Which term describes a mechanism by which the internal conditions of an organism are kept at set values without regard to the external conditions?

a) Negative feedback.
b) Conformational homeostasis.
c) Regulatory homeostasis.
d) Thermoregulation.

c) Regulatory homeostasis.

Regulatory homeostasis involves adjusting the internal conditions of an organism to set values without regard to the external conditions.

Which of the following actions is not a function of the epithelium?

a) Regulates the excretion of waste.
b) Creates an internal environment that is different from the external environment.
c) Allows the internal environment to alter its conditions to match those of the external environment.
d) Controls the exchange of nutrients between the internal and external environments.

c) Allows the internal environment to alter its conditions to match those of the external environment.

The epithelium allows the internal environment to remain constant even if the external environment changes.

True or false? Organisms must maintain homeostasis because optimal enzyme activity is achieved within a very narrow range of conditions.

a) True.
b) False.

a) True.

Enzyme activity depends on conditions within a cell, such as temperature and pH, which must be kept within a certain narrow range.

Which component of a homeostatic system sends instructions based on sensory information?

a) Sensor.
b) Effector.
c) Integrator.
d) Set point.

c) Integrator.

An integrator sends instructions to an effector based on sensory information.

Which component of a homeostatic system perceives changes in some parameter of the environment?

a) Effector.
b) Integrator.
c) Sensor.
d) Set point.

c) Sensor.

A sensor perceives changes in some parameter of the environment.

Which of the following actions acts to warm a homeothermic body?

a) Shivering.
b) Panting.
c) Sweating.
d) Dilating blood vessels.

a) Shivering.

Shivering generates metabolic heat and warms the body.

Which of the following statements describes a negative feedback response?

a) After a meal, blood sugar levels in the body rise; insulin is secreted to lower blood sugar levels.
b) The onset of contractions during childbirth stimulates the release of a hormone that stimulates further contractions.
c) A person who loses 3 pounds continues to diet to lose an additional 10 pounds.
d) The arrival of platelets at a wound site stimulates the recruitment of more platelets to form a clot.

a) After a meal, blood sugar levels in the body rise; insulin is secreted to lower blood sugar levels.

The actions of insulin reverse the internal conditions of high blood sugar levels in the body.

Which of these is an example of negative feedback?

a) As a blood clot begins to form, the process of its formation gets faster and faster.
b) After you eat, glucagon stimulates an increase in blood sugar levels.
c) After you eat, insulin stimulates the lowering of blood sugar levels.
d) The digestive enzyme pepsinogen is converted to pepsin by the action of hydrochloric acid; pepsin itself can then convert pepsinogen into pepsin.
e) Once labor begins, contractions increase in frequency and intensity.

c) After you eat, insulin stimulates the lowering of blood sugar levels.

Eating raises blood sugar levels; insulin stimulates the lowering of blood sugar level. In this example the response to the stimulus (increased blood sugar levels) opposes that stimulus (by lowering blood sugar levels).

An example of a properly functioning homeostatic control system is seen when

a) the blood pressure increases in response to an increase in blood volume.
b) the kidneys excrete salt into the urine when dietary salt levels rise.
c) the level of glucose in the blood is abnormally high whether or not a meal has been eaten.
d) the core body temperature of a runner rises gradually from 37°C to 45°C.
e) a blood cell shrinks when placed in a solution of salt and water.

b) the kidneys excrete salt into the urine when dietary salt levels rise.
Which of the following minerals is associated with its use in animals?

a) iodine – important in nerve function
b) calcium – construction and maintenance of bone
c) magnesium – cofactor in enzymes that make ATP
d) iron – necessary for thyroid function
e) sulfur – ingredient of nucleic acids

b) calcium – construction and maintenance of bone
Some nutrients are considered “essential” in the diets of certain animals because

a) only some foods contain them.
b) they are necessary coenzymes.
c) they cannot be manufactured by the organism.
d) only those animals use the nutrients.
e) they are subunits of important polymers.

c) they cannot be manufactured by the organism.
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