Transcript AP Homeostasis One

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
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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
behavior
Timing and
control
control
disruption
Feedback
loops
response
environment
Shaped by
evolution
HOMEOSTASIS
physiological
abiotic
defenses
development
biotic
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
•
•
•
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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
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
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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 CocaCola 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