LABORATORY 1: HOMEOSTASIS, FEEDBACK CONTROL, AND MEASUREMENTS REVIEW

A set of flashcards covering core concepts from the notes on homeostasis, feedback, and measurements.

What is homeostasis?

The ability of an organism to maintain a constant internal environment despite changes in the external environment.

What is pathophysiology?

The study of diseases and how they disrupt physiological mechanisms.

Why does maintaining homeostasis usually involve more than one organ system?

Because regulation of internal conditions typically requires coordination among multiple organ systems (e.g., nervous, endocrine, cardiovascular).

In the homeostatic control analogy, what is the variable X?

The factor being controlled (for example, room temperature in the thermostat analogy).

What is a setpoint?

The target value around which a physiological variable is maintained.

What is the integrating center (control center) in homeostasis?

The site that processes information and determines the response (e.g., thermostat, hypothalamus).

What are sensors (receptors) in homeostasis?

Structures that detect the variable and send information to the control center.

What is the afferent pathway?

Pathway carrying sensory information toward the control center.

What is the efferent pathway?

Pathway carrying motor information away from the control center to the effector.

What are effectors?

Structures that produce a change to bring the variable back toward the setpoint (e.g., muscles, glands, organs).

What is negative feedback?

A regulatory mechanism in which the response opposes the initial change, helping restore the setpoint.

How does the thermostat illustrate negative feedback?

If the room is cooler than the setpoint, the furnace turns on to raise temperature; when setpoint is reached, the furnace turns off.

What is dynamic constancy?

A state in which the internal environment remains functionally constant with fluctuations around the setpoint.

What are antagonistic effectors?

Two opposing effectors that provide precise control (for example, sweating vs shivering).

What does it mean to have two sensors and two antagonistic effectors?

Using dual sensing and dual opposing actions improves precision and responsiveness of regulation.

What is positive feedback?

A regulatory loop in which the response amplifies the initial change rather than opposing it.

Give an example of a positive feedback loop: Oxytocin and labor

Stretching of the cervix triggers oxytocin release, causing contractions that intensify until birth.

Give an example of a positive feedback loop: Blood clotting

Injury initiates platelet activation and aggregation, releasing substances that recruit more platelets and promote clot formation.

What are the steps in a thermoregulatory negative feedback loop?

Thermoreceptors signal the hypothalamus/posterior hypothalamus, which activates autonomic pathways to sweat glands and skin arterioles to dissipate heat; regulation of blood flow and evaporation cools the body.

What is heat exhaustion?

A state where strenuous exercise or heat overloads homeostatic mechanisms, causing weakness, dizziness, and possible fainting.

What is heat stroke and its treatment?

Thermoregulatory center fails at high temperature; dry, flushed skin; rapid metabolism; treatment includes rapid cooling (e.g., cold water immersion).

What is nonshivering thermogenesis?

Thermogenic responses other than shivering, including vasoconstriction and behavioral strategies to conserve or generate heat.

When does insulin get released and what does it do?

Released when blood glucose rises after a meal; it increases glucose uptake by cells and promotes glycogen storage, lowering blood glucose.

When is glucagon released and what does it do?

Released when blood glucose is low; it stimulates glycogen breakdown and gluconeogenesis to raise blood glucose.

What is the normal fasting blood glucose range?

Approximately 70–110 mg/dL.

What are two key antagonistic hormones that regulate blood glucose?

Insulin and glucagon.

What is the postprandial glucose limit that should be observed after a meal?

Glucose should be below 180 mg/dL after eating.

What glucose tolerance test result indicates diabetes?

Two measurements above 200 mg/dL after the glucose tolerance test.