AP Biology Unit Four Maintaining Homeostasis

Endothermic – maintains a constant body temperature (birds, mammals) Ectothermic – temp of environment

BIG IDEA 2: Biological systems utilize energy and molecular building blocks to grow, to reproduce, and to maintain homeostasis. BIG IDEA 3: Living systems store, retrieve, transmit, and respond to information essential to life processes. BIG IDEA 4: Biological systems interact, and these interactions possess complex properties.

We will cover….. Feedback control AGAIN! Evolutionary development of animal organ systems to control homeostasis with the environment Cellular signaling Specific systems: endocrine, nervous, immune Developmental stages and timing Plants – homeostatic mechanisms and how they respond

Organism Organization Cells Tissues Organs Organ Systems (not technically in plants) Organism The structure of a component of an organism underlies its function.

Homeostasis occurs in ALL organisms Involves all levels (except unicellular organisms): cells, organs, organisms Reflects continuity and change Shaped by evolution Affected by disruptions Defenses evolved to maintain

Remember…. Body systems coordinate their activities to maintain homeostasis.

Boseman videos are helpful! bit.ly/homeoprezi

HOMEOSTASIS

abiotic response physiological behavior biotic Feedback loops environment disruption developmentdefenses Shaped by evolution Timing and control

acclimatization An animal’s normal range of homeostasis may change as the animal adjusts to external environmental changes

Video on Feedback Loops As you watch, take notes on the basic diagram of a negative feedback loop What are the component parts Use two biological examples

Negative Feedback Loops RECEPTOR STIMULUS EFFECTOR RESPONSE Most feed back loops are

Thermoregulation RECEPTOR hypothalamus STIMULUS body temp drops/rises EFFECTOR sweat glands in skin, blood capillaries, muscles in skin RESPONSE blood vessels dilate (high)or constrict (low); sweating (high) shivering (low)

HYPOTHALAMUS Blood capillaries dilate Sweat glands active High Temp Low Temp Blood capillaries constrict Sweat glands inactive Shivering Drop Temp Raise Temp

In mammals, a group of neurons in the hypothalamus functions as a thermostat Fever as a response to infection can reset the hypothalamus set point.

Biological Examples of Negative Feedback Loops Thermoregulation Blood Sugar Levels

Negative feedback: control of sugar in the blood

Blood Glucose Regulation RECEPTOR pancreas receptor cells STIMULUS blood glucose drops/ rises EFFECTOR – alpha and beta cells in pancreas RESPONSE Alpha cells secrete glucagon – adds glucose Beta cells secrete insulin – removes glucose Glycogen is broken down in the liver to produce glucose.

Islets of Langerhans

Positive feedback: oxytocin to induce childbirth

Ethylene in fruit ripening Has anyone told you to put a banana in the bag with your apples or pears to help them ripen?

Platelet formation

Thermoregulation in Animals maintaining an internal temperature within a tolerable range

Sources of heat 1) Internal metabolism 2) External environment Endothermic animals warmed mostly by internal metabolism - ex – mammals, birds, some fish, many insects, a few nonavian reptiles Ectothermic animals gain most of their heat from outside sources - ex – reptiles, fish, amphibians, most invertebrates

Regulation of Body Temperature Why do physiological reactions proceed more slowly when the temperature decreases? How do biochemical reactions speed up as temperature increases but then cease to operate at high temps?

Movement of molecules (kinetic energy) Metabolism decreases/increases If too high, proteins (enzymes) can become denatured and metabolic reactions cease

Regulator or conformer? Regulators – control internal fluctuations – more expensive ( ex – temp in us) Conformers – allow internal conditions to vary with environmental changes (ex - temp in ectotherms)

Thermoregulators (homeotherms) - their body temp stay constant but metabolic rate varies with temp - over relatively mild temps, metabolic rate stays constant (thermoneutral zone TNZ) - as temp drops below TNZ or above the TNZ, what happens to the metabolic rate?

