What Is Life? Homeostasis & Feedback Mechanisms

A set of question-and-answer flashcards covering the lecture material on characteristics of life, homeostasis, and both negative and positive feedback mechanisms.

What are the five shared characteristics of all living things?

(1) Made of cells, (2) grow and maintain structure by taking in chemicals/energy, (3) respond to the external environment, (4) reproduce and pass on genetic information, (5) evolve and adapt at the species level.

What is homeostasis?

The collection of processes that allow an organism to maintain a relatively constant, stable internal environment despite external changes.

Which general type of feedback loop maintains homeostasis by counteracting the original stimulus?

Negative feedback.

In a negative feedback loop, does the response dampen or amplify the stimulus?

It dampens (counteracts) the stimulus.

What pattern does a negative feedback loop typically produce in the regulated variable?

A fluctuation between two levels around a normal set point.

Give an everyday physiological example of negative feedback in humans.

Blood glucose regulation, where insulin and glucagon keep glucose concentration within normal limits.

Which type of feedback loop amplifies the original stimulus instead of canceling it?

Positive feedback.

Why are positive feedback loops described as helping to "drive processes to completion"?

Because each amplification step strengthens the stimulus, pushing the system toward a final end-point where the loop stops.

Name the hormone central to the positive feedback loop during labor.

Oxytocin.

Where is oxytocin produced and stored before release during labor?

Produced in the hypothalamus and stored in the posterior pituitary.

What initial event triggers the release of oxytocin in the labor feedback loop?

Pressure of the baby’s head against the cervix activates sensory nerves that signal the posterior pituitary.

Describe the positive feedback cycle of oxytocin during childbirth.

Cervical pressure → nerve signal to pituitary → oxytocin release → stronger uterine contractions → increased cervical pressure → more oxytocin release, continuing until the baby is delivered.

What terminates the positive feedback loop of oxytocin during labor?

Delivery of the baby, which stops cervical pressure and therefore halts the stimulus and oxytocin release.