A&P Test 3 Flashcards
The European book with NDMA Dr. Smidt was reading was right about everything except:
the nomenclature of NMDA
Why don’t arteries compress in the brain when ICP increases?
Because the arteries have a high Internal pressure.
What is the internal blood pressure of arteries in the skull?
100mmHg
Are the second ascending neurons after a nociceptor myelinated?
most of the time, but not always
Which neuron has a difference in myelination in the fast/slow pain pathways?
the first order nociceptor
Where does inhibition happen in the lateral inhibition pathway?
some happens in the dorsal horn, some happens out in the periphery
Where are metabotropic receptors found compared to the 3 inotropic ones we talked about in A&P
the brain
enkephalins are similar to what?
endorphins
enkephalin is the body’s endogenous
opiate system
what kind of receptor is an enkephalin receptor?
GPCR
Where are enkephalin receptors found on our drawing?
on the presynaptic and postsynaptic neurons
Enkephalin receptors are functionally linked to what type of channel?
Potassium
When opiates hitting enkephalin receptors, what should happen?
potassium channels should open, giving potassium more places to leave the cell. This makes the cell more negative and therefore makes the neuron harder to excite
When someone asks you how opiate receptors work, you would tell them that they
increase cell wall permeability to potassium and that inhibits the cells.
What receptor, besides enkephalin receptors, does the first and second order neuron have on them?
alpha 2 receptors
what do alpha 2 receptors do on the 1st and 2nd order neuron in the spinal cord?
open potassium channels
what type of receptor is an alpha 2 receptor?
GPCR
alpha 2 receptor activation at the synapse is going to do what?
shut down the first order nociceptor and the second order in transmission neuron
What are examples of alpha 2 receptor agonist? A&P
xylazine
clonidine
precedex
xylazine activates which receptors?
alpha 1 and 2
List the alpha 2 receptor agonist from most specific to least specific
precedex
clonidine
xylazine
Precedex, clonidine, and xylazine are all drugs that decrease pain by relaxing the CNS, but differ from opiates in that they
don’t produce the same sensations in the top parts of the brain like euphoria.
alpha 2 receptor agonists do what in the CNS?
slow it down
what CNS depressor do people abuse (A&P)
xylazine
what does the media call a horse tranquilizer?
xylazine
xylazine is basically a
tranquilizer
other things that can affect the synapse would include general effects produced by
volatile anesthetics
all the volatile anesthetic drugs that use a gas typically suppress activity throughout the
CNS
How do volatile anesthetics impact the synapse between the first and second order pain neurons?
by increasing potassium conductance
What is the mechanism of action for volatile anesthetic drugs?
opening potassium channels throughout the CNS
What is another thing that volatile anesthetics do besides open K channels that Dr. Smidt mentioned?
they can interact with inhibitory neurotransmitters
Potassium always ______ the cell despite what the internet says
leaves
Where is cox 2 typically expressed?
in our first and second order ascending pain neurons
what induces cox 2 activity?
activity at the synapse
the more pain we have the _____ Cox 2 is expressed
more
what does cox 2 produce?
prostaglandins
What do prostaglandins interact with in the 1st and 2nd order neuron synapse?
receptors located on both the first and second order ascending pain transmission neurons
What do prostaglandins do to the 1st and 2nd order neurons in the ascending pain transmission pathway?
increases their sensitivity to pain by increasing the likelihood of an action potential firing or the likelihood of having multiple action potentials in succession
What is an odd enzyme that can ramp up pain signals?
One of the forms of nitric oxide synthase, iNOS
What is iNOS?
an inducible form of nitric oxide synthase
Why is iNOS’s role in amping up pain odd?
typically you think of nitric oxide synthase as a good thing. It relaxes the blood vessels, keeps our blood pressure down, and gives us organ perfusion when we need it.
what electrolyte supplement can help with chronic pain?
magnesium
what is a downside to magnesium?
you’re your going to be in the bathroom for hours
Why don’t people take calcium supplements to help with chronic pain?
because although it is typically a suppressing agent, it doesn’t help that much with pain
Where is the 3rd order neuron located on the DIC pathway?
a portion of it is in the dorsal horn and a portion is outside of the horn
are fast pain neurons myelinated in the dorsal horn?
yes! there just isn’t enough to make the dorsal horn white
what are the spinal reflex pathways?
stretch
tendon
withdrawal
crossed extensor
which reflexes are pain reflexes?
withdrawal
crossed extensor
which reflexes are stretch or tension reflexes?
stretch
tendon
What are the components of the general spinal wiring schematic for reflexes?
