Lecture 15: 10/2 - Reflexes pt 1 Flashcards
Test 2
What are the 4 reflex pathways?
Stretch reflex
Tendon reflex
Withdrawal reflex
Crossed extensor reflex
What 2 reflex pathways are responses to pain?
Withdrawal reflex
Crossed extensor reflex
All reflexes have a ______ and ______ component
Sensory
Skeletal
What is the Alpha motor neuron?
Neuron thats stimulated that produces an AP down its axon to the skeletal muscle to produce a reflex
What’s an interneuron?
If the stimulation is not strong enough, body uses interneurons to communicate with the Alpha neuron.
Can be excitatory or inhibitory
What reflex can bypass an interneuron?
Stretch reflex
Where are pain/pressure sensors located?
Peripheries
Can tension cause a reflex? Why?
Yes
Pressure/pain sensors found in tendons therefore when stretched too wide –> reflex
T/F: Reflexes stay within the cord and are not communicated to the brain
F
The brain is communicated that the reflex happened but doesnt make the decision for it to happen.
Where does crosstalk happen in reflexes?
Interneuron
Describe the Stretch reflex
Someone pushes you on the forehead
- Sensory information fed in from the muscle spindle through dorsal horn
- Alpha motor neuron stimulated
- Effector muscle (quadricepts) contracts
If there is an interneuron used, it is inhibitory –> inhibits flexor muscle (hamstring) causing relaxation
What is the goal of the Stretch reflex
Keep muscles a constant length
Keep posture constant on weight bearing muscles
What does the interneuron do in the Stretch reflex?
inhibits flexor muscle
What is the stretch sensor in the Stretch Reflex?
Muscle spindle
Describe the muscle spindle
A spring in muscle
Senses how much tension is in the hamstrings
How do you elicit the Stretch reflex?
- Tap on ligament right under patella w/ mallet
- Patella will drop down
- Quadricept muscle will length
- This causes the foot to twitch forward
What is the most simple reflex?
Stretch reflex
What is the goal of the Tendon reflex?
Protective in nature
Prevents muscles from being torn from insertion points in bone when lifting heavy loads
What is the sensor in the Tendon reflex? What does it do?
Golgi tendon (close to knee)
Detect heavy loads and lots of tension on skeletal muscles
How many sides of the cord does Stretch reflex involve?
1
How many sides of the cord does tendon reflex involve?
1
How many interneurons does tendon reflex use?
2
Describe the Tendon reflex
I try to pick up a 1000 pound car
1.Sensory information fed in from golgi tendon through dorsal horn.
2. TWO interneurons are stimulated and stimulate alpha motor neurons
3. The effector muscle is inhibited and relaxes & the flexor muscle is stimulated and produces a contraction
What is the goal of the Flexor reflex?
Withdraw limbs from painful stimuli to prevent injury
What is another name for the flexor reflex?
Withdrawal reflex
How many sides of the cord does the flexor reflex involve?
1
Describe the Flexor reflex
You stub your toe
- Fast pain is fed in through the dorsal horn on Laminae 1
- Excitatory interneurons are stimulated and contract the flexor muscle (effector)
Ascending & descending interneurons are activated for faster reaction
Ascending and descending interneurons are excitatory interneurons and are activated when _____ is involved
Pain
Where are ascending and descending interneurons located?
Tract of Lissaur
Small space between the dorsal grey horn and spinal border
What do the ascending and descending interneurons do?
Crosstalk with different levels of the spine
What is the only reflex that involves both sides of the cord?
Crossed Extensor Reflex
What pathway uses the most interneurons and is the most complicated?
Crossed Extensor Reflex
How many sides of the cord does Crossed Extensor reflex pathway use?
2
What is the goal of the crossed extensor reflex?
Stabilize body on one leg while pulling away from pain on the other
Describe the Crossed Extensor reflex
Stubs toe while WALKING
- PAIN fed in to laminae I
- excitatory, inhibitory, ascending, and descending interneurons are activated
- On effected leg: flexor muscle contracts & quads relax
- on uneffected leg: this leg is the stabilizer: flexor muscle relaxes and effector muscle (quads) contracts
Cross Extensor reflex is useful when ________
moving
What is the nAch-R in a healthy adult called? (All names)
High conductance channel
Mature nAch-R
Adult nAch-R
Where are Adult nAch-R located?
NMJ only
Describe the binding sites on an Adult nAch-R
2 Alpha binding sites: Alpha & Alpha 1
Epsilon (between the Alphas)
Beta 1
Delta
Describe an Adult nAch-R
Opens for a short period of time
high speed of ion current when open
What is the nAch-R in a newborn called? (All the names)
Low conductance channel
Immature nAch-R
Fetal nAch-R
Where is fetal nAch-R located?
NMJ and can be expressed on other parts of the skeletal muscle
Describe the binding sites on an Fetal nAch-R
How is it different from an Adult?
2 Alpha binding sites: Alpha & Alpha 1
Gamma (between the Alphas)
Beta 1
Delta
Theres a gamma between the alphas instead of epsilon
Describe a Fetal nAch-R
Opens for a longer period of time
slower speed of ion current when open
What happens when you give succs with an increased amount of fetal nAch-R?
Increased K+ permeability –> vfib
Ach fall of the ______ nAch-R the fastest and stays binded to the _______ nAch-R for longer
Adult
Fetal
Where are neuronal nAch-R found?
CNS
