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UNIT 8 NOTES
Chapter 40 Sections 1-4 with numerous examples from other chapters as noted
These two words are almost always seen together because they go hand in hand:
Anatomy –
Physiology –
Those of you going on to college for anything in the medical field will have to take a course
called A&P, Anatomy and Physiology. This is where you learn how you are built and how
you work. Depending on where you go to school some of you may use cats in your lab to
dissect, and others will have cadavers, real dead people. Once you get over the initial
shock, you will be fine. They are dead, feel no pain, and there is no blood. Wait til you see
your first operation. There’s blood and that’s gross. Good Luck.
Animal form and function are correlated at all levels of organization. This means that all
cell organelles like mitochondria and ribosomes, all cells that make up tissues, all tissues
etc. etc. all the way up to large parts of organisms like arms and legs are built the way
they are, generally, because that is the best shape to get the job done. Here is an
example. Polydactyly (extra fingers and toes) is a dominant trait, yet most people only
have five on one limb. Why? Wouldn’t more fingers be better? No. If it were, nature would
have selected for polydactyly and not against it and we would all need new gloves.
Therefore, due to the interaction of an organism with its environment and the genes it
possesses, it looks the way it does because that shape will function best in that
environment. This also explains convergent evolution like you see in Fig 40.2 pg. 853, Slide
5. Remember, this does not mean that these forms are perfect. It just means that given
what there is to work with genetically, this is the best fit so far. Natural selection is a work
in progress.
An animal’s _____________________ and _________________________ directly affect
how it exchanges energy and materials with its surroundings. For single-celled organisms
the plasma membrane has enough surface area to accommodate the whole organism’s
needs for food and wastes. (Review what we learned about cell size in Unit 2, pg. 99 Fig.
6.8. Cells are small to maximize their surface area to volume ratio (SA/V). This will be on
your test.) Even some multicellular organisms like a hydra (Fig. 40.3 pg. 853, slide 7) are
small enough and built so that all their body cells are in contact with the environment. This
also provides them with enough surface area for exchange of materials.
The outer covering of complex multicellular organisms, like you, does not provide enough
surface area. Therefore, these organisms must have specific adaptations that allow them to
function and survive. More complex organisms have highly folded internal surfaces for
exchanging materials (Fig. 40.4 pg. 854, slide 10). Learn some of the examples below!
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What fills the spaces between body cells?
How are animals “organized”?
Cells are organized into 


Within multicellular organisms, specialization of organs contributes to the overall
functioning of the organism. All of these examples from the human body show adaptations
that provide increased surface area internally for diffusion of materials.
Why must there be increased surface area?
Why must it be internal?
The paragraphs below provide you with examples of increased surface area within the
human body for exchange of materials with the environment. Later we will discuss the
body systems as a whole and learn more about the anatomy and physiology of each
system so you will see some of these slides again, but focus on different things.
• Digestion of food – CH. 41.3 The human digestive system contains many organs that
mechanically break apart food (mouth, stomach), secrete various digestive enzymes to
chemically break down food (salivary glands, liver, pancreas), and structures such as villi
and microvilli in the small intestines that aid in absorption. Not only do the villi add
increased surface area, but the system as a whole does too. Your small intestines are not
just a short, straight tube, but very long and convoluted so 20-25 feet of tubing are
squashed into a small space.
• Circulation of fluids – CH. 42.1 All circulatory systems use a fluid to connect all the cells
of an organism’s body to the environment. The fluid is pumped through tubes by a heart.
Cells bathed in fluid (ICF) can use diffusion to get nutrients and oxygen, as well as
removing wastes. Exchange of these materials also takes place between the ICF and the
capillaries, the smallest blood vessels, which branch out to reach almost all cells.
• Exchange of gases – CH. 42.5 This involves taking oxygen into the body and removing
carbon dioxide. It is not breathing or cellular respiration. This exchange takes place by
diffusion at the respiratory surface which can be skin, gills, tracheae, or alveoli inside the
lungs. Because the respiratory surface of a lung is not in direct contact with all other parts
of the body, the gap must be bridged by the circulatory system. Alveoli in the lungs are
surrounded by capillaries.
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• Excretion of wastes – CH. 44.3 All excretory systems involve tubular structures that
collect a filtrate. There is then reabsorption of any desirable molecules and secretion of any
more toxins or wastes into the tube which then leaves the body. In humans this takes
place in the kidneys in a structure called the nephron. Like the alveoli of the lungs,
nephrons are surrounded by capillaries.
In summary:
Villi
in
Capillaries in
small intestines
circulatory system
Alveoli
in
lungs
Nephron
in
kidneys
nutrients into circulatory system
nutrients into cells and wastes out
by way of the ICF
oxygen in and carbon dioxide out
of circulatory system
wastes out of circulatory system
With all this going on constantly inside your body, how do different parts know what to do
and when to do it? Are they just constantly working? Are substances just floating around
willy-nilly? No, of course not. Everything is under control, at least most of the time. There
are times when things are not under control, when things can go wrong. That is when you
are sick. A common way for organisms to keep things under control is feedback.
Remember that? It was one way of regulating enzymatic pathways where the final product
acted as an inhibitor to a beginning enzyme to shut down the pathway when there was
enough product. Well, that same idea is used to regulate your internal environment in a
number of different ways. Let’s take a look.
