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