BIO 203 - Dr. Collins and Erin V. Notes from full semester PDF

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Dr. Collins and Erin V. Notes from full semester...

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Lecture 1--basic principles of physiology

Physiology: how things work! -The biological study of the functions of living organisms and their parts -study of how cells interact with their “environment” to obtain the things required for life (vital substances include water salt oxygen nutrients heat)

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Internal vs external environment ○ Internal environment of an animal contains plenty of cells ○ External is outside of the animal ○ The two environments interact through integuments and exchange systems Exchange systems ○ Any system that allows for the exchange of material from: ■ External to internal env ■ Internal to external env ○ Ex: respiratory, digestive, excretory, circulatory systems Levels of organization in biological systems ○ Cellular ■ Epithelial, connective tissue, nerve, muscle ○ Tissue ■ Groups of cells with a common structure and function ○ Organ ■ Organization of diff tissues to perform specific functions ○ System ■ Several organs organized carry out major body functions Basic principles ○ All life is: ■ Aquatic ● Body fluids of all animals have the same general composition: h2O and salt ● Water is the major component: 75% of body weight, 99% of all molecules ● 0.75% of molecules are salts ● Biochemical substances 0.25% ■ Compartmentalized ● Separation of substances in diff comparents. ● The cell= the basic unit ● Major fluid compartments ○ ICF--inside of cells ○ ECF--outside of cells ■ Interstitial fluid is ECF that is not in circulatory system

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■ Plasma is the liquid portion of blood Deals w same fundamental problems ● How to maintain asymmetry ○ Hard to transport substances selectively between compartments ○ Trade offs ● All life requires input of energy: life is energetically unfavorable ● Many animals solve these problems in interesting ways ○ Gain distinctive insights by looking at diff animals ○ Comparative physiology ● reproduction Constrained by the laws of physics and chemistry ● Ohm’s law ● Boyle’s law ● Ideal gas law ● Gravity ● KE and PE ● Physical environment governs what cells can and cannot accomplish ● Cells utilize these laws to their advantage Can tolerate only a limited range of conditions ● Salts, water, O2, CO2, nutrients, waste elimination, temp, pH, etc ● Maintained through homeostasis: maintenance of a relatively constant internal environment ○ Requires cell-to-cell communication ■ Nervous system, hormonal sys, intrinsic sys ○ Requires negative feedback

ECF vs ICF: asymmetric distribution of ions ○ Sodium: higher in ECF than ICF (100mM vs 1mM) ○ Potassium: higher in ICF than ECF (100mM vs 1mM) ○ Calcium: very low in ICF (nM) and low in ECF (1-3mM) ■ Calcium is very important and doesn't want to be high bc it is a signaling molecule: mechanisms control this level Adenosine Triphosphate (ATP) ○ Principal form of energy used by cells ○ Derived from nutrient energy sources ○ Drives cellular work Cellular respiration ○ Aerobic: oxygen is used ■ CO2 + H2O + 38 ATP ■ More efficient

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Anaerobic: no oxygen ■ Lactic acid + 2 ATP ■ Very fast but not efficient Metabolic Rate (MR) ○ Amount of energy an animal uses in a unit amount of time ○ Measured as O2 consumption in units of cals ○ Sum of all energy requiring biochemical reactions ○ Higher MR, more heat production ■ Basal MR: the minimum amount of energy expenditure that the animal needs to do to stay alive ● Can change when conditions change (not constant) ■ Movement ■ Heat production ■ Anabolic pathways (building biomass)

Clicker Q: large animals have a SMALLER surface area for heat exchange with the external environment than a small animal As an animal gets larger, its surface area grows less rapidly than its volume.

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Size principle--relationship btwn surface area and volume ○ SA/V ratio is an index of relative surface area for exchange ○ As radius increases, SA/V ratio gets smaller and relative surface area for exchange decreases. ○ Larger surface area more heat exchange can occur ○ Large animals have good heat retention and low heat exchange ○ Small animals have poor heat retention and high heat exchange Feedback systems ○ Components: ■ Sensor: measures some aspect of the internal environment ■ Integrator: compares the sensor measurement to a reference value (a set point) ■ Effector: the output of the system that changes the internal environment ○ Negative feedback ■ Thermostat: sensor detects temp, integrator compares the temp to the set point (desired temp) and decides it is “too warm” therefore AC is set to ON. ■ The effector is opposite to the stimulus ■ Critical for maintaining homeostasis ○ Positive feedback ■ The effector increases the initial sensor stimulus

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An increase in temperature measured by the sensor results in the effector causing a further increase in temperature Leads to rapid changes Action potential, giving birth, blood clotting “Anti-homeostasis”

