reflex activation of the antagonistic muscle.
If there is enough tension on the quad to elicit the tendon reflex what would happen?
The inhibitory neurons would cause relaxation of the quad
The excitatory neurons would cause reflex activation of the hamstring to take tension off of quad
Flexor Reflex is also called
withdrawal reflex
Sensory portion of the flexor/withdraw reflex involves _____ sensors
pain
Goal of flexor reflex
Withdraw limbs from painful stimuli to prevent injury
What is one key difference between the flexor reflex and the crossed extensor reflex?
With the simple flexor reflex we are in a static position. With the crossed extensor reflex we are typically moving.
The flexor reflex involves one or both sides of cord?
One side
If you stub your toe the response of an activated flexor reflex results in
contraction of the flexor muscle group (hamstrings) causing leg to move back. Sometimes it can also relax the antagonistic extensor muscle (quadriceps).
With the flexor reflex we involve ______. This allows for _______.
multiple levels of the spinal cord. (2 up and 2 down) This allows recruitment of multiple muscles in the reflex.
What alerts the other portions of the spinal cord to the need for activation of a flexor reflex?
Ascending/Descending interneurons
The ascending and descending interneuron cell body for the flexor reflex is located
Tract of Lissaur (Just posterior to the dorsal gray horn, in the white matter)
How does Crossed Extensor Reflex work if we are walking and stub our big toe
It will use one leg to provide a steady base to keep our balance and allow us to pull the stubbed toe backwards in response to the pain
The crossed extensor reflex requires one or both sides of the cord?
both sides of the spinal cord/body
If the toe we stubbed was on the right side. What will happen to each side?
L side:
-Contraction/activation of extensor muscles (quad)
-Relaxation of antagonistic/flexor muscle (hamstring)
R side:
-Contraction of flexor muscle (hamstring)
-Relaxation of extensor muscles (quad)
What kind of interneurons are involved in the crossed extensor reflex
1- Interneuron initiating contraction of of effected extremity
2- Ascending/Descending interneuron in the tract of Lissauer that involves multiple levels of the spinal cord.
3- Interneuron that crosses over to the other side of the cord to elicit and extensor response of the opposite limb to support our weight/balance.
Which reflex would utilize the most interneurons?
The crossed extensor reflex
Which reflex would utilize the least amount of interneurons?
Stretch reflex (no interneuron required, but can use them sometimes)
To check the effectiveness of a spinal block that we have placed on the lower extremities we could check.
To see if the reflexes are intact. If they are not; we likely have a well working spinal block.
n-ACh receptors are located at the _______ in the _____
NMJ. Skeletal muscle
What are the different nACh-Receptor variants?
- low conductance/immature/fetal
- high-conductance/mature/adult
- Alpha7 ACh-R
The version of n-ACh receptors that we have at the skeletal muscle NMJ in adults is
mature/adult/high conductance
Where are mature/adult n-ACh receptors found?
ONLY at the NMJ
Where does acetyl choline bind on the adult n-ACh receptors?
to alpha and alpha 1
The subunits of the mature (high conductance) n-ACh receptors include.
Alpha
Delta
Beta 1
Alpha
Epsilon
(in that order)
The subunits of the immature (low conductance)
Alpha
Alpha 1
Beta 1
Delta
Gamma
The subunits of the alpha 7 ACh receptor include
5 alpha 7 subunits
The binding subunits of both the mature and immature nACh-R are
Alpha and Alpha-1 subunits.
Characteristics of mature nACh receptors
when open; ions move very quickly through the channel; thus the name high conductance. They also open and close very quickly and only remain open for a very short time.
The low conductance nACh receptor would be found where?
In a very immature patient at the NMJ
Widespread on the skeletal muscle in a patient with a denervating injury (CVA)
Characteristics of the immature nACh receptors
While open, they have slower ion flow compared the the mature nACh receptors; thus the name low conductance. They also stay open for a longer period of time in response to ACh.
Where are the Alpha7 ACh-R found
Within the CNS (autonomic)
What response does Succinylcholine have on the nACh receptors?
Causes both channels to stay open for a longer period of time
What drug would we expect to cause issues when acting on a fetal nACh receptor
Succinylcholine; they will stay open for much longer than a adult nACh receptor causing massive depolarization and cause K to leak out causing a dangerous increase in hyperkalemia which could result in vfib
What happens when the brain sends a signal to contract a muscle but the brain doesn’t get confirmation of the contraction?
It will sense that something is wrong. The response will be to increase ach-r at the NMJ..but it will also turn on the fetal genes and express the fetal ones too all over the muscle not just at the NMJ.
If we give a healthy adult with normal adult nACh-R succinylcholine, what is the affect on the receptors?
It will depolarize the receptors at the NMJ for 4-5 min. But just that little part at the NMJ.
When would we worry about vfib when giving succinylcholine?
If someone has a neuromuscular disorder and had an increase in fetal nACh-r on their skeletal muscles, the succs would cause them to stay open for longer period of time and would cause depolarization which leads to a massive dump of potassium which could cause vfib
