Reflex action | Control & co-ordination | Class 10 Biology | Khan Academy

Summary

Reflex actions are involuntary responses to stimuli, like quickly pulling your hand away from a flame. These actions happen automatically, without conscious thought. In the example of heat from a flame, a sensory neuron detects the stimulus and sends a signal to the spinal cord. Instead of waiting for the brain's input, the signal is quickly relayed through the relay neuron to a motor neuron, which causes the muscle to contract and move the hand away. This quick, automatic response, known as a reflex arc, is vital for survival and is believed to have evolved before our intelligence.

Takeaways

• 😀 Reflex actions are involuntary responses to stimuli.
• 😀 An example of a reflex action is pulling your hand away from a flame when it gets too hot.
• 😀 Reflex actions happen automatically without conscious thought or decision-making.
• 😀 Another example of a reflex action is the pupil of the eye shrinking when exposed to bright light.
• 😀 The reflex action pathway involves three types of neurons: sensory, relay, and motor neurons.
• 😀 Sensory neurons detect the stimulus (like heat) and send the signal to the spinal cord.
• 😀 The signal from the sensory neuron travels to a relay neuron in the spinal cord, bypassing the brain.
• 😀 The relay neuron passes the signal to a motor neuron, which activates a muscle to respond to the stimulus.
• 😀 The reflex arc allows for quick and automatic responses to stimuli, helping with survival.
• 😀 Reflex arcs are believed to have evolved before the development of higher intelligence in organisms.

Q & A

What is a reflex action?

A reflex action is an involuntary response to a stimulus, occurring automatically without conscious thought or decision-making.

Can you give an example of a reflex action?

One example of a reflex action is when your hand moves away from a flame due to the heat. This happens without you thinking about it.

What happens when light is shone into your eyes?

When light is shone into your eyes, your pupil becomes smaller. This is an involuntary response to the light stimulus.

What is the role of the sensory neuron in reflex actions?

The sensory neuron detects the stimulus, such as heat or light, and sends the signal to the spinal cord.

What does the relay neuron do in the reflex arc?

The relay neuron transfers the signal from the sensory neuron to the motor neuron, ensuring quick transmission of the response without waiting for the brain.

How does the motor neuron contribute to reflex actions?

The motor neuron carries the signal to the muscles, which then contract and cause the body to move, such as pulling your hand away from a hot object.

What is a reflex arc?

A reflex arc is the pathway through which a reflex action occurs, involving the sensory neuron, relay neuron, and motor neuron to produce a quick response to a stimulus.

Why are reflex actions considered involuntary?

Reflex actions are considered involuntary because they occur automatically without the need for conscious thought or control from the brain.

Why are reflex arcs important for survival?

Reflex arcs are crucial for survival because they allow quick, automatic responses to harmful stimuli, such as pulling away from heat, which can prevent injury.

How do reflex arcs help protect the body?

Reflex arcs help protect the body by triggering fast reactions to harmful stimuli, like heat or injury, before the brain can process the danger consciously.