Lecture 2: 8/29 ●

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Physiological ecology: the organisms relationship to its physio-chemical environment ○ How do organisms use the basic laws of physics and chem to meet their biological needs and solve basic [physiological problems? Energy production / utilization ○ Macromolecules--metabolize energy ■ carbohydrates(glucose)--> ATP, biosynthesis )increases biomass). Growth of new tissue, fat storage→ HEAT ■ Proteins (amino acids)--> ATP, Cellular work (defending asymmetry): signaling, transport, secretion, muscle contraction → HEAT ● Proteins lead to nitrogenous wastes: ○ Salvaged for amino acid synthesis ○ Excreted ○ In some animals converted to less toxic forms of nitrogen (urea and uric acid) ■ Ingested foods include proteins, carbs, fats ■ The end products of ingested foods are typically CO2 and metabolic H2O ■ Also produces ammonia/NH3 ■ ■

fats→ ATP ATP→ biosynthesis, cellular work, external work (activity costs)

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Excretion of nitrogenous wastes ○ Trade offs--energy expenditure vs water conservation

Nitrogen

advantages

disadvantages

Water

Animal

compound excreted

loss per gram of nitrogen

classification

ammonia

No energy required

Requires lots of water to eliminate

0.5 L

ammonotelic

urea

Less toxic

Requires ATP to synthesize

0.05 L

ureotelic

Uric acid

Requires Requires ATP little water to to synthesize eliminate

0.001 L

uricotelic

○ What type of animal is ammonotelic?---aquatic What type of animal is uricotelic? ---birds, reptiles Ureotelic?---terrestrial, mammals

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Heat Energy and Body Temperature ○ Heat= energy (kinetic--movement of molecules) ○ temperature= measure of heat content; index of molecular motion ■ HOT→ high heat content, high E content, high molecular motion, high temp. Energy can move away from object and into environment ■ COLD→ low heat content, low E content, low molecular motion ■ Heat is TANGIBLE---can flow from one system to another ○ Thermal budget ■ In (heat obtained) ● Heat gain from external environment ○ Conduction, convection, radiation ● Endogenous heat production (metabolism) ○ Generated internally by the organism ○ Metabolic rate (MR) ■ Out (Heat Lost) ● Heat loss to external environment ○ Conduction, convection, radiation, evaporation ■ ***All elements have PASSIVE and REGULATED components!!*** ○ Principles of Heat transfer ■ Conduction: heat transfer through physical contact. (solids, liwuids) ● T1=T2: no net trrasnfer

T2 > T1: net flow from T2 to T1 T1 > T2: net flow from T1 to T2 Driving force for heat transfer: the difference in temperature/gradient between the two blocks ● Factors influencing conduction: ○ Temp gradient (driving force) ○ Surface area of contact influences ease of mvmt ○ Length between objects ○ Composition of interface ○ Differential equations--transport equations ■ DQ/dt= (K * A) / l * (T2-T1) ● A= surface area of contact ● DQ/dt= flow of heat ● K*A/l = ease of movement ● T2-T1= driving force ● l= length btwn objects ● K= thermal conductivity (W/m*K) ○ Metals: 220-430 K ○ Tissue: 0.47 K ○ Water: 0.6 K ○ Air: 0.025 K (REALLY GOOD INSULATOR) ○ **why are water and tissue basically the same?: tissue is basically water ■ Low thermal conductivity so good insulators ● Flow of heat= ease of movement X driving force. Convection: occurs when environmental medium (air or water) moves over the body surface. ● Modified/slower form of conduction ● Transfer equation essentially the same as for conduction ● Free Convection: boundary layers form when there is little or no forced movement of environmental medium. ○ Decreased driving force ○ Because of these layers, body senses ● ● ●

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environmental temperature as 35º, not 20º. Forced Convection: physical movement of environment medium disrupts boundary layers ○ Increased driving force for heat exchange ○ External force makes the medium move across the surface ○ Without these layers, body senses true environmental temp of 20º. (wind chill!) ■ Evaporation: transformation of water from liquid (low heat content) to vapor (high heat content) ● Requires energy, Cools down environment ● 1g H2O→ 580cal (heat of vap) ● Evaporative cooling: when water moves from liq to vapor, it absorbs energy from the body surface→ cooling ○ Sweating, panting ■ Radiation ● Longer wavelengths are less energy (infrared) ● Body surface reflects incident radiation, emits heat (heat loss from body) ○ Absorbed radiation is heat gain from incident radiation (that was absorbed) ● Black surfaces absorb radiation, white surfaces reflect it in ALL directions. ■ Heat transfer Example: ● Exchange of heat between blood and environment ○ A(Tamb) = the air of the environment ○ Blood (Tb) ○ Air moving between the skin and blood through interstitial fluid ■ Key factors: thermal conductivity, driving force, surface area of the skin ○ After exercise: vasodilation: vessels are now closer to the surface of the organism, L term is reduced and the heat flow increases. Area also increases increasing heat flow ○ When the body is cold: vasoconstriction: increases length between vessel and surface, decreases heat flow Sea Gulls: feet on ice? ○ Tbody= 39ºC Tice= 0ºC Blood coming up out of the leg= 31ºC ■ High potential for heat loss. ●

