Cellular Homeostasis

Vocab in a Minute:

• Homeo: Same (Prefix)

• Stasis: State (Root word)

​Body Systems and Homeostasis

• Body Systems Work Together: Body systems are connected because changes in one system affect others (e.g., heart rate and lung function).

• Failure to Maintain Homeostasis: If the body cannot maintain homeostasis, it can lead to serious consequences or even death.

​Homeostasis and Feedback Loops

• Homeostasis: The process by which organisms maintain a stable internal environment.

• Negative Feedback Loop: A process where the body responds to a change by trying to counteract the change.

  • Example: If body temperature rises, the brain signals the body to sweat to cool down.

• When body temperature drops too low, the body may respond by shivering and contracting muscles to generate heat.

Open Ended

What is a negative feedback loop?

Open Ended

What might your body’s response be if your body temperature is falling too low?

​Cellular Transport and Tonicity

• Osmosis: The movement of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration.

• Tonicity: The relative concentration of solutes in a solution.

  • Hypertonic Solution: A solution with a higher concentration of solutes outside the cell, causing the cell to shrink as water moves out.

  • Hypotonic Solution: A solution with a lower concentration of solutes outside the cell, causing the cell to swell as water moves in.

  • Isotonic Solution: A solution with equal concentrations of solutes inside and outside the cell, so water moves in and out equally.

• Effect of Drinking Salt Water: Drinking salt water can cause cells to shrink, leading to dehydration.

Open Ended

What happened to the cells when they were moved from fresh water to salt water?

Open Ended

What might happen to your cells if you drank ocean water?

Body Responses and Homeostasis

• Pulse and Temperature:

  • When exposed to cold, the body responds by increasing the pulse rate to maintain temperature and constricting blood vessels.

• Urinating and Homeostasis: Urination helps regulate fluid balance by removing excess water and waste from the body.

• Pupil Response to Light:

  • When exposed to bright light, the pupils contract to limit the amount of light entering the eyes. This is an example of maintaining homeostasis.

Open Ended

Follow the instructions and record initial pulse.

Open Ended

Follow the instructions and record pulse after ice water.

Open Ended

Explain why you think the individual’s pulse changed after placing their hand in ice water

Open Ended

Follow instructions on card. Use a cellphone light: What happened to the individual's pupils when a light was shined near their eyes?

Warm-Blooded vs. Cold-Blooded Organisms

• Warm-Blooded (Endothermic) Organisms: Can regulate their body temperature internally.

  • Examples: Mammals, birds.

• Cold-Blooded (Ectothermic) Organisms: Rely on external sources to regulate their body temperature.

  • Examples: Fish, reptiles, amphibians.

  • Behavior in Cold Weather: Cold-blooded organisms may slow down or seek warmth when it’s cold.

​https://www.youtube.com/watch?v=NNouyaVA6ck

Open Ended

Which type of organisms can control their own temperature?

Open Ended

What are two examples of cold blooded organisms?

Open Ended

How do cold blooded organisms behave when it’s cold outside? Why?

​Water Intoxication and Homeostasis

• Water Intoxication: Occurs when a person drinks excessive amounts of water, disrupting the balance of electrolytes in the body.

• Example: The death of Jennifer Strange shows how excessive water intake can disrupt homeostasis by causing an imbalance in the body’s fluids.

Open Ended

What was the cause of death of Jennifer Strange?

Open Ended

How does urinating help your body maintain homeostasis?

​Stomata and Plant Homeostasis

• Stomata: Small openings on the underside of leaves that allow for gas exchange.

  • Function: Stomata open to let carbon dioxide in for photosynthesis and release oxygen. They close to prevent water loss.

Open Ended

Why might leaves need cells that are able to open and close? (Hint: what might

need to enter or exit the leaf?)