Execratory System Flashcards
animal life is challenged under changing environmental conditions – ____ ____ ____ compensate for changing conditions and maintain the internal environment within the relatively narrow limits that cells can tolerate
Homeostatic control system
Osmoregulation?
osmoregulation is the regulation of water and ion balance
Excretion do for body?
excretion helps maintain the body’s water and ion balance while ridding the body of metabolic wastes
Thermoregulation?
thermoregulation is the control of body temperature
living cells contain ____, are surrounded by ____, and constantly exchange ____ with their environment
water
What surrounds cell for simple animals?
What about for more complex animals?
for the simplest animals, water of the external environment directly surrounds cells – for more complex animals, an aqueous extracellular fluid (ECF) surrounds the cells
What does ECF contain in animals with a circulatory system?
in animals with a circulatory system, the ECF includes both interstitial fluid and blood plasma
What is osmosis?
in osmosis, water molecules diffuse across a selectively permeable membrane from a region of higher water concentration (low solute concentration) to a region of lower water concentration (high solute concentration)
What is osmolarity? What is it measured in?
the total solute concentration of a solution (osmolarity) is measured in osmoles – the number of solute molecules and ions (in moles) per liter of solution
What is normal human osmolarity?
the osmolarity of body fluids in humans and other mammals is about 300 mOsm/L
What is hypertonic?
the solution with higher osmolarity is hyperosmotic to the other solution
What is hypoosmotic solution?
the solution with lower osmolarity is hypoosmotic to the other solution
What is isosmotic?
if the solutions on either side of a membrane have the same osmolarity, they are isoosmotic
What must animals do to keep metabolic stability?
for metabolic stability, animals must keep their cellular fluids and ECFs isoosmotic
What are osmoconformers?
in osmoconformers, the osmolarity of cellular and extracellular solutions matches that of the environment
What are osmoregulators?
osmoregulators use control mechanisms to keep the osmolarity of cellular and extracellular fluids the same, but at levels that may differ from the osmolarity of the surroundings
What do animals do to control osmolarity?
animals control osmolarity by removing certain substances from body fluids and releasing them into the environment
animals control osmolarity by removing certain substances from body fluids and releasing them into the environment
animals excrete ____ ____, ____ ____ ____ ____, and ___________________________
excretion of ions and metabolic products is accompanied by ____ ____ – ____ is a solvent for those molecules
animals that take in large amounts of water may also excrete ____ to maintain osmolarity
animals control osmolarity by removing certain substances from body fluids and releasing them into the environment
animals excrete H+ ions, nitrogenous products of metabolism, and breakdown products of poisons and toxins
excretion of ions and metabolic products is accompanied by water excretion – water is a solvent for those molecules
animals that take in large amounts of water may also excrete water to maintain osmolarity
What carriers osmoregulation as a generality of all animals?
How are these structures set up?
microscopic tubules formed from a transport epithelium carry out osmoregulation and excretion
the tubules are immersed in body fluids at the proximal end, and open to the body exterior at the distal end
What are four components of osmoregulation?
1 Filtration:
Small molecules and ions from body fluids or blood nonselectively pass through narrow spaces between cells into the tubule.
2 Tubular reabsorption:
Nutrient molecules, some ions, and conserved water are returned to the body fluids or blood by transport epithelium
3 Tubular secretion:
Excess ions and toxic breakdown products are transported selectively from the body fluids or blood into the tubule.
4 Excretion:
Urine (nitrogenous wastes, some ions, toxic breakdown products, excreted water) is released into the environment.
What do transport proteins do to help with osmoregulation?
Where do they do this?
transport proteins move specific molecules and ions into and out of the tubule by either active or passive transport, depending on the substance and its concentration gradient
4 steps tubule function?
Filtration
Tubular reabsorption
Tubular secretion
Excretion
What is filtration?
Filtration is the nonselective movement of water and solutes, but not large molecules such as proteins, into the proximal end of the tubules through spaces between cells
What is tubular reabsorption?
Tubular reabsorption: Important molecules (e.g., glucose and amino acids) and ions are transported by the transport epithelium back into the ECF and eventually into the blood as the filtered solution moves through the excretory tubule
What is tubular secretion?
Tubular secretion is a selective process in which specific small molecules and ions are transported from the ECF and blood into the tubules
What is excretion?
Excretion: Fluid (urine) containing waste materials is released into the environment from the distal end of the tubule – in some animals, waste fluids are concentrated into a solid or semisolid form
What does the metabolism of ingested food produce?
