Touching a warm surface gives you information. Moving your hand is a response. Now separate the incoming message from the outgoing instruction.
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Receptor
A sensory receptor is a detector that responds to a change, such as pressure or temperature.
For example
Receptors in your skin help detect warmth. They send information; a different part carries out the response.
Read all notes for this section
Receptor
A sensory receptor is a detector that responds to a change, such as pressure or temperature. Receptors in your skin help detect warmth. They send information; a different part carries out the response.
Neuron / synapse
A neuron is a nerve cell that carries signals. A synapse is a junction where it communicates with another cell. At most synapses, a neuron releases a chemical messenger called a neurotransmitter. It carries the message across a tiny gap to the next cell.
Hormone / endocrine
A hormone is a chemical message carried by the blood. Cells that release hormones into blood are called endocrine cells. Insulin helps regulate glucose, a sugar in the blood. A cell responds to a hormone only if it has the appropriate receptor, a molecule that recognises the message.
Effector / feedback
An effector is a muscle or gland that carries out a response. Feedback means the result of a response influences what happens next. Sweat glands release sweat. As it evaporates, it cools the skin; reduced warming helps reduce the signal to keep sweating.
Detect → process → respond
Imagine touching something unexpectedly hot. A sensory receptor detects the change. Sensory nerves carry information towards the brain or spinal cord. Motor nerves carry commands out to a muscle or gland. The part that carries out the response is the effector. A gland is a structure that makes and releases a substance, such as sweat.
Two ways to send a message
The brain and spinal cord form the central nervous system. Nerves connecting them to the body belong to the peripheral nervous system. A neuron is a nerve cell. It carries electrical signals and usually passes a chemical message to the next cell at a junction called a synapse. Hormones take another route: endocrine cells release these chemical messages into the blood.
Keep a change within limits
Negative feedback means that a response reduces the change that started it. If your body becomes too warm, sweating can help cool it. As temperature returns towards its usual range, the drive to sweat decreases. “Negative” means opposing the change, not something harmful.
Explore the illustration
Look at the whole view first. Then select one label and connect it to the idea you just read.
A nerve pathway and a neuron
The body view locates the nervous system; the enlarged neuron explains how a cell receives and passes on a signal.
More controls
01 / 7 Brain
The travelling highlight represents an electrical signal along the axon. At the synapse, chemical messengers carry information across the gap. It is a teaching tracer, not a moving particle inside the nerve. Reduced motion is enabled. Use the arrows to study one step at a time, or choose Play.
Brain
The brain is part of the central nervous system and integrates information.
Adapted for this lesson: labels removed, artwork cropped or recoloured, and interactive teaching overlays added. Adapted artwork retains its source licence.
Go deeper
In-depth reading
Follow this example step by step, then try explaining it yourself. The extra reading is optional: you can return to it after exploring the illustration.
Worked example: cooling down after a walk
Detect: your working muscles release heat. Temperature-sensitive receptors in the body provide information about warming. A receptor is the detector, not the structure that performs the cooling.
Coordinate and respond: a brain region called the hypothalamus helps coordinate temperature control. Nerve signals activate sweat glands. The glands release sweat; when it evaporates from the skin, it takes heat away. The glands are effectors.
Close the loop: cooling reduces the original warming. This feedback helps prevent the response continuing unnecessarily. The same pattern—detect, coordinate, respond, reassess—helps explain many body controls. A hormone receptor is a different use of “receptor”: it is a molecule that binds a chemical message, rather than a whole temperature-sensing structure.
Explain it yourself
In this example, which part is the effector, and why?
Show the explanation
The sweat gland is the effector because it carries out the response. The receptor detects the change; it does not make the sweat.
More detail — when you are ready
These notes expand the mechanisms and vocabulary. Read one topic at a time and find the structures in the illustration.
Follow a message from receptor to effector
A receptor detects a change such as pressure, temperature or tissue damage. Sensory, or afferent, pathways carry information towards the brain or spinal cord.
Integration connects the incoming message to an appropriate response. Motor, or efferent, pathways carry output to an effector such as a muscle or gland.
The central nervous system comprises the brain and spinal cord; peripheral nerves connect it to the rest of the body. A withdrawal reflex can be organised through spinal circuits before a person consciously identifies the painful stimulus.
Electrical signals and chemical messengers
An action potential is a brief electrical change that travels along the membrane of a neuron. It is one way a nerve cell sends a signal over a distance.
At a chemical synapse, released neurotransmitter crosses a small gap and binds receptors on another cell; it may make the receiving cell more likely to send a signal (excitatory) or less likely to do so (inhibitory). Endocrine glands release hormones into blood.
Distribution through blood does not mean every cell responds: a target cell needs a matching receptor and the ability to respond. Think of the receptor as recognising the message; simply being near the hormone is not enough.
Nervous and endocrine control cooperate, and speed alone does not perfectly distinguish them. In negative feedback, the response reduces the original disturbance rather than endlessly amplifying it.
Worked example: sensing and responding
During warming, temperature information is integrated and responses such as sweating increase heat loss. The sweat gland is an effector, not the sensor or control centre.
External communication also combines systems: vision, hearing, taste, smell and balance supply specialised information, while proprioception tells you where your body parts are, even without looking at them. Expired air makes vocal folds vibrate in the larynx; the tongue, lips and jaw shape speech.
Facial expression and posture convey non-verbal information. A response to the environment may therefore involve sensation, integration, muscle activity and gland secretion together.
Further reading — optional
Free external resources in English. Internet connection required to open the links. Choose the topic you want to explore; these readings are not required to complete the section.
Start with central versus peripheral, then sensation, integration and response. Leave the detailed names of nerve-cell groups for a second visit.
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Sources and illustration notes
Bilingual teaching notes organised from your supplied anatomy reference pages. Medical SVG artwork is credited beneath each illustration; guided sequences and process overlays support slow, step-by-step study. Anatomy and translation await expert review.
