71Homeostasisandcontrolsys74Urinarysys - Unit 3 Homeostasis...

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Unformatted text preview: Unit 3. Homeostasis 7.1. Homeostasis and Control Systems (pp. 334-336) Homeostasis: “process to keep the internal environment constant despite changes in the external environment” • aka. dynamic equilibrium: condition remaining stable within fluctuating limits • e.g.s. blood glucose levels @ 0.1% (low - exercising, high - eating) body temperature @ 37 C (low - sleeping, high - exercising) systolic blood pressure @ 120 mmHg (low - sleeping, high – exercising) blood pH @ 7.35 (low – eating, high – exercising) • body maintains a constant balance by many monitored adjustments • three components: Monitor (sensors) - sends a signal (chemical/hormones) to the in organ coordinating centre when organ operates outside limits Coordinating centre - brain Regulator - restores the balance Homeostasis and Feedback • negative feedback: process by which a mechanism is activated to restore conditions to their original state (Fig. 3, p. 336) * designed to resist change: changes trigger the coordinating centre to counteract any further change in the same direction prevent any small changes from becoming too large • positive feedback: process by which a small effect is amplified * designed to reinforce the change: moves the variable away from the steady state - e.g. birth process: decrease small increase larger expel decrease progesterone contractions oxytocin contractions newborn oxytocin (no contractions) 7.4. The Urinary System (pp. 346-348) • aorta renal arteries kidneys • Kidneys: organs that filter wastes from blood - can hold 25% of body’s blood at a time Urine flow: kidneys (Fig. 1, p. 346) ureter (tubes) bladder urinary sphincter urethra (tube) outside body Three parts: Cortex - outer connective tissue (Fig. 1, p. 346) Medulla- midlayer Pelvis- inner hollow chambers, joining kidney with uterer tubes • Nephrons: tubules within kidneys (Fig. 2, p. 347) Cortex * site of filtration * high pressure renal afferent glomerulus efferent * peritubular renal artery arterioles (capillary bed) arterioles capillaries venule...
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71Homeostasisandcontrolsys74Urinarysys - Unit 3 Homeostasis...

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