Question Video: Identifying the Main Parts Involved in a Reflex Action in a Given Example Biology

Video Transcript

You reach over a hot oven and accidentally touch a hot baking tray. You immediately pull your arm away. In this reflex action, what is the stimulus? In this reflex action, what is the receptor? In this reflex action, what is the effector? In this reflex action, what is the response?

This question describes a scenario and then asks us to pick out the different parts of the reflex action. The scenario starts with accidentally touching a hot baking tray, which leads to the reflexive action of pulling your arm away. Let’s recall that a reflex action is a response to a stimulus that occurs without the need for conscious thought. The mechanism of this reflexive action is a pattern of events known as a reflex arc. And the steps in this pattern are stimulus, receptor, sensory neuron, relay neuron, motor neuron, effector, and response. For the purposes of this question, we’re specifically interested in the stimulus, the receptor, the effector, and the response.

Let’s recall that the stimulus is the change in the environment. The receptor is the part of the body that detects the stimulus or the change. The effector is the part of the body that carries out the response to the stimulus and the response is the reaction that we observe. The scenario in the question provides our stimulus and our response for us. The stimulus occurs when you touch the hot baking tray, and the response occurs when you pull your arm away. So, now, we’re just left to determine what the receptor and the effector are.

Touching a hot tray hurts. That’s because the heat activates special structures in your skin called pain receptors. Well, we know you eventually pull your arm away, but how? The muscles in your arm are the effector that carry out the response of pulling your arm away. So, now, we have the answers to our questions. In this reflex action, the stimulus is the hot baking tray. The receptor is pain receptors in the skin. In this reflex action, the effector is the muscles in your arm, and the response is the movement of your arm.