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PAP System Interaction in AnimalsHow to systems interact to perform the function of regulation in animals?

Animals contain a wide variety of organ systems that act together to help the individual survive. In so doing, they help to maintain a relatively constant internal environment for cells and tissue, a process known as homeostasis.

Despite their individual differences, nearly all animals have organ systems that perform important functions such as digestion, movement, respiration, and circulation. Coordination between such systems is essential for the maintenance of homeostasis, and the coordination can take a number of forms. In animals, maintaining homeostasis is the most important function of all body systems.

Often homeostasis is maintained by feedback inhibition. Feedback inhibition, or negative feedback, is a system in which the product or result of a process limits the process itself. If your house gets too cold, for example, the thermostat turns on the heat. As heat warms the house, the thermostat turns the heater off.

Interacting SystemsComplex animals, including mammals, use several linked body systems to respond to events in their environment. The nervous system gathers information using cells called receptors that respond to sound, light, chemicals, and other stimuli. Other nerve cells collect and process that information and determine how to respond. An example of this can be seen in the illustration below.

Animals often respond to the information processed in their nervous systems by moving around. Muscle tissue generates force be becoming shorter when stimulated by the

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nervous system. Muscles work together with some kind of skeleton to make up the musculoskeletal system.

Checkpoint:

1. To maintain a relatively constant internal environment for cells and tissue is referred to as …

2. Explain how the nervous system works with the musculoskeletal system in order for a mouse to escape the path of the cat.

Body Temperature RegulationAnother example of how body systems work together is the maintenance of body temperature. In the case of the human body temperature, several systems of the body must interact to maintain homeostasis. One of the most important of these is the system that carries information from one part of the body to the others—the nervous system. Sensory nerves carry information about body temperature to the part of the brain called the hypothalamus. The hypothalamus processes this information and decides whether to raise or lower body temperature. The hypothalamus then stimulates the release of chemical signals that affect things such as sweating, shivering, and the rate of cellular metabolism throughout the body. In carrying out these functions, the hypothalamus controls the endocrine system, which sends out chemical signals that move through the circulatory system.

Checkpoint:

3. What two systems mentioned above work together to regulate body temperature?

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4. What is the job of the hypothalamus?

5. Looking at the diagram, explain the hypothalamus’ response when a warm environment or exercise cause body temperature to increase.

How do systems interact to perform the function of nutrient absorption in animals?

Obtaining FoodBoth herbivores (plant-eaters) and carnivores (meat-eaters) must move to where their nutrients are found, and this involves careful coordination between the nervous system, muscular system, skeletal system, and sometimes the endocrine system.

The jawbone and muscles of mammalian herbivores are also adapted for side-to-side grinding movements.

Digesting FoodAnimals have evolved many ways of digesting and absorbing food. The simplest animals, such as sponges, digest food inside specialized cells that pass nutrients to other cells by diffusion. This digestive process is known as intracellular digestion. Most animals that are more complex rely on extracellular digestion. Extracellular digestion is the process in which food is first broken down outside cells in a digestive system and then absorbed by the cells.

In most animals, the digestive system is a tube that runs from the mouth to the anus. Glands such as the pancreas contribute to digestion by producing enzymes that break down food molecules. The tube is usually surrounded by smooth muscle whose contractions help speed the passage of material through it, and it is associated with the circulatory system so that nutrients can be absorbed and sent to the rest of the body.

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Carnivorous invertebrates and vertebrates typically have short digestive tracts that produce fast-acting meat-digesting enzymes. These enzymes can digest most cell types found in animal tissues. No animal produces digestive enzymes that can break down cellulose in plant tissue, however, cattle, for example, have a pouch-like extension of their esophagus called a rumen (plural=rumina), in which symbiotic bacteria digest cellulose. Animals with rumina, or ruminants, regurgitate food that has been partially digested in the rumen, chew it again, and then re-swallow it. This process is called “chewing the cud.”

