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PHGY 209 > CNS/Motor I > Flashcards

CNS/Motor I Flashcards

1
Q

What are the two types of motor behaviour?

A

Voluntary and reflexive.

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2
Q

What is the difference between extension and flexion?

A

Extension is when you stretch the limb, while flexion is when you shorten the limb.

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3
Q

What is the difference between the extensor and the flexor muscle?

A

The flexor is the muscle that allows for muscle contraction, such as the forearm. The extensor is the muscle that allows for muscle extension.

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4
Q

During extension, how do the flexor and extensor muscles behave?

A

The flexor muscles relax and the extensor muscles contract.

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5
Q

During extension, what muscles are the antagonist and the agonist?

A

The flexor muscle is the antagonist and the extensor muscle is the agonist.

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6
Q

During extension, does the angle around the joint increase or decrease?

A

It increases.

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7
Q

During flexion, how do the extensor and flexor muscles behave?

A

The flexor muscle contracts and the extensor muscle relaxes.

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8
Q

During flexion, which muscles are the agonist and antagonist?

A

The flexor muscle is the agonist and the extensor muscle is the antagonist.

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9
Q

During flexion, does the angle around the joint increase or decrease?

A

It decreases.

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10
Q

Are motor neurons excitatory or inhibitory?

A

They are only excitatory

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11
Q

The neurotransmitter released by motor neurons is […]

A

Acetylcholine (ACh)

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12
Q

What are the two types of motor neurons? What part of the muscle do they innervate?

A

Alpha: innervate skeletal (extrafusal) muscle
Gamma: innervate muscle spindle (intrafusal)

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13
Q

Where are the cell bodies of motor neurons found?

A

Either in the ventral horn of the spinal cord or the brain stem (cranial nerves)

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14
Q

Describe the relationship between the spinal afferent pathways and the motor efferent pathways.

A

Branches from the sensory afferents extend into the grey matter, where they synapse with interneurons. The interneuron also synapses with the motor neuron in the ventral horn. So, motor neurons get activated by sensory information.

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15
Q

Describe the efferent motor pathway beginning at its link with the sensory system.

A

After the brain receives ascending sensory information, motor commands descend to the interneuron, which synapses with the motor neuron in the ventral horn. The signal then travels into the ventral roots and out via the motor efferent.

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16
Q

Name the 4 types of input that interneurons respond to/are involved in.

A

They respond to pain, proprioceptive feedback, voluntary movements, and also coordinate complex movements.

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17
Q

Name 2 types of monitoring done by the spinal interneurons.

A

Length monitoring and tension monitoring.

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18
Q

What are the 3 types of spinal reflexes?

A

Withdrawal reflex, stretch reflex, and inverse stretch reflex.

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19
Q

What is the function of the withdrawal reflex?

A

It protects limbs from injury

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20
Q

What is the function of the stretch reflex?

A

It controls muscle length.

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21
Q

What is the function of the inverse stretch reflex?

A

It controls muscle tension.

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22
Q

Do reflexes respond quickly or slowly? Why?

A

They respond very quickly because they remain in the spinal cord and do not necessitate travel to the brain.

23
Q

Describe the pathway of the flexion withdrawal reflex on the ipsilateral side.

A

Nociceptor detects pain and sends signal through dorsal root into dorsal horn. Synapse on 2 interneurons: one excitatory and one inhibitory. The excitatory will excite the ipsilateral flexor muscle. The inhibitory will inhibit the ipsilateral extensor.

24
Q

Describe the pathway of the flexion withdrawal reflex on the contralateral side. What is this reflex called?

A

This is the cross extensor reflex. The motor neurons innervating the contralateral extensor are excited, while the motor neurons innervating the contralateral flexor are inhibited.

25
Q

What is irradiation?

A

The notion that the magnitude of the withdrawal reflex depends on the magnitude of the pain stimulus.

26
Q

What are the two major parts of the withdrawal reflex? Describe what happens in each one

A

Response development: the rapid withdrawal of the limb
Afterdischarge: the period after withdrawal where it is hard to reextend the limb.

27
Q

What determines the length of the afterdischarge period?

A

Its length is proportional to the amount of pain stimulus received.

28
Q

What is the cause of irradiation?

A

As the nociceptive input becomes more painful, afferents recruit more interneurons.

