How Do Systems Know When to Act?
- Systems only work when they receive accurate information about what is happening inside or outside your body.
- Receptors help them detect those changes, things like temperature shifts, pressure, chemicals, or light, and alert the nervous or endocrine system.
- Once that signal arrives, the system knows exactly when to speed up, slow down, or take action.
Receptor
A specialized cell or structure that notices a change (stimulus) and sends a signal telling the body what to do next.
- Receptors are like messengers.
- They do not make decisions, they simply inform the systems so the systems can respond ("decide themselves").
What Exactly Do Receptors Detect?
- Receptors are built to detect very specific kinds of changes.
- Some look outward (light, sound, touch), others monitor your internal state (oxygen levels, temperature, pressure).
- Each type gives the body a different stream of information so systems can react in the right way.
- To help you see the pattern, here’s a quick overview:
| Receptor Type | What It Detects | Example Location |
|---|---|---|
| Photoreceptor | Light | Retina |
| Chemoreceptor | Chemicals, CO₂ | Nose, tongue, blood vessels |
| Mechanoreceptor | Pressure, vibration | Skin, inner ear |
| Thermoreceptor | Temperature | Skin, hypothalamus |
| Nociceptor | Pain | Throughout the body |
- Understand how "form follows function" and the idea of specialization applies here too:
- Photoreceptors respond to light because they contain light-sensitive pigments.
- Mechanoreceptors respond to pressure because they have stretch-sensitive membranes.
- Trying to detect everything would make receptors slow and unreliable, so the body uses specialists instead.
How Do Receptors Convert Stimuli Into Signals?
Transduction
The process in which receptors turn a stimulus into an electrical or chemical signal the body can interpret.
- The basic idea of transduction is that once a stimulus hits the receptor, the receptor changes its electrical activity, which causes a signal to be sent onward.
- That signal travels through nerves or hormone pathways until it reaches the brain or spinal cord.
- At that point, the body decides what to do, such as adjusting breathing rate or releasing hormones.
- This is how a tiny external or internal change becomes a full-body response.
How Do Receptors Guide Growth, Development, and Life Cycles?
- Receptors do more than just sense the environment, they also control long-term processes inside the body.
- Hormone receptors guide growth, puberty, and repair.
- In plants, receptors detect light and gravity to guide seedling growth and flowering.
- These responses shape the entire life cycle of an organism.
| Process | Receptor Involved | Outcome |
|---|---|---|
| Blood glucose control | Insulin receptors | Cells absorb glucose |
| Plant growth direction | Light receptors | Shoots grow toward light |
| Puberty | Hormone receptors | Development of adult traits |
| Temperature regulation | Thermoreceptors | Sweating or shivering |
- How do receptors help systems decide when to act?
- What is a stimulus, and how do receptors detect one?
- What is the purpose of transduction?
- Why does the body use different receptors for different stimuli?
- Give one example each of an internal receptor and an external receptor.
- How do receptors influence growth and development?
- Why would an organism struggle to survive without functioning receptors?