Lecture 19 Flashcards
What can regulate reflexes?
- Descending Input (from brainstem)
Do Motor Neurons have multiple inputs?
Yes
- IPSPs
- EPESs
What do the inputs on MN do? what might they not do?
Do
- Change the membrane potential
Not Do
- make it reach the threshold
Do reflexes themselves reach the threshold?
- No
Where can descending neurons make synaptic connections?
- With neurons in the reflex arc
What does a descending neuron’s synapse with neurons in the reflex arc do?
- Changes the background level of activity
- Shift membrane of the MNP to make it closer to threshold
- Tonic because neurons might be firing like crazy
What does a descending neuron’s synapse with neurons in the reflex arc do?
- Changes the background level of activity
- Shift the membrane of the MNP to make it closer to the threshold
- Tonic because neurons might be firing like crazy
Can Tonic activity bring the membrane to the threshold?
- NO
How can you generate an AP in the MN with just Tonic and Reflex (peripheral input) activity?
- Combined them
What is the timing of a Action Potential from Tonic and Reflex activity determined by?
- The Reflex input
What happens when you change tonic input in response to reflex activity?
- Responses in the MNP driven by reflex activity
- Can also be inhibitory
What does tonic input do?
- Sets the stage for potential movements to happen
What kind of feedback travels via the reflex pathway? what does it do?
Sensory Feedback
- Influences many types of movement
What travels via the longer loop pathways?
- Sensory Feedback
What is the crossed-extensor reflex? what is it an example of?
Do
- Multiple segments coordinated to all do the same thing
Example
- Sensory Feedback traveling via a longer loop pathway
How would you bias reciprocal inhibition from one muscle but not the other?
- Cortex facilitates MNP with an EPSP
- EPSP facilitates the 1a inhibitory interneuron
What happens when you want to flex your elbow?
- Cortical Drive biases the probability that biceps will contract and triceps wont
What happens when you make any arm movement?
- Cortical Command is turning the agonist muscle on
- Cortical Command is controlling reciprocal inhibition to the antagonist muscle so it wont contract
Can pathways connect to both agonist and antagonist MNPs?
- YES
What happens during an isometric contraction?
- You have descending input that comes down and inhibits both MNPs
- No reciprocal inhibition
- You can contract
How does descending input help control movement?
- Controls the level of inhibition
- creates a balance between excitation and inhibition
Where are Central Pattern Generators?
- In the spinal cord
What do the Central Pattern Generators couple up with?
- Muscle to create motion
What does the segmental feedback regulate in mammalian walking? what else contributes to this?
Regulate
- Motor pattern
- Adaptation to immediate environment
Helps
- Somatosensory Feedback: Cutaneous, Joint, GTO, Spindles
