Reflex action (& reflex arc)

What is a reflex action?

An involuntary response to a stimulus that happens automatically, without conscious thought

Give examples of reflex actions.

Pulling a hand away from heat, pupil constriction in response to light, sneezing, and the knee-jerk reflex

What is a stimulus?

A change in the environment, such as heat, light, or pressure

What is a response?

The body's reaction to a stimulus, such as moving a hand away from heat

What is a reflex arc?

The pathway through which reflex actions occur, involving sensory neurons, relay neurons, and motor neurons

What role do sensory neurons play in reflexes?

Sensory neurons detect the stimulus and carry the signal to the spinal cord

What is the function of relay neurons in a reflex arc?

Relay neurons transfer the signal between sensory and motor neurons in the spinal cord

What do motor neurons do?

Motor neurons carry the response signal from the spinal cord to the muscle to cause movement

Why are reflexes important for survival?

They ensure immediate reactions to dangerous situations, preventing injury

How does the reflex arc bypass the brain?

The signal from the sensory neuron is routed directly to the motor neurons for immediate action without waiting for the brain

Where does the sensory neuron connect in the spinal cord?

The sensory neuron connects to the back side of the spinal cord

Where does the motor neuron exit from in the spinal cord?

The motor neuron exits from the front side of the spinal cord

What is unique about the knee-jerk reflex?

It can involve only two neurons rather than the typical three

How do reflex arcs contribute to quick reactions?

They allow for automatic responses to stimuli, reducing the time it takes to react to dangerous situations

What are the three types of neurons involved in reflex actions?

Sensory neurons, relay neurons, and motor neurons

What does it mean that reflex actions are involuntary?

It means that the body reacts automatically without needing to think about it

Why might relying on the brain for reflex responses be problematic?

It could lead to delays that result in injury in dangerous situations

What types of situations typically trigger reflex actions?

Dangerous situations, such as touching something hot

What is pupil constriction an example of?

A reflex action that responds to changes in light

In the context of reflexes, what is the significance of quick reactions?

They are essential for survival, enabling fast responses to threats