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What happens if there is NO heat exchange between arterial and venous blood? ■ Large driving force for heat exchange from foot to ice→ significant heat loss to environment ■ ■ What happens if there is counter-current (opposite flows) heat exchange btwn arterial and venous blood? ● Blood coming back up is warmer, 35º-37ºC ● Small driving force for heat exchange from foot to ice--minimal heat loss to environment ● This is super important bc it keeps the blood of the animal warm !! ● Trade off??? ○ Lets feet get very cold, must be able to tolerate ○ Does not take energy Counter-current exchange mechanism: ○ Arteries and veins in close contact. ○ High surfaCE AREA OF CONDUCT BETWEEN ARTERIES AND vEINS ○ Higher rate of heat transfer from arterial to venous blood ■ Arterial blood cooled ■ Venous blood warmed ■ Returning blood warmer--less energy needed to re-warm the blood. ● Energy is not needed ■ Small driving force = less heat loss. Core body Temperature (Core Tb) ○ Birds and mammals need to maintain core Tb ■ Humans--Core Tb ~ 37ºC ■ Birds-- Core Tb ~ 39ºC ○ ***requires LOTS of energy!!** ○ Extremities can get much colder than core ○ WHY? ■ There is an optimal temperature that the body works at (enzymes) ■ The reaction rate virtually every process in the body increases exponentially with temp ■ Reaches a certain point and then crashes at a high temp-proteins are denatured, chemical reactions fail ○ General strategies for regulating Tb: ■ Ectothermy: use of external heat to thermoregulate Poikilotherms ● Cold blooded (poor term) ○

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All non-vertebrate species amphibians/reptiles/fish/sharks MR varies with Tamb bc TB is same as Tamb in ectotherms: means that ability to function depends on T amb ○ If it is cold, they are cold (use less energy, slower/easy prey) ○ If it is warm outside, they are warm (use more energy, faster/better predator) ■ Endothermy: use of internal heat to thermoregulate homeotherms ● Warm blooded ● Birds and mammals ● tunas/dinosaurs ● Energetically very costly ● Body temp relatively constant over a wide range of Tamb ● Don't typically lose heat to environment ● Potentially heat gain at high Tamb ● As Tamb gets colder, MR increases to produce heat and maintain Tb ● Thermoneutral Zone: does things to maintain temperature, @ basal MR ● Sweating requires energy! ■ Heterothermy: use of both internal and external heat to thermoregulate ● Temporal heterothermy ● Regional heterothermy Mechanisms of thermoregulation ● ● ●

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ectotherms

endotherms

Regulate Tbody

Yes

Yes

Change physiology

Yes (limited)

Yes

Behaviorally thermoregulate

Yes

Yes

insuation

No

Yes (fat/fur/feathers)

Metabolic rate

Low (low heat prod)

High (high heat prod)

● -Feathers are endotherms bc insulation to trap air -Ectotherms do not have insulation bc it is harder to get heat from the environment to change their body temperature

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Clicker #1: in terms of regulation of body temp, boundary layers would most likely be problematic on a sunny hot day with no wind. TRUE ○ Same as wearing extra clothing #2: in ectotherms, as ambient temperature decreases,metabolic rate decreases which then causes a decrease in body temp. ○ FALSE--the decrease in ambient temperature causes the body temp to decrease which then causes the metabolic rate to decrease. NOT the other way around! Ectotherms Endotherms -as Tamb decreases: -Tamb decreases: -TB decreases -TB decreases -MR decreases -MR increases ●

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Advantages of being an ectotherm ○ Require less energy ■ Require 17X more energy than an ectotherm of the same size/mass ■ More suited to variations in food supply ■ Can tolerate a less predictable environment ○ Can exploit a broader range of body size/shape ■ Since Tb ~ Tamb, freedom from heat-conserving constraints ■ Can function w smaller body mass (small so they can take in more heat from the environment) ■ Greater length/diameter variability ○ More efficient in producing biomass ■ Ingested food/energy available for producing biomass rather than maintaining high Tb Regulation of Tb in ectotherms ○ Behavioral thermoregulation ○ Fish in water--it is the temp of the water ○ Environment needs to be the right temp in order to thermoregulate ■ Explores diff areas and selects the “preferred temperature”--a fairly narrow range (optimum temp for optimal MR) ■ Fish that like cold environments like shallow water bc it is cold in beg of summer (fluke) ○ Anole--a lizard ■ Tamb changes significantly over 24-hours in their habitat ■ At night, it finds a protected area out of the Tamb ■ During the day, it will increase its MR by sitting in a warmer area; in the sun (TB>>Tamb) ■ Afterward, it burrows to minimize heat loss. ■ Multiple ways to do this--conduction, radiation through rocks

