Unit 11 Study Guide
Answer Key
Human Systems
SECTION 28.1. LEVELS OF ORGANIZATION
1. Stem cells go through two processes to become specialized cells.
2. Determination—stem cells commit to becoming only one type of cell. Examples: muscle, nerve, skeletal cells
3. Differentiation—committed cells acquire the structures and functions of specialized cells. Examples: muscle
cells become cardiac, smooth, or skeletal muscle cells
4. Stem cells contain all the genes for a complete organism, and they can become any one of the more than 200
different types of cells in the body.
5. Examples: bundled muscle cells that can extend and contract, bundled epithelial cells with cilia that line
intestinal organs, sperm with whip-like tails, porous bone cells
6. Examples: sperm tails allow sperm to move; long extensions of nerve cells allow them to communicate with
other cells; bone cells are porous to allow nutrients to reach bones; epithelial cells are closely packed to provide
more surface area; smooth and skeletal muscle cells are bundled together and elongated, which allows for
stretching and contracting
7. specialized cells—the smallest units of life with specialized structures and functions; tissues—groups of similar
cells that work together to perform a specialized function; organ—different types of tissues that function
together; organ system—two or more organs working in a coordinated way; organism—life form made up of
different organ systems functioning in a coordinated way to maintain life
8. Determin- = the cells determine to be of one particular type of cell Different- = the cells acquire their different
structures and functions
SECTION 28.2. MECHANISMS OF HOMEOSTASIS
1. The sensors may continue to send a signal, but homeostasis could not be maintained.
2. sensors—gather information on internal/external conditions. control
center—receives information from
sensors, compares to set points; sends messages. communication system—nerves and hormones carry signals to
targets. targets—organs, tissues respond to messages to restore homeostasis
3. The sensors may continue to send a signal, but homeostasis could not be maintained.
4. Diagram “A”—negative feedback; diagram shows change away from a set value is counteracted. Diagram
“B”—positive feedback; diagram shows change away from a set point is increased, then returns to normal
5. Negative—it is counteracting a change away from a set point for internal body temperature by releasing fluid
from the sweat glands to cool the body.
6. As activity increases, sensors send messages to the brain. The brain detects low oxygen levels and sends
messages to the heart and lungs to work harder and bring more oxygen into the body.
7. negative feedback loops counteract any change away from set points; positive feedback loops increase change
away from set points until a certain result is achieved
8. Sample answers: pilot or navigator on plane keeping it on course; thermostat on furnace or air conditioner;
guidance system on a space craft; building sprinklers turning on when a fire starts
SECTION 28.3. INTERACTIONS AMONG SYSTEMS
1. Sample answers: members of a sports team, or an orchestra, or a touring rock band, or a construction crew, or a
movie production working together; each individual has a job to do, but all must work together for the enterprise to
succeed
2. Skin—absorbs UV light to make an inactive form of vitamin D; Liver—changes inactive form of vitamin D into
another compound; Kidneys—converts compound into active vitamin D
3. Hypothalamus acts as a control center that receives data about body temperature and sends messages to target
organs in the skin, respiratory, and circulatory systems.
4. Any of the following: external or internal conditions change too rapidly, serious injuries overwhelm
homeostatic mechanisms, sensors fail to detect internal or external changes, wrong messages are sent or targets
fail to respond, viruses or bacteria change the body’s internal chemistry
5. Long-term disruptions over time affect more and more organs and organ systems, resulting in greater damage to
the body.
6. short term
7. little lasting damage
8. common cold
9. long term
10. diabetes
11. Sample answer: a thermostat or closed circuit or a balance tray that is returned to a center point.
Respiratory and Circulatory Systems
SECTION 30.1. RESPIRATORY AND CIRCULATORY FUNCTIONS
1. transports blood and other materials; carries away wastes from cells; separates oxygen-rich blood from oxygenpoor blood
2. brings in oxygen and expels carbon dioxide and water vapor; exchanges gases in blood with gases in
atmosphere
3. it moves down the trachea, into the bronchi and the lungs, then into the bronchioles, and finally to the alveoli
4. to absorb enough oxygen to supply the body and to expel excess carbon dioxide and water vapor
5. rib cage muscles relax and the rib cage becomes smaller, the diaphragm relaxes and rises, and air flows out
6. Heart: muscular pump that keeps blood moving to all parts of the body. Arteries: blood vessels that move blood
away from the heart. Veins: blood vessels that move blood to the heart from the rest of the body. Capillaries:
