Lecture 14 - neuro reflex Flashcards
Exam 3
Which reflex(s) cross the cord?
crossed-extensor
Which reflex purpose is to keep muscles at a constant length, weight-bearing support?
Stetch/ muscle spindle
Which reflex serves to cease muscle contraction under heavy load to prevent muscle from tearing off bone?
Tendon
which reflex serves to withdraw limbs from painful stimuli to prevent injury
Withdrawal/Flexor
Which reflexes involve multiple levels of the spinal cord above and below?
Pain reflexes:
Withdrawal/Flexor and Crossed-extensor
Where are the ascending and descending interneurons located?
Located in the white matter of dorsal border of dorsal horn = “Tract of Lissauer”
Which variation of nACh-Receptors are located only at the NMJ?
mature/adult
Which variation of nACh-Receptors can be located outside of the NMJ?
Immature/”fetal nACH-R”
Which variation of nACh-Receptors are comprised of 5 alpha domains? where is it located in the body?
alpha 7, CNS
Which type of nACh-R is comprised of
2 alpha binding domains
1 epsilon
1 beta1
1 delta
mature/adult
Which type of nACh-R is comprised of
2 alpha binding domains
1 gamma
1 beta1
1 delta
immature/”fetal”
Which nACh-R has high conductance?
mature/adult
Which nACh-R has low conductance?
immature/fetal
What does it mean if a channel has “high conductance”?
when open, the speed that ions move through the channel is high. They close faster as well.
low conductance= lower speed
Which nACh-R is worse for succinylcholine to bind to, resulting in much higher levels of K+ leakage?
immature/fetal
What are the 4 reflex pathways?
Stretch
Tendon
Withdrawal
Crossed Extensor
An _______ is a bridge between a sensory neuron and a motor neuron
Interneuron - can also allow cross-over
Are interneurons excitatory or inhibitory?
Can be either
Do interneurons travel vertically or horizontally?
Can be either
Stretch reflex usually ______ have interneurons and ______ cross the cord
doesn’t and doesn’t
What is the purpose of interneurons in the stretch reflex if they are present?
Inhibitory interneurons that allow reflex relaxation of the antagonistic muscle set
Which reflex is responsible for maintaining posture?
Stretch
What are the springs called that sense how much tension is in the muscle for the stretch reflex?
Muscle spindle = stretch receptor
Differentiate between a direct reflex arc and a secondary reflex arc
Direct reflex arc:
- Stretch-Contract
- Contract effector (quadriceps, eg)
Secondary reflex arc:
- Inhibitory interneuron
- Inhibit antagonist muscles (hamstring, eg)
What are the sensors that detect tension of tendons on muscles for the tendon reflex?
golgi tendon sensors
What are the two reflexes of the tendon reflex?
Reflex #1: Cease (inhibit) contraction under heavy load to prevent tendon tears
Reflex #2: Contract (excite) antagonistic muscles to speed retraction from load source
Flexor reflex alternate name
Withdrawal reflex
Which pain reflex is used when static vs moving?
Flexor - static
Crossed extensor - moving
What are the two reflexes of the crossed extensor reflex?
Reflex #1: Several levels of left “hamstring” flexor motor output from spinal cord. Withdraws left leg from painful stimuli.
Reflex #2: Several levels of right “quad” extensor motor output from spinal cord. Assures that we have good footing to use as a push-off point for #1 above.
What are the simplest vs most complicated reflexes?
Simplest - stretch
Most complicated - crossed extensor
Pain receptors synapse on _______ in grey matter.
2nd-order interneurons
How can you determine depth of a block with reflexes?
Reflex not present - block deeper
If the nervous system doesn’t get information back from muscle that contraction occurred, the body’s response is to?
