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1. B.10A: Interactions in Animals Biological Processes and Systems • What is the role of homeostasis in system regulation? Part I: Systems Regulation Your Mission: Describe the interactions that occur amongsystems that perform the function of regulation. The endocrine system is primarily responsible for regulating many of the bodily functions that occur in animals to maintain homeostasis, an internal balance. For example, bodies keep calcium, salt, water, and carbohydrates balanced so that ourbasic organs and cells function properly. Regulation is also necessary for growth and development and reproduction. Several glands associated with the endocrine system, including the pituitary, thyroid, adrenal and pancreas, are essential to regulation of body function because they produce hormones. Hormones are chemical substances produced in the body. These have specific regulatory effects on the activity of certain cells or a certain organ. Hormones are absorbed into the bloodstream and transported throughout the body via the circulatory system. Once they reach their target cells, chemical intercellular communication occurs. Often this communication results in the action of other body systems, such as the nervous and muscular systems, in the process of maintaining homeostasis. An example of this regulatory process, or feedback system, is calcium regulation. An animal with low calcium ions in the blood will trigger an endocrine response from the parathyroid gland. Parathyroid hormone is released into the bloodstream, which signals the release of calcium and phosphate from bone in the skeletal system. Simultaneously, the kidney is signaled to increase calcium reabsorption for conservation and the excretion of phosphate through the excretory system. Response Stimuli General Feedback Loop Stimuli Response Stimuli Response Low Blood Calcium Ion Feedback Loop Stimuli Response Continue to next page. 1

2. B.10A: Interactions in Animals Biological Processes and Systems • What is the role of homeostasis in system regulation? Part I: Systems Regulation, continued Your Mission: Describe the interactions that occur among systems that perform the function of regulation. Regulating body temperature is another example of homeostasis important for staying healthy. Thermoregulation involves a variety of mechanisms the used by the body to balance heat-in and heat-out in order to keep its core temperature nearly constant. In humans, body temperature generally stays around 37°C. Our bodies provide different mechanisms for maintaining that temperature, depending on whether we need to cool down or heat up. For example, when we exercise, we sweat; and when we are cold, we shiver. Like regulation for other purposes, thermoregulation is coordinated among a variety of systems. When the variable of environmental temperature makes us cold, sensors in our epidermis, part of the integumentary system, notice the change and respond by alerting the nervous system. The nervous system, in turn, signals the body to respond. For example, it might signal the muscular system to shiver or signals an increase in metabolism so that stored energy in fat is released. Both responses, whether mechanical or metabolic, result in generating heat. Respiration provides oxygen for either process, and the circulatory system spreads the heat through the body, raising its core temperature. Humans, like other mammals, are endotherms, meaning that we can produce heat internally. But other animals, such as most reptiles, are ectotherms. They still need to maintain homeostasis in their body temperatures, but they rely on other types of mechanisms for thermoregulation. They must get heat, externally, that is, from the environment. So, their body systems coordinate behaviors such as basking in the sun to absorb heat or seeking shade to reduce heat input. Similarly to endotherms, sensors signal the nervous system of the temperature condition, which then signals the appropriate other systems, such as the muscular system, to move into the sun or shade. Complete Part I of your Student Journal before moving on. 2

