Structure and
Function in Living
Systems
Chapter 8: Systems in Organisms
8.1: Systems help organisms meet their needs
8.2: Plants have several levels of organization
8.3 Animals have several levels of organization
8.4 Human health depends on a balance among systems
Human health depends on
a balance among systems
Levels of Organization
 Fill in the sequential cluster diagram
epithelial, muscle,
nerve, connective
heart, skin, eyes;
respiratory, circulatory,
nervous, skeletal
How is the human body like a city?
The body’s systems work all the
time
 Human body depends on processes that don’t stop
 needs to:
 Breathe
 circulate blood
 take in food, to digest it, and to eliminate waste materials
 organ systems remain active during sleep
 **working constantly to maintain the balance needed to
survive
Body systems maintain
homeostasis
 Homeostasis: the ability of the body to
maintain internal conditions within normal
ranges
 Conditions are in equilibrium = balanced
 Small changes always occur internally and
externally
 Body must work to regulate:
 Body temperature
 amount of sugar in blood
 oxygen and carbon dioxide levels, and water
and salt balance in body fluids
Homeostasis: Negative Feedback
Homeostasis is often maintained by a negative feedback loop
Homeostasis: Body Temperature
 Normal internal temperature is ~ 37°C (98–99°F).
 homeostatic systems for temperature:
Integumentary, circulatory, muscular, respiratory,
and nervous
 If much above or below 37°C:
 The homeostatic systems are having trouble
maintaining your usual temperature
 Active, or hot day  body temperature may rise
 Body sweats
 Evaporation of sweat from skin cools body  brings
temperature back down
Homeostasis: Ion Concentrations
 Kidneys help keep body water volume constant
 drink a lot of water  kidneys release more water in urine
 do not drink enough water  kidneys make less urine
 Why?
 To maintain the proper concentrations of ions and other
substances in the blood
 Concentration: amount of one substance that is dissolved in
another substance
 The less water, the higher the concentration of dissolved
substances
 The more water, the lower the concentration
Homeostasis: Ion Concentrations
 Ion: an atom of an element that has gained or lost one or more
electrons – “charged” particles (+ or -)
 important to many body processes:
 movement of substances across cell membranes
 sending of nerve impulses
 Electrolytes: sodium, potassium, chloride, and calcium
 skin tastes salty after sweating:
 Sweat contains salts, ex: Sodium and chloride together
 sports drinks contain salts (electrolytes!)
Electrolytes and salts, in ion form, are
substances that conduct electric
current.
Electrolytes in human body fluids
operate similarly to the currents
caused by electrolytes in batteries.
The positive and negative charges of
the ions cause them to move toward
concentrations of the opposite charge.
Electrolytes such as sodium,
potassium, calcium, magnesium,
and chloride ions in the human body
help fluids flow across cell membranes
and help nerve impulses travel.
Homeostasis: Oxygen and Carbon
Dioxide Concentrations
 respiratory system and circulatory system
maintain a balance of oxygen and carbon
dioxide concentrations in the blood
 These dissolved gases are carried by the
blood and delivered to and from the tissues in
plasma
 Exercise: muscle cells use more oxygen and
give off more carbon dioxide than at rest
 increased oxygen need  increased
breathing rate and volume
  heart pumps faster  circulatory system
increases blood supply to the limbs
 Resting: breathing is shallower, heart pumps
more slowly
Homeostasis: Other Nutrients
 Liver
 breaks down large food molecules—carbohydrates, fats, and
proteins—into nutrients
 stores glucose, vitamins, and iron
 produces bile (a fluid used in digestion)
 breaks down alcohol, drugs, and other toxic chemicals
 Filters, stores, and releases materials
 Pancreas
 Part of digestive and endocrine systems
 helps maintain blood glucose levels
Some people with diabetes are
unable to make enough insulin
to regulate their blood sugar.
They often need to take
injections of insulin to keep their
blood sugar in a normal
homeostatic range.
The endocrine system helps
regulate body conditions
 Controls the conditions in the body by making and
releasing hormones
 Hormones: chemicals that are made in one organ, travel
through the blood, and produce an effect in target cells
 Ex: insulin and glucagon produced in the pancreas
 Ex: adrenaline makes your heart beat faster in exciting
situations
 “rush of adrenaline”
 Are often called chemical messengers
 Target cells have special structures, called receptors, that
allow them to respond to the chemical messenger
Hormones and Glands
 Glands: specialized - tissues main structures of the endocrine
system
 Many glands in the body produce hormones  circulatory system
 Pineal Gland:
 Tiny organ sizes of a pea
 near the center of the brain
 sensitive to light
 produces a hormone essential to body rhythms
 Ex: sleep
 Plays a role in maintaining body temperatures, in reproducing, and
in aging
Hormones and Glands
 Hypothalamus
 connects the nervous and endocrine systems
 Produces hormones that control the release of hormones
produced by the…
 Pituitary Gland
 base of the brain
 director of the endocrine system
 produces hormones that control growth, sexual
development, and the absorption of water into the blood by
the kidneys
Hormones and Glands
 Thyroid Gland
 releases hormones necessary for
 Growth
 Metabolism
 regulation of calcium
 Thymus Gland
 helps the body fight disease by controlling the production of white
blood cells called T cells
 Adrenal Glands
 secrete about 30 different hormones
 regulate carbohydrate, protein, and fat metabolism and water and
salt levels in the body
 adrenaline –in response to stress
 makes your heart beat faster
 allows you to react quickly in dangerous or exciting situations
Hormones and Glands
 Pancreas
 part of both the digestive system and endocrine system
 secretes insulin and glucagon
 Regulate levels of glucose in the blood
 Ovaries (female) and Testes (male)
 secrete hormones that control sexual development
 ovaries make more estrogen
 testes make more testosterone
 the different amounts of give males and females different
characteristics

What general area of the body are all the glands of the endocrine system in?

the center

What areas do the hormones produced in the glands generally affect?

all parts

How do the illustrations show the role of hormones as “chemical messengers”?

The glands are located throughout the body and are able to “deliver” hormones
wherever the body needs them

What are the glands of the endocrine system? pineal gland, hypothalamus,

pituitary gland, thyroid, thymus, adrenal glands, pancreas, ovaries, testes
Negative Feedback
 Regulation of hormone levels
 Adjust volume on a sound system
 Friend says just right? stop changing the volume
 You = control center
 Friend = sensor
 Feedback = information coming back to a control center from
a sensor that tells the control center what it needs to do to
maintain a level within an ideal range
 signals to a gland that hormone levels are correct and no
more of the hormone is needed
Homeostasis may be disrupted
 Signs of imbalance range from a mild cold, to dangerous overheating of
the body, to serious and even fatal diseases
 Sneezing help defends the body from foreign substances
 Pathogens (bacteria or virus) in the body signal the immune system
 Symptoms begin to go away when homeostasis is restored
 Exercising  usually sweat
 lose too much water  dehydration
 Signs of heat exhaustion: dehydration, dizziness, nausea, fainting, and a
dangerous drop in blood pressure
 Heat stroke – possible if a person stops sweating  temperature rise
 Hypothermia - body temperature too low
Homeostasis
may be disrupted
 hormone imbalances can cause serious diseases
 Pancreas normally maintains glucose balance in your blood
by releasing insulin and glucagon as needed
 Imbalance  diabetes
  failure of other organs, heart disease, blindness, and
kidney damage
 Kidneys continually filter the blood, taking out waste products
 Malfunction?
 Dialysis: blood is circulated through an artificial kidney machine
that filters out the wastes (3 sessions/week!)