How a signal travels
Before you read
Test yourself first: 5 questions
Question 1 of 5
A neurotransmitter crosses which structure to reach the next neuron?
Answer: A. The synapse is the gap between neurons; the neurotransmitter is released into it and binds receptors on the next cell. The axon carries the impulse to the synapse.
Question 2 of 5
The fatty covering that insulates axons and speeds nerve impulses is the:
Answer: B. The myelin sheath insulates the axon, allowing faster transmission of nerve impulses.
Question 3 of 5
Which structure is the heart's natural pacemaker?
Answer: A. The SA node in the right atrium fires fastest and so sets the rhythm. The AV node, bundle of His and Purkinje fibers conduct the impulse onward and can pace only if the SA node fails.
Question 4 of 5
Which structure produces sperm?
Answer: A. The testes are the male gonads: they make gametes and the principal sex hormone, mirroring the ovaries in the female.
Question 5 of 5
Gas exchange occurs in the alveoli because their walls are:
Answer: A. Structure serves function: alveoli are thin-walled and richly perfused because their only job is diffusion.
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