Thermoconformers (poikilotherms or ectotherms) Poikilo means variable. Their metabolic rate and temperature varies exponentially with the rise and fall of external temp. ectothermic Ex – reptiles, fish, amphibians, most invertebrates Low temps slow metabolic reactions

As temp warms up, metabolism slows down since not as much energy needed to heat the body. As temp rises, more energy Needed to cool the body. Metabolic rate follows temp.

Balancing heat loss and gain Organism exchange heat with their environment by: conduction, convection, radiation, and evaporation

Behavioral Thermoregulatory mechanisms Ectotherms: 1. Seek warm or cool places 2. Certain body postures 3. Huddling in groups Endotherms: 1. Seek warm or cool places 2. Also postures 3. Us - clothing

Other thermoregulatory mechanisms Insulation Evaporative heat loss Regulation of metabolic heat - endotherms use metabolic heat to maintain their body temp - ectotherm gain heat mostly from environment

Raising temp metabolically Mammals and birds regulate rate of metabolic heat production through activity and shivering. Some mammals generate heat through nonshivering thermogenesis, rise in metabolic rate produces heat instead of ATP. Some mammals have brown fat for rapid heat production.

Circulatory adjustments: Countercurrent exchange in temp regulation Common in marine mammals and birds the heat in the arterial blood leaving the body core is transferred to the venous blood

Acclimatization in thermoregulation Adjusting amount of insulation (fur) in endotherms Changing amount of enzymes and saturated/unsaturated lipids in cell membranes used at various temperatures Producing antifreeze compounds

Q 10 – a method to describe the temp sensitivity or process in numerical terms R 1 is the measured reaction rate at temperature T 1 (where T 1 < T 2 ). Note that R 1 and R 2 must have the same unit. R 2 is the measured reaction rate at temperature T 2 (where T 2 > T 1 ). T 1 is the temperature at which the reaction rate R 1 is measured (where T 1 < T 2 ). T 1 and T 2 do not need to be exactly 10 degrees apart but they need to be in C or K, not F.

If not sensitive Q 10 is 1. Most biological systems are between 2 and 3. At Q 10 of 2, means the rate of a reaction or process doubles as temp increases by 10 o C; Q 10 of 3, rate triples.

For example, if a cricket respires 20 molecules of CO 2 25° C and 40 35° C, what is the Q 10 ? Q 10 = (40/20) (10/(35-25)) = 2, so for every 10° C increase in temperature, the rate would double. Thus, the cricket would respire 10 15° C and 80 45° C (if the cricket could withstand that temperature).

If a katydid breathes 6 times per minute at 20° C, and 14 times per minute at 30° C, then what is Q 10 for that process?

Homeostatic mechanisms and organ systems are shaped by evolution. Excretory systems deal with osmoregulation (water balance) and excretion of nitrogenous wastes

Remember….. Balancing water amount is in reality balancing solute concentration.

osmoregulation Prokaryotes respond via altered gene expression to changes in the osmotic environment Protists: Many have contractile vacuoles

Osmoconformers Conform to the surrounding environment as far as solute and water are concerned

Marine animals are usually osmoconformers, while freshwater species are generally osmoregulators. The sharks’ bodies are particularly high in urea and trimethylamine N-oxide.

In Fish Freshwater Fish: Water will diffuse into the fish, so it excretes a very hypotonic (dilute) urine to expel all the excess water. Gills uptake lost salthypotonic A marine fish has an internal osmotic concentration lower than that of the surrounding seawater, so it tends to lose water and gain salt. It actively excretes salt out from the gills.fishsaltgills

Most animals are osmoregulators

dealing with nitrogenous wastes The excretory system in vertebrates: - maintains water, salt, and pH balance - removes nitrogenous wastes (from breakdown of protein and nucleic acids) by filtering the blood - nitrogenous waste type depends on environment

Evolution of a tubular excretory system Excretory system in flatworms

Excretory system in earthworms

In humans

The kidney works closely with the circulatory system in that the salt content, pH, and water balance of the blood is controlled by the kidneys.

