Blood Sugar Regulation, Osmoregulation, and Cell Water Balance

Practice flashcards reviewing blood sugar regulation, liver and pancreas negative feedback mechanisms, osmoregulation, osmosis, and cell tonicity scenarios.

How does the body respond when blood glucose levels rise after eating?

The pancreas releases the hormone insulin, which promotes the uptake of glucose by tissue cells and stores extra glucose in the liver as glycogen, lowering blood sugar.

How does the body respond when blood glucose levels drop?

The pancreas releases the hormone glucagon, which stimulates the liver to break down stored glycogen into glucose and release it into the blood, raising blood sugar.

What is glycogen, and what is its role in blood sugar regulation?

Glycogen is the stored form of glucose in the liver that is formed when insulin is present and broken down into glucose when glucagon is released.

What is negative feedback as demonstrated in blood glucose regulation?

A control response that reverses a change to return a system toward a set point, keeping blood sugar levels stable and maintaining homeostasis.

What is osmoregulation?

The process by which living organisms maintain a balance of water and solutes (like salts and sugars) to keep their cells functioning properly.

What is a solute, and what are common examples found in the blood?

A solute is a substance that dissolves in a solvent (such as water) to form a solution; examples present in blood include sugars, salts, and minerals.

How is osmosis defined, and what physical process drives it?

Osmosis is the movement of water across cell membranes from an area of lower solute concentration (more water) to an area of higher solute concentration (less water), driven by diffusion.

What happens to red blood cells placed in a hypertonic solution?

The cells shrivel because the concentration of water is higher inside the cell than outside, causing water to flow out of the cell.

What happens to red blood cells placed in an isotonic solution?

The cells maintain their normal shape and balance because the concentration of water inside and outside the cell is equal.

What happens to red blood cells placed in a hypotonic solution?

The cells swell and may lyse (burst) because the concentration of water is lower inside the cell than outside, causing water to enter the cell.

If an animal cell with $26\%$ glucose is placed in an external environment of $26\%$ glucose, what will happen to the cell?

The cell will stay the same because the solute and water concentrations are equal inside and outside.

If an animal cell with $15\%$ sugar is placed in an environment of $35\%$ sugar, what will happen to the cell?

Water will move out of the cell toward the higher solute concentration, causing the cell to shrink.

If a plant cell with $19\%$ solute is placed in a solution containing $5\%$ solute, what will happen to the cell?

Water will move into the cell toward the higher solute concentration, causing the cell to swell.

If a cell containing $18\%$ salt is surrounded by a solution of $94\%$ salt, in which direction will water flow?

Water will flow out of the cell from the area of lower solute concentration ($18\%$) toward the area of higher solute concentration ($94\%$).

According to hormone secretion data, what happens to the secretion rates of insulin and glucagon as glucose concentration increases?

The secretion rate of insulin increases, whereas the secretion rate of glucagon decreases.

What units are used to measure glucose concentration and hormone secretion rates in the hormone secretion model?

Glucose concentration is measured in $\text{mM}$, and the secretion rates of insulin and glucagon are measured in $\mu\text{g/min}$.

How would an individual's blood glucose be affected if their pancreas produces normal amounts of insulin, but body cells have a reduced ability to respond to it?

Blood glucose would remain elevated because body cells would absorb less glucose from the blood.

What evidence supports the claim that insulin and glucagon function as part of the same negative feedback mechanism despite having opposite effects?

Both hormones are produced by the pancreas and work in opposition to restore blood glucose concentration back to its normal homeostatic range.

How does the negative feedback loop regulate blood sugar when a person skips lunch?

The stimulus is low blood sugar, which triggers the pancreas to secrete glucagon; glucagon stimulates the liver to break down glycogen into glucose and release it into the blood.

Why do daily fluctuations and peaks in blood glucose concentration not mean that homeostasis has failed?

Homeostasis is dynamic rather than a static flat line; temporary peaks occur after eating, and negative feedback mechanisms continually respond to bring glucose back within the normal range.

How would a daily blood glucose graph differ if an individual could not release enough insulin after meals?

Post-meal glucose peaks would reach much higher levels and remain elevated for longer periods because cells cannot take in glucose and the liver cannot store it as glycogen.