There are two types of organisms. Regulators use internal mechanisms to keep their
internal environments relatively constant, and conformers allow their internal environments
to change with the external environment.
Give an example of each:
Regulators –
Conformers –
What do organisms use homeostasis for?
Give some examples in humans:
Negative feedback is used to keep a variable or condition, like body temperature, for
example, at a set point. It works the same way as a thermostat-furnace system (Fig. 40.8
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pg.861, slide 37) does to maintain room temperature. Here are some examples of negative
feedback:
• Operons in gene regulation – see Unit 6 notes or Ch. 18.1 pg. 351
Remember the trp operon. When bacteria have enough tryptophan it acts as an inhibitor
shutting off the operon that codes for the production of the enzymes to make tryptophan.
That is negative feedback.
• Temperature regulation in animals – see below notes or CH. 40.3 pg. 862
• Plant responses to water limitations – see CH. 36.4 pg. 776
When plants do not have enough water they will close the stomates in the leaves to
prevent excess water loss and start to become droopy.
• Regulation of blood glucose – see CH. 45.2 pg. 982
This is probably the best and most common example of negative feedback in the human
body. You should be familiar with this one and the two hormones insulin and glucagon.
These two hormones are antagonistic, which means they work against each other, or do
opposite jobs.
Here is how this works. You eat something and it gets digested and absorbed into your
blood. This increases your blood glucose (sugar) level. This increase triggers your pancreas
to release insulin into the blood. Insulin tells your liver to take up the extra glucose and
store it as glycogen until it is needed, thus lowering your blood glucose level. Since your
cells keep using glucose all the time for energy, eventually your blood glucose will drop
below the desired level. This signals your pancreas again, but this time it releases glucagon
which tells your liver to convert some of that glycogen to glucose and put it into the blood,
thus raising your blood glucose to the desired level. See Fig. 45.12 pg. 983, slides 40-42.
Does this always work perfectly? No. If it did there would not be anyone suffering from
diabetes. Your endocrine system produces numerous hormones that regulate a multitude
of things in your body. I had you look up several and write down what they did in Unit 4. If
there is a problem with any one of the glands or hormones that will disrupt control and you
will be sick. Below are some examples of diseases or conditions due to lack of control.
• Diabetes mellitus in response to decreased insulin – pg. 983. Pancreatic insulin-producing
cells are destroyed by the immune system so glucose levels in the blood remain high. The
kidneys are not able to reabsorb all the sugar so it stays in the filtrate along with excess
water thus producing large amounts of urine.
• Dehydration in response to decreased antidiuretic hormone (ADH) pg. 969. ADH is a
hormone that tells the kidneys to take up more water to prevent dehydration. It is usually
released after you eat salty food or sweat a lot. If ADH is not produced or the receptors are
blocked somehow, the aquaporins will not open, urine production will not decrease, and
dehydration could result.
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• Graves’ disease (hyperthyroidism) – pg. 990. The thyroid gland does not ‘turn off’ and
continuously produces thyroid hormone.
• Blood clotting – pg. 913
Positive feedback loops occur in animals, but do not usually contribute to homeostasis.
Positive feedback is used to amplify or intensify a change. For example:
• Lactation in mammals – When baby animals nurse the mammary glands are stimulated to
produce more milk. The more the baby drinks, the more milk is produced.
• Onset of labor in childbirth – The pressure of the baby’s head near the opening of the
uterus stimulates the uterus to contract. This puts more pressure on the opening causing
more contractions which increases the pressure, etc. until the baby is born.
• Ripening of fruit – Ethylene (a plant hormone) triggers ripening and ripening triggers
more ethylene production. The result is a huge burst in ethylene production which, since it
is a gas, spreads from fruit to fruit causing them all to ripen at once. See pg. 834.
One of the most important uses for homeostasis in organisms is for thermoregulation.
What is thermoregulation?
There are basically two ways to do this. Define each and give examples of organisms that
use each method:
Endothermy:
Ectothermy:
Endothermy requires more energy than ectothermy, but allows organisms to be active in a
wider range of environmental conditions. Both endotherms and ectotherms use behavior to
control body temperature, but it is much more pronounced in ectotherms. Think lizards
basking in the sun to warm up in the morning.
Thermoregulation in many animals is accomplished in part by the circulatory system. See
CH. 40 pgs. 864-865, slides 48-51. Constricting or dilating blood vessels near the body
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surface alters the surface area that receives blood and can therefore regulate heat loss.
More blood to those vessels, more heat will be lost, and vice versa.
Countercurrent exchange is used to minimize heat loss by maximizing the transfer of
heat in adjacent fluids that are traveling in opposite directions. As blood leaves the core of
the body it transfers heat to blood returning to the core. This is a common method used in
marine mammals, water fowl, and some insects. This is why the geese on the pond can
still swim in the 40o water without freezing.
Other methods of thermoregulation include sweating, panting, and shivering. These are
controlled by a region in the brain called the hypothalamus. The hypothalamus is the
body’s thermostat and works by negative feedback just like the thermostat in your house.
See Fig. 40.16 slide 54, pg. 868.
Believe it or not there are even some plants that can regulate their temperature. Skunk
cabbage is one example. Very early in spring it begins to grow and melt the snow around it
so that it can bloom. It can be found around here in damp places such as the Utica marsh.
