Chapter 3: The Remarkable BodyThe Body’s Cells- Cells- the smallest units in which independent life can exist- Enzyme- any of a great number of working proteins that speed up a specific chemical reaction, such as breaking the bonds of a nutrient without undergoing change themselves- Fat cells- cells that specialize in the storage of fat or form the fat tissue- Inborn error of metabolism- a genetic variation present from birth that may result in disease- Phenylketonuria (PKU)- an inborn error of metabolism that interferes with the body’s handling of the amino acid phenylalanine, with potentially serious consequences to the brain and nervous system in infancy and childhood.- Tissues- systems of cells working together to perform specialized tasks (muscles, nerves, blood, bone)- Organs- discrete structural units made of tissues that perform specific jobs (heart, liver, brain)- Body system- a group of related organs that work together to perform a function (circulatory, respiratory, nervous systems)The Body Fluids and the Cardiovascular System- Blood- the fluid of the cardiovascular system; composed of water, red and white blood cells, nutrients, oxygen, etc.- Lymph- the fluid that moves from the bloodstream into tissue spaces and then travels in its own vessels, which eventually drain back into the bloodstream- Arteries- blood vessels that carry blood containing fresh oxygen supplies from the heart to the tissues- Veins- blood vessels that carry blood, with the carbon dioxide it has collected, from the tissues back to the heart- Capillaries- minute, web like blood vessels that connect arteries to veins and permit transfer of materials between blood and tissues- Plasma- the cell-free fluid part of blood and lymph- Extracellular fluid- fluid residing outside the cells that transports materials to and from the cells- Intracellular fluid- fluid residing inside the cells that provides the medium forcellular reactions- Lungs- the body’s organs of gas exchange. Blood circulating through the lungs releases its carbon dioxide and picks up fresh oxygen to carry to the tissues- Intestine- the body’s long, tubular organ of digestion and the site of nutrient absorption- Liver- a large, lobed organ that lies just under the ribs. It filters the blood, removes and processes nutrients, manufactures materials for export to otherparts of the body, and destroys toxins or stores them to keep them out of the circulatory system- Kidneys- a pair of organs that filter wastes from the blood, make urine, and releases it to the bladder for excretion from the bodyThe Hormonal and Nervous Systems- Hormones- chemicals that are secreted by glands into the blood in response to conditions in the body that require regulation; serving as messengers, acting on other organs to maintain constant conditions- Pancreas- an organ with two main functions- Endocrine function: the making of hormones such as insulin, which it releases directly into the blood- Exocrine function: the making of digestive enzymes, which it releases through a duct into the small intestine to assist in digestion- Insulin- a hormone from the pancreas that helps glucose enter cells from the blood- Glucagon- a hormone from the pancreas that stimulates the liver to release glucose into the bloodstream- Cortex- the outermost layer of something (ex. The brain cortex, where conscious thoughts take place)- Hypothalamus- a part of the brain that senses a variety of conditions in the blood, such as temperature, glucose content, salt content, etc. It signals other parts of the brain or body to adjust those conditions when necessary- Fight-or-flight reaction- the body’s instinctive hormone- and nerve-mediated reaction to danger (also known as stress response)- Neurotransmitters- chemicals that are released at the end of a nerve cell when a nerve impulse arrives there. They diffuse across the gap to the next cell and alter the membrane of that second cell to either inhibit or excite it- Epinephrine- the major hormone that elicits the stress response- Norepinephrine- a compound related to epinephrine that helps to elicit the stress response- Metabolism- the sum of all physical and chemical changes taking place in living cells; includes all reactions by which the body obtains and spends the energy from foodThe Immune System- Microbes- bacteria, viruses, or other organisms invisible to the naked eye, some of which cause diseases (also called microorganisms)- Antigen- a microbe or substance that is foreign to the body- Immune system- a system of tissues and organs that defend the body against antigens, foreign materials that have penetrated the skin or body linings- Lymphocytes- white blood cells that participate in the immune response; B-cells and T-cells- Phagocytes- white blood cells that can ingest and destroy antigens. They are the first to defend body tissues against invaders. It forms a pocket in its own outer membrane and engulfs the invader, which it can attack with oxidizing chemicals, digest, or destroy the invader. They leave a chemical trail behind so that other cells can find the infection faster.- T-Cells- lymphocytes that attack antigens. T stands for the thymus gland of the neck, where the T-cells are stored and matured. These cells read and remember the chemical messages that phagocytes use to identify invaders. T-cells seek out and destroy all invaders with the same identity. (defend against fungi, viruses, parasites, etc)- B-Cells- lymphocytes that attack produce antibodies. B-cells respond rapidly to infections by releasing antibodies into the bloodstream they travel to the site of the infection and stick to the surface of the foreign particles, killing or inactivating them. - Inflammation- the immune systems response to cellular injury characterized by an increase in white blood cells, redness, heat, pain, and swelling. The Digestive System- The preference for sweet, salty, and fatty tastes seems to be inborn and can lead to overconsumption of foods that offer them- The digestive tract is a flexible, muscular tube that digests food and absorbs its nutrients and some non nutrients- Digestive system- the body system composed of organs that break down complex food particles into smaller, absorbable products. The digestive tract and alimentary canal are names for the tubular organs that extend from the mouth to the anus. - Digest- to break molecules into smaller molecules; a main function of the digestive tract with respect to food-
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