tiny blood vessels that transport blood to and from the cells
7. Hot weather — The heart pumps harder and blood vessels dilate to bring excess heat to the skin. Cold weather
— blood vessels constrict to conserve heat
8. The diaphragm is a dome-like muscle located in the midriff of the body.
9. Samples answers: river and streams network, major and smaller highway network, communications networks
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Human Systems and Homeostasis
SECTION 30.2. RESPIRATION AND GAS EXCHANGE
1. Oxygen and carbon dioxide are carried by the blood; gases move by diffusion; the alveoli lining must be moist
to help gases diffuse.
2. They provide a huge surface area to bring in enough oxygen to meet the body’s needs.
Diagram A
capillary and alveolus walls— Oxygen diffuses from alveolus into the capillary; Capillary—oxygen binds to
hemoglobin in the blood and is carried to the cells.
Diagram B
alveolus— carbon dioxide and water vapor separate and are exhaled; capillary walls and alveolus — carbon
dioxide and water vapor diffuse into alveolus.
3. each molecule of hemoglobin binds with four oxygen molecules
4. Sensors send information to the brainstem, which sends messages to the muscles of the rib cage and to the
diaphragm to work harder
5. Smoking: Chemicals in smoking cause mutations that may lead to lung cancer and damage the alveoli so that
gas exchange is impaired. Emphysema: The alveoli are so damaged or destroyed that the lungs can no longer
bring enough oxygen into the body; eventually the lungs fail. Asthma: Muscle spasms cause bronchioles to
constrict, reducing air flow and gas exchange. Cystic Fibrosis: Lungs produce thick, sticky mucus that can
block airways and lead to lung infections.
6. In an asthma attack, airways are restricted and people literally pant for air.
7. It is an iron-based protein that binds with oxygen molecules; iron gives blood its reddish color.
SECTION 30.3. THE HEART AND CIRCULATION
1. pulmonary: to carry oxygen-poor blood to the lungs, pick up oxygen and release CO2 and water vapor, then
bring oxygen-rich blood back to the heart. Systemic: to carry oxygen-rich blood to the rest of the body and
bring oxygen-poor blood back to the heart.
3. blood first enters the heart through the atrium; in the heartbeat, the atrium is the first to contract
4. Students might make a table showing word origins and the definitions of the two types of circulation or draw a
diagram of the two circulations and use the word origins in the labels.
SECTION 30.4. BLOOD VESSELS AND TRANSPORT
Y Diagram:
Arteries—carry oxygen-rich blood away from heart; made of 3 layers with thick muscle, elastic fibers; smaller
arteries called arterioles connect to capillaries; Veins—carry oxygen-poor blood back to heart; made of 3 layers,
larger diameter, thinner walls; valves and skeletal muscles keep blood moving; smaller veins called venules
connect to capillaries; Both—carry blood throughout the entire body; made of same three layers of tissues; have
smaller vessels that connect to capillaries
1. capillaries are much smaller than veins and arteries and have only one layer;
walls are one cell thick; materials diffuse easily into and out of them; form dense networks
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Human Systems and Homeostasis
SECTION 30.5. BLOOD
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
red blood cells
white blood cells
platelets
plasma
90% water
minerals
proteins
albumin
fibrinogen
immune proteins
plasma proteins help stabilize blood volume, control bleeding, fight pathogens; concentrations of molecules
dissolved in water as plasma control which substances diffuse into and out of the blood
RBC structure: round with concave center, no nucleus or organelles, contains hemoglobin; protein markers
for blood type; Functions: transport oxygen, waste products, and nutrients to and from the cells. WBC
structure: contains no hemoglobin; Functions: fight infection, remove foreign matter and dead cells; also
part of immune system. Platelets structure: cell fragments that can change their shape; Functions: help to
repair torn or injured blood vessels, control bleeding
The person’s immune system will attack the foreign protein, and the blood will
start to clump, which can block blood vessels and cause death.
They form spiky extensions that weave into a complex net at the wound; they release clotting factors that form
another net and trap platelets and white blood cells that form a clot.
