Lecture 19 Flashcards

1
Q

What can regulate reflexes?

A
  • Descending Input (from brainstem)
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2
Q

Do Motor Neurons have multiple inputs?

A

Yes
- IPSPs
- EPESs

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3
Q

What do the inputs on MN do? what might they not do?

A

Do
- Change the membrane potential
Not Do
- make it reach the threshold

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4
Q

Do reflexes themselves reach the threshold?

A
  • No
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5
Q

Where can descending neurons make synaptic connections?

A
  • With neurons in the reflex arc
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6
Q

What does a descending neuron’s synapse with neurons in the reflex arc do?

A
  • 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
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7
Q

What does a descending neuron’s synapse with neurons in the reflex arc do?

A
  • 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
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8
Q

Can Tonic activity bring the membrane to the threshold?

A
  • NO
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9
Q

How can you generate an AP in the MN with just Tonic and Reflex (peripheral input) activity?

A
  • Combined them
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10
Q

What is the timing of a Action Potential from Tonic and Reflex activity determined by?

A
  • The Reflex input
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11
Q

What happens when you change tonic input in response to reflex activity?

A
  • Responses in the MNP driven by reflex activity
  • Can also be inhibitory
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12
Q

What does tonic input do?

A
  • Sets the stage for potential movements to happen
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13
Q

What kind of feedback travels via the reflex pathway? what does it do?

A

Sensory Feedback
- Influences many types of movement

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14
Q

What travels via the longer loop pathways?

A
  • Sensory Feedback
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15
Q

What is the crossed-extensor reflex? what is it an example of?

A

Do
- Multiple segments coordinated to all do the same thing
Example
- Sensory Feedback traveling via a longer loop pathway

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16
Q

How would you bias reciprocal inhibition from one muscle but not the other?

A
  • Cortex facilitates MNP with an EPSP
  • EPSP facilitates the 1a inhibitory interneuron
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17
Q

What happens when you want to flex your elbow?

A
  • Cortical Drive biases the probability that biceps will contract and triceps wont
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18
Q

What happens when you make any arm movement?

A
  • Cortical Command is turning the agonist muscle on
  • Cortical Command is controlling reciprocal inhibition to the antagonist muscle so it wont contract
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19
Q

Can pathways connect to both agonist and antagonist MNPs?

A
  • YES
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20
Q

What happens during an isometric contraction?

A
  • You have descending input that comes down and inhibits both MNPs
  • No reciprocal inhibition
  • You can contract
21
Q

How does descending input help control movement?

A
  • Controls the level of inhibition
  • creates a balance between excitation and inhibition
22
Q

Where are Central Pattern Generators?

A
  • In the spinal cord
23
Q

What do the Central Pattern Generators couple up with?

A
  • Muscle to create motion
24
Q

What does the segmental feedback regulate in mammalian walking? what else contributes to this?

A

Regulate
- Motor pattern
- Adaptation to immediate environment
Helps
- Somatosensory Feedback: Cutaneous, Joint, GTO, Spindles

25
Q

How do the Tonic Signals help mammalian walking?

A

Signals from brainstem
- overlaid on top of CPG

26
Q

How does Supraspinal control from motor cortex and the brain stem help in mammalian walking?

A
  • Balance and Stability
  • Task Selection
  • Navigation
  • Obstacle Avoidance
27
Q

How do mammals avoid obstacles when walking?

A

Supraspinal Control
- Changing locomotor pattern

28
Q

How does navigation work in mammalian walking?

A

Supraspinal Control
- Visual Locomotor Control

29
Q

How does task selection work in mammalian walking?

A

Supraspinal Control
- Accommodating obstacles
- Change in footing
- Pace change

30
Q

What is involved in the neuronal organization of mammalian walking?

A
  • Central Pattern Generator: create motion
  • Segmental/somatosensory feedback: adaptation to the immediate environment
  • Tonic Signals: Overlaid on top of CPG
  • Supraspinal Control: environmental navigation and balance/stability
31
Q

What is faster? Pre-programed responses (M2 and M3), M1, or Volitional Activity?

A

Fastest: M1 Response
Fast: Pre-programmed
Slowest: Volitional Activity (response to stimuli)

32
Q

How fast do Pre-programmed responses happen?

A
  • 400ms
33
Q

Why are M2 and M3 responses called pre-programmed responses?

A
  • They can be tuned in advance of the disturbance
  • Either up or down
34
Q

What drives M2 and M3 responses?

A
  • Afferent system
35
Q

How do M2 and M3 Responses occur?

A
  • Get the MNP started when need to make corrective responses
  • Think about whats going to happen
36
Q

How do we know there is a Central Pattern Generator in the Spinal Cord?

A

Severed Spinal Cord
- Hind legs continue to walk with the presence of afferent feedback (without descending input from the brain)

37
Q

What happens when you deafferent the hind legs?

A

Oscillation
- Uncoordinated

38
Q

What does the Spinal Cord contain in regards to walking?

A

Central Pattern Generator
- Network of interneurons that generate oscillation needed for walking

39
Q

How does Scaffolding work in the CPG? what makes the CPG work efficiently?

A

Scaffolding
- Adds to the model of locomotion
Efficiently
- Afferent Feedback

40
Q

What does afferent feedback do?

A
  • Initiates walking
  • Phase Transitions
  • Regulate Different types of muscle activity
  • Correct for unexpected distrubances
41
Q

How does afferent feedback initiate walking?

A
  • Jumpstarts the CPG
42
Q

How does afferent feedback help with phase transitionS?

A
  • Helps decide when its safe to put one leg from stance to swing
43
Q

What is an example of when afferent feedback can help regulate different types of muscle activity?

A

Tilt treadmill to a different angle
- Can still walk

44
Q

How does afferent feedback help correct for unexpected disturbances?

A

If you Slip/Trip/Stumble
- Balance corrections
- Layers on top of CPG

45
Q

How does the stimulation of group 1 afferents inhibit flexion in a decerebrate walking cat?

A
  • Nervous system is told the leg was carrying weight/loaded
  • It won’t flex
46
Q

What happens when you stimulate a group of 1 afferents in a decerebrate walking cat?

A

Stop transition from stance to swing
- inhibits flexion
- stops locomotion

47
Q

Describe the foot in the hole experiment

A
  • Just as cat hit step, the step drops
  • ## the cat shifts amount of force on plate until it stops moving
48
Q

What happens to the EMG levels during the foot in the hole experiment?

A
  • Anticipatory burst is the same
  • EMG levels drop when plate drops instantaneously
  • Big burst in EMG when plate stops, corresponds with loading
49
Q

What can explain the reaction during the foot-in-the-hole experiment?

A
  • Afferent feedback layering on top of the CPG