When a hand hits a hot pot it jerks away at once: the body senses a stimulus and reacts fast.
Neurons pass electrical signals through dendrite, cell body, axon, and terminal; reflexes go via the spinal cord, conscious acts via the brain.
Hormones travel in the blood, acting slowly but longer, and with nerves they keep homeostasis.
Here you can compare neuron structure, reflex versus conscious paths, and key hormones.
Nerves: electrical (fast, short) | Hormones: chemical (slow, long)
They work together to maintain homeostasis
🎯 Exam Points
①Neuron: dendrites→cell body→axon→axon terminal
②Reflex: via spinal cord (fast) — knee, pupil reflex
③Conscious response: via brain — writing, speaking
④Hormones: travel through blood to target organs
⑤Homeostasis: keeping temperature, blood sugar, etc. stable
Examples and Unit Test
Example 1
How does the nerve path of pulling your hand away from a hot object differ from the path of crossing the street after seeing a traffic light?
1
Pulling the hand away is a reflex: stimulus → receptor → sensory nerve → spinal cord → motor nerve → effector, which skips the brain and is very fast.
2
Crossing at a light is a conscious response: along the same path the brain, not the spinal cord, makes the decision and then commands, so it is slower.
▸ Reflex = through the spinal cord (skips the brain, fast) / conscious response = through the brain (after judging, slower)
A reflex that avoids danger skips the brain to shorten the reaction time.
Example 2
When blood sugar rises, how does insulin act, and how does a hormone differ from a nerve in the way it sends signals?
1
Insulin is released from the pancreas, travels through the blood to target organs, and lowers blood sugar.
2
A nerve uses electric signals that act fast and briefly, while a hormone travels through the blood slowly and its effect lasts long.
▸ Insulin (pancreas) → blood → target organ → blood sugar down / hormones are slow but lasting, nerves are fast but brief
Nerves and hormones work together to keep homeostasis such as body temperature and blood sugar.
Unit Test
Which statement about the nervous system and hormones is correct?
①A reflex happens after the brain makes a judgment
②In a neuron the signal travels from the axon terminal toward the dendrites
③Hormones act on target organs through the blood
④Nerve signals are slower and last longer than hormones
⑤Insulin is a hormone that raises blood sugar
▸ ③ Hormones act on target organs through the blood
1
A reflex passes through the spinal cord without the brain (① wrong), and a neuron signal runs dendrite → cell body → axon → axon terminal (② wrong).
2
Nerve signals are fast and brief (④ wrong), and insulin lowers blood sugar (⑤ wrong); hormones act on target organs through the blood (③ correct).