Clots can block blood vessels to cause a heart attack or stroke; the inability to form clots means a person might
bleed to death from even a minor cut.
A group of four different blood types—A, B, AB, O—produced by the most common proteins markers, A and
B, on red blood cells
Nutrient Absorption and Waste
SECTION 32.1. NUTRIENTS AND HOMEOSTASIS
1. water—fluid balance, chemical reactions
2. carbohydrates, simple and
complex—energy
3. proteins—growth, repair, enzymes, hormones
4. fats, saturated and unsaturated—energy, used in many structures
5. minerals—homeostasis, building, repair tissues
6. vitamins, water– and fat-soluble—regulate cell functions, growth, development
7. you lose about this much each day through sweat, urine, and respiration
8. vegans must combine plant foods such as beans and rice to obtain all eight essential amino acids
9. saturated fats are solid at room temperature; unsaturated fats are liquid at room temperature
10. carbohydrates and fats
11. vitamins are necessary to support the many life functions of cells, the smallest unit of life
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Human Systems and Homeostasis
SECTION 32.2. DIGESTIVE SYSTEM
1. to break down large complex molecules in food into smaller molecules that can be used by the body
2. mechanical digestion: chewing food, smooth muscles churning and mixing food; chemical digestion: enzymes
breaking down food, stomach acid digesting protein, or other chemicals such as bile breaking down fats
3. smooth muscles contract and relax to keep food moving, and sphincters prevent food from backing up.
4. nutrients are absorbed and distributed to the cells; undigested materials are eliminated as liquid and solid wastes
5. salivary amylase, amylase: break down starches into simpler sugars; pepsin, peptides: break down proteins;
lipase: breaks down fats
Process Diagram: Mouth—salivary amylase break down starches into simple sugars; Stomach—HCl and
pepsin break down proteins; chyme forms; Small Intestine—pancreas helps finish digestion of sugars and break
down fats; liver and gallbladder release bile to digest fats
6. Pepsin is active only when there is food in the stomach; a layer of mucus keeps stomach acids from digesting
the lining
7. esophagus “carries food” from the mouth to the stomach
8. Examples: two hands squeezing dough out of a plastic tubing; squeezing toothpaste out of a tube
SECTION 33.2. MUSCULAR SYSTEM
1. bones; bones; voluntary, some involuntary
2. digestive organs, blood vessels; moves food/changes the size of the organ; involuntary
3. heart; blood; involuntary
SECTION 32.3. ABSORPTION OF NUTRIENTS
1. Absorption is the process by which nutrients move out of the digestive system and into the circulatory and
lymphatic system. Without absorption, nutrients cannot reach the cells.
2. lining of the small intestine, villi, microvilli
3. the lining is ridged and folded, thousands of villi cover the lining, and thousands of microvilli cover each villi,
greatly increasing surface area
4. to allow more time for nutrients to be absorbed
5. Materials absorbed— simple sugars, amino acids, minerals; Distribution— circulatory and lymphatic systems
Part of intestine: jejunum; Materials absorbed: glucose, amino acids, vitamin C, B vitamins, some water
Part of intestine: ileum; Distribution: circulatory and lymphatic systems
6. Enzymes use some of the nutrients to build more complex molecules that cells need; the liver stores some
nutrients for future use.
7. by absorbing some water and salts
8. undigested plant fiber, bile pigments, dead bacteria, traces of undigested fat and protein
9. helpful—some bacteria synthesize vitamins K and B12; harmful—if some harmless bacteria overgrow other
bacteria, they can reduce water absorption and cause severe diarrhea
10. the rectum stores the feces; feces pass out of the body through the anus.
11. they can help students remember that the microvilli are very tiny, hairlike projections on the villi.
12. Sample answers: Students might sketch a paper towel absorbing a spill or think of clothes absorbing liquids
spilled on them,
paper absorbing ink, or chemicals absorbing oil spilled on a beach
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Human Systems and Homeostasis
SECTION 32.4. EXCRETORY SYSTEM
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
lungs, skin, kidneys, ureters, urinary bladder, urethra
through sweat, urine, and exhalation
carbon dioxide and water vapor
the cortex, medulla, nephron, renal artery and renal vein
They remove waste products from the blood and help to maintain electrolyte, pH, and fluid balances
to filter the blood and remove smaller molecules, which produces the filtrate Process Diagram: answer given
 most materials in filtrate are reabsorbed into the capillaries  urine moves into loop of Henle; water is
reabsorbed; urine moves into collecting duct
They can damage the capillary walls in the glomerulus, making them more porous. As a result, the nephrons
lose their ability to filter the blood.
