hnology, and many beneficial medical breakthroughs (Lafferty et al., 1996, 55). This large increase in life expectancies does not necessarily mean that human bodies can endure heavier use, or more wear and tear, but that it takes longer for our bodies to deteriorate now than it did in previous years. At the molecular level, lipofuscins, or aging pigments, appear with increasing frequency in non-dividing cells. Because they contain oxidized lipids, it has been theorized that they are products of oxidative chemical reactions such as those involving free radicals (Ricklefs and Finch, 1995, 34). Modifications in Hormonal and Neuroendocrine Systems The pituitary, ovaries, and testes are part of a system of glands that secrete hormones into the blood stream and which are controlled by the brain. This system is called the neuroendocrine system. At puberty, a signal is sent by the pituitary gland to the ovaries and testes, telling them to produce more sex hormones such as estrogens and progesterone in women and androgens in men. In women, menopause, a stage in which the reproductive system is shut down, is reached. From this point in a woman=s life these hormones are no longer produced and many changes are experienced. Because some neurons can become Aaddicted@ to estrogens, the absence of these hormones induces the brain to respond in different ways, such as sending a surge of blood to the skin. This is sometimes called a Ahot flash@ (Ricklefs and Finch, 1995, 37). Unlike hot flashes, a woman may experience harmful or dangerous changes because of menopause: osteoporosis, or the loss of compact bone is accelerated because bone-mineral metabolism is dependent on estrogen. Once this condition has reached a certain stage, it reduces the ability of bones to support body weight. It also immensely elevates the risk of bone fractures. In fact, as a woman increases in age, her risk of bone fracture due to osteoporosis increases exponentially (Ricklefs ...
