Homeostasis

The human body comprises many levels of organization, including organ systems. Human body temperature is regulated by a combination of three organ systems that work together to maintain homeostasis. They are the nervous system, the muscular system, and the circulatory system. These three systems are shown in the image Temperature regulation is controlled by a feedback loop. A positive feedback loop works to intensify the effect of a change, while a negative feedback loop works to decrease the effect of a change.

Humans sweat to reduce their body temperature and maintain homeostasis. Which BEST describes the feedback mechanism involved in sweating?

• It is a negative feedback loop because it is an attempt to reverse a change in the body's condition.

• It is a negative feedback loop because the body is pulling in heat from the skin.

• It is a positive feedback loop because the body is adding heat to the skin.

• It is a positive feedback loop because it is an attempt to intensify a change in the body's condition

Answer explanation

Sweating is a negative feedback loop because it helps to reverse the increase in body temperature, promoting cooling and restoring homeostasis.

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Which BEST describes how Type 2 Diabetes affects feedback mechanisms in the body?

• The feedback mechanisms no longer function to increase blood sugar levels.

• The feedback mechanisms no longer function to lower blood sugar levels

• The feedback mechanisms work slower to increase blood sugar levels

• The feedback mechanisms work faster to lower blood sugar levels

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NGSS.HS-LS1-3

Austin and Marissa selected two coneflower plants and put them in separate containers. They gave one very little water (simulating drought conditions) and gave the other regular water each day. They noted the plant that received less water had fewer open stomata and seemed to be growing slower over the summer.

What could be happening in each plant? Select all that apply.

• The plant receiving water is growing faster because its stomata are open, and it is losing more moisture through the stomata. The water it loses will help it grow, and the plant does not need to close stomata to retain its osmotic balance

• The plant under drought conditions is losing less moisture through open stomata because it has been receiving less moisture overall. Having open stomata would not affect the moisture loss, and the plant would remain in a neutral osmotic state.

• The plant under drought conditions is closing its stomata to prevent moisture loss and to help conserve water. It is growing more slowly because it is conserving water to retain its osmotic state and nutrients in order to stay alive.

• The plant that is receiving water has more open stomata because it does not need to conserve water as much as the plant not receiving water. It can lose more moisture from the open stomata; it does not have to close stomata to conserve moisture.

• The plant that is receiving less water is growing more slowly because it doesn't have enough water to carry out life processes. The open stomata are a result of exposure to light, not how much water the plant receives

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Using information from Marissa and Austin's research, complete the statement about the relationship between precipitation and open stomata.

Drag and drop the correct answers to the boxes to make the statement true

The percent of open stomata​ ​ (a)   when plant is under drought conditions. This is because the plant needs to ​ ​ (b)   ​ water loss.

• decreases
• reduce
• increases
• elevate

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NGSS.MS-LS1-5

NGSS.MS-LS2-1

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When would a buffer system become activated in a human?

• when too much salt has been ingested, causing the blood to become hypertonic

• when too many carbohydrates have been ingested, raising blood glucose levels

• after exercise, when the bloodstream pH is acidic, because excess CO₂ is present

• after exercise, when the body temperature has increased

Answer explanation

A buffer system is activated when the blood pH drops, such as after exercise when excess CO2 leads to acidity. This helps maintain pH balance, making the correct choice about post-exercise conditions.

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NGSS.HS-LS1-3

A scientist is viewing samples of red blood cells taken from three different solutions. The diagram below shows the three samples of cells.
Which sample most likely contains red blood cells that were placed in a solution with a high salt concentration?

• First One

• Second one

• Third One

• None of them

Answer explanation

The first sample most likely contains red blood cells in a high salt concentration solution, causing them to shrink (crenate) due to osmosis, as water moves out of the cells to balance the salt concentration outside.

The Sun transfers heat to Jane and Theo’s bodies as they sit on the sunny bench, increasing their body temperature. Which of the following responses by their bodies would help decrease their temperature and maintain homeostasis? Choose all that apply.

• Sweating; the water released from their skin will evaporate

• Vasodilation; their skin will turn red as blood is moved to the surface of the skin.

• Shivering; their muscles will begin moving quickly.

• Vasoconstriction; their extremities will turn pale or blue as blood moves to the core of the body.

• Goosebumps; the muscles under the hair in their skin will contract

Using information from Figure 2, complete the statement below about how Jane’s and Theo’s bodies reacted when they stood in the cold room. Drag and drop the correct answers into the boxes to make the statement true. The initial stimulus jane and Theo experienced in the first five minutes of the cold room was a(n)​ (a)   in body temperature. This was a result of the body moving​ (b)   homeostasis. Their bodies responded by ​ (c)   their body temperature.

• decrease
• away from
• raising
• increase
• towards
• lowering