The document discusses several body systems and how they contribute to homeostasis. It explains that homeostasis is the process by which organisms maintain stable internal conditions despite external changes. Negative feedback loops are described as a key mechanism, where a change triggers a response that acts to reverse the change. Several body systems, including the nervous, digestive, urinary, circulatory, respiratory, skeletal, and muscular systems, are discussed in terms of how they utilize feedback loops to keep conditions like temperature, blood sugar, water levels, and more within normal ranges. Diseases that can disrupt homeostasis in each system are also listed.

1. Homeostasis
“Keeping things in balance”
K.Seefloth

2. Definition
 Homeostasis is:
 According to your Biology book: a process by
which organisms keep internal conditions
relatively constant despite changes in external
environments. Maintained by feedback loops.

3. Feedback Loop
 Our body utilizes negative feedback loops
the most.
 This is when the amount of product of a
reaction controls how fast (or slow) the
reaction goes.
 In negative feedback, change in the
controlled value (body temperature, for
example) initiates responses that bring the
function of the organ back to within the
normal range (shivering or sweating).

4. In other words….
 Negative feedback loops are like a
thermostat in your house.
 If the temperature inside the house drops
below the point at which the thermostat is
set and the thermostat turns on the
furnace.
 As the temperature within the house rises,
the thermostat again senses this change
and turns off the furnace when the
programmed temperature is reached.

5. What we need to keep the same in
our body:
 Temperature (98.6 F)
 Blood pH (7.4) almost neutral
 Blood pressure (average 120/80)
 Heart rate (80 beats per minute)
 Blood sugar level
 Hydration/amount of water
 Amount of salts
 Amount of blood (2 pints per every 25 lbs)

6. What it really means (in English!)
 The human body needs to maintain things
like body temperature (98.6 F). If you get
too hot or cold then your body will not
thrive.
 Too hot and your brain will overheat and
“cook”
 Too cold and your body’s systems will shut
down

7.  Each system of the body contributes some
aspect to maintaining homeostasis (stable
internal balance)

8. Nervous System
It is more than “the brain controls
everything”!

9. Nervous System
 Central Nervous System
 Brain and spinal cord: The brain is like your
body’s central computer and the spinal cord is
the network that the nervous system uses to
send messages to and from the body.
 Peripheral Nervous System
 All the nerves and neurons throughout the
body: Sensory neurons (cells) send signals to
the brain and then the brain instructs motor
neurons to move/react.

10.  Autonomic Nervous System subdivided
into the:
 Sympathetic – responds to stress and danger.
“Fight or Flight” response…release of
adrenaline
 Parasympathetic – dominant during sleep.
Controls all functions that just “happen” like
heart beating, breathing, and digestion.

11. Nervous System
 Hypothalamus - controls body temperature
with the following feedback loop:
 If too low, causes shivering of muscles and
reduced blood flow (blue skin) to create heat
 If too hot, causes sweating and increased
blood flow (red skin) to get rid of heat

12.  Brain Stem - Controls heart rate with the
following feedback loop:
 If too low, increases nerve impulses to make
heart beat faster
 If too high, decreases nerve impulses to keep
the heart rate at 80 beats per minute

13. Diseases/afflictions of the nervous
system
 Stroke
 Aneurism
 Brain Cancer
 Depression
 Bipolar disorder
 headaches

14. Activity
 Lab: Fight or Flight ???

15. Digestive System
Doesn’t just break down food so
you can eat!

16. Digestive System
 The digestive system is made up of the
digestive tract—a series of hollow organs
joined in a long, twisting tube from the
mouth to the anus—and other organs that
help the body break down and absorb
food

17.  Organs that make up the digestive tract
are the mouth, esophagus, stomach, small
intestine, large intestine—also called the
colon—rectum, and anus.
 Inside these hollow organs is a lining
called the mucosa. In the mouth, stomach,
and small intestine, the mucosa contains
tiny glands that produce juices to begin
the process of digestion.
 The digestive tract also contains a layer of
smooth muscle that helps break down
food and move it along the tract.

18.  Two “solid” digestive organs, the liver and
the pancreas, produce digestive juices
that reach the intestine through small
tubes called ducts.
 The gallbladder stores the liver’s digestive
juices until they are needed in the
intestine.

19.  The small intestine allows the broken
down food (in the form of glucose and
other molecules of life) to be absorbed by
the bloodstream and transported to all
parts of the body.
 The large intestine allows water to be
reabsorbed by the body. All leftover
wastes are left over to be excreted out of
the body.
 Parts of the nervous and circulatory
systems also play major roles in the
digestive system.

20. Digestive System
 Liver – Controls blood sugar level with the
following feedback loop:
 If too low, converts stored glycogen (glucose)
into sugar
 If too high, removes sugar from the blood and
stores as glycogen

21. Diseases/afflictions of the digestive
system
 Diabetes
 Ulcers
 Acid reflux/heartburn
 Stomach or liver cancer
 Cavities/gum disease/root canal
 Tonsillitis
 Gall stones/gall bladder removal

22. Urinary/Excretory
System
Besides getting rid of wastes and
filtering toxins out of the blood, it
also…..

23. Urinary/Excretory System
 Works closely with the digestive,
circulatory and nervous systems.
 As the heart pumps blood around the
body, the blood carries fresh oxygen to
various cells and organs, then picks up
waste products like carbon dioxide, salt
and urea.
 There is an artery and a vein that runs into
and out of each kidney to take the blood
there and back.