3. B.10A: Interactions in Animals Biological Processes and Systems • How do systems in animals interact to achieve nutrient management? • Which systems in animals interact to achieve reproduction? • How do systems in animals interact to protect them from injury or illness? Part II: Nutrition, Reproduction, and Protection Your Mission: Describe the interactions that occur among systems that perform the function of nutrient absorption, reproduction, and defense from injury or illness. Nutrient management is essential to the chemical processes that occur in order for animals to carry out life processes. Such management is also very complex, as it involves three main processes: digestion, absorption, and regulation. Furthermore, several systems interact to perform nutrient management. These include the digestive, nervous, muscular, endocrine, circulatory, and excretory systems. Digestion begins when the body ingests food. Food particles are then broken down into smaller molecules through the process of hydrolysis. The pancreas is one endocrine gland that aids this process by secreting digestive enzymes. It also produces hormones, such as insulin, which is crucial to regulating fat and carbohydrate metabolism in the body. The nervous system controls the involuntary muscular contractions that occur in the esophagus, stomach, and intestines that keep things moving along. The next step in nutrient management is absorption. Once the smaller molecules enter the large intestine, they pass over intestinal villi. Here, nutrients are absorbed into capillaries of the circulatory system and moved throughout the body to be utilized or stored. Nutrients in the bloodstream are monitored by sensors of the nervous system to keep tabs on the body’s the internal balance. As needed, these sensors trigger responses from the endocrine system to regulate the excess or deficiency of nutrients within the bloodstream. As food moves through the digestive system, waste gets collected and is eventually released through the excretory organs. Circulatory System Digestive System Continue to next page. 3

4. B.10A: Interactions in Animals Biological Processes and Systems • How do systems in animals interact to achieve nutrient management? • Which systems in animals interact to achieve reproduction? • How do systems in animals interact to protect them from injury or illness? Part II: Nutrition, Reproduction, and Protection, continued Your Mission: Describe the interactions that occur among systems that perform the function of nutrient absorption, reproduction, and defense from injury or illness. Reproduction also involves a variety systems and isgenerally regulated by the endocrine system. Most mammals mate according to the female estrous cycle, in which the female’s ovary regulates hormones that trigger the release of an egg for fertilization. These hormonal changes are vital to successful reproduction. Once the egg is fertilized in the uterus, more hormones are released that regulate the development of the fetus. In humans, the zygote (fertilized egg) implants into the wall of the uterus. The zygote will develop into a fetus during a gestational period of 9-10 months. When the birth process begins, the fetus presses against the cervix sending nerve impulses to the brain. The nervous system then signals the pituitary gland of the endocrine system to release the hormone oxytocin into the circulatory system via the bloodstream. This action stimulates the muscular system to contract in the smooth muscle of the uterus. Many factors effect an organism’s ability to reproduce. Changes in daylight and temperature can be detected in the nervous system by receptors in the brain; these receptors then use this information to regulate the body’s hormone levels. Even slight variations in these hormones can impact the overall success of reproduction. While the endocrine system is paramount to the process of reproduction, the entire process is delicately balanced among the performance of multiple body systems. Continue to next page. 4

5. B.10A: Interactions in Animals Biological Processes and Systems • How do systems in animals interact to achieve nutrient management? • Which systems in animals interact to achieve reproduction? • How do systems in animals interact to protect them from injury or illness? Part II: Nutrition, Reproduction, and Protection, continued Your Mission: Describe the interactions that occur among systems that perform the function of nutrient absorption, reproduction, and defense from injury or illness. The integumentary system is any human or animal’s primary line of defense from the outside world, forming a barrier between the more vulnerable inside of an organism and any bacteria, viruses, or other pathogens that are encountered. In mammals, hair is also an important structure of the integumentary system that works to protect them from environmental conditions, helping in thermoregulation, and repelling dirt and rain. The skeletal system of many animals is also highly specialized to provide protection from injury, especially to the vital organs, such as the heart, liver, and lungs. In some animals, parts of the skeletal system have evolved into highly protective “armor”, such as in the tortoise, whose rib cage is what forms its shell. The muscular system also helps protect from injury by responding to stimuli so that the body moves away from harm. A muscle also protects bone from injury, for example, by absorbing an impact; the muscle may suffer a bruise, but the bone remains unbroken. Organisms are also equipped with defenses on a microscopic level, launched by the immune system. The immune system defends against pathogens, such as bacteria and viruses. When a foreign invader is detected in the body, the immune system is triggered. This response involves an intricate process of cellular communication (illustrated in the diagram on right) that requires the help of the nervous, endocrine, and circulatory systems. Depending on the foe, anti-bodies or other defenses, are activated and targeted to overcome the invader. Complete Part II of your Student Journal before moving on to the activity. 5