All ectotherms depend on their environmental source of heat to thermoregulate to maintain their MR ○ Ectotherms will normally not tolerate rapid temp changes… ■ Catfish: maximum critical temp (CTmax) ● THE TEMP AT WHICH SOME PERCENTAGE OF ANIMALS WILL DIE WHEN PLACED IN IT. ● Changes with the seasons. (lower in winter) ● **catfish (bullheads) acclimated to warm temp can better tolerate high temp than ones acclimated to cold temp*** Heliotherm: heat source is the sun Thigmotherm: heat source is the substrate (earth) ○ How its gained (IN)--conduction/convection/radiation ○ We do this all of the time--energetically VERY CHEAP Thermal acclimation ○ Selective synthesis of multiple forms of the same enzyme ○ Isoenzymes(isoforms)--isoform A and isoform B (only one produced at a time) ○ Isoenzymes have diff optimal temps--function at diff rates at diff temps ○ Fish is acclimated to 20ºC (optimal MR) ■ What happens when rapidly moved to 10ºC? ■ Acute response--rapid drop in MR--fish becomes VERY slow!! (happens in short amt of time) ■ Chronic response (acclimation)--slow increase in MR (entire curve makes a left shift--optimal MR is restored, optimal temp has changed) ○

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Optimum MR

10º C

20º C

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Thermoneutral zone--range of ambient temps over which the organism can thermoregulate without having to increase heat production / significantly increase MR ○ The animal IS thermoregulating this zone ○ vasoconstriction/vasodilation: physiological regulation used in the TZ ○ Behavioral thermoregulation used throughout the entire time ○ This zone is NOT constant/ not a fixed number Endotherms in the cold! ○ Increase MR→ heat prod→ energetically costly! ○ Thermogenesis: convert chemical energy into heat ■ Shivering thermogenesis--muscle contraction to produce heat. ● Groups of antagonistic muscles are activated--little net movement other than shivering. ● Skeletal Muscles are activated and deactivated very quickly ● Fast contraction increases blood flow ● Muscle contraction is only 25% efficient--75% of energy expended is released as heat. ■ Nonshivering thermogenesis--metabolism of brown fat to produce heat. ● Very little energy is conserved in the form of ATP ● Directly produces heat ● BROWN FAT (brown adipose tissue BAT) ○ Specialization for fat fueled thermogenesis ○ Change thermal conduction (regulated process) ■ Decrease driving force ● Countercurrent exchange in limbs ● Pulsatile blood flow to limbs ■ Decrease SA ● Less heat loss ■ Increase size ● SMALLER SA/VA ratio ● Body shape reflects environment (large body long limbs = warm area; small short limbs = cold environment) ■ Increase insulation ● Fur fat and feathers ■ Avoidance ● Hibernation, torpor ○ CLICKER #3: in a cold environment, a large animal is more efficient at maintaining body temp than a small animal even though it has a higher MR. ■ TRUE→ in colder temp, larger animal loses less heat

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because they have a small SA/V ratio. (maintain body temp with a lower body temp to mass ratio) SMALL ANIMAL: ■ Low whole animal MR ■ Very high unit MR LARGE ANIMAL: ■ High whole animal MR ■ Very low unit MR ****LARGER ANIMALS USE LESS ENERGY PER UNIT MASS TO STAY WARM*** ■ Each cell has to make less heat if there are more cells, losing less to the environment

How do we (endotherms) manipulate the size principle? ○ Huddling--penguins ■ Decreased effective surface area reduces heat loss (decrease SA/V ratio collectively) ○ Increase insulation ■ fur/hair: trapping of air ● Piloerection--goose bumps ■ Feathers--trapping of air ● Birds--fluffing feathers in cold ■ Fat (walrus) ■ ■ Effect of insulation: ● MR decreases toward the BMR without insulation ● Once BMR is reached, MR increases at a certain Tamb ● With insulation, MR decreases less rapidly than without insulation ○ Expanded TZ ○ Less increases in MR needed to maintain Tb ○ Retains heat ○ Avoidance--great savings cost in terms of energy ■ Animals that have high unit MR ■ Hibernation: regulate Tb but at a lower set point value (Temp at which the organism is trying to regulate) ● Bears; 25-30ºC ■ Torpor: suspend thermoregulation and allow Tb to get very low ● Small mammals, hummingbirds Endotherms--moderate heat stress (Tb>Tamb) ○ Physiological /behavioral thermoregulation: facilitate heat transfer to external environment with little or not increase in MR ■ Vasodilati...