Form Fits Function
Coordination of Body Systems
Concept 40.3: Homeostatic processes for thermoregulation involve form, function, and behavior
• Thermoregulation is the process by which
animals maintain an internal temperature within a tolerable range
© 2011 Pearson Education, Inc.
• Endothermic animals generate heat by
metabolism; birds and mammals are endotherms
• Ectothermic animals gain heat from external
sources; ectotherms include most invertebrates, fishes, amphibians, and nonavian reptiles
Endothermy and Ectothermy
© 2011 Pearson Education, Inc.
• In general, ectotherms tolerate greater variation in internal temperature, while endotherms are
active at a greater range of external temperatures
• Endothermy is more energetically expensive than ectothermy
© 2011 Pearson Education, Inc.
• Heat regulation in mammals often involves the integumentary system: skin, hair, and nails
• Five adaptations help animals thermoregulate:
– Insulation
– Circulatory adaptations
– Cooling by evaporative heat loss – Behavioral responses
– Adjusting metabolic heat production
© 2011 Pearson Education, Inc.
Size and Metabolic Rate
• Metabolic rate is proportional to body mass to the power of three quarters (m3/4)
• Smaller animals have higher metabolic rates per gram than larger animals
• The higher metabolic rate of smaller animals
leads to a higher oxygen delivery rate, breathing rate, heart rate, and greater (relative) blood
volume, compared with a larger animal
© 2011 Pearson Education, Inc.
Torpor and Energy Conservation
• Torpor is a physiological state in which activity is low and metabolism decreases
• Torpor enables animals to save energy while avoiding difficult and dangerous conditions
• Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity
© 2011 Pearson Education, Inc.
Countercurrent heat exchange
Many birds, mammals, and some fish have
countercurrent heat exchangers, circulatory adaptations that allow heat to be transferred
from blood vessels containing warmer blood to those containing cooler blood. The arteries of their arms and legs run parallel to a set of deep veins.
To see how this works, let's look at an example
of a sea bird whose legs are wading in cold sea
water.
Parallel pipes that flow in the opposite direction are called countercurrent.
Countercurrent heat exchangers transfer heat between fluids flowing in opposite directions and reduce heat loss.
Parallel pipes that flow in the same direction are called concurrent, and are not as efficient as countercurrent flow in retaining energy.
External environment Food
Mouth
Animal body
Respiratory system CO2 O2
Lung tissue (SEM)
Cells
Interstitial fluid
Excretory system Circulatory
system
Nutrients
Digestive system
Heart
Blood vessels in kidney (SEM) Lining of small
intestine (SEM)
Anus
100 m
Unabsorbed matter (feces)
50 m250 m
Metabolic waste products (nitrogenous waste)
Figure 40.4
Figure 40.6
Chemical digestion of duodenum can be summarized as follow:
• 1. Carbohydrates – pancreatic amylases break starch, glycogen, and small polysaccharides into the disaccharide maltose. The breakdown of
maltose and other disaccharides (sucrose and lactose) into their monomers occurs at the wall of the duodenal epithelium.
• 2. Proteins: Pepsin begins breakdown of protein in stomach. In
duodenum, they are broken down into smaller chains of polypeptides and then into amino acids.
• 3. Nucleic Acids: Most of the enzymes responsible for nucleic acid
digestion enter the duodenum from the pancreas. The breakdown starts with hydrolysis of DNA and RNA into their respective nucleotides. The nucleotides are then broken down to nitrogenous bases, sugars, and phosphate groups.
• 4. Fats : Fats are emulsified by bile secreted by liver in the small intestine. The enzyme lipase, which is produced in the pancreas, hydrolyzes the small fat droplets into fatty acids and glycerol.
Transport System for Nutrients
• The epithelial lining of small intestine has folds called villi, which in turn bear projections called microvilli-both of which radically increase the surface area available for absorption.
• In each villus are capillaries for the absorption of monomers, including monosaccharides and amino acids.
• Each villus also has a lymph vessel, termed a lacteal, which absorbs small fatty acids.
• Passive facilitated diffusion and active transport are used to move monomers across the intestinal membrane and into blood vessels.
