bio 126, week 1
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This 17 page Class Notes was uploaded by Joanne Saldanha on Sunday June 5, 2016. The Class Notes belongs to BIO 126 at Drexel University taught by Dr. Togna & Dr. Smith in Spring2015. Since its upload, it has received 13 views. For similar materials see Physiology and Ecology in Biology at Drexel University.
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Date Created: 06/05/16
Homeostasis and Endocrine Signaling ENDOCRINE GLANDS AND THEIR FUNCTIONS: An endocrine gland is a gland of the endocrine system that secretes its products, usually hormones, directly into the blood rather than through a duct. Hormones are chemical messengers that are secreted directly into the blood, which carries them to organs and tissues of the body to exert their functions The endocrine system includes: Adrenal, Hypothalamus, Ovaries, Pancreas, Parathyroid, Pineal Gland, Pituitary Gland, Testes, Thymus, Thyroid. HOMEOSTASIS: Homeostasis is an organism’s ability to maintain a “steady state” or internal balance regardless of external environment. It doesn’t mean that everything in the body is kept the same. It is a dynamic equilibrium i.e. Working to get changes in temp, pH, etc. back into the correct range. Homeostasis involves positive and negative feedback. In the nervous system, neurons transmit signals along dedicated routes, connecting specific locations in the body The nervous system works hand in hand with the endocrine system to maintain homeostasis. THERMOREGULATION: The hypothalamus acts as the body’s thermostat because it ensures that the body temperature is constantly maintained within the optimal range. This is called thermoregulation. Thermoregulation occurs in response to external stimuli (signal) that causes the hypothalamus to spring into action. When we get a fever, the body temperature rises beyond normal body temperature. This is the stimulus required for the hypothalamus to release hormones that bring about vasodilation (dilation or expansion of blood vessels). This causes sweating which cools the body down and the temperature returns back to normal. When the external temperature is too low, our body temperature also tends to slightly drop. If temperature is too low, the hypothalamus signals for vasoconstriction (shrinking or constriction of the blood vessels) which holds the blood in the core of the body to keep the body warm. This leads to the ends of the body (hands and feet) becoming colder than the core and results in shivering. Shivering is a form of work and produces heat, eventually leading to a rise in body temperature. CELL SIGNALING: Hormones are released by endocrine glands into the blood (circulatory system). These hormones come in contact with every cell in the body. Only those cells with the correct receptors are able to respond to the hormone and carry out the expected functions. Cells that lack the correct receptors are unable to receive the chemical information carried by the hormone and hence do not carry out the expected function. CLASSES OF HORMONES The three classes of hormones based on chemical composition are: Peptides and proteins, Amino acid derivatives and steroids. Peptides and proteins: they are made from chains of amino acids Amino acid derivatives: they are simple molecules Steroids: they are derived from cholesterol. The classes of hormones based on solubility are: Lipophilic – lipidsoluble and Hydrophilic – watersoluble. Lipophilic hormones: 1. Are soluble in lipids. 2. They cannot dissolve in blood. 3. They are carried by a transport protein. 4. Receptors are inside the cell because the hormones is lipid soluble and can hence cross the plasma membrane of the cell. 5. They are very quick and lead to quick responses but their effects usually last for shorter time periods (minutes to an hour). Hydrophilic hormones: 1. Are soluble in water. 2. They can dissolve in blood. 3. They do not require to be carried by a transport protein. 4. Receptors are in the plasma membrane of the cell because the hormones are insoluble in lipids. 5. Their effects usually last for longer time periods (1– 6hrs). ENDOCRINE GLANDS ARE THEIR HORMONES: Hypothalamus Pituitary gland: Posterior pituitary – Oxytocin, Vasopressin (antidiuretic hormone, ADH) Adrenal glands: Adrenal medulla Epinephrine and norepinephrine; Adrenal cortex Glucocorticoids, Mineralocorticoids. Pancreas: Insulin, Glucagon 2 Ovaries (in females) Progestin, Estrogen Testes (in males) Androgens Parathyroid glands Parathyroid Hormone (PTH Thyroid gland: Thyroid hormone (T and T ), Calcitonin 3 4 Pineal gland: Melatonin 3 Ecology 1. Ecology: Study of interactions among organisms and their environment. 2. Biotic: Interactions among living things 3. Abiotic: Interactions between organisms and their nonliving environment 4. Biotic and Abiotic factors can influence organisms living in that niche (environment). 5. Environmental science: Application of ecology to real world problems 6. Scale of Ecology: Organismal Ecology, Population Ecology, Community Ecology, Ecosystem Ecology Organismal Ecology: How an organism deals with stresses in the environment to sustain itself. The organism needs to deal with its environmental stresses by physiological and behavioral adaptations. Physiological and behavioral adaptations need to happen simultaneously to have an effect. 