Homeostasis - regulating the inside Heat exchange and Water Balance
Thermoregulation – • Heat always moves from hotter to cooler area. Cold doesn’t get in, heat gets out.
Figure 44.4 The relationship between body temperature and ambient (environmental) temperature in an ectotherm and an endotherm Which is the conformer?
Countercurrent Heat exchange • Opposite flowing tubes of blood exchange heat well • Warm arterial blood arriving to extremity releases heat to returning blood • Arterial blood arrives cold to extremity and blood going to core is warm • Keeps core blood warm
Countercurrent flow also helps fish exchange gases across gill filaments
Compare degree of oxygen exchange in the 2 systems Same direction Opposite directions
Skin as an organ of thermoregulation Hair/fur Sweat glands Capillary blood supply Subcutaneous fat vasodilation vasoconstriction piloerection…. Hair stands up, traps air, holds heat
Brown fat – used as a heat source in some hibernating mammals and babies • Nonshivering thermomgenesis – food energy is converted to heat instead of ATP • Other behaviors – panting, huddling, nocturnal activity, burrowing
The thermostat function of the hypothalamus and feedback mechanisms in human thermoregulation
Water Balance – keeping right amount of water in cells, blood, interstitial fluid etc. Adaptations include: • Waterproofing – keratnized skin, scales, skin oils • Kidneys conserve/excrete water • excretion of various nitrogen wastes require different amounts of water • Uric acid • Ammonia ( NH3 ) Urea • Amniote egg; internal fertilization, internal respiratory surface ( lung ) – all conserve water loss on land • Osmoregulation – controlling water loss and uptake in animals; ( animal cells swell/shrink )
Salt-excreting glands in birds Active transport moves salt into Tubule ( secretion)
Nitrogen wastes are toxic and come from deaminating amino acids • Urea – excreted by mammals. Requires less water to excrete; excreted by mammals • Ammonia – excreted by aquatic animals. Requires a lot of water to excrete; is highly toxic Uric Acid – excreted by reptiles, insects, birds; nontoxic, requires little water to excrete
Figure 44.13 Nitrogenous wastes deamination in Kreb’s Cycle
Osmoconformers – do not osmoregulate • Osmoregulators – expend a lot of energy pumping out/in water/ salt..to control their inner osmolarity. ( control is “costly” in terms of energy)
Osmoregulation in a saltwater fish…… Hypertonic outside Solution – take on Water and salt and Conserve water in urine
Figure 44.14b Osmoregulation in a freshwater fish hypotonic by active transport
Figure 44.16 Water balance in two terrestrial mammals Cell respiration makes metabolic water
Figure 44.17 Key functions of excretory systems: an overview Filter – forcefully screens, is non selective Reabsorbs –blood takes back needed substances ( active transport ) into the blood Secretes - active transport into the tubule from the blood Excretes – sends it out the body
Planarian – flame bulb Flame cells – mainly osmoregulate
Figure 44.19 Metanephridia of an earthworm2/ segment Coelomic fluid
Insect malpighian tubules • Produce a dry pasty waste of uric acid released from the rectum • Has help insects survive on land
Rich blood supply to kidneys, 20% of body blood In kidneys at all times Urine production = diuresis Diuretics are drugs that stimulate urine production and water loss from the body tissues ureter
The nephron and collecting duct: regional functions of the transport epithelium
Figure 44.23 How the human kidney concentrates urine in a juxtamedullary nephron in birds/ mammals.
Figure 44.23 How the human kidney concentrates urine: getting rid of solutes and conserving water Impermeable to water
Figure 44.23 How the human kidney concentrates urine: Urea and NaCl in the interstitial fluid outside of nephron help reabsorb water from filtrate to make a hyperosmotic urine.
Nervous system and hormones regulate the kidney • Antidiuretic hormone (ADH) made by the hypothalamus helps conserve body water. (ADH - anti- urine production ) Hypothalmus has osmoreceptor cells • ADH causes distal tubule and collecting duct to become more permeable to water, thus, more water is reabsorbed back into blood from filtrate
Figure 44.24 Hormonal control of the kidney by negative feedback circuits Antidiuretic Hormone reduces water loss in urine, decreases osmolarity of blood Too much water in body
Renin- Angiotensin-Aldosterone • Are secreted in response to low blood pressure. • Together they simulate the distal tubule to reabsorb water and Na+. This increases blood volume but does not change the osmolarity. Angiotensin alone also causes capillaries to constrict, raising blood pressure • Aldosterone is from the adrenal glands
Figure 44.24 Hormonal control of the kidney by negative feedback circuits
Figure 44.25 A vampire bat (Desmodus rotundas), a mammal with a unique excretory situation Hypo-osmotic urine right after a blood meal before flight home Hyperosmotic urine during sleep.
Homeostasis requires the coordinated action of several body systems • Give 2 examples supporting the above statement. For each, state the condition being controlled, the systems involved and explain how the systems interact to achieve homeostasis.