BIO 311D 2nd Edition Lecture 25 Outline of Last Lecture I. Diabetes Mellitus II. Hypothalamus and pituitary controlIII. Feedback control of thyroid functionIV. The adrenal glands- two part response to stressOutline of Current Lecture I. Wrap up hormone examples (3-23 and 3-25)II. Principles of transport and exchange in animalsIII. How excretory tubules help with homeostasis?Current LectureI. Wrap up hormone examplesA. Adrenal medulla hormone- epinephrine1. In response to neural stimuli, neurosecretory cells in adrenal medulla secrete epinephrine into the blood2. G proteins can either activate or inhibit pathways. In smooth muscle cells around blood vessels:a. One receptor: G protein activates cAMP, muscles tighten, vessel constrictsb. Other epinephrine receptor G protein inhibits cAMP production, muscle relaxes, vessel expands B. Two separate feedback systems to control blood glucose around a set level1. Are the hypothalamus and pituitary directly involved? a. Adrenal cortex is involved with the hypothalamusb. Adrenal medulla is independent from the hypothalamus-pituitary pathway. The hypothalamus CAN affect the medulla though.C. How long-term stress affects your body1. Digestive system (stomach ache, diarrhea, weight gain)2. Nervous system (sleep disturbance, depression)3. Immune system (decreased inflammation, decreased helper T cell response)4. Other systems (increased asthma, etc.)D. Module and Discussion Section 1. The functions of the digestive system are ingestion, digestion, absorption andelimination2. How is the structure of our digestive system adapted for these functions? Specialized regions within the digestive tract, making it more efficient 3. How could hormones help control functions?4. Nutrient absorption: small intestine blood liver II. Principles of transport and exchange in animalsA. Homeostasis of conditions for cells:1. Oxygen/CO2 regulation2. Glucose regulation3. pH regulation4. Temperature regulation5. Osmoregulation (water: solute balance)6. Eliminating nitrogenous wastes B. In a homeostatic system, the blood pH set point is about pH 7.4. If a monitor detected a change towards higher blood pH, which of these would be part of an appropriate negative feedback response? (Application problem)Kidney epithelial cells secrete H+ ions into blood C. Nitrogenous wastes: cellular waste products from the breakdown of proteins andnitrogenous bases, NOT digestive wastes 1. Ammonia: most aquatic animals (including bony fishes), most soluble, toxic 2. Urea: mammals, most amphibians, sharks, some bony fishes, toxic if it gets tohigh concentration 3. Uric Acid: many reptiles (including birds), insects, land snails, least soluble, not toxic D. Osmoregulation1. Here’s the problema. Freshwater: solutes 10 mOsm/Lb. Human blood: 300 mOsm/Lc. Seawater 1000 mOsm/L2. Transport epithelium is structured to control what gets across- or doesn’t!a. Tight junctions: controls what can leak through and what cannot leak throughb. Microvilli: increase surface area for absorption 3. By what mechanisms do saltwater and freshwater fish maintain their internal osmolarity? Fig. 44.4a. Salt-water fish: excretion of salt ions and small amounts of water in scantyurine from kidneys (getting rid of salt and conserve water a bit)b. Fresh-water fish: excretion of large amounts of water in dilute urine from kidneys 4. Case study: Salmon hatch in freshwater, move out to streams, then move out to open oceans for the majority of their adult life. At sexual maturity theyswim upstream, to their native streams and ponds, where they spawn and die. What osmoregulation changes must occur?a. In fresh water environment (0.3 % solutes), how would gill epithelial cells use ATP to maintain osmotic homeostasis?Positively charged ions pumped in, Cl- ions follow through b. In seawater environment (3.5% solutes), how would gill epithelial cells use ATP to maintain osmotic homeostasis? Pump sodium up; charge gradient, passive transport of Cl- c. Transition period: change the membrane proteins III. Excretory TubulesA. General Filtration: kidney tubules and other osmoregulation tubules work by filtration of most water and solutes from the blood into the tubule B. Selection Reabsorption: the tubules change the composition of the filtrate by selective secretion and reabsorption of specific solute molecules C. Excretion: what’s left in the excretory tubules, leaves through urine D. Excretory tubule demonstrates1. Structural adaptations 2. Physiological responses
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