6.1. Physiological stresses include salinity, climate, predation, etc. 6.2. Physiological ecology – investigates how organisms are physically and chemically adapted to their environment 6.3. Behavioral ecology – how the action/inaction of an individual organism contributes to survival and reproductive success 6.4. Wide variety of physical adaptations: 6.4.1. Regulation how different systems regulate each other. For example, the endocrine system regulates the digestive system. 6.4.2. Camouflage ability to become one with surrounding to avoid detection. 6.4.3. Digestion carnivores and herbivores have different digestive systems. 6.5. Wood frogs can completely freeze. Usually limbs and other body part would fall off when an organism freezes. On a cellular basis, freezing causes water to expand. Thus, all the water in every cell would expand and the organism would die. Wood frogs can change the freezing point of fluids in their body, thus they can freeze over the winter. The heart starts beating once the temperature rises and the body unfreezes. 6.6. Brown fat and hibernation: Bears usually take a long time to come out of hibernation. Their massive size is advantageous in doing so. However, bats are relatively smaller and need to be able to come out of hibernation quickly so that they can feed and grow. Thus, in bats brown fat enables digestion to release heat energy rather than ATP. This is inefficient in terms of energy production but it raises body temperature and is thus an adaptation in winter. 6.7. White nose syndrome fungus on their nose wakes bats up and they continually burn brown fat, soon they run out of brown fat deposits and eventually freeze and die in winter. 7. Physiological and behavioral adaptations are not free. They involve paying costs of energy and exposure to danger for the benefits of resource acquisition (feeding and mating), avoidance of greater danger (predation), physiological optimization (maximum utilization of their physiological adaptations). 8. Physiological reactions begat behavioral responses 9. Behavioral adaptations in reptiles (e.g. snakes): A snake uses energy from the environment because it can’t produce its own body heat. It modifies its behavior to keep its body temperature within a relatively consistent range. Body temperature affects enzymatic activity which is why maintaining a steady temperature range is crucial. Mammals can do this physiologically; snakes and other reptiles maintain their body temperature behaviorally. They move to microhabitats that have their desired temperature. 10. Blue minimum temp of environment Red max temp of environment Orange body temperature of snake. A snake (Western garter snake) adjusts its daily life to stay within the operative temperature range. When it’s too hot, the snake moves into shade, when it’s too cold the snake basks in warmer places. Population ecology: Focuses on groups of interbreeding individuals (populations). 11. Goal to understand factors affecting population growth, density and size: 2 11.1. Relative abundance 11.2. Includes studies of species interactions: Predation, competition, commensalism and parasitism Community ecology: Studies how populations of species interact and form functional communities. They don’t interact on the reproductive level. They share the same resource pool, predators and prey, etc. Focuses on why some areas are species rich while others are species poor. Focuses on why some areas are species rich while others are species poor. Also studies succession – how species composition and community structure change over time, particularly after disturbance Ecosystems ecology: a. Studies the flow of energy and cycling of chemical elements among organisms within a community and between organisms and the environment b. Levels in food chains called trophic levels c. Food chains may interconnect forming food webs 15. ECOLOGICAL METHODS HYPOTHESIS TESTING a. Observational Studies Collect data on existing/dynamic conditions b. Experimental Studies Manipulate factors to test a hypothesis c. The best project mixes theses two. d. We often start of observational study, pick out a relationship that we can test and then conduct experiments to see if it matches with what we observed. 