Obviously this plant is not regulating its temperature all the time since it does not grow all
winter long. It begins to increase its temperature when it gets cues from the environment
that spring has arrived. Other organisms also respond to changes in their external
environment and may show patterns or cyclic changes like the skunk cabbage. What is this
process called?
Thermoregulation is just one example of responding to changes in external environments.
The following several examples illustrate this concept and are pulled from many different
chapters in your text as noted.
Some of these we will discuss in class. You must be familiar with some of these as general
examples of this concept, but you do not need to know them all.
• Photoperiodism and phototropism in plants – plants bloom in response to day/night
length; plants grow toward the light. pgs. 839 and 825, respectively.
• Taxis and kinesis in animals – animals move toward or away from something in their
environment (taxis); or a change in activity in response to a stimulus (kinesis). See CH. 51.
These are both behavioral responses.
• Chemotaxis in bacteria, sexual reproduction in fungi – bacteria change their movement in
response to chemicals. See pg. 559. Fungi change to a mode of sexual reproduction in
response to a chemical stimulus released by neighboring fungi. See pg. 639.
• Nocturnal and diurnal activity: circadian rhythms pgs. 1072 and 1122. This concept will
be discussed more in Unit 9.
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The following example is in the PowerPoint, slides 56-58, pg. 872.
• Hibernation and migration in animals – animals enter a physiological state of low activity
and lower metabolism (torpor) or change location in response to external cues of
decreasing temperature and food scarcity. This allows the animal to conserve energy and
survive on less through times of stress. Migration is a behavioral mechanism whereas
hibernation is an actual physiological change within the organism. Estivation is similar to
hibernation but occurs during periods of high temperature such as July.
Homeostatic mechanisms reflect both common ancestry and divergence due to
adaptation in different environments.
We will now take a look at some different ways organisms have developed to gain
nutrients, remove wastes, and exchange gases. Keep evolution in mind as we discuss these
and try to see the similarities and differences. Several different organisms may have the
same mechanisms for maintaining homeostasis such as countercurrent exchange or a
closed circulatory system. This indicates a common ancestor at some point. However,
these mechanisms can still have differences because these organisms have adapted to
different environments and beneficial changes were selected for by natural selection to
best suit those particular environments. Again, there are numerous examples listed here
with accompanying page numbers where they can be found in your text. I encourage you
to read those sections ONLY. Don’t read all of these chapters- there is way too much
information. Concentrate on one or two examples (dot bullets) under each bolded heading
so that you can use them as examples on a test in a short answer question.
Organisms have various mechanisms for obtaining nutrients and eliminating
wastes.
Digestive Compartments
Why do animals process food in specialized compartments?
• Digestive mechanisms in animals such as food vacuoles, gastrovascular cavities, one-way
digestive systems. See pgs. 882-884, slides 59-65.
 Protists have food vacuoles, organelles that contain enzymes to break down
food. This is intracellular digestion.
 Hydra have a gastrovascular cavity. It is a digestive compartment that has one
opening and also functions to distribute nutrients. This is extracellular
digestion. Undigested material is eliminated through the same opening.
 Earthworms, grasshoppers, birds, and humans all have one-way tube systems
with specialized compartments. Systems like these are called complete
digestive tracts or alimentary canals. Food enters one end of the tube and is
digested along the way. Whatever the body needs is absorbed and what is left
over is eliminated from the other end of the tube. This waste was NEVER IN
THE BODY!!
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Gas exchange occurs across specialized respiratory surfaces which must be
moist.
What is gas exchange?
The respiratory surface is where gas exchange takes place. By what process?
• Respiratory systems of aquatic and terrestrial animals. See pgs. 916-919, slides 66-76.
 In very simple animals such as sponges and flatworms, every cell of the body is
close enough to the external environment for gases to diffuse quickly between
all cells. These animals stay wet or moist for this to occur.
 Larger aquatic organisms have gills. Gills are outfoldings of the body surface
that are suspended in the water. This provides a great increase in surface area.
Water must constantly move over the surface for gas exchange to occur. Blood
flows in the opposite direction that the water flows (countercurrent exchange)
allowing for more efficiency.
 Terrestrial animals have branching tube systems. Insects have tracheal systems
that have fine branches that take air close to the surface of every cell in the
body. Larger animals have lungs that provide a large surface for gas exchange
but must also use the circulatory system to transport the gases to and from all
body cells.
• Gas exchange in aquatic and terrestrial plants – Terrestrial plants have stomates in their
leaves that are regulated by guard cells. When open the stomates allow gas exchange and
water vapor to leave (transpiration). The majority of these stomates are on the underside
of the leaves so that when the sun is shining it is not pulling too much water out of the
plants. Aquatic plants have stomates on the upper leaf surface because the lower surface is
in the water. Having holes in the lower leaf surface here would fill the leaf full of water. I
have no idea what completely submerged plants like kelp do. My guess is simple diffusion,
but I may be wrong?
Osmoregulation balances the uptake and loss of water and solutes.
What is osmoregulation?
Osmoregulation is discussed in CH. 44 pgs. 954-957.
• Osmoregulation in bacteria, fish and protists
Any of these organisms living in freshwater will tend to take in water due to osmosis and
lose salts by diffusion. Too much water will cause cells to bloat and possibly burst, so there
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UNIT 8 NOTES
must be a mechanism for removing excess water. Bacteria have cell walls that function to
keep some water out and allow the cell to maintain its shape. Freshwater fish do not drink
much and excrete large amounts of dilute urine. Marine fish do the opposite- drink a lot
and excrete salts and very little urine. Protists have a contractile vacuole that acts as a
pump to remove excess water. Salts must be replaced in the diet or by active transport.