Checkpoint:

6. No animal produces digestive enzymes that can break down _______________________________ in plant tissue.

7. How are the nervous system, muscular system, skeletal system, and circulatory system involved in digesting food?

Absorbing and Processing NutrientsNutrients absorbed through the inner lining of the digestive system pass into the circulatory system, where they are carried to cells throughout the body. In many animals, including humans, systems interact to regulate the level of the simple sugar glucose. Glucose is obtained from the foods we eat, and cells use glucose from the blood to serve as a source of energy for their everyday activities. Naturally, right a meal, as the body absorbs food molecules, the level of glucose in the blood begins to rise. The pancreas secretes insulin. Insulin is a hormone that prompts glucose to move from the flood into body cells, resulting in a lower glucose level in the blood. As the body uses glucose for energy, the pancreas releases stored glucose to keep the level of sugar from dropping too low.

The pancreas’ role in keeping blood glucose levels within a certain range is critical. If there is too little glucose, the cells of the nervous system will slow down to the point that you may lose consciousness and pass out. On the other hand, too much glucose gradually damages cells in the eyes, kidneys, heart, and even the immune system. Abnormally high

Food intake increases blood glucose level

INSULINpromotes glucose

uptake

Between meals, blood glucose level drops.

GLUCAGONpromotes

breakdown of glycogen

Pancreas releases insulin or glucagon in

response to blood glucose

levels.

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levels of glucose are associated with a disease called diabetes. In diabetes, changes occur in either the pancreas or body cells that affect the cells’ ability to absorb glucose. Diabetes, one of the fastest growing health problems in the developed world, is the result of failure of homeostasis with respect to blood glucose levels.

8. What is the role of the pancreas? What body system does it belong to?

9. How are the circulatory and endocrine systems involved in absorbing and processing nutrients?

10. Diabetes is the result of what happening to blood glucose levels?

How to systems interact to perform the function of reproduction in animals?

No system is more important to the long-term survival of a species than its reproductive system. The reproductive system produces offspring that help to ensure species survival over many generations. Most animals reproduce sexually by producing haploid gametes. Sexual reproduction helps create and maintain genetic diversity, which increases a species’ ability to evolve and adapt as the environment changes. Many invertebrates and a few vertebrates can also reproduce asexually. It allows animals to increase their numbers rapidly but does not generate genetic diversity.

The Reproductive SystemThe principal job of the reproductive system is to prepare and deliver reproductive cells or gametes. Gametes carry half the number of chromosomes found in body cells. Typically, male animals produce small gametes, called sperm, which swim. Females produce larger gametes called eggs, which do not swim. When haploid gametes join during fertilization, they produce a zygote that contains the diploid number of chromosomes.

Reproductive TimingMany animals depend on other systems of the body, especially the nervous system, to determine the right time to engage in reproductive behavior. Deer in North America, for example, generally mate only in the fall. This enables their young to be born in early summer, when nutritional conditions are best. Their nervous systems sense the changes in light-dark cycles that occur in the fall. This causes changes in behavior that encourage mating to take place. In all such cases, proper interactions between the nervous system and the reproductive system are the key to successful reproduction.

The Endocrine SystemIn many animals the endocrine system is closely aligned with the reproductive system. The endocrine system coordinates body functions by means of chemical signals known as hormones. In humans, the pituitary gland, part of the endocrine system, produces hormones that regulate the activities of the ovaries (in females) and testes (in males). At the beginning of puberty, signals from the endocrine system activate ovaries and testes, which then begin to produce the primary male and female sex hormones. These hormones, testosterone in males and the estrogens in females, help produce the secondary sexual

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characteristics associated with puberty. Proper development of both sperm and egg, therefore, requires careful coordination between the endocrine and reproductive systems.

Checkpoint:

11. By reproducing sexually, animals increase their abilities to __________________________

12. How do the nervous and reproductive systems work together in some animals?

13. What gland regulates the release of male and female hormones? _____________________

14. The ovary is stimulated to produce what female hormone?____________________________

15. The testes are stimulated to produce what male hormone?____________________________

How do systems interact to perform the function of defense from injury or illness in animals?

