ADD and Brain Structure and Function

Scientists have access to technologies that enable them to view the brain in the same manner that X-rays help physicians check for broken bones. Some neuro-biologists, biologists who study the nervous system, use these technologies to find physical evidence in the brain structures of people diagnosed with Attention Deficit Disorder, or ADD. Some neurobiologists believe they have found subtle differences in the structure and function of the brains of people with ADD. One study, which compared...

The Natural Selection of HIV

During the asymptomatic period of HIV infection, the numbers of HIV virus particles in an infected person's bloodstream is relatively low. However, the immune response to HIV does not completely eliminate the virus. HIV persists inside immune-system structures called lymph nodes where it continues to infect and kill T4 cells. The dying T4 cells release the virus into the bloodstream, where anti-HIV antibodies quickly eliminate them. At the same time, the infected individual is maintaining a...

Learning the Basics

Describe the structure of a typical bacterium and a typical virus. 2. Describe how bacteria and viruses reproduce. 3. What roles do B cells and T cells have in the immune response 4. How do B cells and T cells produce their receptors 5. How do prions cause spongiform encephalopathies b. undergoes genetic rearrangement in response to different antigens c. is able to make many antigen receptors by rearranging DNA of immune cells d. can always devise an antibody that will bind to an antigen 7....

The Endocrine System

The endocrine system is an internal system of communication involving hormones, the glands that secrete them, and the target cells that respond to them. Secretes gonadotropin-releasing hormone (GnRH). Pituitary gland Responds to GnRH by secreting the pituitary gonodatropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Secrete adrenaline, corticosteroids, testosterone (masculinizing hormone), and estrogen (feminizing hormone). Respond to FSH and LH by secreting estrogen,...

AIDS is a Disease of the Immune System

The increased susceptibility to illness in these men resulted from a decline in their immune-system function. As is discussed in detail in Chapter 11, the role of the immune system is to maintain the integrity of the body. The cells of the immune system constantly patrol the tissues and organs of the body for anything that is not clearly produced by the body that is, anything that is non-self. Upon encountering non-self entities, the immune system acts to eliminate it this is known as an immune...

Producing Egg Cells

Oogenesis, the formation and development of female gametes, occurs in the ovaries and results in the production of egg cells (Figure 12.8a). A small percentage of these egg cells will be ovulated, and an even smaller percentage may be fertilized. While spermatogenesis begins at puberty, oogenesis actually begins while the female is still in utero, then pauses until puberty when it continues each month until menopause. Amazingly, the egg cell that helped produce you started developing inside...

Recreational Drugs and the Nervous System

Drugs affect each of us differently because of differences in overall metabolism, weight, and gender. The gender difference is clearly illustrated by the way alcohol consumption affects males and females. It takes the liver one hour to metabolize one drink (a 12-ounce beer, a 6-ounce glass of wine, or a mixed drink with one ounce of alcohol) in a person who weighs approximately 150 pounds. Prior to its metabolism, the alcohol moves from the stomach throughout the body via the circulatory...

Fishing for Useful Products

The National Cancer Institute (NCI) has taken a brute-force approach to screening species for evidence of cancer-suppressing chemicals. NCI scientists receive frozen samples of organisms from around the world, which they then chop up, mix with various chemical solvents, and separate into a number of extracts, each probably containing hundreds of components. These extracts are then tested against up to 60 different types of cancer cells to evaluate their efficacy in stopping or slowing growth of...

Modern Agriculture and Future Food Production

The use of pesticides, herbicides, fertilizer, and irrigation has increased food production so dramatically that even with twice as large a human population and a higher level of food consumption per person, food prices are lower today than they were in the 1940s. Low food prices are a sign that food is abundant. The steady decline in food prices was the basis for some economists' assessment that Earth's potential agricultural production is more than enough to support the growing human...

Cured Birth Rate And Death Rate

This results in the current growth rate of 1.2 growth rate birth rate - death rate 1.2 2.2 - 1.0 Today's relatively high growth rate, compared to the historical average of 0.1 , is the result of a large difference between birth and death rates. Prior to the Industrial Revolution, both birth rates and death rates were high in most human populations. Although women gave birth to many children, relatively few children lived to adulthood. The rapid increase in population growth rate that occurred...

Chapter

4.2 The Role of Genes in Determining Traits 4.3 Genes, Environment, and the Individual If a woman chooses a donor with the right genes, will her child look like her partner If a woman chooses a donor with the right genes, will her child look like her partner The Fairfax Cryobank is a nondescript brick building located in a quiet, tree-lined suburb of Washington, DC. Stored inside this unremarkable edifice are the hopes and dreams of thousands of women and their partners. The Fairfax Cryobank is...