• The capillaries and veins that drain the nutrients away from the villi flow into hepatic portal vein, a blood vessel that goes to the liver. The liver then regulates the distribution of nutrients to the body.
Villi in Small Intestine
• Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs
• Exhaled air passes over the vocal cords in the larynx to create sounds
• Cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx
• This “mucus escalator” cleans the respiratory system and allows particles to be swallowed into the
esophagus
© 2011 Pearson Education, Inc.
• Gas exchange takes place in alveoli, air sacs at the tips of bronchioles
• Oxygen diffuses through the moist film of the epithelium and into capillaries
• Carbon dioxide diffuses from the capillaries across the epithelium and into the air space
© 2011 Pearson Education, Inc.
Bohr Effect
Carbon dioxide is carried in blood in the form of carbonic acid. Carbon dioxide reacts with water as shown in the following equation:
CO2+ H2O <---> H+ + HCO3-
As the amount of carbon dioxide increases, more H+ are formed and the pH will decrease. According to Bohr, the lower pH will cause Haemoglobin to
deliver more oxygen! The H+ displace the oxygen from hemoglobin.
Haemoglobin
Figure 42.32 Body tissue
Capillary wall Interstitial
fluid
Plasma within capillary
CO2 transport from tissues CO2 produced
CO2
CO2
CO2 H2O
H2CO3 Hb Red
blood
cell Carbonic acid
Hemoglobin (Hb) picks up CO2 and H+.
H+ HCO3 Bicarbonate
HCO3
HCO3
To lungs
CO2 transport to lungs
HCO3
H2CO3
H2O CO2
H+
Hb
Hemoglobin releases CO2 and H+.
CO2
CO2
CO2
Alveolar space in lung
Open and Closed Circulatory Systems
• In insects, other arthropods, and most molluscs, blood bathes the organs directly in an open
circulatory system
• In an open circulatory system, there is no
distinction between blood and interstitial fluid, and this general body fluid is called hemolymph
© 2011 Pearson Education, Inc.
Figure 42.3
(a) An open circulatory system Heart
Hemolymph in sinuses surrounding organs
Pores
Tubular heart
Dorsal vessel (main heart)
Auxiliary hearts Small branch vessels in each organ
Ventral vessels Blood
Interstitial fluid Heart
(b) A closed circulatory system
• In a closed circulatory system, blood is confined to vessels and is distinct from the interstitial fluid
• Closed systems are more efficient at transporting circulatory fluids to tissues and cells
• Annelids, cephalopods, and vertebrates have closed circulatory systems
© 2011 Pearson Education, Inc.
Single Circulation
• Bony fishes, rays, and sharks have single circulation with a two-chambered heart
• In single circulation, blood leaving the heart passes through two capillary beds before
returning
© 2011 Pearson Education, Inc.
Figure 42.4a
Bony fishes, rays, and sharks have single circulation with a two-chambered heart Blood leaving the heart passes through two capillary beds before returning.
Artery
Heart:
Atrium (A) Ventricle (V)
Vein
Gill
capillaries
Body
capillaries Key
Oxygen-rich blood Oxygen-poor blood
Evolution of heart is evident by number of Heart Chambers
• Amphibians and reptile have a three-
chambered heart: two atria and one ventricle
• Mammals and birds have a four-chambered heart with two atria and two ventricles. The
left side of the heart pumps and receives only oxygen-rich blood, while the right side
receives and pumps only oxygen-poor blood Mammals and birds are endotherms and
require more O
2than ectotherms
Figure 42.4b
(b) Double circulation
Systemic circuit
Systemic capillaries Right Left
A A
V V
Lung
capillaries Pulmonary circuit
Key
Oxygen-rich blood Oxygen-poor blood
Respiratory Surfaces Adaptation
• Animals require large, moist respiratory surfaces for exchange of gases between their cells and the respiratory medium, either air or water
• Gas exchange across respiratory surfaces takes place by diffusion
• Respiratory surfaces vary by animal and can
include the outer surface, skin, gills, tracheae, and lungs
© 2011 Pearson Education, Inc.
Gills in Aquatic Animals
• Gills are outfoldings of the body that create a large surface area for gas exchange
© 2011 Pearson Education, Inc.