What is this used for?
the metabolism of ingested food produces metabolic water that is used in chemical reactions and is involved in physiological processes such as the excretion of wastes
What are nitrogenous by products excreted as?
What are the 3 substances that make these?
How is it determined which form will be used?
the nitrogenous products of the breakdown of proteins, amino acids, and nucleic acids are excreted as ammonia, urea, uric acid, or a combination of these substances
the particular molecule or combination of molecules produced depends on a balance among toxicity, water conservation, and energy requirements
What structure of ammonia? What is it the product of?
ammonia (NH3) is the result of a series of biochemical steps beginning with the removal of amino groups (—NH3+) from amino acids as a part of protein breakdown
What are 2 characteristics of ammonia?
How does that dictate how it should be excrete? Example?
ammonia is soluble in water, but highly toxic – it must be either excreted or converted to a nontoxic derivative
ammonia can be excreted only in dilute solutions – possible only in animals with a plentiful supply of water, such as aquatic invertebrates, teleosts, and larval amphibians
all mammals, most amphibians, some reptiles, some marine fishes, and some terrestrial invertebrates combine ammonia with HCO3– and convert the product to ____, a soluble and relatively nontoxic substance
urea
What animals convert ammonia to urea?
all mammals, most amphibians, some reptiles, some marine fishes, and some terrestrial invertebrates combine ammonia with HCO3– and convert the product to urea, a soluble and relatively nontoxic substance
What is benefit of converting ammonia to urea?
although producing urea requires more energy than forming ammonia, excreting urea instead of ammonia requires only about 10% as much water
terrestrial invertebrates, reptiles, and birds form ____ ____ instead of ammonia or urea
uric acid
What is pro and con of creating uric acid?
uric acid is nontoxic and insoluble – it precipitates in water as a crystal and can be excreted as a concentrated paste
What animals form uric acid?
terrestrial invertebrates, reptiles, and birds form uric acid instead of ammonia or urea
What is characteristic of uric acid?
uric acid is nontoxic and insoluble – it precipitates in water as a crystal and can be excreted as a concentrated paste
uric acid excretion conserves about __% of the water required to excrete the same amount of nitrogen as ammonia
99%
most marine invertebrates are ____ – the osmolarity of their intracellular and extracellular fluids and the surrounding seawater is the same, about ____ mOsm/L
osmoconformers
1000
all freshwater invertebrates are ____ – they must expend energy to excrete excess water to keep their internal fluids hyperosmotic to their surroundings
osmoregulators
What do freshwater invertebrates transport in? Through what do they transport this in?
freshwater invertebrates also actively transport salt ions from the water, through skin or gills, into their bodies
What three types of tubules to osmoregulators use?
What animal uses each?
invertebrate osmoregulators use three types of tubules for carrying out excretion:
Protonephridia, the simplest form of excretory tubule, found in flatworms and larval mollusks
Metanephridia, found in annelids and most adult mollusks
Malpighian tubules, found in insects and other arthropods
What do protonephridia feature?
What happens as hemolymph passes through?
Where is urine released?
proximal branches of the tubule network end with a flame cell containing cilia that move fluid through the tubule
when hemolymph passes through protonephridia, some molecules and ions are reabsorbed, and nitrogenous wastes are secreted into the tubules
urine is released through pores at the distal ends of the tubules where they reach the body surface
What animal has metanephridia?
Where are these located and how many?
Where does hemolymph enter?
What is reabsorbed?
What is excreted and where?
metanephridia in the earthworm
a pair of metanephridia are located in each body segment, one on each side of the body
hemolymph enters a funnel-like proximal end surrounded with cilia
some molecules and ions are reabsorbed
nitrogenous wastes are secreted into the tubule and excreted from the distal end at the body surface
What are Malpighian tubules found in?
What is there structure?
What is proximal end structure?
How and what are substances taken in?
How and what are reabsorbed?