Sensory portion (afferent)
a way to talk to the motor portion
motor portion (efferent)
Where are reflex sensors located?
in the periphery either pain or
tension receptors found in either the skeletal muscles or within the tendons of the skeletal muscles
What is found embedded in the muscle that can sense the amount of tension that’s found on the muscle?
a spring like tension sensor called a muscle spindle
What gives the CNS information about position changes in the skeletal muscles?
tension sensors called muscle spindles
What are the two ways that a sensory neuron can talk to a motor neuron in the spine during a reflex?
direct connection of axon to cell body in the ventral horn
via an interneuron(s) found between the dorsal and ventral horn
interneurons can either be
excitatory or inhibitory
how many intermediary neurons are there?
can be just 1 or can be multiple
for the sake of keeping the pictures clean, they have cut out many pathways around the reflex arc, but reflex arcs also send information to the
brain
in order to involve both sides of the body, we’d have to have some kind of pathway for one side of the cord to talk to the other. This cross over is achieved by
an interneuron
if we have multiple sides of the cord involved in a reflex, we have to use an
interneuron
what is the simplest reflex?
stretch reflex
what is the goal of the stretch reflex?
keep muscles a constant length. Applicable for weight bearing muscles in the body, like the legs
which reflex helps us keep our posture when someone pushes on our forehead?
the stretch
which muscles feel the tension when someone pushes you back by your forehead? What is the muscle doing?
quadricept muscle
contracting and shortening back to their original length so that your body doesn’t tip over
what is an example of an activity that causes reflex activation of the muscle group quadricep that is being stretched?
being pushed back on the forehead
The sensory neuron in the stretch reflex arc don’t need _____ to talk to the motor neurons, it typically ____________________ instead.
an interneuron
it typically goes all the way through the cord and can sit on the motor neurons in the anterior horn
In the stretch reflex arcs that do have interneurons, the inhibitory interneurons job is to
allow for the reflex relaxation of the antagonistic muscle set.
What is the antagonistic muscle to the quadricep in the upper leg?
hamstring
What does the relaxation of the hamstring cause?
extension of the leg
Which reflex arc is useful for standing up straight?
the stretch reflex
Does the stretch reflex cross to the other side of the cord?
no
What do muscle spindles do?
sense how much stretch tension is being put on the muscle and sends that information to the cord which then activates the stretch arc and makes the muscle relax and contract as appropriate
How do you clinically test if the sensors are a complete circuit with the reflex stretch arc in the leg?
You set the patient on a table or stool with their leg suspended and relaxed. Tap on the ligament that is right underneath the patella. The leg should lengthen
Why does the leg lengthen when you do the patella reflex?
striking the ligament pulls the patella down which is attached to the quadricep tendon thereby lengthening/contracting the quadricep muscle
is the patellar reflex activating the muscle spindles?
no, just lengthening the quad muscle
the tendon reflex is ____ in nature
protective
Where are stretch sensors located in the tendon reflex?
the collagen and fibrin tissues that make up our tendons
What do stretch sensors in the tendons do?
detect large amounts of tension in the tendon
If we have a massive load on the skeletal muscles, what happens?
the tendon stretch sensors detect it and we have a reflex relaxation of the muscles that are attached to the tendon
How is the tendon reflex protective?
it prevents us from ripping our skeletal muscles out of their insertion points in bone
A guy falls out of a tree and lands on his feet. He probably breaks a lot of bones, but what doesn’t break and why?
his muscles, because of the tendon reflex sensing the massive amounts of pressure and relaxing the muscles
In what situation would your tendon reflex not kick in when it should? how does this work?
When you’re lifting a 5,0000lb car off a kid.
Smidt doesn’t know
which muscles are involved in the tendon reflex?
both the muscle having a lot of pressure put on it and the antagonistic muscle
How many interneurons are involved in the tendon reflex?
two
What do the interneurons do in the tendon reflex?
one is excitatory. it causes reflex activation of the antagonistic muscle set
one is inhibitory. it is in charge of inhibiting activity in the motor neuron that attaches to the muscle with a lot of pressure on it
if we had an obscene amount of tension on the quadricep muscle, what would the muscles do in response?
the quad would relax and the hamstring would contract
what is the purpose of the reflex activation of the antagonistic muscle set?
to pull the limb away form the source of pressure
does the tendon reflex involve one or both sides of the cord?
one
what is another name for the withdrawal reflex?
flexor reflex
what does the sensory portion of the flexor reflex involve?
pain signals
What reflex arc helps us pull our body away from something that is painful when we are still?
the flexor/withdrawal arc
which muscles are typically activated in the flexor/withdrawal arc and what are they doing?
the flexor muscles contract
and the antagonistic muscles relax
what are the flexor muscles in the leg?
the hamstring
do neurons activate both sides of the cord in the flexor/withdrawal arc?
no, just the side that has the pain
How is the flexor reflex more involved than the stretch or tendon reflex?