24.  As the waste products arrive, the kidneys
perform a filtration process that removes
hazardous toxins and products that the
body can not use from water and nutrients
that can be reclaimed and recycled.
 The kidneys return the reclaimed water
back to the body, but mix the waste
products into a liquid waste compound
known as urine.

25.  The kidneys direct the urine to the
bladder, where it is collected and held until
it is either manually expelled or forced out
by involuntary muscle contractions.

26.  The excretory system takes advantage of
sweating by providing waste liquids to
accomplish the cooling effect.
 Sweat is not pure water; instead, it is a
solution of approximately 94 percent water
and six percent waste products.
 By excreting weak urine through the skin's
pores, the excretory system can perform
the dual functions of ridding the body of
waste products while also keeping it cool.

27. Urinary/Excretory System
 Kidneys - Controls amount of water and
salt in body with the following feedback
loop:
 If too low, retains water/salt and keeps them
from going to the bladder
 If too high, pushes more water and salt into
the bladder

28. Diseases/afflictions of the
urinary/excretory system
 Diarrhea
 UTI infection
 Colon Cancer
 Constipation
 Kidney stone
 Flatulence
 incontinence

29. Activity
 Data Lab: Urinalysis

30. Circulatory/
Cardiovascular System
Besides controlling blood
pressure and moving blood
throughout the body it……

31. Circulatory/Cardiovascular
System
 The main function of the circulatory
system is to provide nutrients and oxygen
to the various parts of the body, via the
blood, which is circulated through the
veins and arteries, like a giant
transportation system.
 Arteries carry the oxygenated blood from
the heart to the cells and tissues, whereas
veins return the oxygen-depleted blood
from the cells to the heart.

32. The Two forms of Circulation
 In systemic circulation, arteries collect the
oxygen-rich blood from the heart and is
transported to the body tissues. In the
process, oxygen from the blood is diffused
into the body cells; whereas carbon
dioxide from the cells is diffused in the
blood. This exchange of gases takes
place with the help of capillaries that
surround the body cells

33.  The pulmonary circulation is a loop from
the heart to the lungs. It is that portion,
where deoxygenated blood from the heart
is carried to the lungs and in turn, returns
oxygenated blood to the heart.

34.  The circulatory system works with the
respiratory system and digestive system to
supply oxygen and nutrients to the body.
 Blood carries the messenger chemicals -
hormones, secreted by the organs of the
endocrine system. Thus, the circulatory
system is also responsible for circulating
hormones for proper communication
between the body organs.

35. Circulatory/Cardiovascular System
 Capillaries (smallest of blood vessels) -
Controls flow of oxygen to cells and
carbon dioxide from cells using the
following feedback loop:
 If oxygen too low, gases flow from areas of
high concentration (capillaries)to low
concentration (cells) to maintain levels
 If too high, the opposite happens, gases flow
from areas of high concentration (cells) to low
concentration (capillaries).

36. Diseases/affliction of the
cardiovascular/circulatory system
 Heart attack
 High blood pressure
 Hemophilia
 Stroke
 Sepsis (infection)
 Bruises/contusions (hickey)

37. Respiratory System
More than just breathing…

38. Respiratory System
 Air first enters your body through your nose
or mouth, which wets and warms the air.
(Cold, dry air can irritate your lungs.) The air
then travels through your voice box and down
your windpipe. The windpipe splits into two
bronchial tubes that enter your lungs.
 A thin flap of tissue called the epiglottis
covers your windpipe when you swallow. This
prevents food or drink from entering the air
passages that lead to your lungs.

39.  Except for the mouth and some parts of
the nose, all of the airways have special
hairs called cilia that are coated with sticky
mucus. The cilia trap germs and other
foreign particles that enter your airways
when you breathe in air.
 These fine hairs then sweep the particles
up to the nose or mouth. From there,
they're swallowed, coughed, or sneezed
out of the body. Nose hairs and mouth
saliva also trap particles and germs.

40.  Within the lungs, your bronchi branch into
thousands of smaller, thinner tubes called
bronchioles. These tubes end in bunches
of tiny round air sacs called alveoli.
 Each of these air sacs is covered in a
mesh of tiny blood vessels called
capillaries. The capillaries connect to a
network of arteries and veins that move
blood through your body.

41.  The muscle that helps the lungs breath is
called the diaphragm. Breathing is
something that happens passively,
something that we don't even think
about...that is unless it is something that
becomes difficult to do.

