2.2: Motor Hierarchy

Summary

The video discusses three types of movements: reflexes, stereotyped movements, and intentional movements. Reflexes, like withdrawing from a hot surface, happen without conscious thought. Stereotyped movements, such as walking or vomiting, are repetitive actions controlled by central pattern generators. Finally, intentional movements, which involve self-expression or deliberate actions, are controlled by the brain's cortical motor centers. As movements become more complex, higher levels of the brain are engaged, turning basic muscle responses into meaningful, intentional actions.

Takeaways

• 🤖 Reflexes are automatic movements, such as withdrawing from a hot surface or the knee-jerk reaction at the doctor’s office.
• 🧠 Reflexes occur without brain involvement and are managed by lower levels of the motor hierarchy.
• 💪 Skeletal muscles require input from motor neurons to contract, unlike cardiac muscles that contract independently.
• ⚙️ Motor neurons are grouped into circuits that control basic movements, which are the foundation of reflex actions.
• 🔄 Stereotyped movements are repetitive actions like walking, chewing, and even rare actions like vomiting, which are controlled by central pattern generators (CPGs).
• 🎥 Vomiting is an example of a stereotyped movement, often shown in films with just the torso motion to indicate what's happening.
• 🏃 Movements like walking and posture control are managed by the brainstem motor control centers, which engage more complex actions.
• 🎨 Intentional movements are deliberate and emotional actions that originate from the cortical motor control centers, such as reaching, talking, or writing.
• 🧩 The motor hierarchy progresses from simple muscle twitches to complex movements as more parts of the brain are involved.
• 🌟 Movements become meaningful and intentional only when the neocortex is involved, transforming simple movements into purposeful actions.

Q & A

What are the three types of movements discussed in the video?

The three types of movements discussed are reflexes, stereotyped automatic movements, and movements of self-expression.

What is a reflex, and how does it function?

A reflex is an automatic, involuntary response to stimuli, such as withdrawing your hand when touching a hot stove. Reflexes occur without conscious thought and are controlled by lower levels of the motor hierarchy.

What role do motor neurons play in skeletal muscle movement?

Skeletal muscle movement requires input from motor neurons. Unlike cardiac muscles that can contract on their own, skeletal muscles need signals from motor neurons to function.

What are stereotyped movements, and can you provide examples?

Stereotyped movements are repetitive, automatic movements like walking, chewing, or even vomiting. These actions are produced by central pattern generators, which control regular, rhythmic movements.

What are central pattern generators, and why are they important?

Central pattern generators are neural circuits that produce rhythmic, stereotyped movements like walking or vomiting. They are important because they allow for automatic, consistent movements without requiring higher brain involvement.

How do movements of self-expression differ from reflexes and stereotyped movements?

Movements of self-expression are intentional and meaningful actions, such as dancing or talking. These involve the cortical motor control centers and are imbued with purpose or emotion, unlike reflexes and stereotyped movements that are automatic.

What is the role of cortical motor control centers in movement?

Cortical motor control centers are involved in complex, intentional movements that carry meaning, such as reaching for an object, speaking, or writing. These movements require higher-level brain functions.

How do brainstem motor control centers contribute to movement?

The brainstem motor control centers are responsible for basic postural control, walking, and orienting movements. These are simpler actions compared to the more complex, intentional movements governed by the cortex.

What is the significance of the motor hierarchy mentioned in the video?

The motor hierarchy refers to the levels of control in movement, starting from simple reflexes controlled by lower centers, to complex, meaningful actions governed by higher cortical areas. The higher up the hierarchy, the more involved the brain becomes in the movement.

What does the video mean when it says movements become 'imbued with meaning' at the cortical level?

At the cortical level, movements are no longer just mechanical actions. They carry intentional meaning and are linked to self-expression, emotions, or deliberate purposes, turning basic movements into purposeful actions.