Distribution of ions between compartments

ECF vs ICF

ECF high sodium, low potassium low calcium

ICF low sodium, high potassium, very low calcium

Cell Respiration

Aerobic vs. anaerobic metabolism

anaerobic(no oxygen)

Aerobic(oxygen)

Aerobic is more efficient

The amount of energy an animal uses in a unit amount of time.

Measured as O₂ consumption measured in units of calories.

Size Principle

Surface area(SA) vs Volume(V)

large animals/cells

exchange substances poorly but retain substances well

small animals/cells 

exchange substances well but retain substances poorly

Feedback Systems

Sensor: measures some aspect of the environment. ex. temperature.

Integrator: compares the sensor measurement to a reference value(setpoint). ex. normal temp.

Effector: the output of the system that changes the interl environment. ex. increase temp.

Negative feedback: the effector counteracts the initial sensor stimulus

critical for maintaining homeostasis

Positive feedback: the effector increases the initial sensor stimulus

leads to rapid changes

Excretion of nitrogenous waste

AMMONIA

Advnatages: no energy required

Disadvantages: req. lots of water

loses .5l of water per gram of nitrogen

classification: ammonotelic(fish)

MOST SOLUBLE

Excretion of nitrogenous wastes

UREA

Adv: less toxic

Disadv: req. ATP to synthesize

.05L water loss per gram of nitrogen

Classification: Ureotelic(mammal)

Excretion of nitrogenous wastes

URIC ACID

Adv: requires little water

Dis: requires ATP to synthesize

.001L of water used per gram of nitrogen

Classification: Uricotelic(birds/lizards)

LEAST SOLUBLE

What is heat

Ways of Heat Gain

External environment

Endogenous heat production(metabolism)

Heat transfer

conduction

heat transfer through physical contact

(solids, liquids)

temperature gradient is driving force

surface area influences ease of movement

composition of material influences ease of movement

heat transfer

Counter-current heat exchange

between arterial and venous blood

creates a small driving force to create minimal heat loss

Humans core is 37 degrees celcius

Birds 39 degrees celcius

Extremeties are allowed to get much colder.

heat transfer 

convection

Occurs when environmental medium(air or water) moves over the body surface.

modified form of conduction(slower)

free convection: environment medium not mechanically moved. Ex. hot air rises.

Force convection:environmental medium physicaly moved. Ex. fans

layers of heat around surface.

free convection: boundary layers are not disturbed

Forced convection: boundary layers are removed 

Ex. fan, windchill

Heat transfer

evaporation

transformation of water from liquid to vapor(gas)

Evaporative cooling: when water moves from liquid to gas energy is absorbed from surroundings.

Heat transfer

radiation

Incident radiation can be either absorbed, increasing heat gain, or reflected, no heat gain.

Emitted radiation causes heat loss

Thermal Budget

Heat In Vs Heat out

Heat in: conduction, convection, radiation, endogenous heat production(metabolic rate)

Heat out: conduction, convection radiation, evaporation.

All elements have passive and regulated components

Endotherms(warmblooded)

VS.

Ectotherms(coldblooded)

Both regulated body temperature

Both change physiology Ex. vasoconstriction

both thermoregulate

Warmblooded have insulation coldblooded dont.

coldblooded have low metabolic rate warmblooded has high rate.

Endotherms

Endotherms have low MR at thermal neutral zone.

Metabolic rates increase to maintain temperature at low and high temps; sweating takes energy.

Require less energy

variable in size

blood temperature increases with ambient temp

MR directly proportional to T_b

more efficient in storing biomass due to not needing to keep high body temp.

will not tolerate rapid changes

Behavioral Thermoregulation

Selecting temperature by behavior.

Heliotherm: heat source is the sun

Thigmotherm: heat source is substrates(earth,rock)

energy gained through conduction/convection/radiation

Humans do this by putting on sweater

Different isoforms(isoenzymes) are produced

Isoform A and Isoform B

only one gets produced

Isoform A for cold acclimation

Isoform B for warm acclimation

Acute response: rapid drop in MR, fish slows

Chronic Response(acclimates):slow increase in MR

HETEROTHERMS

Animals capable of varying degrees of endothermic heat production.

Temporal Heterotherms: T_b varies over time

Ex. hibernation, torpor

Regional heterotherms: different parts of body at different temperatures.

Ex. Testicles.

Thermogenesis: convert chemical energy into heat

Shivering thermogenesis: muscle contraction to produce heat. only 25% efficient.

Nonshivering Thermogenesis: metabolism of fat to produce heat.

Decrease driving force(counter-current exhange)

Decrease surface area(small ears short limbs)

Increase size(smaller surface area/volume ratio)

Increase insulation(fat,furs,feather)

Avoidance(hibernation, torpor)

Metabolic rate 

VS.

Size

Small animals

-low WHOLE animal metabolic rate

-VERY HIGH unit metabolic rate(per unit mass)

Large Animals

-High WHOLE animal metabolic rate

-VERY LOW unit metabolic rate

With insulation

-expanded thermoneutral zone

-less increase in metabolic rate needed to maintain temperature of blood.

Hibernation 

VS.

Torpor

Hibernation

-REGULATES T_B but at a lower value

Torpor

-SUSPENDS thermoregulation and allows T_b to get very low

Mammal extremities are allowed to become much more variable in temperature.

Hypothalmus

cooling increases MR and T_b

Heating leads to panting and lower T_b

What does a fever do?