What is excreted?
malpighian tubules in a grasshopper
have a closed proximal end immersed in hemolymph
distal ends empty into the gut
tubules secrete K+ into the lumen of the proximal segment, which draws in Cl– from the hemolymph
water follows the KCl
uric acid is secreted into the tubule
when fluid reaches the hindgut, K+ `and Cl– are reabsorbed, followed by water
uric acid precipitates as crystals – released with feces
What three features interact to conserve nutrients and water, balance salts, and concentrate wastes for excretion?
the loop of Henle, which descends through the medulla and returns again to the cortex
differences in permeability along the nephron, established by specific membrane transport proteins in each region
a concentration gradient of molecules and ions in the interstitial fluid of the kidney, which increases from the renal cortex to the deepest levels of the renal medulla
glomerular filtration occurs in ____ ____, which cups around a ball of arterial capillaries (the ____)
Bowman’s capsule
glomerulus
a ____ ____ ____descends into the renal medulla in a U-shaped bend called the____ ____ ____ and then ascends again to form a ____ ____ ____
proximal convoluted tubule
loop of Henle
distal convoluted tubule
____ ____ reabsorb important molecules and ions from the filtrate
Peritubular capillaries
What do peritubular capillaries do?
peritubular capillaries reabsorb important molecules and ions from the filtrate
Describe what structures are present to allow for glomerular filtration to take place, and what factors cause filtration to take place?
Filtration in Bowman’s Capsule:
glomerular capillaries have pores that make them more permeable to water and solutes than other capillaries
blood pressure drives fluid containing solutes through the pores of the capillaries into Bowman’s capsule – blood cells and plasma proteins are retained in the capillaries
the diameter of the afferent arteriole delivering blood to the glomerulus is larger than that of the efferent arteriole – maintaining a high level of glomerular capillary pressure
What takes place in the PCT?
What is the state of the filtrate after this?
Reabsorption in the PCT:
Na+/K+ pumps in the epithelium of the convoluted tubule move Na+ and K+ from the filtrate into the interstitial fluid surrounding the tubule
a voltage gradient causes Cl– ions to be reabsorbed from within the tubule with the positive ions
water moves from the tubule into the interstitial fluid by osmosis – aided by transport proteins (aquaporins)
specific active transport proteins reabsorb glucose, amino acids, and other nutrient molecules into the interstitial fluid, making the filtrate hypoosmotic to the interstitial fluid
nutrients and water that entered the interstitial fluid move into the capillaries of the peritubular network
reabsorbed ions, nutrients, and water are transported into the interstitial fluid, then into peritubular capillaries
H+ ions enter the tubule by active transport – products of detoxified poisons (from the liver) enter by passive diffusion
What happens in the ascending loop of Henle?
Why is this important?
What is the osmolarity now?
the ascending segment has membrane proteins that transport salt ions, but no aquaporins – water is trapped, while salt ions move out of the tubule
reabsorption of salt ions helps establish the concentration gradient of the medulla – high near the renal pelvis and low near the renal cortex
at the top of the ascending loop, filtrate osmolarity has dropped to about 150 mOsm/L
What happens in the descending loop of Henle?
What features allow water to leave?
What is the osmolarity?
Descending Loop of Henle:
filtrate leaving the proximal convoluted tubule enters the descending segment of the loop of Henle, where water is reabsorbed
this segment descends through regions of increasingly higher solute concentrations in the interstitial fluid of the medulla – water moves out of the tubule through aquaporins
osmolarity of the filtrate gradually increases to a peak of about 1,200 mOsm/L at the bottom of the loop
What happens in collecting ducts?
What are the permeable to?
What is the osmolarity?
collecting ducts are permeable to water but not salt ions
as they descend from the cortex through the medulla of the kidney, they encounter an increasing solute concentration
water moves out os
motically, increasing the concentration of the urine – up to 1,200 mOsm/L at the bottom of the medulla
passive urea transporters near the bottom of the medulla contribute to the concentration gradient of solutes in the medulla
What happens in the distal convoluted tubule?
What controls this?
What is the osmolarity?
Secretion via the DCT:
additional water is recovered by osmosis from the fluid in the distal convoluted tubule in response to hormones triggered by changes in the body’s salt concentrations
varying amounts of K+ and H+ ions are secreted into the fluid, and Na+ and Cl– ions are reabsorbed – urea and other nitrogenous wastes remain the same
by the time the fluid (urine) enters the collecting ducts, it is isoosmotic with blood plasma (about 300 mOsm/L) but very different in composition
How do cells not die in the renal medulla from high osmolarity?
What molecule helps?
What is this molecule really?
the hyperosomotic state of the interstitial fluid toward the bottom of the medulla would damage the medulla cells if they were not protected against osmotic water loss
the protection comes from high concentrations of otherwise inert organic molecules called osmolytes in the cytoplasm of these cells
the osmolytes, primarily a sugar alcohol called sorbitol, raise the osmolarity of the cells to match that of the surrounding interstitial fluid
What is thermoregulation?
