Homeostasis Flashcards
Homeostasis
- Maintenance of a relatively stable internal environment despite continuous outside changes
- A dynamic state of equilibrium
Homeostatic Control Mechanisms
Involve continuous monitoring and regulation of many factors (variables)
Nervous and endocrine systems accomplish the communication via
nerve impulses and hormones
Components of a Control Mechanism
- Receptor
- Control center
- Effector
Receptor
(sensor)
Monitors the environment
Responds to stimuli (changes in controlled variables)
Control center
Determines the set point at which the variable is maintained
Receives input from receptor
Determines appropriate response
Effector
Receives output from control center
Provides the means to respond
Response acts to reduce or enhance the stimulus (feedback)
Negative Feedback
The response reduces or shuts off the original stimulus
Examples:
Regulation of body temperature (a nervous mechanism)
Regulation of blood volume by ADH (an endocrine mechanism)
Negative Feedback: Regulation of Blood Volume by ADH
- Receptors sense decreased blood volume
- Control center in hypothalamus stimulates pituitary gland to release antidiuretic hormone (ADH)
- ADH causes the kidneys (effectors) to return more water to the blood
Thermoregulation
the process by which animals maintain an internal temperature within a tolerable range
Endotherms
animals that primarily produces its own heat
Ectotherms
animals that primarily gains heat through the environment
Homeotherms
animals that have a constant body temperature
Poikilotherms
animals whose body temperature varies depending on the environment
Organisms exchange heat by four physical processes
radiation, evaporation, convection, and conduction
the integumentary system
skin, hair, and nails; heat regulation in mammals