Pyrogens(fever-producing substances) raises the setpoint of the hypothalmus.

Exogenous pyrogens can both increase set point by acting directly on the hypothalmus or by stimulating the release of endogenous pyrogens.

Water and Ion Balance

(osmolarity and body volume)

What is the basic biological need:

-All cells need to exit in and aqeous environment

-Water and salts(ions) need to keep relatively constant: homeostasis, thermo budget.

-Tightly associated with temperature regulation

evaporative cooling

Body fluids--compartmentalized

Intracellular fluids(ICF) - high in potassium

Extracellular fluids(ECF)/Intersitial - high in sodium

Body fluid(BF) == ECF

total 60kg

5L blood; 2L red blood cells, 3L plasma

23L of other cells

12L of bodyfluid

20kg are solutes

the movement of a substance from a region of high concentration to a region of low concentration.

-does not require energy

-random thermal motions

CONCENTRATION GRADIENT = driving force

-moves from high to low

Permeable to certain ions and substances and not others

Ex.Membrane is permeable to sodium and not calcium

Lipid bilayer(lipid barrier)

-contains a polar hydrophillic head and hydrophobic tails

-phospholipids forms bilayers with hydrophillic heads which are exposed to water on both sides.

-the phospholipid bilayer is a barrier to hydrophillic substances due to hydrophobic core

Hydrophobic substances can easily diffuse through lipid bilayers

Hydrophillic substances cannot pass directly through lipid bilayers(blocked by hydrophobic core)

Transmembrane aqueous pores provide paths for movement of water and ions.

-highly regulated

Passive tranport(hydrophobic)

-diffusion no energy required

-neds a concentration gradient

-requires some way for substance to cross mem.

Active transport

-requires energy(ATP)

-can move a substance against a concentration gradient

hydrophobis solutes - diffuse through memberanes easily

Hydrophillic solutes - diffuse through aqueous pores in membranes

Ion channnels can be in an open state(conducting) or closed state(non-conducting)

Open

-High permeable state, conducting state

Closed

-low permeable state, impermeable state.

ion channel are selective and allow certain ions to pass but not other ions.

Ex. Sodum channels permeable only to sodium and impermeable to potassium

Potassium channels permeable to potassium but impermeable to sodium.

-Requires energy

- can move against concentration gradient

-requires some enzyme system

-no aqueous pore needed

No machanism to actively transport water across membranes

-only mechanism is osmosis

-need to think in terms of movement of solutes.

Osmolarity

Osmolartiy = Mole of solute/L of solution

water will move from region of low osmolarity to region of high osmolarity.

Osmolarity: simplifying assumptions

1) 1mmole of any substance = 1mOsm soln

2) Do molecules of solute dissociate in water?

1- not necessarily true since protein has a larger volume than urea but for dilute solutions OK, does not depend on the specific molecular species.

2- 1M sucrose = 1 osmolar

1M NaCl solution = 2 osmolar

3- different dissolved solutes add independently in determining osmolarity.

Isosmotic-no net movement of water

Hypoosmotic-if B has more osmolarity than a then A is hypoosmotic to B

Hyperosmotic- if A has more osmolarity than B then A is hyper osmotic relative to B

The effect a solution has on a cell

Hypotonic: cell has more solutes than surrounding, cell absorbs water and expands.

Hypertonic: cell has less solutes than surrounding, cell loses water to surrounding and shrivels

Isotonic: cell and surrounding has equal concentration

Water and ion balance

Osmoregulator

osmoconformer

euryhaline

stenohaline

BFOC-body fluid osmotic concentration

Osmoregulator: an animal that maintains BFOC with surroundings.

Osmoconformer: an animal that follows the osmotic concentrations of the environment

Euryhaline: animal that can survive over a wide range

stenohaline: an animal that can tolerate only a small change.

Most cases, verterbrates are osmoregulators with a BFOC of ~300mOsm.

Excess water they secrete water

too little water they retain and obtain water

excess ions they secrete ions

too few ions they retain and obtain ions.

volume of water and ionic composition are regulated together. 

water and ions are regulated together because water usually moves when solutes move.

Ex. 300mOsm = 300mMoles/1L = 150mMoles/0.5L

Factors to consider in water/ion balance

1.Availability or water and salts

aquatic vs. terrestrial animals

seawater vs fresh water

terrestrial: desert vs humid

2.Respiration/temperature

respiration is major source of water loss

higher temp higher water content

Factors to consider in terms of water/ion balance

part 2

Permeability of skin

-amphibians highly permeable skin

-mammals reptiles birds, desert amphibians skin is highly impermeable.

Feeding- diet affect salt uptake.

Excretion

-all osmoregulators have some mechanism to excrete excess water.

Fresh water fish 

VS

Salt water fish

Fresh

gain water osmotically accross gills

removes water via kidney

OC of urine << BFOC

actively uptakes ions across gills

Salt

lose water osmotically through gills

drinks a lot

absorbs ions actively and water passively

OC urine = BFOC

secretes ions across gills

General features of transport epithelias

-Asymmetrical distribution of transporters

-epithelial cells are connected by tight junctions

many types

-abundant mitochondria to meet energy demands of ion transport

Types of transport in Epithelia cells

Transcellular transport

-movement of solutes or water THROUGH the cell

Paracellular transport

-movement of solutes or water BETWEEN the cells