Immune Response

Even though we have a single immune system, it is diversified into two subsystems so we can combat the multitude of infectious agents we encounter in our lifetimes. This diversification is a result of the differing approaches that B and T cells have to ridding the body of infectious agents once they are found. B cells provide a response called humoral immunity, while T cells provide a cell-mediated immunity. Humoral Immunity Blood and lymphatic fluid were referred to as body humours in medieval...

There Is No Immune Response to Prions

Cjd Pathology

People die from infectious diseases when their immune systems have not made enough B or T cells to fight off the infection. In some cases, infectious agents carry antigens for which no amount of DNA rearrangement can yield the proper receptor. In other cases, one group of people may be able to rearrange their DNA to produce the right receptors while others do not. This partly explains why some people do not become ill when exposed to an infectious disease, while others die from the same...

The Nervous System

Juice Cure Neveus Sistem

Every second, millions of signals make their way to your brain and inform it about what your body is doing and feeling. Your nervous system interprets these messages and decides how to respond. Responding to stimuli requires the actions of specialized cells called neurons. Neurons are capable of carrying electrical and chemical messages back and forth between your brain and other parts of the body. These electrochemical message-carrying cells are often bundled together, producing structures...

Sex Differences That Arise During Development

The hypothalamus, pituitary gland, and adrenal glands of both males and females produce the same hormones in similar amounts it is the hormones secreted by the ovaries and testes that determine biological sex differences. Once a fetus develops either testes or ovaries they produce hormones that influence the development of other structures involved in reproduction. Sex differences in reproductive organs are the result of the developmental pathways followed by males and females. These pathways...

Essay 151 ipat

Paul Ehrlich and John Holdren popularized this equation in 1971 as a way to evaluate the environmental impact (I) of a growing human population. According to their model, environmental impact is a function of not only population size (P) but the affluence (A) of the population as measured by per capita income and of the technology (T) employed by the population as measured by the amount of pollution produced per unit of income. The I PAT model allows comparisons of the environ mental damage...

Producing Sperm Cells

Secondary Spermatocyte

Spermatogenesis, the production of sperm, begins to occur in the testes at puberty. The testes consist of many highly coiled tubes surrounded by connective tissues. These tubes are the seminiferous tubules, where sperm are formed. The Leydig cells that are interspersed between the seminiferous tubules produce testosterone and other androgens (Figure 12.7a). Cells that will undergo meiosis to produce sperm line the walls of the seminiferous tubules. Recall from Chapter 6 that meiosis is cell...

I

Cancer Contact Inhibition

Nonfunctional tumor-suppressor protein fails to stop tumor growth. Nonfunctional tumor-suppressor protein fails to stop tumor growth. Figure 5.7 Control of the cell cycle. (a) Checkpoints at G1, G2, and metaphase determine if a cell will continue to divide. (b) Normal cell-cycle proteins regulate cell division. (c) Normal tumor suppressor proteins suppress cell division. Media Activity 5.1B Mutations and Cancer factor. When it is normal, the receptor on the surface of the cell signals the...

Interphase

Which Diagram Illustrates Metaphase

A cell spends most of its time in interphase Figure 5.5b . During this phase of the cell cycle, the cell is performing its required functions different cell types spend varying amounts of time in interphase. Cells that frequently divide spend less time in interphase than those that seldom divide. While in interphase, a cell may also be preparing for division, which includes the replication of DNA. Interphase can be separated into three phases, Gi, S, and G2. During the G1 first gap phase, most...

Meiosis I

Duplicated Chromosome Picture

Cell growth and preparation for division wdttk S and G phases similar to the S and G phases of mitosis wdttk S and G phases similar to the S and G phases of mitosis Interphase consists of G1, S, and G2 and is followed by two rounds of nuclear division, meiosis I and meiosis II. DNA Replication When a DNA molecule is to be replicated, or copied, it is split up the middle of the helix, and new nucleotides are added to each side of the original parent molecule, maintaining the A T and G C...

The Use and Misuse of Heritability

Remember that heritability is a measure of the relative importance of genes in determining variation in qualitative traits among individuals. For example, with a heritability of 0.30, we can say that only 30 of the variation among dairy cow milk production is due to variation in genes among these cows. However, the calculated heritability value is unique to the population in which it was measured and to the environment of that population. The specificity of heritability means that we should be...

While Most People Realize There Is A Wide Range Of Body Types And Sizes Attractiveness Tends To Be More Narrowly

Most Natural Breast Inplants

2.2 Converting Food into Energy Most college students are, for the first time, making all their own choices about food. Most college students are, for the first time, making all their own choices about food. The average college student spends a lot of time thinking about his or her body and ways to make it more attractive. While most people realize that there are a wide range of body types and sizes, attractiveness tends to be more narrowly defined by the images of men and women we see in the...