1.2 Homeostasis

Johnny eats three glazed doughnuts for breakfast, which caused his blood glucose levels to increase. In response to this, his pancreas secretes insulin, which results in the transfer of glucose from the blood into the cells. This process decreases Johnny's blood glucose and he starts to feel hungry again. Johnny is studying for a test and doesn't have time to go home for lunch. As his blood glucose levels continue to drop his pancreas then secretes glucagon. Johnny's liver then responds by releasing glucose into the blood. Which of the following statements about this scenario is correct? 1. Blood sugar level is the set point in this scenario. 2. The release of insulin helps with negative feedback in this scenario. 3. The release of glucagon helps with negative feedback in this scenario. 4. The release of insulin helps through positive feedback 5. The release of glucagon helps through positive feedback 1 1, 4 1, 3, 5 1, 4, 5 1, 2, 3 2, 4

Answer: 1,2,3

A researcher was studying the control of the level of Hormone X in rats. If the level of hormone X in the blood is controlled by a positive feedback loop, then injecting a rat with a small amount of Hormone X would have the following effect: (A)stimulate the release of more Hormone X into the blood. (B)block the release of more Hormone X into the blood. (C)block the effect of Hormone X in the rat. (D)none of the above.

Answer: A

Bob has just finished donating plasma to earn some extra money. Donating plasma took longer than he thought and he is in a hurry to meet up with some friends. As he stands up and starts to walk toward the door he begins to feel light-headed due to decreased blood flow to his brain. Luckily, another person saw Bob beginning to faint and caught him just in time. When Bob awakes he is told that he fainted due to orthostatic hypotension; a rapid drop in blood pressure. Fainting helps Bob's body restore homeostasis by __________. (A) increasing blood pressure and blood flow to the head (B)decreasing his heart rate through the baroreceptor reflex (C)further decreasing blood pressure to allow more blood flow to the brain (D)activating a positive feedback loop

Answer: A

What is NOT an example of the body systems trying to maintain homeostasis? (A)laughter (B)hyperventilation (C)shivering and goose bumps (D)increased heart rate

Answer: A

Which is an example of a positive feedback mechanism? (A)During pregnancy, uterine stretching : stimulates uterine muscle contraction (B)Increase blood pressure : heart rate decreases (C)Rise in body temperature : sweat glands increase secretion (D)Increase in blood glucose levels : stimulates insulin secretion

Answer: A

A researcher discovered a new hormone in the human body that raises blood calcium levels. According to the principles of negative feedback, this hormone would be secreted when (A) blood calcium levels increase. (B) blood calcium levels decrease. (C) when blood calcium levels increase or decrease from the set point. (D) none of these would cause the secretion of this hormone.

Answer: B

Male saltwater crocodiles can reach lengths of 17 feet, with the largest salt water crocodile ever found reaching a length of over 21 feet. These massive animals are loaded with muscle yet they have dramatic insufficiencies in their ability to thermoregulate. In other words, they depend on the sun to warm them up and the water to cool them off. If the crocodile senses a change in temperature it must move to the water or bask in the sun to regulate body temperature. Based on your knowledge of the thermoregulatory systems in humans and the feedback loops involved, which of the following statements MOST likely explains why the crocodiles cannot thermoregulate like humans? (A)Saltwater crocodiles lack a control center and therefore lack the ability to properly signal any effectors to compensate for any temperature change. (B) Saltwater crocodiles have the ability to accomplish body temperature homeostasis, but they use different effectors than humans (C) Saltwater crocodiles lack an efferent pathway so they cannot ever respond to fluctuations in temperature changes. (D) Saltwater crocodiles have the ability to accomplish body temperature homeostasis, but they lack a receptor to detect temperature change.

Answer: B

Some people compare the mechanisms that maintain homeostasis to driving the speed limit. Which of the following situations provides the best analogy of positive feedback in our driving example? (A)The car runs out of gas (B)A police officer is seen in the rear view mirror and the driver gets scared and steps on the gas (C)A dog runs out into the road and the driver steps hard on the brake (D)The passenger in the car asks the driver to slow down

Answer: B

Which of the following BEST explains why a person with a fever is shivering but is hot to the touch? (A)The integrating (control) center controlling their body temperature isn't responding to the afferent signals. (B) The set point for the homeostatic temperature has been increased and their body is trying to match the new set point. (C)The skeletal muscles are being over stimulated by the efferent signals. (D)The receptors in the skin are not functioning correctly.

Answer: B

Which of the following contains three components of the homeostatic control system? (A)stimulus, integrating (control) center, set point (B)receptor, integrating (control), effector organ (C)receptor, effector organ, set point (D)receptor, integrating (control) center, positive feedback

Answer: B

Regarding the body, homeostasis is maintaining a constant __________. (A)external environment. (B)internal environment. (C)normal range of a particular variable. A and C B and C

Answer: B and C

Ben Hitt was involved in a motorcycle accident and suffered severe trauma to his leg resulting in severe blood loss. Initially, Ben's heart rate elevated, but his blood pressure continued to decrease. After the bleeding was stopped and Ben was given a blood transfusion, his blood pressure increased back to set point. Which of the following statements is MOST consistent with the symptoms and results. (A)Ben's body never even attempted negative feedback in this situation (B) Negative feedback systems were adequate and a blood transfusion was probably unnecessary (C) The blood transfusion overcame the effects of a likely positive feedback loop (D) Blood pressure normally drops at times of trauma, blood loss and pain and this is why the heart rate increased. (E) b and d are both correct

Answer: C

Blood pressure decreases and the body responds in a way that causes the blood pressure to decrease even more. Which of the following would fit this statement the BEST? (A)Homeostasis (B)Negative feedback (C)Positive feedback (D)Regulation

Answer: C

What statement is true about homeostasis? (A) is the acceptance that the environment within the body is in a state of constant change (B) variables have a large range for deviation prior to regulation by feedback mechanisms (C) is the maintenance of a variable around a set point (D) the organ systems work against each other to develop the balance necessary in the body

Answer: C

Which of the following is NOT an example of a negative feedback loop? (A) Low blood sugar causing the liver to break down glycogen and release sugar into the blood. (B) Internal bleeding causing the heart rate to increase. (C) High body temperature causing muscle shivering and increased metabolism. (D) When the release of estrogen from the ovary shuts down the production and release of more estrogen.

Answer: C

Which of the following is an example of a "beneficial" deviation from normal set point in homeostasis? (A)water retention at high altitudes (B)inadequate delivery of blood to the heart (C)high blood pressure during exercise (D)excess release of the thyroid hormones

Answer: C

Feedback mechanisms contain all of the following EXCEPT a(n) __________. (A)set point (B)control center (C)effector (D)equilibrator

Answer: D

Which is a true statement about positive feedback? (A) It can create a cycle that leads away from homeostasis (B)It means any deviation from the set point is made smaller or is resisted (C)It has at least 3 components: a receptor, a control center and an effector (D)The response is homeostatic and common in healthy individuals.

Answer:A