What is it based on?
What detects these changes?
temperature regulation (thermoregulation) is based on negative feedback pathways in which temperature receptors (thermoreceptors) detect changes from a set point
What do signals from thermoreceptors trigger?
signals from receptors trigger physiological and behavioral responses that return the temperature to the set point
all responses triggered by ____ ____ ____ involve adjustments in rate of heat-generating ____ reactions within the body – coupled with adjustments in rate of heat gain or loss at the body surface
negative feedback mechanisms
oxidative
within the ____°C to ____°C range of tolerable temperatures, an animal’s ____ ____ (biochemical, physiological, and whole-body processes) varies greatly
0C-45C
organismal performance
What are the four methods of heat exchange?
What is necessary to maintain constant body temperature?
all animals gain or lose heat by a combination of conduction, convection, radiation, and evaporation
to maintain constant body temperature, the heat gained and lost through these pathways must balance
What is conduction?
conduction is the flow of heat between atoms or molecules in direct contact
What is convection?
convection is the transfer of heat from a body to a fluid, such as air or water, that passes over its surface
What is evaporation?
evaporation is heat transfer through the energy required to change a liquid to a gas
What are cold blooded animals called?
Examples?
How do they obtain heat?
“cold-blooded” animals (ectotherms), including most invertebrates, fishes, amphibians, and reptiles, obtain heat primarily from the external environment
What is radiation?
radiation is the transfer of heat energy as electromagnetic radiation
What are warm blooded animals called?
Examples?
How do they obtain heat?
“warm-blooded” animals (endotherms), including birds, mammals, some fishes, sea turtles, and some invertebrates, obtain most of their heat from internal physiological sources
most aquatic invertebrates are limited ____ – their body temperature closely follows their surroundings
thermoregulators
What type of animals regulate their body temperatures the most tightly?
invertebrates living in terrestrial habitats regulate body temperatures more closely
What type of responses do animals use to regulate body temperature?
many use behavioral responses, such as moving between shaded and sunny regions, to regulate body temperature
some winged arthropods use behavioral and heat-generating physiological mechanisms for thermoregulation
What are fishes body temperatures
What do they do to maintain body temperature?
body temperatures of most fishes remain within one or two degrees of their environment
many fishes use behavioral mechanisms to keep body temperatures at optimal performance levels
What are amphibians body temperature?
What do they do to maintain body temperature?
body temperatures closely match the environment
some terrestrial amphibians bask in the sun to raise their body temperature, and seek shade to lower body temperature
What type of animals are endotherms?
What structures do they have?
endotherms – mostly birds and mammals – have highly specialized body structures, and physiological and behavioral mechanisms, to keep body temperature within a narrow range
How good are reptiles at maintaining body temperature?
What do they do to maintain body temperature?
some lizard species can maintain temperatures that are nearly as constant as those of endotherms
small lizards commonly shuttle between sunny (warmer) and shady (cooler) regions
in deserts, lizards and other reptiles retreat into burrows during the hottest part of summer days
desert iguanas lose excess heat by panting
What is thermal acclimatization?
What animals do this?
Why do they do this?
Example?
many ectotherms undergo physiological changes (thermal acclimatization) in response to seasonal shifts in environmental temperature
[EXAMPLE: In carp living in colder environments, higher proportions of cholesterol and of double bonds in membrane phospholipids make it harder for the membrane to freeze]
What do ectotherms do when temperature do when temp falls below 0C?
when temperatures fall below 0°C, some ectotherms add molecules to their body fluids that act as antifreeze to depress their freezing point and retard ice crystal formation
EXAMPLE: In carp living in colder environments, higher proportions of cholesterol and of double bonds in membrane phospholipids make it harder for the membrane to freeze
What is core temperature?
core temperature: the temperature within the central core of the body consisting of the abdominal and thoracic organs, the CNS, and the skeletal muscles
What is typical body temperature for birds and mammals?
typically, body temperatures of active individuals are held constant at levels between about 39°C to 42°C (102°F to 108°F) in birds, and 36°C to 39°C (97°F to 102°F) in mammals
Where are thermoreceptors found?
in the human body, thermoreceptors are found in the skin (integument), spinal cord, and hypothalamus
What range are thermoreceptors good in?
