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The benefits of regulating an internal variable, such as body temperature, should be evaluated.
The organ systems of animals allow them to maintain a relatively constant internal environment despite fluctuations in the external environment.
Animals vary in the degree to which they regulate the internal environment.
All animals, including fish, amphibians, and reptiles, are "cold-blooded", meaning that their body temperature can change depending on the environment.
This approach may restrict the ability of these species to live in hot environments.
Being able to adapt to many different environments is the evolutionary advantage of this approach.
Homeostasis is a dynamic fluctuation around a set point.
The bicyle takes in food and digests it to provide vitamins and minerals to the body.
Oxygen and carbon dioxide are added to the blood and removed from the body.
The blood is taken out of it's function as a source of energy and stored in the body as glycogen.
The blood sugar levels are constant.
In response to elevated blood sugar, the pancreas producesinsulin, which helps regulate glycogen storage.
Under hormonal control, the kidneys excrete salts that can affect the blood's pH.
Disease or death can result when homeostasis fails.
The nervous system is ultimately responsible for controlling homeostasis.
The brain in humans has regulatory centers that control the function of other organs.
Negative feedback systems often include regulatory centers.
A control center and a sensor are components of a homeostatic mechanism.
The control center starts an action to bring the conditions back to normal after detecting a change in the internal environment.
The sensor ceases to work when normal conditions are reached.
A negative feedback mechanism is present when the system outputs less than expected.
The control center in the brain is signaled when blood pressure rises.
The center stops sending impulses to the walls.
The control center no longer receives signals once the blood pressure drops.
A home heating system can be used to show how a negative feedback mechanism works.
You set the thermostat at a certain temperature.
When the room temperature is above or below the set point, the thermostat will detect.
The thermostat has a control center that turns the furnace off when the room is warm and on when the room is cool.
The room warms a bit when the furnace is on.
Negative feedback mechanisms usually have a fluctuation above and below normal.
Negativefeedback is used to regulate room temperature.
The control center is in the thermostat.
The control center turns off the furnace when the room is too hot.
The room cools down.
The control center turns on the furnace when the room is too cold.
TheStimulus is no longer present when the temperature goes back to normal.
The control center for body temperature is located in a part of the brain called the hypothalamus.
The control center directs the blood vessels of the skin to dilate when the body temperature is above normal.
The result is that more blood flows near the surface of the body.
The nervous system and sweat glands help lower body temperature.
Body temperature gradually decreases to 37.0degC (98.6degF).
Body temperature doesn't get cold because a body temperature below normal will cause a change in temperature.
The control center directs the blood vessels of the skin to dilate when the body temperature falls below normal.
The action conserves heat.
The control center sends nerve impulses to the muscles if the body temperature falls.
Body temperature goes up to 37.0degC after a while.
The control center is off when the temperature goes up.
When body temperature rises above normal, the hypothalamus senses the change and causes blood vessels to dilate and sweat glands to excrete, so that body temperature returns to normal.
Coldness may bring the body temperature back to normal.
The original stimuli are removed in this way.
Positive feedback can change body processes in a short period of time.
When a woman is giving birth, the head of the baby begins to press against the cervix, stimulating the sensory receptors in the birth canal.
The brain causes the pituitary to release a hormone when it reaches the brain.
The uterus contracts when roxtocin travels in the blood.
The uterus becomes stronger as labor continues and the cervix becomes more stimulated.
Positive feedback is shown in this diagram.
The signal causes a change in direction until there is a definite cutoff point.
There are changes in the metabolism that push the temperature higher.
Positive feedback loops such as those involved in childbirth, blood clotting, and the stomach's digestion help the body complete a process that has a definite cutoff point.
Discuss how negative feedback is similar to a thermostat.
Organ systems and tissues make up the organisms.
The tissues are attached to the basement.
Most of the neurons have a cell body and an axon.
Nerves contain only axons, while the brain and spine contain complete neurons.
Nerve impulses are conducted by axons.
The brain and spine are in the dorsal cavity.
The heart and lungs are in the thoracic cavity, while the abdominal cavity contains most other internal organs.
The organ system protects tissues against desiccation, trauma, and pathogens.
The skin has two regions.
There is a layer of tissue on top of each other.
Animals have different approaches to regulating certain variables.
The kidneys regulate the pH and keep the blood sugar constant, which are special contributions made by the liver.
The body systems are regulated by the nervous and hormonal systems.
Tendons and ligaments are dense.
The abdominal cavity is separated from the thoracic cavity by the ___________.
When we are hot, the hair follicles and blood vessels in the skin expand.
There is a layer between the epidermis and the dermis.
It keeps us warm.
The superficial blood vessels dilate when a person is cold.
Air conditioning lowers off when room temperature goes up.
The output cancels the input.
In nervous tissue, a nerve fiber is an axon and its myelin sheath.
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