Chapter 44
Regulating the Internal Environment
Homeostasis: regulation of internal environment
Thermoregulation internal temperature
Osmoregulation solute and water balance
Excretion nitrogen containing waste
Regulation of body temperature
Thermoregulation 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
Sources of body heat: Ectothermic: determined by
environment Endothermic: high metabolic rate
generates high body heat
Regulation during environmental extremes
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 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
Very Toxic, need access to lots of water to keep concentration low
Low toxicity, so lots of water is not needed,
Liver combines amonia with CO2
Disadvantage, energy is needed
Low toxicity, insoluble in water, semi-solid so little water loss, more energy needed
Osmoregulators 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 Production of urine by 2 steps:
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
Dead-end tubeDraws water and solutes
in from the interstitial fluid, filters it, moves urine outward through the tubule, exits through openings
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
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%)
Nephron Structure
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
http://www.lakemichigancollege.edu/liberal/bio/anat/urin.html
Basic Nephron Function
QuickTime™ and aCinepak decompressor
are needed to see this picture.
http://www.biologymad.com/resources/kidney.swf
http://www.getbodysmart.com/ap/urinarysystem/kidney/externalanatomy/tutorial.html
Nephron Function, I Proximal tubule: secretion and reabsorption
QuickTime™ and aCinepak decompressor
are needed to see this picture.
http://www.sumanasinc.com/webcontent/animations/content/kidney.html
Nephron Function, II Loop of Henle: reabsorption of water and salt Distal tubule: secretion and reabsorption
QuickTime™ and aCinepak decompressor
are needed to see this picture.
http://www.physiology.ubc.ca/undergrad_files/urine.swf
Nephron Function, III Collecting duct: reabsorbs water, salt, some urea
QuickTime™ and aCinepak decompressor
are needed to see this picture.
http://www.physiology.ubc.ca/undergrad_files/transport.swf
Kidney regulation: hormones
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 (renin-angiotension-aldosterone system; RAAS)
Atrial natriuretic factor (ANF) ~ walls of atria; inhibits release of renin, salt reabsorption, and aldosterone release
http://www.wisc-online.com/objects/AP2204/AP2204.swf
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter20/animation__hormonal_communication.html
http://www.health.bcu.ac.uk/physiology/renalsystem.htm#top