Animal: Lecture 6 Flashcards
Animals do what or what to regulate physiological parameters?
Animals either regulate their
physiological parameters OR allow their bodies to conform to external conditions
River otter vs. Largemouth bass?
- Regardless of environmental temperature, river otters are able to maintain their internal temperature. They are thermoregulatory (REGULATE and maintain stable)
- The largemouth bass pretty much conform to the environmental temperature. This makes them thermoconformers as they conform and vary with temperature.
What do regulators do?
Regulators use homeostatic mechanisms to control internal changes.
- Despite large external fluctuations, there are small internal fluctiations
What do conformers do?
Conformers allow their internal condition to change in response to external changes.
- They may be able to tolerate greater ranges for physiological parameters (cells are adapted to handle change)
- Internal stability is possible in stable environments (go to stable environments that don’t change much ~> tropical areas with an environment that rarely changes.
What are the physiological parameters being regulated?
Thermoregulation (temperature regulation) and Osmoregulation (body water, and solute/salt concentration)
What is thermoregulation?
Thermoregulation os the maintenance of a internal temperature within a tolerable range.
Why does body temperature matter?
Biochemical and physiological processes are sensitive to changes in temperature
- Enzyme reaction rate decreases when temperature decreases.
- Proteins and enzymes can be denatured when temp increases
- Membrane fluidity can vary with temperature.
Each animal species has an optimal internal temperature range:
- can be narrow (small changes) or wide (large changes)
- Temperatures outside range impairs functioning, which could lead to death.
Body temperature can be..?
Body temperature can be variable or relatively stable .
Poiklotherm?
The body temperature of poikilotherms varies with environment. They have a wide range and can handle changes.
Homeotherm?
Homeotherms have a relatively constant body temperatures. They have a narrow range and don’t really withstand changes.
Thermal strategies?
Thermal strategies can be defined based on source of heat.
Endotherms?
Endotherms rely on (internal)
metabolism as their major heat
source.
- not to say that we cannot get heat from sunbathing, but the majority of our heat comes from metabolic processes.
Ectotherms?
Ectotherms rely primarily on
external environment as their
major heat source (i.e., don’t
produce enough body heat to
raise above external temperature;
rely mostly on behaviour)
- like sunbathing for a lizard on a rock.
Source vs. range of temperatures?
Some endotherms are poikilotherms
and some ectotherms are homeotherms:
- Most mammals and birds are endotherms and homeotherms
- Most birds and mammals that undergo hibernation and some insects are poikilotherms and endotherms.
- Some tropical reptiles, as well as antarctic and deep-sea fish are ectotherms and homeotherms
- Most invertebrates, amphibians, reptiles and fish are ectotherms and poikilotherms.
What does thermoregulation require?
Thermoregulation requires maintaining equal rates of heat gain and heat loss.
Through which processes do we regulate our temperature?
Anatomical/physiological:
- Evaporative heat loss
- Circulatory adaptations
- Metabolic heat production
- Insulation
Behavioural responses
Evaporative heat loss?
Evaporative heat loss:
- Water lost from moist surfaces cools/carries away heat
- Adaptations that augment this cooling effect include panting and sweating
- The blood brings heat up to the surface and cools it before bringing it back to the body
Circulatory adaptations?
Vasoregulation:
* common to endotherms and ectotherms.
* ability to control blood vessels and capillaries
Countercurrent heat exchangers:
* found in birds and mammals
*vessels in one direction are close to vessels in another direction
Vasoregulation?
Vasoregulation is achieved via nerve
impulses and hormones.
- hypothalamus sends out nerve impulses and hormones to control how much blood is being flown into capillaries.
Vasodilation?
Vasodilation relaxes smooth muscle
walls of surface blood vessels
– Allows more blood to flow from core to surface for cooling
- causes us to get red because of the proximity to the surface - cools blood before its brought back.
Vasconstriction?
Vasoconstriction tenses smooth
muscle walls of surface blood
vessels
– Reduces blood flow from core to
surface to prevent heat loss
– good when we are cold as the warm blood can be kept inside to make sure that our core body is kept functioning (brain, heart over fingers)
Potential problem areas in maintaining body heat for goose?
Feet get cold in water??
Countercurrent heat exchanges?