• Osmoregulation in aquatic and terrestrial plants
Terrestrial plants must have ways of preventing water loss. Leaves have a waxy cuticle
covering them and it is usually thinker in plants that live in dry areas. Some plants (cacti)
have modified their leaves and stems so much they do not resemble other types of land
plants. Stomates also function in water balance in plants. The guard cells will close the
stomates when water becomes low. Again, I have no idea what aquatic plants do. They
may be isoosmotic and therefore neither gain nor lose water.
An animal’s nitrogenous wastes reflect its phylogeny and habitat.
• Nitrogenous waste production and elimination in aquatic and terrestrial animals. See pgs.
959-964 slides 79-96.
Nitrogenous wastes are produced from the breakdown of proteins and nucleic acids.
Excretion is the process of removing these and other metabolic wastes. The particular
waste that an animal produces generally depends on its habitat and access to water. Fig.
44.9 pg. 959, slide 80, shows the different nitrogenous wastes.
 Ammonia is highly toxic and requires a lot of water to dilute so it is mainly
excreted only by small aquatic animals and fish mostly by diffusion.
 Mammals and larger marine fishes and sharks produce urea from ammonia.
The liver produces the urea and it then removed from the blood by the kidneys
and excreted in urine. Urea requires less water to dilute to safe levels than
ammonia, but does require more energy to make.
 Insects, reptiles, and birds excrete uric acid. It requires much more energy to
produce, but is relatively nontoxic and does not dissolve in water. It is excreted
as a paste so access to water is not an issue.
Key functions of most excretory systems:
– Filtration: pressure-filtering of body fluids
– Reabsorption: reclaiming valuable solutes
– Secretion: adding toxins and other solutes from the body fluids to the
filtrate
– Excretion: removing the filtrate from the system
• Excretory systems in flatworms, earthworms and vertebrates See pgs. 961-963, slides 8996.
 Flatworms have protonephridia – a system of dead-end tubules capped by
flame bulbs that filter ICF and release filtrate into the tubules. The filtrate then
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is released to the external environment. These function mainly in
osmoregulation.
 Earthworms have metanephridia – a system of tubules that have an internal
opening. These function in both excretion and osmoregulation. Each segment
of the worm has a pair. Fluid enters through the opening and moves through
the tubule to a bladder that opens to the outside. The tubule is surrounded by
capillaries and most solutes are reabsorbed. Wastes stay in the tubule and are
excreted to the outside.
 Vertebrates have kidneys – specialized organs that function in both excretion
and osmoregulation. The functional unit of the kidney is the nephron which is
a collection of tubules that receives filtrate from the blood. As the filtrate
passes through the tubules water and salts are reabsorbed and wastes remain
in the tubule to be excreted. More or less water is reabsorbed depending on
internal conditions.
Circulatory systems link exchange surfaces with cells throughout the body.
What are the two types of circulatory systems?
What are the three basic components?
An example of an organism with an open system is
Vertebrates such as you have closed systems with three types of vessels. List all three and
state where each carries blood from and to:
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UNIT 8 NOTES
• Circulatory systems in fish, amphibians and mammals. See pgs. 900-903, slides 104-107.
Pay closes attention to Fig. 42.5 pg. 902, slide 107. The construction of the heart in each
of these different types of animals gets more complex as you move from left to right in the
diagram. This also shows you the pattern of evolution since mammals and birds came
later.
 Fish have a closed circulatory system with single circulation and a two
chambered heart. Blood leaves the heart, goes to the gills for gas exchange,
and then travels to the rest of the body before returning to the heart.
 Amphibians have a closed circulatory system with double circulation and a
three chambered heart with two atria and one ventricle. Most of the oxygen
poor blood leaves the ventricle and goes to the lungs, but there is some
mixing. Blood returning from the pulmonary circuit enters the other side of the
heart and most of it is sent out to the body.
 Reptiles also have a closed circulatory system with double circulation and a
three chambered heart with two atria and one ventricle. Here the ventricle is
partially divided by a septum, except in alligators.
 Mammals have a closed circulatory system with double circulation and a four
chambered heart. Blood coming back from the body enters one side of the
heart and then goes to the lungs for gas exchange. Blood returning from the
lungs enters the other side of the heart and then goes out to the body. There
is no mixing of oxygen rich and oxygen poor blood. This is very important for
endotherms due to their higher energy demand. This type of circulation can
deliver more oxygen more efficiently.
Before we talk about energy allocation and use, let’s put together everything we just
learned about. The only way to really learn about the human body, or any organism, is to
look at all the parts, learn their names and functions, and where each one is located. Done.
Now to really understand you have to put it all together and see how each part works with
other parts and how the organism functions as a whole. Two sections from the course
outline I was given from the College Board are:
Interactions and coordination between organs provide essential biological
activities.
• Stomach and small intestines
• Kidney and bladder
• Root, stem and leaf
Interactions and coordination between systems provide essential biological
activities.
• Respiratory and circulatory
• Nervous and muscular
• Plant vascular and leaf
(These are just some examples. Every part works with many other parts.)
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In other words, all of your body’s organs and organ systems need to work together for you
to function and remain healthy. Try to think of the many ways your different parts interact.
