Unit 28 Human Body
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Transcript of Unit 28 Human Body
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28.1 Levels of Organization
KEY CONCEPT The human body has five levels of organization.
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28.1 Levels of Organization
Specialized cells develop from a single zygote.
• Organisms are made up of specialized cells.
red blood cell nerve cell
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28.1 Levels of Organization
• Zygotes first divide into embryonic stem cells.
• Stem cells develop in two stages. – determination, or
committing to become one cell type
– differentiation, or acquiring specialized structures and functions
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28.1 Levels of Organization
cell
Specialized cells function together in tissues, organs, organ systems, and the whole organism. • Specialized cells perform specific tasks. • Tissues are groups of similar cells working together.
tissue
– epithelial tissue – connective tissue – muscle tissue – nervous tissue
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28.1 Levels of Organization
• Organs are different tissues working together. • Organ systems are two or more organs working together.• Organism is all organ systems working together.
ORGANS
ORGAN SYSTEM
ORGANISM
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28.1 Levels of Organization
• There are 11 major organ systems in the human body.
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28.2 Mechanisms of Homeostasis
KEY CONCEPT Homeostasis is the regulation and maintenance of the internal environment.
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28.2 Mechanisms of Homeostasis
Conditions within the body must remain within a narrow range.
• Homeostasis involves keeping the internal environment within set ranges.
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28.2 Mechanisms of Homeostasis
• Control systems help maintain homeostasis. – sensors gather data– control center receives
data, sends messages – communication system
delivers messages to target organs, tissues
– targets respond to change
pore
sweat glands
hairfolliclemuscle
goosebump
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28.2 Mechanisms of Homeostasis
Negative feedback loops are necessary for homeostasis.
• Feedback compares current conditions to set ranges.• Negative feedback counteracts change.
Negative Feedback Loop
Holding breath, CO2
levels rise,
Control system forces exhale, inhale
O2 / CO2 level returns to normal
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28.2 Mechanisms of Homeostasis
• Positive feedback increases change. – Torn vessel stimulates release of clotting factors
– growth hormones stimulate cell division
platelets
fibrin
white blood cellred blood cell
blood vessel
clot
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28.3 Interactions Among Systems
KEY CONCEPT Systems interact to maintain homeostasis.
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28.3 Interactions Among Systems
Each organ system affects other organ systems.
• An organ system must do a specific job. • Organ systems must also work together to keep the
organism healthy.
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28.3 Interactions Among Systems
• Organ systems must also work together to keep the organism healthy.– Organ systems work together to produce Vitamin D.– Thermoregulation maintains a steady body temperature.
1
2
3 4
Skin absorbs UV light
Liver produces inactive vitamin D
Kidneys produce active vitamin D Active vitamin D used in bones
UV light
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28.3 Interactions Among Systems
A disruption of homeostasis can be harmful.
• Homeostasis can be disrupted for several reasons. – sensors fail – targets do not receive messages– injury – illness
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28.3 Interactions Among Systems
• Short-term disruption usually causes little or no harm.• Long-term disruptions can cause more damage.• Diabetes is a serious long-term disruption of homeostasis.
1
2
3 4
Pancreas cells attacked;insulin declines
Blood glucose levels rise,
Body burns fat; blood more acidic, Cells impaired; all organs damaged.
pancreas
fats
kidneys