Heat is transferred between fluids flowing in opposite directions
Heat from warm arterial blood is transferred to cooler venous blood as it returns to the body core.
- Artery and vein are close and heat is transferred due to the proximity, keeping the blood warm as it reentered the body.
Metabolic heat production?
All metabolic activity produces heat
- Endotherms have much higher metabolic rates than similarly sized
ectotherms
Muscle contraction
- Activity
- Shivering
Brown adipose tissue (some mammals)
-High concentration of mitochondria
- Cellular respiration produces heat instead of ATP
- animals in the arctic or up north have more of this
Hypothalamus thermostatic function when hot?
Stimulus: increased body temperature
Sensor/control center: thermostat in hypothalamus (two things)
- response: sweat
- response: blood vessels in skin dilate
RESULT: body temperature decreases, homeostasis internal body temperature (36-38) is reached
Hypothalamys thermostatic function when cold?
stimulus: decreased body temperature
sensor/control: thermostat in hypothalamus (2 responses)
- response: shivering
- response: blood vessels in skin constrict
RESULT: body temperature increases; homeostatic internal body temperature (36-38) is reached
Insulation?
Fur, feathers, fat
- Major adaptation to prevent heat loss in mammals and birds
Traps air between the skin and the fur or feathers. They move around and the layer of air is warmed by the internal body temperature. This warm air remains close to skin and fur, keeping the animal warm
Blubber is thick and warm and a good insulator (especially for aquatic animals)
Behavioural responses?
Shade seeking, sun basking, migration.
- They can be fairly easy tasks that do not reqire much energy like sun basking, or they can be huge energy takers–MIGRATION
Blubber is a thick layer of vascularized adipose tissue under the skin of all cetaceans, pinnipeds, penguins, and sirenians. Would
you expect blubber to contain more or fewer blood vessels than
human skin?
Fewer!
Water crosses cell membranes via…
A. Simple diffusion
B. Facilitated diffusion
C. Active transport
D. A and B
E. A and C
D! both simple diffusion and facilitated diffusion!
What is osmoregulation?
Osmoregulation is the control of solute concentrations and the balance of water
gain and loss from the body
What are the physiological parameters for osmoregulation?
Body water (volume)
* E.g., in blood, in interstitial fluid, within cells
Total solute concentration
* E.g., calcium + potassium + sodium + urea + certain amino acids + water soluble hormones
Individual solute concentrations
* E.g., calcium vs potassium vs sodium vs urea vs certain amino acids vs water soluble hormone
- these change based on the area: something needed in a liver cell will be in high concentration in those areas but low in the brain for example.
What is osmosis?
Osmosis is the movement of water across a selectively permeable membrane
Osmosis example in a beaker?
On one side we have Hyperosmotic
solution: higher solute concentration and lower free H2O concentration.
On the other side we have Hypoosmotic solution: lower solute concentration and higher free H2O concentration
- Solutes can not cross the membrane
- Water will want to equalize the concentrations on both sides, therefore it will go to the hyper osmotic side!
What are animal cells affected by?
Animal cells are affected by the relative osmolarity of their surrounding fluid.
Hyperosmotic fluid?
- higher concentration of solute outside the cell
- Water leaves cells through osmosis
- Cells that lose too much water shrivel and may die as the water will all go to the environment.
Hypoosmotic fluid?
Lower concentration of solutes outside the cell, higher concentration of solutes inside.
- Water enters cells through osmosis
- Cells that gain too much water burst and die.
Isoosmotic fluid?
- Same concentration of solutes inside and outside the cell ( it is balanced )
- No net movement of water into or out of cells.
What might the fluid be?
Blood plasma, hemolymph, or interstitial
Two strategies for maintaining water balance?
Osmoconformers and osmoregulators
Osmoconformers?
Osmoconformers are isosmotic with their environment (like sharks):
- No tendency to gain or lose water
- All are marine
- Some have stable osmolarities while other tolerate variable osmolarities.
- Actively transport specific solutes between membranes to maintain homeostasis. (REQUIRES ATP)
Osmoregulators?
Osmoregulators maintain a stable internal osmolarity
– Found in marine, freshwater, and terrestrial environments
– A particular internal osmolarity is achieved by actively transporting solutes into or out of cells
— Water then flows in response to osmotic gradients
Kidneys: they will move solutes from one place to make sure that there’s water that flows in and through to balance things out.
osmoregulation requires…?