What happens to a PBJ when you eat it? How are you able to walk to your next class?
Being able to trace that PBJ from your mouth to becoming energy to creating waste to the
toilet is what this whole section is about. All of your parts work together to function as a
whole and none of your parts can function without the rest. Together they all maintain
homeostasis and keep you functioning.
What happens if there is a disruption in homeostasis? Yup. You get sick because something
is not working the way it should. This can be caused by injury, disease, or even an
environmental cause. Here are just a couple examples. We will discuss your immune
system in much more detail in CH 43 next.
Biological systems are affected by disruptions to their dynamic homeostasis.
Disruptions at the molecular and cellular levels affect the health of the
organism.
• Physiological responses to toxic substances – toxins often interfere with cell
communication thus preventing cells from doing something they have been told to do or
doing something they haven’t been told to do. Some toxins can alter the permeability of
membranes thus changing osmolarity and causing osmotic imbalances for the organism.
• Dehydration – lack of water can prevent wastes from being removed or other cellular
processes from taking place.
• Immunological responses to pathogens, toxins and allergens – See CH. 43 below.
Energy Allocation and Use
All living systems require constant input of free energy.
Organisms use free energy to maintain organization, grow and reproduce.
Review: What is the process that releases this energy from food and puts it into the usable
form of ATP?
What is metabolic rate?
There is a relationship between metabolic rate per unit body mass and the size of
multicellular organisms — generally, the smaller the organism, the higher the metabolic
rate.
Scientists are not sure why just yet. It may be due to the larger surface area to volume
ratio for smaller animals which causes them to lose more heat/volume.
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UNIT 8 NOTES
Reproduction and rearing of offspring require free energy beyond that used for
maintenance and growth. Different organisms use various reproductive strategies in
response to energy availability.
• Seasonal reproduction in animals and plants – organisms reproduce only at times when
there is plenty of food and water available for young, or when seed dispersal methods can
be best used.
• Life-history strategy (biennial plants, reproductive diapause)
 Biennial plants require two years to complete their life cycle. They flower and
produce fruit only in the second year. Radishes and carrots are common
examples, but we eat them after the first year. Another is Equisetum, or
horsetail, a plant commonly found on the side of the road. One year it grows in
its gametophyte form and the other its sporophyte form, one of which looks
like a horse’s tail.
 Reproductive diapause occurs often in insects and plants. It is a period when
growth or activity is greatly diminished or stopped. This occurs in eggs, insect
pupae, seeds, or any time the life cycle can be suspended for a while, usually
to wait for better living conditions.
Excess acquired free energy versus required free energy expenditure results in energy
storage or growth. Energy (food) taken in beyond what is needed to maintain a BMR is
extra and can be used by the organism to increase in size or weight, or biosynthesis.
Storing the extra for later is often referred to as weight gain in humans.
Insufficient acquired free energy versus required free energy expenditure results in loss of
mass and, ultimately, the death of an organism. 
Chapter 43 Sections 1-4
Plants and animals have a variety of chemical defenses against infections that
affect dynamic homeostasis.
Pathogens are infectious agents such as bacteria and viruses that cause disease. An
immune system enables organisms to defend themselves against pathogens. There are
two types of defense systems: nonspecific, or innate immunity, and specific, or acquired
immunity.
When does an organism get innate, nonspecific immunity and what does it consist of?
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When does an organism get acquired, specific immunity and what does it consist of?
Refer to Fig. 43.2 pg. 931, slide 118 for a brief description of both. To keep these two
straight, try this. Innate means something you are born with. It has the same root as natal
(birth), prenatal (before birth), and neonatal (new birth). Here the innate response is the
defense mechanisms you are born with to fight off disease, which really isn’t a lot, so it
works in a very general way, like skin keeping pathogens out of the body. Acquired
immunity is going to be immunity that your body develops towards specific pathogens that
you encounter during your life. This kind of immunity you are not born with, but get, or
acquire, as you live.
Plants, invertebrates and vertebrates have multiple, nonspecific immune
responses.
Yes, even plants and lowly insects have some form of defense from pathogens. They DO
NOT, however, have specific immune systems that produce antibodies. If a virus invades a
plant leaf the plant can just drop the leaf and be done with it. That takes far less energy
than maintaining a specific immune response. Sometimes these organisms have genetic
mutations that make them resistant to certain things such as viruses or pesticides.
RESISTANCE IS NOT IMMUNITY!! Resistance is genetic and immunity involves antibody
production. If you do not have the capability of producing antibodies you can not become
immune.
Innate or nonspecific immune responses include barriers such as an exoskeleton or
skin, mucous membranes, and other secretions to keep pathogens out of the body. If this
doesn’t work and a pathogen gets inside, there are other internal defenses that kick in.
These would be phagocytic cells that attack and eat the invaders, antimicrobial peptides
that attach to and destroy pathogens, an inflammatory response, or natural killer cells.
• Plant defenses against pathogens include molecular recognition systems with systemic
responses; infection triggers chemical responses that destroy infected and adjacent cells,
thus localizing the effects. Plants that get an infection or virus in a leaf can destroy
surrounding tissue and actually cause the leaf to fall off without infecting the rest of the
plant.
• Invertebrate immune systems have nonspecific response mechanisms, but they lack
pathogen-specific defense responses.
