By the end of this lesson
- Describe nervous and hormonal communication.
- Compare their speed, duration and targeting.
- Select an appropriate system for a response.
BIG QUESTION
Why does touching a hot surface demand nerves, while growth and reproduction often depend on hormones?
Electrical signalling through neurones is rapid and targeted; chemical signalling in blood is slower but often longer lasting.
Nervous signalling follows wired pathways
Receptors generate electrical impulseAn electrical signal carried along a neurone. that travel along sensory neurones to the central nervous system. Motor neurones carry impulses to particular muscles or glands.
At synapses, chemical neurotransmitters cross a tiny gap before a new electrical impulse is generated.
Hormonal signalling uses the circulation
Endocrine glands release hormoneA chemical messenger made by an endocrine gland and carried in the blood plasma to target organs, where it causes a response. into blood. Blood distributes a hormone widely, but only cells with complementary receptors respond.
Hormone concentration can remain elevated, producing coordinated effects across several tissues.
Different properties suit different tasks
Nervous responses are usually rapid, short-lived and spatially precise, suiting reflexes and movement. Hormonal responses are usually slower, longer-lasting and potentially widespread, suiting growth, metabolism and reproduction.
The systems interact: the nervous system can stimulate endocrine release, and hormones can alter nervous activity.
Nervous and hormonal communication
The contrast is relative rather than absolute.
| Feature | Nervous system | Hormonal system |
|---|---|---|
| Signal | Electrical impulses; neurotransmitter at synapses. | Chemical hormone. |
| Route | Specific neurones. | Blood circulation. |
| Speed | Usually very fast. | Usually slower. |
| Duration | Usually short-lived. | Often longer-lasting. |
| Targeting | Precise effector pathway. | Any cell with the correct receptor. |
| Example | Withdrawal reflex. | Menstrual-cycle regulation. |
Language that earns precision
- neurone
- Specialised cell that transmits electrical impulses.
- hormone
- Chemical messenger released into blood by an endocrine gland.
- target cell
- Cell with receptors that allow it to respond to a particular signal.
- endocrine gland
- Gland that secretes hormones directly into blood.
Common misconceptions
Claim: Hormones affect every cell they pass.
Correction: Only target cells with appropriate receptors respond.
Claim: Nervous communication is electrical across every part of the route.
Correction: Most synapses transmit chemically using neurotransmitters.
Claim: The nervous and endocrine systems work independently.
Correction: They frequently coordinate and regulate one another.
Match the answer to the command word
Use paired points for route, speed, duration and target.
Match rapid protective actions to nerves and prolonged regulation to hormones.
Recall, apply, then justify
Compare nervous and hormonal communication.
Hint
Signal, route, speed, duration, target and one similarity.
Suggested marking points
- Nervous signalling uses electrical impulses whereas hormones are chemical messengers.
- Nervous signals travel along neurones whereas hormones travel in blood.
- Nervous responses are usually faster.
- Nervous responses are usually shorter-lived.
- Nervous pathways are more spatially precise while hormones can reach many tissues.
- Both require target cells/effectors able to respond to the signal.
Explain why nervous control is suited to withdrawing from a hot object.
Hint
Speed and targeting reduce harm.
Suggested marking points
- Impulses travel rapidly along a specific pathway.
- A particular skeletal muscle is activated quickly.
- Rapid withdrawal limits tissue damage.
Explain how one stress response can involve both nervous and hormonal communication.
Planning hint
Begin with detection, then link to adrenal release.
What a strong design includes
- A receptor detects a threatening stimulus.
- Nervous impulses travel to and within the CNS.
- Autonomic nerve output rapidly changes organ activity.
- The adrenal glands are stimulated to release adrenaline.
- Adrenaline travels in blood and prolongs/co-ordinates effects in target tissues.
- The combined response is rapid yet distributed.