The blood circulates through the dialysis machinery, which cleans and chemically balances the blood just as the
kidneys do.
excrete—excretory; urinate—ureter
dialysis “breaks apart” the blood by separating smaller molecules from the blood to filter and clean it before
returning the blood to the body.
Regulation
SECTION 29.1. HOW ORGAN SYSTEMS COMMUNICATE
1. Homeostasis is the maintenance of a stable internal environment.
2. Communication systems allow the body to detect and respond to stimuli.
Comic Strip: Students’ drawings should show the body sensing a stimuli and producing a response. Y
diagram: Nervous system—students’ answers might include any of the following: quick rate of reaction;
connected tissues; central nervous system; peripheral nervous system; brain; spinal cord; nerves; electrical
signal; chemical signal. Endocrine system—students’ answers might include any of the following: slow reaction
rate; isolated organs; chemical signals; longer-term processes. Both—students’ answers might include any of
the following: communication system; stimulates other tissues; produces responses to stimuli.
3. stimulus
4. endocrine system
5. peripheral nervous system
6. nervous system
SECTION 29.2. NEURONS
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
motor neuron
sensory neuron
interneuron
produces responses
detects stimuli
passes signals between sensory and motor neurons
dendrite receives impulses; axon transmits impulses
It maintains Na+ and K+ concentration gradients.
Students’ answers will vary.
An action potential is generated.
neurotransmitter
synapse
terminal
action potential
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Human Systems and Homeostasis
SECTION 29.4. CENTRAL AND PERIPHERAL NERVOUS SYSTEMS
1. brain and spinal cord
2. motor neurons and sensory neurons
Cause and Effect Diagram stimuli; the spinal cord; the spinal cord; brain; brain; produces a response
3. to process information relating to the senses
4. cerebrum, cerebellum, brain stem
5. Somatic: voluntary; muscles. Autonomic: involuntary; digestive organs, glands, heart, blood vessels.
Sympathetic: involuntary; heart, brain, lungs, muscles. Parasympathetic: involuntary; heart, lungs, arteries.
6. A reflex arc is a pathway that moves in the shape of an arch from the sensory neuron, through the spinal cord,
and out a motor neuron.
7. Functions controlled by the autonomic nervous system are those that are automatic, involuntary, and occur
without thinking about it.
8. The cerebral cortex is the outer most layer of the cerebrum.
9. The sympathetic nervous system is favorable for maintaining homeostasis.
SECTION 29.6. THE ENDOCRINE SYSTEM AND HORMONES
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
by traveling through the bloodstream
the receptors on and in the cell
Steroid hormones enter the cell, but nonsteroidal hormones do not.
brain; growth, stimulates reproductive maturity
pituitary; growth, water balance in the blood
thyroid; neck
thymus; maturation of white blood cells
adrenal glands; above the kidneys/abdomen
pancreas; between the intestines and stomach/abdomen
reproductive development and functions
TRH and TSH
increase in body temperature
When the body warms, TRH and TSH will stop being released. Without these releasing hormones, the thyroid
will not be stimulated.
14. Hormones are sent to the bloodstream throughout the body. If a gland produces too much or too little hormone,
it will over-stimulate the target cell, causing illness.
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Human Systems and Homeostasis
Defense
SECTION 31.2. IMMUNE SYSTEM
1. The body system that protects the body from infection
2. skin—physically blocks pathogens from entering; mucus membrane—traps pathogens so they cannot enter
through the nose or mouth; circulatory system—transports white blood cells to the infection site
3. Basophil cells release chemicals that attract phagocytes to the infection site.
4. They fight infection by causing pathogens to clump, by making them ineffective, or by activating complement
proteins.