The Integumentary SystemThe largest single organ in the body is our skin, which makes up a large part of the integumentary system. In many animals, skin may be covered with scales, fur, or even thick, bony plates, forming a first line of defense against injury and attack. But for many animals, the most important protective function of the skin if to keep pathogens, or disease-causing organisms, outside the body.

Very few pathogens can penetrate the layers of dead cells that for the skin’s surface. But your skin doesn’t cover your entire body. Pathogens could easily enter your body through your mouth, nose, and eyes—if these tissues weren’t protected by other nonspecific defenses. For example, saliva, mucus, and tears contain an enzyme that breaks down bacterial cell walls. Mucus in the nose and throat traps pathogens, and cilia push the mucous-trapped pathogens away from the lungs. Stomach secretions destroy many pathogens that are swallowed.

Inflammatory ResponseIf pathogens do make it into the body—through a cut in the skin, for example—the body’s second line of defense swings into action. These mechanisms include a powerful reaction knows as the inflammatory response. The inflammatory response gets its name because it causes infected areas to become red and painful, or inflamed. As shown in the figure below, the response begins when pathogens stimulate cells to release chemicals known as histamines. Histamines increase the flow of blood and fluids to the affected area. Fluid leaking from expanded blood vessels causes the area to swell. White blood cells move from the circulatory system into the infected tissues. Many of these white blood cells are phagocytes, which engulf and destroy bacteria. All this activity around a wound may cause a local rise in temperature, which is why a wounded area sometimes feels warm.

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The Lymphatic/Immune SystemThe main function of the immune system is to inactivate or kill foreign substances or cells that enter the body.

How does the immune system recognize “foreign” cells or substances? Immune defenses are triggered by molecules called antigens. An antigen is any foreign substance that can stimulate an immune response. Antigens are located on the outer surfaces of bacteria, viruses, or parasites. The immune system responds to antigens by increasing the number of cells that either attack the invaders directly or produce proteins called antibodies. The main role of antibodies is to tag antigens for destruction by immune cells.

The immune system guards the entire organism, which means its cells must travel throughout the body, patrolling through the circulatory system as well as other systems of the body. The main working cells of the immune response are B lymphocytes (B cells) and T lymphocytes (T cells). B cells are produced in, and mature in, red marrow. T cells are produced in the bone marrow but mature in the thymus—an endocrine gland. Each B cell and T cell is capable of recognizing one specific antigen. When mature, both types of cells travel to lymph nodes and the spleen, where they will encounter antigens. Although both types of cells recognize antigens, they go about it differently. B cells, with their embedded antibodies, discover antigens in body fluids. T cells must be presented with an antigen by infected body cells or by immune cells that have encountered antigens. When either type of lymphocyte encounters an antigen, the lymphocytes organize a powerful immune response that helps to counteract the infection.

One of the most interesting properties of the immune system is that it has a kind of “memory” for the infections it has encountered. The specific B and T cells that have been stimulated by a particular antigen grow and divide to form a pool of “memory” cells ready for a second encounter with the same antigen. If pathogens carrying the same antigens appear again, much larger numbers of cells are ready to fight the infection, and the immune response is even more effective. This is why vaccines are so effective in preventing disease. When you are inoculated with a vaccine against polio or measles or diphtheria, a small amount of the antigen found on these pathogens is introduced into your body. The immune system reacts to the vaccine by producing thousands of memory cells. That way, if you are exposed to the real thing, the active pathogen, your immune system is able to fight off the infection quickly and with no ill effects.

16. What system is the body’s first line of defense against infection? _____________________

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17. What system is the body’s second line of defense should foreign particles or cells enter the body?

18. Explain the inflammatory response.

19. How does the immune system recognize “foreign” cells and substances?

20. What is the function of antibodies?

21. What endocrine gland is involved in the immune response? __________________________