Anaphy Homeostasis Recit Flashcards
What is Homeostasis?
Maintenance of relatively stable conditions in the body’s internal environment
Another definition of Homeostasis
is the tendency to resist change in order to maintain a stable, relatively constant internal environment.
regulation of body temparature by a negative feedback
high temperature will be detected by sensors—primarily nerve cells with endings in your skin and brain—and relayed to a temperature-regulatory control center in your brain. The control center will process the information and activate effectors—such as the sweat glands—whose job is to oppose the stimulus by bringing body temperature down.
example of a broken negative feedback loop
Diabetes, for example, is a disease caused by a broken feedback loop involving the hormone insulin. The broken feedback loop makes it difficult or impossible for the body to bring high blood sugar down to a healthy level.
what is a negative feedback?
action in which the system responds in such a way as to reverse the direction of change
what is a positive feedback?
tend to increase the original disturbance
(stimulus) and to push the variable farther from its original value.
operation of a feedback system
1) the receptor, 2) the control center and 3) the effector
The receptor receives information that something in the environment is changing. The control center or integration center receives and processes information from the receptor and lastly, the effector responds to the commands of the control center by either opposing or enhancing the stimulus. This is an ongoing process that continually works to restore and maintain homeostasis.
Homeostatic regulation of blood pressure by a negative feedback system
Blood vessels have sensors called baroreceptors that detect if blood pressure is too high or too low and send a signal to the hypothalamus. The hypothalamus then sends a message to the heart, blood vessels, and kidneys, which act as effectors in blood pressure regulation. If blood pressure is too high, the heart rate decreases as the blood vessels increase in diameter (vasodilation), while the kidneys retain less water. These changes would cause the blood pressure to return to its normal range. The process reverses when blood pressure decreases, causing blood vessels to constrict and the kidney to increase water retention.
Positive feedback control of labor contractions during birth of a baby
The first contractions of labor (the stimulus) push the baby toward the cervix (the lowest part of the uterus). The cervix contains stretch-sensitive nerve cells that monitor the degree of stretching (the sensors). These nerve cells send messages to the brain, which in turn causes the pituitary gland at the base of the brain to release the hormone oxytocin into the bloodstream. Oxytocin causes stronger contractions of the smooth muscles in of the uterus (the effectors), pushing the baby further down the birth canal. This causes even greater stretching of the cervix. The cycle of stretching, oxytocin release, and increasingly more forceful contractions stops only when the baby is born. At this point, the stretching of the cervix halts, stopping the release of oxytocin.