5 thermoreceptor types are active in different temperature ranges, from less than 8°C to above 52°C
Where are thermoreceptor signals integrated?
signals are integrated in the hypothalamus and other regions of the brain to bring about compensating physiological and behavioral responses
What happens when core temperature falls below the set point?
What compensatory responses result?
when core temperature falls below the set point, the hypothalamus sends signals through the autonomic nervous system that trigger compensating responses
immediate responses to cold include:
constriction of arterioles in the skin (vasoconstriction)
contraction of smooth muscles erecting hair shafts in mammals – reducing convective heat loss
behavioral responses to reduce heat loss
What happens if immediate responses to cold do not return the body to set point?
if immediate responses do not return body temperature to the set point, the hypothalamus triggers further responses:
shivering releases heat from oxidative reactions
epinephrine and thyroid hormones stimulate oxidation of fats and other fuels (nonshivering thermogenesis)
What is the function of brown adipose tissue?
in some mammals, brown adipose tissue can produce heat rapidly by a mechanism that uncouples electron transport from ATP production in mitochondria
What is hyperthermia?
How much temperature increase can cause this?
What is the result?
if body responses fail to raise body temperature to the set point, the result is hypothermia, a condition in which core temperature falls below normal for a prolonged period
in humans, a drop in core temperature of only a few degrees affects brain function and leads to confusion
continued hypothermia can lead to coma and death
What happens when core temperature rises above the set point?
What are immediate compensatory responses?
when core temperature rises above the set point, the hypothalamus sends signals through the autonomic system that trigger responses lowering body temperature
immediate responses to heat include:
dilation of arterioles in the skin (vasodilation)
secretion of sweat, which absorbs heat as it evaporates from the surface of the skin
panting in animals
that lack sweat glands
behavioral responses to cool the body
if body responses fail to lower body temperature to the set point, ____ results
hyperthermia
What does an increase of temperatures above normal result in?
an increase of only a few degrees above normal for a prolonged period disrupts vital biochemical reactions and damages brain cells
At what temperature of hyperthermia do people become unconscious?
What temperature do they die?
most adult humans become unconscious if body temperature reaches 41°C (106°F) and die if it goes above 43°C (110°F) for more than a few minutes
What prevents water loss in human skin?
cells of the epidermis are packed with highly insoluble keratin fibers – a surface layer of dead epidermal cells forms a tough, nearly impermeable layer that limits water loss
What does the dermis contain?
the dermis contains sweat glands, hair follicles, and thermoreceptors – arterioles delivering blood to capillary networks of the skin constrict or dilate to control blood flow
What does the hypodermis contain?
the hypodermis contains larger blood vessels and an insulating layer of fatty tissue which holds heat within the body core – mammals in cold environments have blubber
What is daily torpor? What animals do this?
many small animals and birds enter into daily torpor, a period of inactivity keyed to variations in daily temperature
What is torpor?
when the environment is cool, a lowered temperature set point reduces energy needed to maintain body temperature
in many animals, reductions in metabolic, nervous, and physical activity produce a sleeplike state known as torpor
How is counter current exchange used to store heat?
a countercurrent exchange system can be used to conserve core heat:
a set of arteries and veins is packed closely together in a region between the core and the periphery of the body
warm arterial blood flows next to cold blood from the body periphery that is in the veins
by conduction, heat moves from the artery to the vein and warmed venous blood continues to the core
What is hibernation?
What do hibernator store?
What can internal body temp drop to?
extended torpor during winter (hibernation) reduces metabolic expenditures when food is unobtainable – typically, hibernators store large quantities of fats as energy reserves
in some small hibernating mammals, body temperature can drop to near 0°C
____ ____ helps limit heat loss in nasal passages of birds and mammals:
in outgoing breaths, some ____ in the air condenses on the nasal folds
inhaled air
evaporates some of the ____ on the nasal folds, which cools the folds for the next outgoing breath
mammals can reclaim up to ____% of the water in expelled air, along with its heat content
countercurrent exchange helps limit heat loss in nasal passages of birds and mammals:
in outgoing breaths, some water in the air condenses on the nasal folds
inhaled air
evaporates some of the water on the nasal folds, which cools the folds for the next outgoing breath
mammals can reclaim up to 45% of the water in expelled air, along with its heat content
What is estivation?
Where is it discovered?
some mammals enter seasonal torpor during hot summers (estivation) when water is scarce
first discovered in the fat-tailed lemurs (shown here) from Madagascar
