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What is the correct name for the structure that brings about a response in a reflex action?
The effector — usually a muscle or gland that carries out the body’s response.
What happens at a synapse when an impulse arrives?
The impulse triggers the release of neurotransmitters, which diffuse across the synapse and start a new impulse in the next neurone.
Why is it dangerous if signals from the skin don’t reach the brain?
The brain can’t process the stimulus and can’t send a response, so the person may not react to dangers like heat or pain.
How does a camel’s hump help it survive in the desert?
The hump stores fat, which the camel can break down into energy and water when food and water are scarce.
Why do desert plants often have no leaves or spines?
To reduce water loss through transpiration in hot, dry conditions.
How do bacteria make us feel ill?
Bacteria reproduce rapidly and produce toxins that damage cells.
How do viruses make us feel ill?
Viruses invade body cells, reproduce inside them, and damage or destroy the cells.
Why might a person become addicted to a recreational drug?
Some drugs cause chemical changes in the brain, leading to dependence. Stopping them can cause withdrawal symptoms, which reinforces continued use.
How does tobacco harm a developing fetus?
Carbon monoxide in smoke reduces the oxygen carried in the blood, leading to low birth weight or poor development.
Which organ produces cholesterol in the body?
The liver.