This means invertebrates, like insects, do not produce antibodies against pathogens. They
only rely on barrier defenses, phagocytic cells, and antimicrobial peptides to defend against
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pathogens. Invertebrates produce many types of antimicrobial peptides that target classes
of microbes such as fungi or bacteria rather than a specific fungus or specific bacterium.
• Vertebrate immune systems have nonspecific and nonheritable defense mechanisms
against pathogens.
Vertebrates use their skin and mucus as the first line of defense. Enzymes found in mucus
help to destroy many microbes as does stomach acid. There are also phagocytic white
blood cells (neutrophils and macrophages) that circulate throughout the body and
congregate in the spleen and lymph nodes to attack any pathogens that have gotten in.
Antimicrobial peptides and proteins also attack microbes or stop them from reproducing.
Vertebrates also have a second line of defense that invertebrates do not have. This
includes the inflammatory response and natural killer (NK) cells.
Describe the inflammatory response:
Local swelling at the site of injury, redness, fever, and pus are all part of the inflammatory
response and are considered normal. Septic shock, however, is a systemic (whole body)
response to a pathogen that can be life threatening. Basically, your body tries so hard to
kill off the pathogen that it damages itself.
Natural killer cells attack any cells in the body (except RBCs) that no longer exhibit the
“self” antigen (a class 1 MHC protein) on their surface. Many cells that have become
infected by a virus or become cancerous no longer have this antigen so they are no longer
recognized by the NK cells and are destroyed.
How can some pathogens avoid destruction?
Mammals use specific immune responses triggered by natural or artificial agents that
disrupt dynamic homeostasis.
Specific immune responses are slower to occur than nonspecific responses, but once
activated usually last throughout the life of the organism. Specific responses are triggered
by actual exposure to an infecting agent. This can be from infection by a pathogen
(actually getting sick) or by vaccination.
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UNIT 8 NOTES
In acquired immunity, lymphocyte receptors provide pathogen-specific
recognition.
The mammalian immune system includes two types of specific responses: cell mediated
and humoral. See Fig. 43.16 pg. 942, slide 142, and below. Your immune system is very
complicated and can be difficult to understand. You may need to read this several times
and be sure to ask questions if you don’t get it. Remember, you aren’t the only one. Also,
this is a general overview. There are gory details that have been left out to, hopefully,
make it easier for you to understand. If you want to be an immunologist or toxicologist
then read the book and good luck.
Both of these responses use white blood cells called lymphocytes.
What do lymphocytes do?
What are the two types and where do they mature?
Each individual lymphocyte is ____________________________________to
recognize a specific type of molecule. For this reason you have hundreds of different
lymphocytes to recognize hundreds of different molecules. Lymphocytes have thousands of
receptors to recognize its specific molecule and each one is the same.
What is an antigen?
So if an antigen is the foreign molecule the lymphocyte responds to, then all those
receptors on one lymphocyte are recognizing the same antigen. Something like what you
see in Fig. 43.9 pg. 937, slide 133.
Let’s start with the humoral response. Here is where the B cells come in. B cells
produce plasma cells that make antibodies or immunoglobulins. Each antibody is
specific to the particular antigen that the original B cell could recognize and is basically a
copy of the B cell receptors. These antibodies are proteins that are secreted by the plasma
cell. They have a Y shape.
The antibody recognizes the antigen by shape. Since each antigen has a unique
shape every antigen will be recognized only by the antibody with the corresponding shape,
and different antigens will have to have different corresponding antibodies. This is why you
need multiple vaccinations- the chicken pox antibodies will not recognize the flu antigens,
and vice versa.
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UNIT 8 NOTES
Now let’s take a look at the cell-mediated response. This involves T cells. Fig. 43.12 pg.
939, slide 133 shows the basics.
When antigens are displayed by Class I MHC molecules (antigen presentation) they are
recognized by cytotoxic T cells that kill those infected cells. Cells that display Class I MHC
molecules are usually body cells that have been infected. Cells that display Class II MHC
molecules are macrophages and B cells that have found foreign material circulating in the
body. Helper T cells, as well as cytotoxic T cells, can bind to these molecules and activate
both cytotoxic T cells and B cells to produce antibodies and mount a full scale attack.
What does MHC stand for?
A second exposure to an antigen results in a more rapid and enhanced immune response.
This is because once your body has been exposed to a particular antigen you make
memory B and T cells that recognize that antigen. Upon exposure again, you can
immediately produce plasma B cells, antibodies, and cytotoxic T cells to reduce or eliminate
infection. Fig. 43.16 pg. 942, slide 142 sums everything up nicely for you.
Humoral immune response involves activation and clonal selection of B cells, resulting in
production of secreted antibodies.
Cell-mediated immune response involves activation and clonal selection of cytotoxic T cells.
Fig. 43-16
Humoral (antibody-mediated) immune response
Cell-mediated immune response
Key
Antigen (1st exposure)
+
Engulfed by
Antigenpresenting cell
+
Stimulates
Gives rise to
+
+
B cell
Helper T cell
+
Cytotoxic T cell
+
Memory
Helper T cells
+
+
+
Antigen (2nd exposure)
Plasma cells
Memory B cells
+
Memory
Cytotoxic T cells
Active
Cytotoxic T cells
Secreted
antibodies
Defend against extracellular pathogens by binding to antigens,
thereby neutralizing pathogens or making them better targets
for phagocytes and complement proteins.
Defend against intracellular pathogens
and cancer by binding to and lysing the
infected cells or cancer cells.