Within the kidney, fluid and dissolved substances are filtered from the blood and pass through nephrons where some of the water and dissolved substances (nutrients) are reabsorbed. The remaining liquid (including toxins) and wastes form urine. Increasing salt concentration draws water out of tubule.

What homeostatic mechanisms work here? Concentrated blood (too much salt, too little water) signal receptors in the hypothalamus to stimulate release of ADH (AntiDiuretic Hormone) by the pituitary gland which influences kidney to reabsorbs water, making blood more dilute. Antidiuretic – anti pee

If, on the other hand, a person drinks an excess of water, the sodium in the blood becomes more dilute and the release of ADH is inhibited. The lack of ADH causes the nephrons to become practically impermeable to water, and little or no water is reabsorbed from them back into the blood. Consequently, the kidneys excrete more watery urine until the water concentration of the body fluids returns to normal. A song……

Alcohol inhibits the release of ADH, causing the kidneys to produce dilute urine.

It’s really a salt thing!

Osmoregulation RECEPTOR STIMULUS EFFECTOR RESPONSE

Development of respiratory systems

The Respiratory System The respiratory system: - delivers oxygen to and removes CO 2 from the circulatory system and eventually the tissues - in humans, this occurs in the alveoli of the lungs which are covered in capillaries The respiratory system works closely with the circulatory system.

Exchange of gases in alveoli

Aquatic organisms such as fish: respiratory system Less Oxygen in water…. Design of gills important….

Countercurrent exchange

How are lungs perfected for terrestrial living?

lungfish Transition…..both.

How does structure correlate with the function of the parts?

What homeostatic mechanisms are at work here? Breathing is controlled by the medulla of the brainstem. It repeatedly triggers contraction of the diaphragm initiating inspiration. The rate of breathing changes with activity level in response to carbon dioxide levels, and to a lesser extent, oxygen levels, in the blood. Carbon dioxide lowers the pH of the blood (water and CO 2 make carbonic acid H 2 CO 3 ). Hemoglobin carries oxygen and also can carry bicarbonate ions (form of CO 2 )..

There are chemosensors in the carotid artery and the arch of the aorta. The sensors of the aortal are sensitive to the level of oxygen in the blood. Sensors near the medulla are sensitive to the level of carbon dioxide in the blood. If oxygen level falls or carbon dioxide levels vary too greatly from the set point, a negative feedback mechanism increases respiratory rate.

Mammals are most sensitive to carbon dioxide levels because the amount of CO 2 varies most in respiration in response to different metabolic and environmental conditions.

Oxygen-hemoglobin dissociation curves Hemoglobin carries oxygen and releases it to the tissues. Look at the hemoglobin-oxygen dissociation curve above. At which pH is the hemoglobin least saturated with oxygen? _____________ What has happened to the oxygen and why? Think about when CO 2 is in the tissues, the pH drops due to the formation of carbonic acid. CO 2 + H 2 O H 2 CO 3 (carbonic acid)

At lower pH, the Hemoglobin is less saturated because it has given up its oxygen to the tissues to compensate for the low pH due to CO 2 concentration.

Muscles also needs oxygen particularly in times of exercise. A special protein in muscles called ___myoglobin____ (myo – muscle) has more affinity for oxygen than hemoglobin. Notice the graph below.

Fetal vs normal hemoglobin Fetal hemoglobin has a higher affinity for oxygen.

Respiration Regulation RECEPTOR chemoreceptors in the brainstem medulla (CO2) and carotid artery and aorta (O 2 ) STIMULUS – amount of CO 2, O 2 and pH EFFECTOR – diaphragm muscles RESPONSE breathing rate

Circulatory System Function – moving substances around: nutrients (from digestion), wastes (from excretion), O 2 and CO 2 (from respiration), hormones (endocrine), immune substances, and lymph fluid. Closely tied to the digestive, excretory, respiratory, endocrine, immune, and lymphatic system.