It involves a couple of spinal vertebra levels up and a couple of spinal vertebra levels down, maybe 2 up and 2 down.
what does the activation of multiple levels of the cord in the flexor/withdrawal reflex do?
it allows us to recruit or use multiple muscles in those muscle groups
The larger section of the cord that is involved in the reflex, the more muscles that can be recruited and the better reflex we’ll have.
How does information travel up and down the cord to facilitate multiple levels of the spinal cord being used in the flexor/withdrawal reflex?
through the use of ascending and descending interneurons
where are ascending and descending interneurons located?
in an area of the cord that is just posterior to the dorsal border of the dorsal gray horn.
an area between the posterior border of the dorsal grey horn and the edge of the cord
called the tract of Lissauer lissaur in class
what part of the cord is the cell body of the ascending and descending neuron found?
in the grey matter
What is the most complicated of the reflexes?
crossed extensor reflex
When is the crossed extensor reflex useful?
when we are moving and come across pain
which reflex involves both sides of the cord?
crossed extensor reflex
what does the crossed extensor reflex do if you are walking and stub your right big toe?
it will activate the left leg to straighten out and allow us a base to balance on while we pull our right leg back from the source of pain
What type of interneurons do we have in the crossed extensor reflex?
ascending interneurons
descending interneurons
interneurons in the horizonal plane
interneurons that travel from one side of the cord to the other
If we stub our right big toe, what are the muscles in the right and left leg doing?
right: quadricep relaxes and hamstrings contracts
left: hamstring relaxes quadricep contracts
what are the extensor muscles in the leg?
quadricep
what can inhibit our spinal reflexes?
strong drug causes reduced activity in the CNS
How can you tell if you have a deep enough block?
check for reflexes. It’s not a guarantee that pain transmission will be avoided but it’s a good rule of thumb.
what version of nAChr do we have on an adult in good health in their 30’s?
the adult/mature/high conductance nAChr
where are mature nAChr found in a healthy 30yo adult?
only at the NMJ
how many domains does an adult nAChr have?
5
what are the different types of domains on the adult nAChr?
binding domains
* alpha
* alpha 1
epsilon subunit
beta1
delta
where is the epsilon subunit located on the adult nAChr?
between the alpha and alpha 1 subunits
What are the alpha and alpha 1 binding domains on the adult nAChr?
The place where ACh binds
What is the order of the subunits on the adult nAChr?
alpha 1
delta
beta1
alpha
epsilon
why are adult nAChr thought of as high conductance channels?
because when it’s open, ions move through the channel at a high speed, and then closes quickly
a healthy adult 30 year old should only have which form of nAChr
adult/mature
what is the difference in the immature/feta/low conductance nAChr?
it switches the epsilon subunit for a gamma subunit
how are the immature/feta/low conductance nAChr different from adult/mature/high conductance nAChr?
placement: fetal nAChr are found outside of the nmj
function: while fetal nAChr are open, they stay open longer but ions move through slower
what is the third type of ACh receptors?
alpha7
what kind of subunits are on the alpha7 AChr?
all of the subunits are ACh binding domains
where are alpha7 nAChr found?
in the CNS
What effect does succs have on a immature/feta/low conductance nAChr?
the channel is open for an even longer period of time than normal. this can lead to increased levels of K+
what happens when the brain sends a message to the muscle to contract, but the muscle can’t for whatever reason?
the brain recognizes this and increases the number of nAChr in response. these nAChr are usually the immature/feta/low conductance nAChr.
this might help in myasthenia gravis, but won’t help all problems
day to day, immature/feta/low conductance nAChr found outside of the NMJ usually isn’t a problem, why?
ACh is broken down quickly so ACh never floats around and reaches these receptors
If you have overexpression of immature/feta/low conductance nAChr an you give them succs, what happens?
succs binds to them and holds them open for a longer period of time, increasing the amount of tissue dumping potassium. With this much tissue hemorrhaging potassium, you can send someone into Vfib
In what patient populations should you avoid succs?
patient’s who have had a stroke that wipes out part or whole of the motor cortex
how long does it take to upregulate nAChr after a stroke?
within a few days of injury
