Which of the following is an age-related change affecting the elderly?

The correct answer is the loss of beta 2 receptor sites, as this is a significant age-related change that is observed in the elderly population. As individuals age, there is a decline in the number and responsiveness of various hormone and neurotransmitter receptors, including beta-adrenergic receptors. Beta 2 receptors are responsible for mediating responses in various tissues, including smooth muscle relaxation and modulation of cardiovascular function. This loss can lead to diminished responses to certain medications and hormones, which is an important consideration in managing the health of older adults.

Other choices reflect changes that do not align with typical aging processes. For example, increased muscle mass is generally not characteristic of aging; rather, there is usually a gradual decline in muscle mass and strength, often termed sarcopenia. Improved vision is also not typical, as many elderly individuals experience conditions like presbyopia or other age-related vision changes. Additionally, increased kidney function is not expected; instead, renal function commonly declines with age, impacting the excretion and metabolism of various substances, including medications.