29
Q

What is the cause of afterdischarge?

A

Feedback loops in the spinal cord.

30
Q

During the withdrawal reflex, on the ipsilateral side of the input, the flexor muscles […] and the extensor muscles […]

A

Contract, relax

31
Q

During the withdrawal reflex, on the contralateral side of the input, the flexor muscles […] and the extension muscles […]. This is called […]

A

Relax, contract, cross extensor reflex

32
Q

Is the withdrawal reflex monosynaptic or polysynaptic?

A

It is polysynaptic, as there are interneurons between sensory input and motor output.

33
Q

The knee jerk is an example of which reflex?

A

The monosynaptic stretch reflex.

34
Q

Name the 5 steps of the monosynaptic stretch reflex.

A
  1. Stretch extensor muscle
  2. Activation of stretch receptor
  3. Signal travels into spinal cord and excites motor neurons innervating the ipsilateral extensor (without synapsing).
  4. Also from the spinal cord, inhibition of motor neurons innervating the ipsilateral flexor.
35
Q

What part of the monosynaptic stretch reflex produces a kick in the case of the knee jerk reflex?

A

The inhibition of motor neurons innervating the ipsilateral flexor, as this will cause the muscle to release.

36
Q

Is the stretch reflex monosynaptic or polysynaptic? Explain.

A

It is both. The portion that innervates the extensor, which was tapped, is monosynaptic, as there is no interneuron between the efferent and afferent neurons. The portion that innervates the flexor is polysynaptic, as there is an interneuron between the efferent and afferent.

37
Q

What are tendons in a muscle?

A

They connect muscle to bone.

38
Q

What is the Golgi tendon organ and where is it found?

A

It is located in the tendon and measures the force of muscles.

39
Q

The Golgi tendon organ is [in parallel/in series] with muscle fibers.

A

In series.

40
Q

What are the two types of muscle fibers and where are they located?

A

Extrafusal: located on the outside of the muscle
Intrafusal: on the inside of the muscle.

41
Q

Extrafusal muscle fibers are activated by […] and intrafusal muscle fibers are activated by […]

A

Alpha motor neurons, gamma motor neurons

42
Q

What are muscle spindles and where are they located?

A

They are part of intrafusal muscle fibers wrapped in a capsule and have a stretch receptor.

43
Q

Muscle spindles are [in parallel/in series] with muscle fibers.

A

In parallel

44
Q

What are stretch receptors and where are they located?

A

They are a part of the muscle spindle that is activated when the muscle changes length. They transmit information about the length of the muscle.

45
Q

What types of afferents surround muscle spindles?

A

Ia (primary) and II (secondary)

46
Q

Describe how Ia and II afferents respond to a linear stretch.

A

When the muscle is in the process of stretching, Ia fibers will fire action potentials more rapidly and there will be no change in the II fibers. Once the muscle has completed the stretch and is statically longer, the II fibers will fire action potentials more rapidly and the Ia will return to normal.

47
Q

Describe how Ia and II afferents respond to a tap/stretch reflex.

A

When the muscle briefly stretches, the Ia afferents fire off action potentials more quickly before returning to normal. The II afferents will stay the same throughout, as the muscle is not permanently changing length.

48
Q

Ia afferents signal […]

A

Dynamic changes in muscle length (and some static length)

49
Q

II afferents signal […]

A

Static muscle length.

50
Q

During extension, muscles are [lengthened/shortened], and there is an [increase/decrease] in […] afferent activity.

A

Lengthened, increase, spindle

51
Q

During extension, are alpha or gamma neurons active (or both)? Why?

A

Only alpha motor neurons, as the muscle spindle still retains its sensitivity.

52
Q

During flexion, muscles are [lengthened/shortened], and there is an [increase/decrease] in […] afferent activity.

A

Shortened, decrease, spindle.

53
Q

During voluntary flexion, are alpha or gamma neurons active (or both)? Why?

A

Both are active. This is because when the muscle shortens, the muscle spindle becomes floppy and loses its sensitivity, reducing how often it sends action potentials (action spindle collapse). Gamma motor neurons are needed to pull the spindle tighter again and maintain its sensitivity to muscle length.

54
Q

During voluntary flexion, the neuronal activity is referred to as the phenomenon […]

A

Alpha-gamma coactivation

PHGY 209 (33 decks)

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