Dan has been lost in the desert for 2 days with very little water. As a result of this exposure, you would expect to observe which of the following? 
(a) Increased ADH levels
(b) Decreased blood osmolarity
(c) Normal urine production
(d) Increased blood volume
(e) Cells enlarged with fluid

Verified step by step guidance

1. Step 1: Understand the physiological context. Dan has been without much water for 2 days, which means his body is likely experiencing dehydration.
2. Step 2: Recall the role of Antidiuretic Hormone (ADH). ADH is released by the posterior pituitary gland in response to increased blood osmolarity (concentration of solutes in the blood) to conserve water by reducing urine output.
3. Step 3: Analyze the expected changes in blood osmolarity. With dehydration, water loss exceeds solute loss, so blood osmolarity increases rather than decreases.
4. Step 4: Consider urine production. Due to increased ADH, the kidneys will conserve water, leading to decreased urine volume, not normal urine production.
5. Step 5: Evaluate blood volume and cell size. Dehydration causes blood volume to decrease and cells to shrink as water moves out of cells to balance osmolarity, so cells would not enlarge with fluid.

Key Concepts

Antidiuretic Hormone (ADH) Function

ADH is a hormone that helps the body conserve water by reducing urine output. When the body is dehydrated, ADH levels increase to promote water reabsorption in the kidneys, concentrating the urine and maintaining blood volume.

Blood Osmolarity and Hydration Status

Blood osmolarity measures the concentration of solutes in the blood. Dehydration increases blood osmolarity because of water loss, signaling the body to retain water and restore balance through mechanisms like ADH release.

Cellular Fluid Balance During Dehydration

In dehydration, extracellular fluid becomes more concentrated, causing water to move out of cells by osmosis. This results in cell shrinkage rather than enlargement, as cells lose water to balance osmotic pressure.