Question

1. what is the main function of structure e?

a they exchange oxygen and carbon dioxide directly with the blood.
b. they carry blood cells and nutrients into the lungs.
c. they contract and relax to pump air in and out of the lungs.
d. they filter air with cilia and mucus as it passes toward the alveoli.

1. kayden is walking barefoot on the beach when he suddenly steps

immediately pulls his foot away to hold it. which best describes why
a his sensory neurons in the pns detected pain and sent signals to
and sent commands back through motor neurons in the pns to m
b. his motor neurons in the cns detected pain and sent signals to t
and sent commands back through sensory neurons in the cns to
c. his motor neurons sensed the seashell directly, carrying the pain
to contract without any role from the sensory neurons.
d. his spinal cord absorbed the pressure from the seashell, prevent
produced a response without needing any sensory input.
the image shows a model of a body system. use it to answer

Explanation:

Question 18

To determine the main function of structure E (assuming it's an alveolus or related respiratory structure), we analyze each option:

• Option A: Alveoli (if E is alveoli) exchange O₂ and CO₂ with blood. This matches gas exchange.
• Option B: Carrying blood cells/nutrients is not alveoli's function (blood vessels do this). Eliminate B.
• Option C: Pumping air in/out is done by respiratory muscles (like diaphragm), not structure E. Eliminate C.
• Option D: Filtering air with cilia/mucus is done by upper respiratory tract (trachea, bronchi), not alveoli. Eliminate D.

So the correct answer is A.

For the reflex action:

• Sensory neurons in the Peripheral Nervous System (PNS) detect stimuli (pain from stepping on something). They send signals to the Central Nervous System (CNS, spinal cord/brain). Then motor neurons in PNS send commands back to muscles to react (pull foot away).
• Option A: Correctly describes PNS sensory neurons detecting pain, sending to CNS, and motor neurons in PNS sending commands.
• Option B: Motor neurons don't detect pain (sensory do), and motor neurons are not in CNS for this reflex (PNS motor neurons act). Eliminate B.
• Option C: Motor neurons don't sense stimuli (sensory do), and reflex needs sensory input. Eliminate C.
• Option D: Spinal cord needs sensory input to produce a response (reflex arc requires sensory → CNS → motor). Eliminate D.

So the correct answer is A.

Answer:

A. They exchange oxygen and carbon dioxide directly with the blood.

Question 19