Put more ACh-R at the NMJ
- Also end up on places other than NMJ (entire muscle)
- Fetal nACh-R instead of mature
ACh-R found in the NMJ are called _____
junctional
ACh-R found in the borders of the NMJ are called _____
peri-junctional
ACh-R found away from the NMJ are called _____
post-junctional
_________ is a strong enough voltage to allow depolarization to generate an AP in the underlying neurons
Supramaximal stimulus - voltage that is strong enough stimulus to recruit all motor neurons/skeletal muscles
TOF stimulation Hz/seconds
2 Hz over 2 seconds = 4 twitches
Repetitive, high frequency stimulation for a short period of time
Tetanic contraction
_________ - impulses after tetanic contraction
Post-tetanic count (PTC)
What kind of nerve stimulation shows the health of a synapse?
Post-tetanic count (PTC)
A _______ is a series of tetanic contractions
DBS: Double-burst stimulation
The ulnar nerve innervates the ______ muscle
Adductor Pollicis
What happens with contraction of the Adductor Pollicis muscle?
thumb comes forward and/or pinky twitches
What are the alternatives to neuromuscular monitoring in muscles other than the Adductor Pollicis?
- Ophthalmic branch of Facial nerve
- Peroneal nerve
- Posterior tibial nerve
A _______ is a graphical depiction of underlying muscle activity to determine response
EMG
What are the 3 ways to of neuromuscular monitoring?
Velocity meters
EMG
Visual assessment
How quickly does sux begin to wear off?
3 min
Differentiate between TOF stimulation of a NDMR vs Sux
NDMR: first contraction is the strongest (A), last contraction is the weakest (B)
Sux: equal strength of contractions
What is the TOF ratio?
B/A
- Weakest contraction/strongest contraction
- only works for NDMR
- need all 4 stimuli to measure
The Sux TOF ratio is always ___
1
As the NDMR wears off, the TOF ratio does what?
Gets closer to 1
Why are the contractions of the NDMR unequal, while the Sux contractions are equal?
muscle relaxants act on the motor neuron and the skeletal muscle
- autoreceptors reduce amount of ACh being released from the motor neuron due to ion current (VP-1 to VP-2)
- NDMR contractions differ because Sux primarily works on the skeletal muscle, not the motor neuron
What is the makeup of autoreceptors?
3 alpha
2 beta
What determines transition of VP-1 vesicles to VP-2?
- autoreceptors on the motor neuron ion current
The more important a muscle is, the more ______ it is to polarize
difficult - more robust NMJ (more receptors)
What spinal level does the phrenic nerve connect to the diaphragm?
C3-C5
The _______ is a skeletal muscle that separates the abdominal cavity from the thoracic cavity
diaphragm
What nerve connects C3-C5 to the diaphragm?
The phrenic nerve
4th Twitch Disappears: ____% nACh-R’s blocked
~75-80%
3rd Twitch Disappears: ____% nACh-R’s blocked
85
2nd Twitch Disappears: ____% nACh-R’s blocked
~85-90%
All Twitches Disappear when ____% nACh-R’s blocked
~90-95
How high can a spinal nerve injury be and still be able to ventilate?
C4
Would the diaphragm or the adductor pollicis muscle recover first from a paralytic?
Diaphragm
A patient who is able to lift their head has ____% nACh-R’s blocked
70
A patient can probably breath on their own when there are ____ twitches present on the TOF
all 4
What is the normal setting for TOF?
50-80 mA - curent
What are the 3 ways K+ is lost when Sux is bound to ACh-R?
- leak channels
- V-G K+ channel
- K+ loss through ACh-R
Which muscle is controlled by multiple motor neurons?
occular muscle in eye socket
If you give sux to the skeletal muscle in the eye socket, what would you expect to happen?
Since multiple motor neurons control the muscle, you would expect increased IOP (increased Ca++ entry), putting stress on optic nerve - potential blindness
What are the 2 most important inhibitory NTs in the spinal cord?
GABA and glycine
What are the 3 NT that increase CNS activity?
Histamine, glutamate, NE
How does dopamine effect the CNS? Which disease is caused by decreased dopamine production?
Inhibits motor activity; Parkinson’s (overactive motor system)
How does acid base balance effect CNS activity?
Acidosis → increased free Ca++ → reduced CNS activity
Alkalosis → decreased free Ca++ → increased CNS activity
