1.2 Homeostasis

Homo:

"similar or same"

Stasis:

"standing still or remaining the same."

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, 2, & 3

1.2.1 Homeostasis

1.2.1 Homeostasis

1.2.2 Homeostatic Control Systems

1.2.2 Homeostatic Control Systems

1.2.3 Feedback Response Loop

1.2.3 Feedback Response Loop

Set Point for Sodium is?

142 mmol/L.

Set Point for Glucose is?

85 mg/dl

Set Point for Body Temperature is?

98.6

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? The car runs out of gas A police officer is seen in the rearview mirror and the driver gets scared and steps on the gas A dog runs out into the road and the driver steps hard on the brake The passenger in the car asks the driver to slow down

A police officer is seen in the rearview mirror and the driver gets scared and steps on the gas

What would happen if the body did not maintain homeostasis?

An inability to maintain homeostasis may lead to death or diseases such as: diabetes, dehydration, hyperthermia, and even allergic reactions.

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

B and C

Homeostatic Control System Drawing:

Be able to draw and explain

Ch 1.2 Quiz Homeostasis

Ch 1.2 Quiz Homeostasis

Stimuli

Changes in the environment

Homeostatic Control System

Composed of the receptor, afferent pathway, control center, efferent pathway, and effector.

Communication

Essential part of homeostasis. 2 ways pathways; nervous and endocrine systems

Negative Feedback

Feedback response loops start with a stimulus that changes a variable and ends with an effector that changes the variable. The variable is changed in a way that brings it back towards set point. (negative to indicate that the resulting change in the variable is opposite of the initial change.)

Which of the following is an example of a "beneficial" deviation from normal set point in homeostasis? Water retention at high altitudes Inadequate delivery of blood to the heart High blood pressure during exercise Excess release of the thyroid hormones

High blood pressure during exercise

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

High body temperature causing muscle shivering and increased metabolism.

Efferent Pathway

If information flows from the control center to the effector,

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

It can create a cycle that leads away from homeostasis.

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

It is the maintenance of a variable around a set point.

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 which of the following effects?

It would stimulate the release of more Hormone X into the blood.

What is not an example of the body systems trying to maintain homeostasis? Laughter Hyperventilation Shivering and goose bumps Increased heart rate

Laughter

Consider the picture below. The Y-axis represents heart rate and the X-axis represents the amount of blood lost. Which of the statements is most true for the portion labeled A on the graph?

Negative feedback appears to be active.

Blood pressure decreases and the body responds in a way that causes the blood pressure to decrease even more. Which of the following would best fit this statement? Homeostasis Negative feedback Positive feedback Regulation

Positive feedback

Consider the picture below. The Y-axis represents heart rate and the X-axis represents the amount of blood lost. Which of the statements is most true for the portion labeled B on the graph?

Positive feedback must be happening.

Which of the following contains three components of the homeostatic control system? Stimulus, integrating (control) center, set point Receptor, integrating (control), effector organ Receptor, effector organ, set point Receptor, integrating (control) center, positive feedback

Receptor, integrating (control), effector organ

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?

Saltwater crocodiles have the ability to accomplish body temperature homeostasis, but they use different effectors than humansn

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? Ben's body never even attempted negative feedback in this situation. Negative feedback systems were adequate and a blood transfusion was probably unnecessary. The blood transfusion overcame the effects of a likely positive feedback loop. Blood pressure normally drops at times of trauma, blood loss, and pain, and this is why the heart rate increased. B and D are both correct.

The blood transfusion overcame the effects of a likely positive feedback loop.

Positive Feedback

The response to a stimulus results in a change to the variable that increases the deviation from the set point. (positive feedback loops are the result of negative feedback systems that do not adequately correct the problem)

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

The set point for the homeostatic temperature has been increased and their body is trying to match the new set point.

How does the body maintain homeostasis for temperature?

To stay warm, the body can increase metabolism, divert blood flow away from the surface, or cause muscles to shiver. All of these mechanisms generate heat. To stay cool, the body releases water droplets on the surface of the skin, forming sweat, which acts to dissipate heat as the water evaporates. It all happens subconsciously.

Which is an example of a positive feedback mechanism? Uterine stretching during pregnancy: Stimulates uterine muscle contraction Increased blood pressure: Heart rate decreases Rise in body temperature: Sweat glands increase secretion Increase in blood glucose levels: Stimulates insulin secretion

Uterine stretching during pregnancy: Stimulates uterine muscle contraction

Feedback mechanisms contain all of the following except: a set point a control center an effector an equilibrator

an equilibrator

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

blood calcium levels decrease

Afferent Pathway

if communication flows toward the control center from the receptor.

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 lightheaded due to decreased blood flow to his brain. Luckily, another person saw Bob beginning to faint and caught him just in time. When Bob awakens, he is told that he fainted due to orthostatic hypotension: a rapid drop in blood pressure. Fainting helped Bob's body restore homeostasis by

increasing blood pressure and blood flow to the head

Homeostasis:

is the ability of the body to maintain relatively stable internal conditions (internal environment) even though the outside world (external environment) is changing.

Set Point:

is the physiological value around which the normal range fluctuates.

Control Centers

located throughout the body, often in the brain, and are responsible for determining the set point and the appropriate course of action to correct deviations from the set point. Communicate though Effectors

Effector

provides the means to correct the deviation; causes the body to effectively takes action

Receptor

type of sensor that monitors the environment and detects changes in variables