homeostasis

positive feedback

Some processes in the body are regulated by positive feedback. Positive feedback is when a response to an event increases the likelihood of the event to continue. An example of positive feedback is milk production in nursing mothers. As the baby drinks her mothers milk, the hormone prolactin, a chemical signal, is released. The more the baby suckles, the more prolactin is released, which causes more milk to be produced. Other examples of positive feedback include contractions during childbirth. When constrictions in the uterus push a baby into the birth canal, additional contractions occur.

maintaining homeostasis

So how does your body maintain homeostasis? The regulation of your internal environment is done primarily through negative feedback. Negative feedback is a response to a stimulus that keeps a variable close to a set value ( Figure For example, your body has an internal thermostat. During a winter day, in your house a thermostat senses the temperature in a room and responds by turning on or off the heater. Your body acts in much the same way. When body temperature rises, receptors in the skin and the brain sense the temperature change. The temperature change triggers a command from the brain. This command can cause several responses. If you are too hot, the skin makes sweat and blood vessels near the skin surface dilate. This response helps decrease body temperature. Another example of negative feedback has to do with blood glucose levels. When glucose (sugar) levels in the blood are too high, the pancreas secretes insulin to stimulate the absorption of glucose and the conversion of glucose into glycogen, which is stored in the liver. As blood glucose levels decrease, less insulin is produced. When glucose levels are too low, another hormone called glucagon is produced, which causes the liver to convert glycogen back to glucose. For additional information, see Homeostasis at . Feedback Regulation. If a raise in body temperature (stimulus) is detected (recep- tor), a signal will cause the brain to main- tain homeostasis (response). Once the body temperature returns to normal, neg- ative feedback will cause the response to end. This sequence of stimulus-receptor- signal-response is used throughout the body to maintain homeostasis.

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homeostasis and feedback regulation

When you walk outside on a cool day, does your body temperature drop? No, your body temperature stays stable at around 98.6 degrees Fahrenheit. Even when the temperature around you changes, your internal temperature stays the same. This ability of the body to maintain a stable internal environment despite a changing environment is called home- ostasis. Homeostasis doesnt just protect against temperature changes. Other aspects of your internal environment also stay stable. For example, your body closely regulates your fluid balance. You may have noticed that if you are slightly dehydrated, your urine is darker. Thats because the urine is more concentrated and less water is mixed in with it.

instructional diagrams

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questions

your body temperature drops on a cold day.

a. true

-->  b. false

your body temperature always tries to be around 98.6 degrees fahrenheit, even if it is very hot outside.

-->  a. true

b. false

your bodys internal thermostat is regulated by

-->  a) negative feedback.

b) positive feedback.

c) homeostasis.

d) receptors in the skin and the brain.

which is an example of positive feedback?

a) maintaining stable blood glucose levels

-->  b) the production of milk in a nursing mother

c) maintaining a stable body temperature

d) all of the above

which hormone stimulates the removal of sugar from the blood?

a) glucose

b) glucagon

-->  c) insulin

d) glycogen

which is the proper sequence of events in maintaining homeostasis?

a) 1. signal, 2. receptor, 3. stimulus, 4. response

b) 1. stimulus, 2. response, 3. signal, 4. receptor

c) 1. receptor, 2. stimulus, 3. signal, 4. response

-->  d) 1. stimulus, 2. receptor, 3. signal, 4. response

which is an example of negative feedback?

-->  a) maintaining stable blood glucose levels

b) the production of milk in a nursing mother

c) contractions of the uterus during childbirth

d) all of the above

diagram questions

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