What cells aid in both responses?
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UNIT 8 NOTES
There are several slides here that explain the roles of helper T cells, cytotoxic T cells and B
cells. These are here to show you how these parts work together. For example, activated
helper T cells secrete cytokines which stimulate other lymphocytes. The parts of your
immune system work together for the good of the whole just like the rest of your organs
and organ systems work together.
What is the difference between active immunity and passive immunity?
What is in a vaccine?
What molecules cause organ rejection?
People, and animals, generally remain healthy as long as the immune system functions
properly. Unfortunately, sometimes it doesn’t. Like any other system of the body there can
be malfunctions.
What is an allergy?
What is released by the mast cells that causes all the typical allergy symptoms?
And what type of drugs do you take for an allergy?
Now you know why they are called that.
What causes an autoimmune disease?
What is antigenic variation? Give an example.
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UNIT 8 NOTES
What is latency? (Hint: the lysogenic life cycle of viruses)
Inborn immunodeficiency is caused by a defect in the immune system. It may have a
genetic or developmental cause that prevents it from functioning properly. Acquired
immunodeficiency syndrome (AIDS) has a different cause.
What causes AIDS?
Why is it such a devastating disease?
What about this virus makes it so hard to defend against or produce a vaccine?
Chapter 48 Sections 1-4
The neuron is the basic structure of the nervous system that reflects function.
Neurons are nerve cells that transfer information within the body.
Neurons use two types of signals:
1.
2.
Animals have nervous systems that detect external and internal signals, transmit and
integrate information, and produce responses.
Processing of information takes place in simple clusters of neurons called ganglia or a
more complex organization of neurons called a brain.
Nervous systems process information in three stages:
1.
2.
3.
Neuron Structure and Function
A typical neuron has a cell body, axon and dendrites. The structure of the neuron allows
for the detection, generation, transmission and integration of signal information. Many
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UNIT 8 NOTES
axons have a myelin sheath that acts as an electrical insulator. State what each part does
and draw and label a picture of a typical neuron below. Use Fig. 48.4 pg. 1049, slide 167.
Cell body –
Dendrites –
Axon –
A synapse is a junction between an axon and another cell. In your drawing above indicate
where the synapse would be and draw the cell body and dendrites of another cell making
sure to show that the two cells DO NOT TOUCH each other.
How does information get across the synapse?
As you can see, neurons are funky looking, very specialized cells. Some are fairly short and
others are extremely long. Clusters of long neurons make up your spinal cord. Once you
reach adulthood and stop growing your neurons have also reached adulthood and have
entered the G0 state of the cell cycle. This is why spinal cord and brain injuries are so
devastating. Neurons in the G0 state can not regenerate or repair themselves so they can
no longer function for communication. There is a tremendous amount of research going on
in this field, but no one has as yet been able to figure out how to induce a neuron to grow
or repair itself. There has been some success in rerouting other neurons, say from one arm
to a leg to get some mobility, but that is about it. Sometimes one part of the brain may
take over functions once performed by a damaged part, but that takes much time and does
not always happen. Why? Don’t know. Sometimes when you have surgery and nerves are
cut you may lose some feeling. Again, sometimes it comes back and sometimes it doesn’t.
Why? Don’t know. As complicated as your immune system is, your nervous system is much
more and still holds many secrets we are unable, as yet, to figure out.
At the beginning of this chapter we said that neurons use two types of signals, electrical
and chemical. The neurotransmitter that crosses the synapse is the chemical signal. More
on that later. Its fairly simple. The electrical signaling is, of course, more complicated.
Remember when we learned about respiration and photosynthesis and how ATP was
made? There was a proton pump at work in chemiosmosis that pumped protons to the
outside of a membrane as electrons traveled through the ETC. This set up a membrane
20
UNIT 8 NOTES
potential with a positive charge on one side and negative on the other. The charge
difference, as well as the concentration gradient, helped the protons to flow back through
the ATP synthase and make ATP.
Neurons also use a pump and have a membrane potential or voltage across their
plasma membranes. This voltage is measurable with many of today’s diagnostic tools. A
message travels down the axon of a neuron as a change in membrane potential.
What is the resting potential?
Formation of the Resting Potential
Membranes of neurons are polarized by the establishment of electrical potentials across the
membranes.
• In a mammalian neuron at resting potential, the concentration of K+ is greater
inside the cell, while the concentration of Na+ is greater outside the cell
• Sodium-potassium pumps use the energy of ATP to maintain these K+ and
Na+ gradients across the plasma membrane
• These concentration gradients represent chemical potential energy
• The opening of ion channels in the plasma membrane converts chemical
potential to electrical potential
• A neuron at resting potential contains many open K+ channels and fewer open
Na+ channels; K+ diffuses out of the cell
Fig. 48-6
• Anions trapped inside the cell contribute to the negative charge within the
neuron
•
See Fig. 48.6 pg. 1050, slide 172
Key
Na+
K+
OUTSIDE
CELL
OUTSIDE [K+]
CELL
5 mM
INSIDE [K+]
CELL 140 mM
[Na+]
[Cl–]
150 mM 120 mM
[Na+]
15 mM
[Cl–]
10 mM
[A–]
100 mM
INSIDE
CELL
(a)
(b)
21
Sodiumpotassium
pump
Potassium
channel
Sodium
channel
UNIT 8 NOTES
When a neuron is at rest, just hangin’ out, the inside of the membrane is negatively
charged and the outside is positively charged. This charge difference is maintained by the
action of the sodium-potassium pump that keeps pumping K+ in and Na+ out. There are
numerous other ion channels found within the membrane, some open, some closed. When
a stimulus is received by a dendrite changes take place in the plasma membrane which
could cause the cell to temporarily open some ion channels that were closed and change
the membrane potential.