• Ventilation moves the respiratory medium over the respiratory surface
• Aquatic animals move through water or move water over their gills for ventilation
• Fish gills use a countercurrent exchange system, where blood flows in the opposite
direction to water passing over the gills; blood is always less saturated with O2 than the water it meets
© 2011 Pearson Education, Inc.
Figure 42.23
Gill arch
O2-poor blood O2-rich blood
Blood vessels Gill arch Operculum
Water flow
Water flow
Blood flow
Countercurrent exchange PO (mm Hg) in water
2 150
PO (mm Hg) in blood 2
120 90 60 30 140 110 80 50 20
Net diffu- sion of O2
Lamella
Gill filaments
Energetics of Osmoregulation
• Osmoregulators must expend energy to maintain osmotic gradients
• The amount of energy differs based on
– How different the animal’s osmolarity is from its surroundings
– How easily water and solutes move across the animal’s surface
– The work required to pump solutes across the membrane
© 2011 Pearson Education, Inc.
Figure 44.3
(a) Osmoregulation in a marine fish (b) Osmoregulation in a freshwater fish Gain of water
and salt ions from food
Excretion of salt ions from gills
Osmotic water loss through gills and other parts of body surface
Gain of water and salt ions from drinking seawater
Excretion of salt ions and small amounts of water in scanty urine from kidneys
Gain of water and some ions in food
Uptake of salt ions by gills
Osmotic water gain through gills and other parts of body surface
Excretion of salt ions and large amounts of water in dilute urine from kidneys Key
Water Salt
Concept 44.2: An animal’s nitrogenous wastes reflect its phylogeny and habitat
• The type and quantity of an animal’s waste products may greatly affect its water balance
• Among the most significant wastes are
nitrogenous breakdown products of proteins and nucleic acids
• Some animals convert toxic ammonia (NH3) to less toxic compounds prior to excretion
© 2011 Pearson Education, Inc.
Figure 44.8
Proteins Nucleic acids
Amino acids
Nitrogenous bases
—NH2 Amino groups
Most aquatic animals, including
most bony fishes
Mammals, most amphibians, sharks,
some bony fishes
Many reptiles (including birds), insects, land snails
Ammonia Urea Uric acid
Urea
• The liver of mammals and most adult
amphibians converts ammonia to the less toxic urea
• The circulatory system carries urea to the kidneys, where it is excreted
• Conversion of ammonia to urea is energetically expensive; excretion of urea requires less
water than ammonia
© 2011 Pearson Education, Inc.
Uric Acid
• Insects, land snails, and many reptiles, including birds, mainly excrete uric acid
• Uric acid is relatively nontoxic and does not dissolve readily in water
• It can be secreted as a paste with little water loss
• Uric acid is more energetically expensive to produce than urea
© 2011 Pearson Education, Inc.
The Influence of Evolution and
Environment on Nitrogenous Wastes
• The kinds of nitrogenous wastes excreted
depend on an animal’s evolutionary history and habitat, especially water availability
• Another factor is the immediate environment of the animal egg
• The amount of nitrogenous waste is coupled to the animal’s energy budget
© 2011 Pearson Education, Inc.
Excretory Processes
• Most excretory systems produce urine by refining a filtrate derived from body fluids
• Key functions of most excretory systems – Filtration: Filtering of body fluids
– Reabsorption: Reclaiming valuable solutes – Secretion: Adding nonessential solutes and
wastes from the body fluids to the filtrate – Excretion: Processed filtrate containing
nitrogenous wastes, released from the body
© 2011 Pearson Education, Inc.
Figure 44.10
Capillary
Filtration
Excretory tubule
Reabsorption
Secretion
Excretion
FiltrateUrine
2 1
3
4
Malpighian Tubules
• In insects and other terrestrial arthropods, Malpighian tubules remove nitrogenous wastes from hemolymph and function in osmoregulation
• Insects produce a relatively dry waste matter, mainly uric acid, an important adaptation to terrestrial life
• Some terrestrial insects can also take up water from the air
© 2011 Pearson Education, Inc.