42. Respiratory System
 Lungs - Controls blood pH, amount of
carbon dioxide in blood using the following
feedback loop:
 If gets too low (acidic, pH below 7.4), gets rid
of excess CO2 (which caused the acid)
 If gets too high (basic, pH above 7.4), retains
more CO2

43. Diseases/afflictions of the
respiratory system
 Cold/flu
 Pneumonia
 Asthma
 Lung cancer
 Sinus infection
 allergies

44. Activity
 Taking your pulse
 Lab: Measuring Lung Capacity

45. Skeletal System
Besides keeping you upright….

46. Skeletal System
 The skeletal system offers protection,
support, blood cell formation, stores
minerals and energy and aids movement.
 Calcium and phosphorus are stored within
your bones.

47.  Bones are considered to be living organs
because they are made up of nerve,
muscle and epithelial tissue, as well the
connective tissue that binds everything
together.
 If you were to look at the cross section of
a long bone, such as your femur, you
would see a shaft that contains either red
or yellow marrow. Red is newly produced
marrow. As bones age, the red marrow
converts into yellow. This special, yellow
marrow is an energy source.

48.  Within the bones, red and white blood
cells are produced, along with platelets.
 There is a fibrous sheath called a
periosteum that contains blood vessels
which supply oxygen and nutrients to the
bone tissues.
 Blood vessels get in and out of the bones
by little openings called nutrient canals.

49. Skeletal System
 Bone Marrow - Controls blood levels using
the following feedback loop: 2 pints for
every 25 pounds
 If too low (2 pints for every 25 pounds), bone
marrow produces necessary white and red
blood cells.

50. Diseases/afflictions of the skeletal
system
 Broken/fractured bones
 Anemia (low RBC and/or iron)
 Osteo arthritis
 Torn ligament(s)
 Torn cartilage
 sprains

51. Muscular System
Yes, it helps us move, but it
also….

52. Muscular System
 The muscles in our body are divided into
three classes: cardiac, smooth, and
skeletal.
 Muscles often work in pairs so that they
can pull in different or opposite directions.
 The cells that make up muscles contract &
then relax back to their original size.
 Tiny microscopic fibers in these cells
compress by sliding past each other like a
sliding door being opened & shut again.

53.  At every joint, tendons and ligaments also
help out. Muscles wouldn't be very useful
alone because they don't directly connect
to the bone, so even if they contract, they
wouldn't be moving anything.
 Muscles are connected to tendons, which
are connected to the bones. When the
muscles contract, they pull on the
tendons, which in turn pull on the bones,
and that causes movement.

54.  But without ligaments, that movement
wouldn't be too useful because it would
not be directed movement.
 Without ligaments, instead of bones
bending or rotating about each other when
muscles contract, they would slide by
each other. Ligaments are what hold the
bones together. They connect at the ends
of muscles and keep them from slipping
and sliding, and force them to bend.

55.  The muscular system interacts with other
systems of the body.
 During inhalation, the muscles between
the ribs relax, allowing the lungs to draw in
air.
 When you digest food, muscles in your
esophagus interact with the digestive
system.
 Your nervous system tells your muscles
when to move.
 Even your skeletal system needs your
muscular system because your muscles
keep your bone structure intact

56. Muscular System
 All muscles - Control body position using
the following feedback loop:
 If muscle strength too low: Systems that rely
on the muscles to do the work necessary for
homeostasis (heart, lungs, brain, digestive
organs….) could not function

57. Diseases/afflictions of the muscular
system
 Muscular dystophy
 Multiple schlerosis (MS)
 Muscle cramps

58. Activity
 Lab: Reaction Rates

59. Lymph
(Endocrine/Immune)
System
This one is super important…

60. Lymph (Endocrine/Immune)
System
 The immune system is made up of many
different cells, organs, tissues and
substances within your body.
 Each aid in eliminating foreign organisms
from your body and protecting you from
various diseases and illnesses.
 These foreign organisms come in the form
of viruses, bacteria, parasites and fungi.
They are known as “microbes.”

61. First Line of Defense – The Skin
 The skin is thick and very hard to penetrate
and produces a variety of substances that
are harmful to invaders.
 The eyes, nose, and mouth are protected by
fluids or sticky mucus that capture harmful
attackers.
 The respiratory tract has cilia, tiny hairs that
remove particles.
 Intruders that get as far as the stomach are
up against a sea of stomach acid that kills
most of them.

62. Second Line of Defense – White
Blood Cells
 There are several types of immune cells,
each possessing specific duties and
characteristics. Several travel through the
body killing foreign substances as they
find them.
 Others patrol the gastrointestinal tract
lining and blood vessels, safeguarding
particular organs.

63.  The lymphatic system, which includes the
lymph nodes, the spleen, bone marrow
and thymus gland, produces these cells
and transports them throughout the body.
 Lymph nodes and the spleen serve as
filters designed to keep harmful organisms
out of the blood stream. Most immune
cells are produced in the bone marrow,
the thymus or the spleen.

64. Lymph (Endocrine/Immune)
System
 Lymph Nodes - Controls against invaders
such as bacteria and viruses
 Maintains/produces white bloods cells (B
cells, T cells) to battle against foreign cells in
the body. Prevents major illnesses from
taking over the body

65. Diseases/afflictions of the lymphatic
system
 Lymphoma (cancer)
 Leukemia (abnormal WBC)
 Any other infections
 acne

66. Activity
 ??