Regulating the Internal Environment: Thermoregulation & Osmoregulation.

Regulating the Internal Environment:

• Thermoregulation &

Osmoregulation

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 (electromagnetic waves) Not transferred by molecules.

• 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~ low activity;

decrease in metabolic rate.

• 2 types:

• Hibernation- long term or winter torpor (winter cold and food scarcity); bears, squirrels

• Estivation- short term or summer torpor (high temperatures and water scarcity); fish, amphibians, reptiles

• Both often triggered by length of daylight

Thermoregulation amongst the Phyla….

• Invertebrates: most have no direct control over body temperature (complete ectotherms)

• May orient body to maximize or minimize heat from the sun.

• Some flying insects can generate internal heat by contracting flight muscles in synchrony.

• Social insects can use interaction between each other….

• Huddle to stay warm; fan each other to cool

• Reptiles/Amphibians: most are generally ectothermic.

• Again, seek warmer or cooler “microenvironments” to adjust temperatures.

• Some reptiles can use vasoconstriction to minimize heat loss or shiver to generate a few extra degrees of heat.

Still amongst the phyla…..• Fish: again, generally ectothermic.• Some are partial endotherms:• (tuna, swordfish, sharks)• Heat production in swimming muscles, combined

with countercurrent circulation can raise the temperature of the body core.

• Mammals/Birds: true endotherms• Maintain relatively high temperature over a very

narrow range.• 36o –38o C for Mammals• 40o-42oC for Birds• Warming Mechanisms:

– Shivering– Vasoconstriction centralizes warmth– Fat burning.

• Cooling Mechanisms:– Vasodilatation dissipates heat– Sweating increases evaporative cooling

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; • It’s all about “Deamination” resulting in:

• Ammonia: most aquatic animals, many fish Diffuses easily out of soft body surfaces

• Uric acid: birds, insects, many reptiles.• Much less soluble than ammonia• Eliminated as a paste through “cloacae”.• Allows reproduction though shelled eggs

because it can precipitate out without becoming toxic.

• Urea: mammals, most amphibians, sharks, bony fish.

• Less toxic. • Produced in liver by combining ammonia

with CO2 then transported to kidneys.

Water Balance• Osmoconformer: no active adjustment of internal osmolarity. Isoosmotic to

environment. Most marine animals.

• Osmoregulator: adjust internal osmolarity (freshwater, marine, terrestrial).

• Freshwater fishes (hyperosmotic)- gains water, excretes large amounts of urine. Salt replenished by consuming high salt content foods or actively transporting ions.

• Marine fishes (hypoosmotic)- loses water, gains salt; drinks large amount of saltwater secrete very little urine.

• Anhydrobiosis- dehydrated animals. Often have “trehalose”- a disaccharide that replaces water around membranes and proteins.

Excretory Systems• Production of urine by 2 steps:

• 1.) Filtration (nonselective) 2.) Reabsorption (secretion of solutes)

• Protonephridia ~ flatworms (“flame-bulb” systems) weblink

• Metanephridia ~ annelids (ciliated funnel system)

• Malpighian tubules ~ insects (tubes in digestive tract)

http://entochem.tamu.edu/insec

• Kidneys ~ vertebrates

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

Basic Nephron Function

• D:\bc_campbell_biology_7\0,7052,3117252-,00.html

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) ~ when blood volume/pressure is low it secretes enzyme renin which increases blood pressure/volume by constricting capillaries; initiates conversion of angiotensinogen (plasma protein) to angiotensin II (peptide).

• Angiotensin II also stimulates adrenal glands to secrete aldosterone; acts on distal tubules to reabsorb more sodium, thereby increasing blood pressure (renin-angiotensin-aldosterone system; RAAS)

• Atrial Natriuretic Factor (ANF) ~ walls of atria; inhibits release of renin, salt reabsorption, and aldosterone release

Hormonal Control

• D:\bc_campbell_biology_7\0,7052,3117252-,00.html