16. Hypothesis testing involves: i. Observations ii. Hypothesis formation iii. Experimentation iv. Data analysis v. Acceptance or rejection of hypothesis 17. Locust example: a. What causes outbreaks of locust? b. Draw up a web of interactions affecting locust population size i. Abiotic factors such as temperature, rainfall, wind, and soil pH ii. Natural enemies predators, including bird predators, insect parasites, and bacterial parasites iii. Competitors, including other insects and larger vertebrate grazers iv. Host plants, including increases or decreases in either the quality or quantity of the plants 3 c. Our observations indicate that locust numbers are affected by bird predation levels (inverse relationship) Locust numbers d. Level of Inverse relationship predation between locust numbers and bird predations – hypothesis that predation levels determine locust numbers However, if points were not tightly clustered, we would have little confidence in relationship e. Graphs imply a correlation or meaningful relationship between two variables. This is not always the case. Correlation does not mean causation. f. In an experiment, we remove predators from locust populations i. Experimental group with predators removed (placing a giant screen) ii. Control group – predators intact iii. Any differences in two groups should be due to predation iv. Perform replicates of experiment g. We find that without predators, the mean number of locusts is double that surviving with predators h. We could use a variety of statistical tests to see if the results are significant 4 Environment’s Impact on Distribution: 18. The ecosystem consists of two basic interacting parts:Living = biotic; Physical = abiotic 19. Populations keep increasing till something stops them. Sometimes it can be a cliff, ocean, competitive species, change in pH, rainfall, resources, etc. 20. We can see this even on small scales like a garden. A light deprived area lacks vegetation compared to one with ample light. 21. Factors responsible for distribution: a. Temperature: i. Most important factor in the distribution of organisms ii. Effects on biological processes iii. Inability of most organisms to regulate body temperature precisely iv. Coral reef organisms abundant only in warm water due to effects of temperature on coral deposition v. Frost is the most important factor limiting geographic distribution of tropical and subtropical plants vi. Cactus distribution limited to places where the temperature does not remain below freezing for more than one night vii. High temperatures: Corals expel symbiotic algae when temperatures are too high. This is called coral bleaching (coral reef fails). viii. Giant sequoias depend on fire to enhance seed release and clear out competing vegetation. ix. Poikilotherms can’t generate their own body heat. Temperature management in large poikilotherms is that they need exposure to high temperature to bring their body temp up. This is why they only inhabit tropical regions. As size increases, temp needed to raise body temp rises and they can only survive in smaller areas. 5 Climate and feedback mechanisms Negative feedback occurs when some function of the output of a system, process, or mechanism is fed back in a manner that tends to reduce the fluctuations in the output, whether caused by changes in the input or by other disturbances. For example, if the body is too cool, the hypothalamus triggers a warming response. In a negative feedback loop the response counteracts, rather than enhances, the deviation from the set point and returns the body's temperature to its set point. A positive feedback mechanism is the exact opposite of a negative feedback mechanism. With negative feedback, the output reduces the original effect of the stimulus. In a positive feedback system, the output enhances the original stimulus. A good example of a positive feedback system is child birth. During labor, a hormone called oxytocin is released that intensifies and speeds up contractions. The increase in contractions causes more oxytocin to be released and the cycle goes on until the baby is born. The birth ends the release of oxytocin and ends the positive feedback mechanism. Albedo and Climate: Energy reflects off of and absorbs into materials. Reflecting energy keeps a surface cool. Absorbed energy heats up the surface Albedo is the fraction of solar energy reflected from the Earth back into space. It is a measure of the reflectivity of the earth's surface. Snow has the highest albedo and open ocean has the lowest ocean. Since nearly 70% of the earth’s surface is covered in water, albedo can greatly affect seasonal climate changes Surface Albedo Reflective Snow 0.40.9 Desert Sand 0.4 Grasslands 0.25 Forest 0.10.2 Ocean 0.1 Absorpti ve Ice with snow reflects the most sunlight, thus preventing the heat from transferring into the water and hence preventing the formation of clouds. Bare ice reflects most of the sunlight. However, some heat is transferred into the water body. Moreover, this heat melts the ice. The water then evaporates and leads to the formation of a few clouds. In the case of an open ocean, there is no hindrance on the water surface and only a small amount of heat energy is reflected. Most of the heat energy is absorbed into the water’s surface and leads to a rise in temperature. This leads to an extensive amount of evaporation, Thus the cloud coverage in this case is the most. 2 \ 3 Activity: Objectives: o Determine the direction of the scale o Determine the northern hemisphere season for each map. o Explain the variation over time for: North America Northern Africa Hint: Autumn is wet season in North Africa. More rain, more vegetation, lower albedo. Scale: Blue represents absorption (low albedo) which would indicate the absence of ice. Hence we could conclude that temperatures would be higher on this end of the scale. Red represents reflection (high albedo). This would indicate the presence of ice. Hence we could conclude that temperatures would be lower on this end of the scale. 