5. passive immunity
6. DNA
7. genetic immunity
8. mother’s milk
9. inherited immunity
10. active immunity
11. a pathogen enters the body
12. getting sick by the same pathogen
13. Students’ answers will vary.
14. A phagocyte is a cell that eats other cells.
15. Interferons interfere with viral reproduction.
SECTION 31.3. IMMUNE RESPONSES
1. Specific responses are unique for every pathogen. Nonspecific responses are the same for every pathogen.
2. redness, swelling, itching, burning; causes leaky blood vessels which allow white blood cells to squeeze out of
the circulatory system and toward the infection site
3. increased body temperature; causes white blood cells to mature faster
4. The immune system detects antigens.
5. Memory cells are the cells that respond quickly when a pathogen invades a second time.
Y Diagram: Humoral Immunity—students’ answers may include: T cells destroy infected cell; memory T cells
produced; phagocyte activates T cell. Cellular Immunity—students’ answers may include: antibodies; T cells activate
B cells; memory B cells produced. Both—Students’ answers may include: memory cells produced; T cells important;
phagocytes important; produces active immunity.
6. few
7. weaken
8. antigen on pathogens that have invaded previously
9. Rejection means refusal to accept. When the body rejects a tissue, it will not accept it.
10. Antigens are proteins on a pathogen, and pathogens destroy living cells.
SECTION 31.6. DISEASES THAT WEAKEN THE IMMUNE SYSTEM
Leukemia: abnormal white blood cells  cannot mature  producing other blood cells  fight off pathogens
1. sharing needles, sexual intercourse, from a mother to her unborn baby through the umbilical cord
HIV Infection: T cells  reproduce HIV; start dying  replace the dying T cells  infect the body  AIDS
2. human immunodeficiency virus; the immune system has a deficiency
3. acquired immune deficiency syndrome; a syndrome is a condition or a disease
4. A pathogen that causes an opportunistic infection causes disease whenever there is an opportunity, in this case,
a weak immune system.
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Human Systems and Homeostasis
SECTION 30.6. LYMPHATIC SYSTEM
1. To collect excess fluid that leaks out of the blood vessels, clean and filter the fluid, and return it to the
circulatory system
2. skeletal muscles squeeze the vessels to keep lymph moving forward; valves in the vessels prevent lymph from
flowing backwards.
Cycle Diagram: blood leaves the heart and circulates to the rest of the body (filled in)  excess fluid leaks out
of the capillaries into areas between the cells (filled in)  interstitial fluid enters lymphatic vessels and
becomes lymph  lymph enters nodes, where it is filtered and cleaned  lymph vessels carry cleaned lymph
out of the nodes  lymph vessels return lymph to the circulatory system and to heart
3. fluid would be trapped in the tissues and begin to build up, resulting in swelling in that area
4. Tonsils filter bacteria and viruses that escape the body’s outer defenses. Lymphocytes develop in the thymus.
The spleen filters and cleans the lymph, contains lymphocytes and other white blood cells that destroy
pathogens
5. a type of cell found in the lymphatic system
6. “an inflammation of the lymph glands”; it indicates that your body is fighting an infection
Reproduction
SECTION 34.2. REPRODUCTIVE PROCESSES
1. Female: meiosis I and II;
Male: meiosis I and II
2. Female: before birth; Male: at puberty
3. Female: FSH, LH, estrogen; Male: FSH, LH, testosterone
4. monthly changes in the female reproductive system that includes producing and releasing an egg and preparing
the uterus to receive
an egg
5. Flow phase, the endometrium detaches and is expelled from the uterus; follicular and luteal phases, it thickens
again.
6. When one sperm penetrates the membrane, the egg changes so that no other sperm
can enter.
7. the 23 chromosomes of the sperm unite with the 23 chromosomes of the egg
8. Identical twins are genetically the same, developing from the same zygote; fraternal twins develop from two
different zygotes.
9. Any of the following three answers: too narrow a vas deferens, low sperm count; damaged reproductive organs
due to injury or disease; defective eggs
10. It must be passed from person to person through sexual contact.
11. Bacterial Infection: Examples—chlamydia, syphilis, gonorrhea; Effects—attacks reproductive organs causing
infertility; Treatment—antibiotics cure infections Viral Infections: Examples—hepatitis B, genital herpes,
HPV, HIV;
Effects—attacks body cells;
Treatment—medications control symptoms; no cures available
12. Menopause is when a female stops menstruating.
13. Transmitted means “to pass,” and an STD is a disease that is passed through sexual contact.
14. Fertile means “can reproduce.” If a person is infertile, he or she cannot reproduce
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Human Systems and Homeostasis