AP Biology Unit Four

Maintaining Homeostasis

2/11 – 3/29

Just bear with me……

• 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

• 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

http://www.youtube.com/watch?v=TeSKSPPZ6Ik

HOMEOSTASIS

HOMEOSTASIS

abiotic

response

physiological

behavior

biotic

Feedbackloops

environment

disruption

developmentdefenses

Shaped byevolution

Timing andcontrolcontrol

Regulator or conformer?

• Regulators – control internal fluctuations (us)

• Conformers – allow internal conditions to vary with environmental changes (temp in ectotherms)

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

http://www.youtube.com/watch?v=q_e6tNCW-uk

Negative Feedback Loops

RECEPTOR

STIMULUS

EFFECTOR

RESPONSE

• 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.

Other 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

Other thermoregulatory mechanisms

• Insulation

• Evaporative heat loss

• Behavioral responses

• 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.

Negative feedback: control of sugar in the blood

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?

Biological Examples of Negative Feedback Loops

Thermoregulation Blood Sugar Levels Blood volume Respiratory Rate

Negative Feedback Loops

RECEPTOR

STIMULUS

EFFECTOR

RESPONSE

Homeostatic mechanisms and organ systems are shaped by evolution.

• Excretory systems deal with osmoregulation (water balance) and excretion of nitrogenous wastes

osmoregulation

Prokaryotes respond via altered gene expression to changes in the osmotic environment

Protists: Many have contractile vacuoles

• Freshwater: Water will diffuse into the fish, so it excretes a very hypotonic (dilute) urine to expel all the excess water. Gills uptake lost salt.

• 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.

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

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.

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.

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

• 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.

Development of respiratory systems

The Respiratory System

• The respiratory system:

• - delivers oxygen to and removes CO2 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.

Fish respiratory system

Countercurrent exchange

How are lungs perfected for terrestrial living?

lungfish

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 CO2 make carbonic acid H2CO3).

• Hemoglobin carries oxygen and also can carry bicarbonate ions (form of CO2)..

• 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 CO2 varies most in respiration in response to different metabolic and environmental conditions.

Circulatory System

• Function – moving substances around: nutrients (from digestion), wastes (from excretion), O2 and CO2 (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

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

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

 

How does negative feedback loops work here?

For regulating heart beat

• Receptor

• Stimulus

• Effector

• response

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

Case Study

• The story of Darlene Etienne and her miraculous homeostatic mechanisms!

http://www.reuters.com/article/video/idUSTRE60O29A20100128?videoId=34511738

• "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.

• 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

http://news.bbc.co.uk/2/hi/americas/8459090.stm