Renee, Pregnant for the First Time, Wonders How the Developing

question 32

Multiple Choice

Renee, pregnant for the first time, wonders how the developing organism receives nutrients and oxygen and rids itself of waste. Her obstetrician tells her that this exchange will occur through the ______.

• A) placenta
• B) amnion
• C) umbilicus
• D) mesoderm

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Definitions:

Excitatory Signals

These are biochemical impulses that promote or increase neural activity or the firing of neurons.

All-or-none Response

A biological principle indicating that a nerve or muscle fiber reacts completely or not at all to a stimulus.

Sodium/Potassium Pump

A vital cell membrane protein that pumps sodium out of cells and potassium into cells, maintaining the necessary concentration gradients for nerve impulse transmission and muscle contractions.

Positively Charged Ions

Particles, either atoms or molecules, which have become positively charged by losing one or more electrons.