Osmoregulation requires energy.
Cost of osmoregulation energy?
Energy costs are reduced by minimizing osmotic differences between body fluids and the surrounding environment
– E.g., freshwater molluscs have lower internal osmolarities than do marine molluscs
- Start at less extreme to not have to spend more or as much energy maintaining osmoregulation in freshwater.
If osmoregulation is energetically costly, why aren’t all animals osmoconformers?
This gives the access to more niches and resources.
Benefits > costs
Osmotic challenges depend on..?
The osmotic challenge faced by osmoregulators depends on their environment.
Substance vs. Solute concentration?
Body fluids of most vertebrates = ~300 mOsm/L
Freshwater lake/pond = 20-40 mOsm/L
Seawater = 1000+ mOsm/L
Natural tendencies of osmoregulators?
- Freshwater osmoregulators → gain water
- Marine osmoregulators → lose water
- Terrestrial animals → lose water
You may have heard the expression “drinking like a fish”, but do fish drink water?
Some do and some don’t
Osmoregulation in a marine fish?
Marine fish are hypo osmotic relative to the seawater (hyper osmotic environment)
- Loss of water increases internal osmolarity (so how can the fish recoup water?)
- Osmotic water lost through gills and other parts of body surface
- Get water from food, but also salt ions as well as getting water from drinking seawater (also brings salt ions)
- Excretion of salt ions from gills (Cl-) and in small amounts of water in scanty urine from kidneys (scanty = high concentration of salt and low amount of urine)
RESULT: Marine fish drinks seawater to replace water lost across the body surface
Osmoregulation in a freshwater fish?
Freshwater are hyper osmotic relative to the lake/river (hypo osmotic environment)
- Gain of water decreases internal osmolarity (so how can the fish get rid of excess water?)
- Osmotic water gained through gills and other parts of the body surface
- Gain some ions in food, but also some water.
- Uptake of salt ions by Cl- cells in the gills
- Excretion of large amounts of water in dilute urine from kidneys, but also salt ions are lost.
RESULT: Freshwater fish excretes water but must also take up salt ions to bring internal osmolarity back up. Freshwater fish drinks almost NO water.
Dehydration?
Dehydration is a challenge for terrestrial animals.
Adaptations to reduce water loss?
Adaptations to reduce water loss
– Body coverings: cuticle, shells, keratinized skin (prevent water evaporation)
– Nocturnal (come out in cooler environments)
How do terrestrial animals maintain water balance?
Maintain water balance by drinking and eating moist food and producing metabolic water through cellular respiration
Animals control..?
Animals control the solute concentration of an internal body fluid.
How do they control this?
Via transport epithelia
– One or more layers of epithelial cells specialized for moving particular solutes in controlled amounts and in specific directions. This process takes ATP.
Which structural characteristic is most important for transport epithelia involved in osmoregulation?
A. A large lumen (internal space)
B. Several layers of thick muscle
C. A large surface area
D. Rigidity
C. A large surface area!
Transport epithelia have large surface areas (ensures exchange occurs)?
Some face the external environment directly (e.g., gills)
- But many line tubular networks that connect to the outside by an opening on the body surface (e.g., those in salt glands or kidneys)
-Transport epithelia are closely connected to circulatory fluid to remove extra salts
Salt excreting glands?
Seabirds, sea turtles, and marine iguanas remove excess salt, taken in when drinking sea water, through salt-excreting glands
- This is through sneezing or tear ducts, which remove the salt
Salt glands and countercurrent exchange?
Salt glands have transport epithelia
that rely on countercurrent exchange to draw in extra salts from blood to inside.
- Salt concentration is always higher in the blood vessel than the secretory tubule. The blood becomes less salty as time move on!
Animals can do what with their environmental conditions?
Animals can regulate physiological parameters or conform to environmental conditions
Animals have what mechanisms for thermoregulation?
Animals have anatomical, physiological, and behavioural mechanisms for thermoregulation
Animals in different environments?
Animals in different environments have different osmotic challenges and osmoregulatory physiology
Countercurrent exchange?
Countercurrent exchange is a homeostatic mechanism seen in multiple contexts
