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Chapter 44
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Regulating the Internal
Environment
Homeostasis:
regulation of internal environment
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Thermoregulation
internal temperature
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Osmoregulation
solute and water balance
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Excretion
nitrogen containing waste
Regulation of body temperature
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Thermoregulation
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4 physical processes:
Conduction: transfer of heat between
molecules of body and environment
Convection: transfer of heat as
water/air move across body surface
Radiation: transfer of heat produced
by organisms
Evaporation: loss of heat from liquid
to gas
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Sources of body heat:
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Ectothermic: determined by
environment
Endothermic: high metabolic rate
generates high body heat
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Regulation during environmental
extremes
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Torpor: physiological state of
low activity; decrease in
metabolic rate
1- Hibernation: long term or
winter torpor (winter cold and
food scarcity); bears, squirrels
2- Estivation: short term or
summer torpor (high
temperatures and water
scarcity); fish, amphibians,
reptiles
Both often triggered by length
of daylight
Water balance and waste
disposal
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Osmoregulation: management of
the body’s water content and solute
composition
Nitrogenous wastes: breakdown
products of proteins and nucleic
acids; ammonia-very toxic
Ammonia: most aquatic animals,
many fish
Urea: mammals, most amphibians,
sharks, bony fish (in liver;
combo of NH3 and CO2)
Uric acid: birds, insects, many
reptiles, land snails
Low toxicity, so
lots of water is
not needed,
Liver combines
amonia with
CO2
Disadvantage,
energy is
needed
Very Toxic, need
access to lots of
water to keep
concentration low
Low toxicity,
insoluble in
water, semisolid so little
water loss,
more energy
needed
Osmoregulators
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Osmoconformer: no active adjustment of internal osmolarity
(marine animals); isoosmotic to environment
Osmoregulator: adjust internal osmolarity (freshwater, marine,
terrestrial)
Freshwater fishes (hyperosmotic)- gains water, loses; excretes
large amounts of urine salt vs. marine fishes (hypoosmotic)- loses
water, gains salt; drinks large amount of saltwater
Takes in salt with the water, needs to keep the
water and get rid of the salt, keep the water, result
less urine
Takes in fresh water and ions, needs to keep the
ions and get rid of excess, result lots of urine
Excretory Systems
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Production of urine by 2 steps:
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Filtration (nonselective)
Reabsorption (secretion of solutes)
Protonephridia: flatworms (“flame-bulb” systems)
Metanephridia: annelids (ciliated funnel system)
Malpighian tubules: insects (tubes in digestive tract)
Kidneys: vertebrates
Flatworm: Phylum Platyhelminthes
Draws water and solutes
in from the interstitial
fluid, filters it, moves
urine outward through the
tubule, exits through
openings
Dead-end
tube
Earthworm: Annelids
Metanephridium: excretory
and osmoregulatory
Insects and other terrestrial
Arthropods
Immersed in hemolymph: (circulatory
fluid)
Key adaptation
that
contributed to
the success of
these animals
on land
Kidney Functional Units
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Renal artery/vein: kidney blood flow
Ureter: urine excretory duct
Urinary bladder: urine storage
Urethra: urine elimination tube
Renal cortex (outer region)
Renal medulla (inner region)
Nephron: functional unit of kidney
Cortical nephrons (cortex; 80%)
Juxtamedullary nephrons (medulla;
20%)
http://www.lakemichigancollege.edu/liberal/bio/anat/urin.html
Nephron Structure
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Afferent arteriole: supplies blood to
nephron from renal artery
Glomerulus: ball of capillaries
Efferent arteriole: blood from glomerulus
Bowman’s capsule: surrounds glomerulus
Proximal tubule: secretion & reabsorption
Peritubular capillaries:
from efferent arteriole;
surround proximal & distal tubules
Loop of Henle: water & salt balance
Distal tubule: secretion & reabsorption
Collecting duct: carries filtrate to renal pelvis
Basic Nephron Function
http://www.biologymad.com/resources/kidney.swf
http://www.getbodysmart.com/ap/urinarysystem/kidney/externalanatomy/tutorial.html
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Nephron Function, I
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Proximal tubule: secretion and reabsorption
http://www.sumanasinc.com/webcontent/animations/content/kidney.html
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Nephron Function, II
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Loop of Henle: reabsorption of water and salt
Distal tubule: secretion and reabsorption
http://www.physiology.ubc.ca/undergrad_files/urine.swf
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Nephron Function, III
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Collecting duct: reabsorbs water, salt, some urea
http://www.physiology.ubc.ca/undergrad_files/transport.swf
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Kidney regulation: hormones
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter20/animation__hormonal_communication.html
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Antidiuretic hormone (ADH) ~ secretion
increases permeability of distal tubules
and collecting ducts to water (H2O back
to body); inhibited by alcohol and coffee
Juxtaglomerular apparatus (JGA) ~
reduced salt intake--->enzyme renin
initiates conversion of angiotension
(plasma protein) to angiotension II
(peptide); increase blood pressure and
blood volume by constricting capillaries
Angiotension II also stimulates adrenal
glands to secrete aldosterone; acts on
distal tubules to reabsorb more sodium,
thereby increasing blood pressure (reninangiotension-aldosterone system; RAAS)
Atrial natriuretic factor (ANF) ~ walls of
atria; inhibits release of renin, salt
reabsorption, and aldosterone release
http://www.health.bcu.ac.uk/physiology/renalsystem.htm#top
http://www.wisc-online.com/objects/AP2204/AP2204.swf