If more K+ channels open and more K+ diffuse out, then the inside becomes MORE
negative and the magnitude of the membrane potential increases. This is called
hyperpolarization and does not create a signal that is sent to other cells.
Other stimuli the cell receives may cause different channels to open causing a
depolarization or reduction in the magnitude of the membrane potential. If the stimulus
is strong enough and enough voltage-gated Na+ channels open then a massive
depolarization may take place causing an action potential. As ion channels in the
membrane open and close along the axon, the electrical signal (action potential) is
transmitted from one end of the cell to the other. Think of it as doing the wave at a ball
game. You stand up then sit back down and the next person stands up and sits back down,
etc. In a neuron ion channels open then close then the channels next to those open then
close, etc.
Every stimulus does not generate an action potential. When does an action potential occur?
An action potential is an all-or-nothing response. If the stimulus is not strong enough to
cause depolarization to reach that threshold, there will be no action potential. Action
potentials are the nerve impulses, or signals, that carry information along axons. One
neuron can produce hundreds of action potentials a second, and frequency can be an
indication of the strength of a stimulus. Even as rapid fire as this may seem, a second
action potential can not be initiated for a short period right after an action potential. What
is this called?
What causes this?
Action potentials can only travel in one direction. Toward what?
Why?
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UNIT 8 NOTES
Schwann cells, which form the myelin sheath, are separated by gaps (nodes) of
unsheathed axon over which the impulse travels (jumps) as the signal propagates along
the neuron.
This insulating layer causes what to happen to the action potential, or impulse?
OK. We have now received a stimulus, created an action potential, and transmitted that
impulse down an axon and have reached the axon terminal at a synapse. Now what does it
do? We still have no response so it can’t just quit. When an impulse reaches the end of the
axon it triggers the release of a chemical called a neurotransmitter. The impulse causes
this neurotransmitter to be released by the presynaptic neuron. The neurotransmitter is
then received by the postsynaptic neuron which transmits the signal and generates a
response. The response can be stimulatory or inhibitory. See Fig. 48.15 pg. 1057, slide
194. Notice that the postsynaptic neuron has ligand-gated ion channels that open when
they receive the neurotransmitter and allow Na+ and K+ to start diffusing and change the
membrane potential.
Once the neurotransmitter has done its job, it needs to leave the synaptic cleft so that
another signal can be sent at another time without interference. It can be taken up by
other cells, diffuse away, or be degraded by enzymes.
The same neurotransmitter can produce different effects in different types of cells. Some
common neurotransmitters are:
• Acetylcholine – most common
• Epinephrine
• Norepinephrine
• Dopamine
• Serotonin
• GABA
Drugs are often made to physically resemble neurotransmitters so that some neural
pathways can be turned on or off artificially. Sometimes this is good, as is the case with
opiates that are used as pain killers for people with chronic pain. Sometimes this is bad
when people without pain use them just to feel good and become addicted.
Chapter 49 Sections 1-3
So now you know how a neuron works. If you put a bunch of them together throughout an
organism, you have a nervous system. This system is capable of receiving signals from
the internal or external environment and affecting homeostasis. Together with the
endocrine system in your body it regulates pretty much everything that goes on inside you,
as well as how you think and move. For the most part we will concentrate on your nervous
system, but, just so you know, there are other types. The simplest one is a nerve net
found in cnidarians (hydra, jellyfish). These are just a bunch of interconnected nerve cells,
23
UNIT 8 NOTES
but a system nonetheless. You are a higher order animal and therefore, have a more
complicated system with nerves.
What are nerves?
Your entire nervous system has two parts- the central nervous system (CNS) and the
peripheral nervous system (PNS).
What two parts make up your CNS?
Your PNS is all the rest of your nerves. They receive signals from your spinal cord. Your
spinal cord also controls all of your reflexes without bothering your brain. That’s a good
thing because if you took time to think about responding to some stimuli you might be
injured or dead before you came to a conclusion.
What is the function of cerebrospinal fluid?
Label the main parts of the brain as you go through slides 206-213:
Different regions of the vertebrate brain have different functions.
List some of the functions for each part:
• Midbrain (brainstem)
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UNIT 8 NOTES
• Hindbrain (cerebellum)
• Forebrain (cerebrum) contains right and left cerebral hemispheres in humans
The two hemispheres of the cerebrum are connected by the corpus callosum which allows
them to communicate. Your right hemisphere controls the left side of your body and the
left hemisphere controls the right side of your body.
The cerebral cortex, the outer part, or gray matter, is where you do all your thinking. Each
half of your brain is divided into four lobes that have different functions. There are areas
that are for emotions, motor skills and movement, hearing, vision, smell, taste and math.
The left hemisphere is better at math and language- the “book smart” people, and the
right side is better at pattern recognition and emotions- the “artsy” people. This is called
lateralization, the differences between the two sides. This is a generalization too. It does
not mean that if you can draw well you can’t do math. Most learning depends on how
much effort you are willing to put in to learn.
25