Chapter 2: Control of the Internal Environment Flashcards
(20 cards)
What is homeostasis?
Maintenance of a relatively constant internal environment
Observed during resting conditions, such as a normal mean arterial pressure of 93 mmHg, which fluctuates but maintains an average.
What is steady state?
Steady and unchanged level of some physiological variable during exercise conditions
For example, body temperature rises during exercise and then reaches a plateau.
What are the components of biological control systems?
- Sensor
- Control Center
- Effectors
These components work together to maintain a chemical or physical parameter of the body near a constant value.
What role do sensors play in control systems?
Receptor capable of detecting change in a variable
For example, thermal receptors in core temperature regulation.
What is the function of the control center in a biological control system?
Integrates incoming signals from sensors and sends messages to effectors
The brain, specifically the hypothalamus, acts as the control center in core temperature regulation.
What are effectors in the context of biological control systems?
Bring about appropriate response to correct disturbance
For example, blood vessels dilate or constrict to regulate core temperature.
What is an example of core temperature regulation in a control system?
- Sensors: Thermal receptors throughout the body
- Control Center: Brain (hypothalamus)
- Effectors: Blood vessels (dilate/constrict), sweat glands
What is the negative feedback mechanism?
Restores normal values of a variable to maintain homeostasis
The response is opposite to the stimulus, such as in CO₂ regulation.
Give an example of positive feedback.
Labor contractions
The head pushing the cervix leads to contractions, which increases pressure and causes more contractions.
What does gain refer to in control systems?
Precision with which a control system maintains homeostasis
A large gain indicates better capability of correcting a control system.
What is the formula for gain in control systems?
Gain = Amount of correction needed / Amount of abnormality that exists after correction
Define hormesis.
Process where low-to-moderate doses of potentially harmful stress have beneficial adaptive effects
What is adaptation in the context of cellular homeostasis?
Change in structure/function of cells/organs resulting in improved ability to maintain homeostasis during stress
What is acclimation?
Environmental adaptation
For example, heat exposure.
What are the types of cell signaling mechanisms?
- Intracrine
- Juxtacrine
- Autocrine
- Paracrine
- Endocrine
What is intracrine signaling?
Chemical signaling within the same cell
Define juxtacrine signaling.
Chemical signaling with a neighboring cell
What is autocrine signaling?
Chemical signaling where messenger is released into cytoplasm and acts on same cell
What does paracrine signaling involve?
Chemical signaling that acts upon nearby cells
How does endocrine signaling function?
Chemical signals (hormones) carried through the body in bloodstream