4 Weather: Picture 1 Winter: Here, the north pole doesn’t show any data. This indicates that weather conditions were too extreme for data to be collected. Hence we can conclude that it was winter at the north pole. Picture 2Spring: Here, at the north pole we see a higher density of red. This indicates that ice is present at the north pole. However, North America and North Africa have a higher density of dark and light blue and green indicating that the ice has recently melted. Thus we conclude that it is spring. Picture 3 Summer: Here, the south pole doesn’t show any data. This indicates that weather conditions were too extreme for data to be collected. Hence we can conclude that it was winter at the south pole. As the seasons are reversed in the northern and southern hemispheres, we can conclude that it is summer in the northern hemisphere. Picture 4 Autumn (Fall): Here, at the south pole we see a higher density of red. This indicates that ice is present at the south pole. North America and North Africa have a greater density of dark blue as compared to picture 2. This indicates that the weather is getting colder. Hence, we can conclude that it is fall. 5 Homeostasis Problem Set – 4/2/2015 BIO 126 Active Learning ANSWER KEY 1) If your body temperature is below normal A. commands from the hypothalamus will stimulate sweating. B. blood vessels in the skin will dilate. C. hypothalamic temperature is likely to be below the set point for shivering. D. hypothalamic temperature is likely to be above the set point for sweating. E. blood flow to the skin will increase. Answer: C 2) If the hypothalamus is cooled, what happens to the body temperature? A. It increases. B. It decreases. C. There is no effect on body temperature. Answer: A 3) In regulatory systems, the phenomenon of negative feedback A. is the least common type of feedback mechanism. B. stimulates a return to set point. C. amplifies a response. D. disrupts homeostasis. E. None of the above Answer: B 4) The upper temperature limit at which cells can function is determined by the A. boiling point of water. B. melting point of water. C. melting point of fats. D. denaturation point of proteins. E. denaturation point of nucleic acids. Answer: D 5) Which of the following animals is behaving as an endotherm to warm its body? A. A moth that quivers its wings before flight B. A black beetle that absorbs solar radiation C. A snake that lies on a warm blacktop road D. A fish that moves to a warm, shallow part of a pond E. An insect that positions its body for maximum exposure to sunlight Answer: A 6) Increased heat for thermoregulation (thermogenesis) is produced either by shivering or by nonshivering mechanisms. Which of the following is involved in nonshivering thermogenesis? A. Brown fat B. The uncoupling of oxidative phosphorylation C. High levels of iron in the diet D. The restriction of metabolic precursors E. Both a and b Answer: E 7) Countercurrent heat exchange A. moves warm blood coming from the muscles past cold blood flowing into the muscles. B. allows “hot” fish to maintain body temperatures higher than the surrounding water temperature. C. is found in large, rapidly swimming fish. D. increases a fish's sustainable power output threefold for every 10°C rise in muscle temperature. E. All of the above Answer: E 8) Compared to “cold” fish, “hot” fish, such as bluefin tuna, keep a higher temperature difference between their body and the surrounding water because they A. produce thermogenins. B. have a countercurrent heat exchange system of veins and arteries. C. shiver to create heat. D. have much brown fat tissue. E. have a large dorsal aorta that keeps them warm. Answer: B 9) Evaporative cooling is used only as a last resort by animals in hot and dry environments because A. it is ineffective at dissipating heat. B. it can cause dehydration. C. sweating requires energy expenditure. D. it requires an insulating layer in the skin. E. it requires a resetting of the animal's thermostat. Answer: B 10) The thermoregulatory response of the hypothalamus to a rise in temperature is A. increased metabolic heat production. B. a resetting of the thermostat to a higher setting. C. dilation of blood vessels in the skin. D. an overall increase in body temperature. E. the initiation of shivering movements. Answer: C 1) Endotherms like the one shown below have a number of mechanisms to increase heat generated in a cold environment. Which of the following statements about mechanisms of heat generation is false? A. Shivering involves muscle contractions that increase heat generation without producing movement. B. Nonshivering thermogenesis involves the production of heat by uncoupling oxidative phosphorylation. C. Brown fat can increase heat production in many mammals. D. Skeletal muscle generates heat by uncoupling oxidative phosphoryaltion. E. Movement itself would increase heat production by muscles. Answer: D
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