Mechanisms of Spasticity and Baclofen [Macroscopic view ONLY]

The video explains the connection between upper and lower motor neurons, focusing on spasticity. It describes how spasticity results from an imbalance of excitatory and inhibitory signals, particularly in the absence of descending inhibitory input. The stretch reflex and its exaggeration in spasticity are discussed, along with the effects of upper motor neuron lesions. The video also covers the role of Baclofen in managing spasticity by inhibiting specific neurons, and concludes with a discussion on flexor synergy in upper motor neuron lesions.

What is the primary role of upper motor neurons in muscle contraction?

• To directly innervate skeletal muscles

• To activate lower motor neurons

• To provide sensory feedback to the brain

• To inhibit lower motor neurons

What happens when there is more excitation than inhibition on a lower motor neuron?

• The muscle will atrophy

• The muscle will become spastic

• The muscle will contract

• The muscle will relax

What is the default state of lower motor neurons?

• Inhibition

• Excitation

• Spasticity

• Neutral

What is the role of muscle spindles in the stretch reflex?

• To prevent muscle fatigue

• To provide energy to muscles

• To detect muscle stretch

• To inhibit muscle contraction

How does a cerebral infarct affect the stretch reflex?

• It enhances inhibition on lower motor neurons

• It causes an exaggerated stretch reflex

• It reduces muscle tone

• It prevents muscle contraction

Which nuclei, when activated, inhibit the stretch reflex?

• Ventromedial bulbar reticular formation

• Vestibular nuclei

• Cerebral cortex

• Dorsal reticular formation

What is the effect of losing upper motor neurons on the stretch reflex?

• Increased inhibition

• Decreased muscle tone

• Excessive activation of the stretch reflex

• No effect

How does Baclofen help in reducing spasticity?

• By inhibiting the 1A afferent neuron

• By stimulating upper motor neurons

• By enhancing the stretch reflex

• By increasing muscle contraction

What is a common posture seen in upper motor neuron lesions?

• Extension synergy

• Flexion synergy

• Neutral posture

• Inverted posture

Why do flexors overpower extensors in upper motor neuron lesions?

• Extensors are more inhibited

• Extensors are stronger

• Flexors have more spasticity force

• Flexors are unaffected by cerebral insults