Digestive tract
Midgut (stomach)
Malpighian tubules
Rectum
Intestine Hindgut
Salt, water, and nitrogenous
wastes
Feces and urine Malpighian
tubule
To anus
Rectum
Reabsorption
HEMOLYMPH
Figure 44.13
Birds and Other Reptiles
• Birds have shorter loops of Henle but
conserve water by excreting uric acid instead of urea
• Other reptiles have only cortical nephrons but also excrete nitrogenous waste as uric acid
© 2011 Pearson Education, Inc.
Figure 44.14a
Human Excretory Organs
Posterior vena cava
Renal artery and vein
Aorta Ureter Urinary bladder
Urethra
Kidney
Figure 44.14b
Kidney Structure
Renal cortex Renal medulla Renal artery Renal vein
Ureter
Renal pelvis
Nephron – Functional unit of Kidney
Concept 44.4: The nephron is organized for stepwise processing of blood filtrate
• The filtrate produced in Bowman’s capsule
contains salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules
© 2011 Pearson Education, Inc.
From Blood Filtrate to Urine: A Closer Look
Proximal Tubule
• Reabsorption of ions, water, and nutrients takes place in the proximal tubule
• Molecules are transported actively and passively from the filtrate into the interstitial fluid and then capillaries
• Some toxic materials are actively secreted into the filtrate
• As the filtrate passes through the proximal tubule, materials to be excreted become concentrated
© 2011 Pearson Education, Inc.
Proximal tubule Distal tubule
Filtrate CORTEX
Loop of Henle
OUTER MEDULLA
INNER MEDULLA Key
Active transport Passive transport
Collecting duct
Nutrients NaCl
NH3 HCO3 H2O K
H
NaCl H2O
HCO3
K H
H2O
NaCl
NaCl
NaCl H2O
Urea Figure 44.15
Descending Limb of the Loop of Henle
• Reabsorption of water continues through channels formed by aquaporin proteins
• Movement is driven by the high osmolarity of
the interstitial fluid, which is hyperosmotic to the filtrate
• The filtrate becomes increasingly concentrated
© 2011 Pearson Education, Inc.
Ascending Limb of the Loop of Henle
• In the ascending limb of the loop of Henle, salt but not water is able to diffuse from the tubule into the interstitial fluid
• The filtrate becomes increasingly dilute
© 2011 Pearson Education, Inc.
Distal Tubule
• The distal tubule regulates the K+ and NaCl concentrations of body fluids
• The controlled movement of ions contributes to pH regulation
© 2011 Pearson Education, Inc.
Collecting Duct
• The collecting duct carries filtrate through the medulla to the renal pelvis
• One of the most important tasks is reabsorption of solutes and water
• Urine is hyperosmotic to body fluids
© 2011 Pearson Education, Inc.
Solute Gradients and Water Conservation
• The mammalian kidney’s ability to conserve water is a key terrestrial adaptation
• Hyperosmotic urine can be produced only
because considerable energy is expended to transport solutes against concentration
gradients
• The two primary solutes affecting osmolarity are NaCl and urea
© 2011 Pearson Education, Inc.
Antidiuretic Hormone
• The osmolarity of the urine is regulated by nervous and hormonal control
• Antidiuretic hormone (ADH) makes the
collecting duct epithelium more permeable to water
• An increase in osmolarity triggers the release of ADH, which helps to conserve water
© 2011 Pearson Education, Inc.
Figure 44.19-2
Thirst
Hypothalamus
ADH
Pituitary gland Osmoreceptors in hypothalamus trigger
release of ADH.
STIMULUS:
Increase in blood osmolarity (for
instance, after sweating profusely)
Homeostasis:
Blood osmolarity (300 mOsm/L) Drinking reduces
blood osmolarity to set point.
H2O reab- sorption helps prevent further
osmolarity increase.
Increased permeability Distal
tubule
Collecting duct
• Binding of ADH to receptor molecules leads to a temporary increase in the number of
aquaporin proteins in the membrane of collecting duct cells
© 2011 Pearson Education, Inc.
Collecting duct
ADH receptor
COLLECTING DUCT CELL
LUMEN
Second-messenger signaling molecule Storage
vesicle
Aquaporin water
channel
Exocytosis
H2O
H2O
ADH
cAMP
Figure 44.20