AP Biology, Chapter 44
Controlling the Internal Environment

SUMMARY
INTRODUCTION

REGULATION BODY TEMPERATURE
	Introduction
	Four physical processes account for heat gain or loss
	Ectotherms derive body heat mainly from their surroundings; endotherms derive it 
	mainly from metabolism
	Thermoregulation involves physiological and behavioral adjustments
		1. Locate the body's thermostat.
			a. Hypothalamus
		2. List some of the physiological responses used to maintain homeostasis of body 
		temperature.
			a. Vasoconstriciton saves heat
			b. Vasodilation sheds heat
			c. Shivering generates heat
			d. Evaporation of sweat sheds heat
			e. Contraction of arrector pili muscles raises fur and saves heat
	Most animals are ectothermic, but endothermy is widespread
	Torpor conserves energy during environmental extremes

WATER BALANCE AND WASTE DISPOSAL
	Introduction
	Water balance and waste disposal depend on transport epithelia
		3. Rate the major sources of water gain and loss.
			a. Gain: beverages, food moisture, metabolism
			b. Loss: urine, evaporation, feces
	An animal's nitrogenous wastes are correlated with its phylogeny and habitat
	4. Describe the origin of the three nitrogenous waste products found in the mammalian 
	blood.
			a. Urea from liver metabolism of amino acids
			b. Uric acid from nucleic acid metabolism
			c. Creatinine from creatine metabolism in muscle
	Cells require a balance between osmotic gain and water loss
	Osmoregulators expend energy to control their internal osmolarity; osmoconformers 
	are isoosmotic with their surroundings
		5. Discuss the problems that marine, freshwater, and terrestrial organisms face in 
		maintaining homeostasis and explain what osmoregulatory adaptations serve as solutions 
		to these problems.
			a. Problems
				i. Marine, too much salt
				ii. Freshwater, not enough salt
				iii. Terrestrial, not enough water
			b. Adaptations
				i. Marine: salt glands, gills excrete salt, scanty urine
				ii. Freshwater: gills take up salt, pee a lot
				iii. Terrestrial: high pressure kidney, pee insoluble uric acid, water 
				impermeable skin

EXCRETORY SYSTEMS
	Introduction
	Most excretory systems produce urine by refining a filtrate derived from body fluids: 
	an overview
		6. List excretory, endocrine, and nutritional functions of the kidneys.
			a. Excretory: eliminate N-waste, toxins, drugs
			b. Homeostatic: maintain blood volume and chemistry
			c. Endocrine: secrete renin and erythropoietin
			d. Nutritional:  converts vitamin D
	Diverse excretory systems are variations on a tubular theme
		7. Why is the nephron considered the functional unit of the kidney?
			a. Smallest urine-formers
	Nephrons and associated blood vessels are the functional units of the mammalian 
	kidney
		8. Describe the general structure and function of the ureters, bladder, and urethra. 
			a. Ureters: tubes that carry urine from the kidneys to the bladder
			b. Bladder: muscular sac, lined w/ transitional epithelium, for storing and 
expelling urine
			c. Urethra: canal through which urine passes to the outside
	From blood filtrate to urine: a closer look
		9. How does the filtrate in Bowman's capsule differ from the blood in the glomerular 
		capillaries?
a. Filtration contains substances smaller than proteins
		10. Trace and rationalize the movements of a glucose molecule between the renal artery 
		and renal vein.
			a. Renal artery ==> glomerular capillaries
			b. High pressure: glucose passes into Bowman's capsule by filtration
			c. Active transport: glucose pumped out of the tubule into the peritubular 
			capillaries
			d. Peritubular capillaries ==> renal veins
		11. Describe the importance of tubular secretion.
			a. Gets rid of drugs, ions
			b. Helps control blood pH
	The mammalian kidney's ability to conserve water is a key terrestrial adaptation
	12. By what mechanism is water reabsorbed from the kidney tubule? 
		a. Osmosis
		13. Describe the composition of normal urine.
			a. Urochrome, yellow color from hemoglobin breakdown
			b. No bacteria
			c. Slightly acid
			d. Water plus solutes: Na, K, urea, uric acid
	Nervous system and hormonal feedback circuits regulate kidney functions
		14. Explain the role of ADH in the regulation of water balance by the kidney. 
			a. Blood pressure drop + incr. concentration on osmoreceptors of hypothalamus
			b. Posterior pituitary secretes ADH
			c. ADH causes cells of tubule and collecting duct to reabsorb water
		15. Explain the role of aldosterone in sodium and potassium balance of the blood.
a. Blood pressure drop, high K-low Na, renin-angiotensin mechanism
b. Adrenal cortex releases aldosterone
c. Acts on distal tubule + collecting duct
d. Increases Na reabsorption, K secretion
e. Water follows by osmosis
	Diverse adaptations of the vertebrate kidney have evolved in different habitats