Types: Open – blood mixes with internal organs directly (insects, arthropods, mollusks) Closed – blood stays in vessels (earthworms, some mollusks such as octopi, vertebrates

Structures vary for types of animals: Fish – one ventricle, one atrium, gill capillaries, single loop Amphibian – one v, 2 a, lung and skin capillaries, double circulation (one to body, one to lungs) Reptiles – partially divided v, 2 a, other same as amphibs Mammal, Birds – 2 v, 2 a, lung capillaries, double circulation

The ventricle is the most muscular.

Flow of blood in Mammalian Heart: right, right, lungs, left, left, body (right side unoxygenated traveling to lungs the pulmonary artery (arteries – away, veins – toward heart). R R lungs L L body

1 –body – 10,11 – 2 – 4 (valve) – 3 – 5 (valve) – 6 – lungs - 7 – 8 – 12 (valve) - 9 – 1.

Beating of the heart controlled when cardiac muscles transfers an electrical signal via the SA (sinoatrial) node or “pacemaker” (in top right atrium) to the AV (atrioventricular) node between the right a and v.

Blood Pressure Force of blood against an artery. Measured as Systolic (Super Top Most….when ventricles are contracting) over Diastolic (down, minimum, when ventricles fill with blood); normal 120/80

Homeostatic mechanisms to regulate blood pressure A negative feedback loop An increase in blood pressure is detected by receptors in the blood vessels that sense the resistance of blood flow against the vessel walls. The receptors relay a message to the brain, which in turn sends a message o the effectors, the heart and blood vessels.

Response The heart rate decreases and blood vessels increase in diameter which causes the blood pressure to fall back within the normal range or set point. Conversely, if blood pressure decreases, the receptors relay a message to the brain, which in turn causes the heart rate to increase and the blood vessels to decrease in diameter.

Circulatory (BP) Regulation RECEPTOR pressure receptors in blood vessels STIMULUS – resistance of flow in vessels EFFECTOR – heart and blood vessels RESPONSE heart rate change, diameter of vessels changes

Development of Digestive Systems Intracellular Digestion – ex amoeba Extracellular Digestion – bacteria, us

Digestive Systems in Animals One opening – sac (cnidarians, flatworms) Tube – roundworms and on Why more advantageous?

The Digestive System in Humans Ingestion, mechanical and chemical breakdown of food, absorption of nutrients, elimination of wastes

Pathway Oral Cavity – only carbs broken down here! Mechanical digestion - teeth Esophagus – just a muscular tube, peristalsis pushed food down Stomach – only protein broken down here! (low pH due to secretion of gastric juice), lots of churning in another muscular organ

The Big Boys…..small intestines and accessory glands Carbs, proteins, and lipids broken down here. Most digestion and absorption here! Pancreatic enzymes and bile (for fat) from the liver via the gallbladder released in this area. Microvilli extend the surface area.

Microvilli in the small intestine

Finishing up… Large intestine (colon)- no digestion, just reabsorbs water and creates feces

Can you live without your…How? Stomach? Small Intestine? Large intestine?

How does the homeostatic evolution of these systems reflect: Continuity Divergence

What about dehydration? And other issues affecting homeostasis? 8&list=PLFCE4D99C4124A27A&index=27 Boseman

Case Study The story of Darlene Etienne and her miraculous homeostatic mechanisms!

"We cannot really explain this because that's just (against) biological facts," Lambert told a news conference. "We are very surprised by the fact that she's alive.... She's saying that she has been under the ground since the very beginning on the 12th of January so it may have really happened — but we cannot explain that." Authorities say it is rare for anyone to survive more than 72 hours without water, let alone 15 days. But Etienne may have had some access to water from a bathroom of the wrecked house, and rescuers said she mumbled something about having a little Coca- Cola with her in the rubble.Coca- Cola Fuilla said Etienne did not suffer a broken leg, as first reported, but that both legs were trapped under debris. "Both legs are very sore," he said.

Rescuers said the 16-year-old, who was severely dehydrated and covered in dust, possibly survived by drinking bathwater but could not have lasted much longer. Earthquake survival stories