Homeostasis

Lecture #6Ms. Day/ Honors Biology

Organization of Life &

What are Cells?What are Cells?• Definition: basic unit of structure and function

of life• Although ALL living things are made of cells,

organisms may be:–Unicellular – composed of one cell–Multicellular- composed of many cells

Multicellular OrganismsMulticellular Organisms• Cells in multicellular organisms often specialize

(take on different shapes & functions)

Cell Specialization = DIFFERENTIATION

Cell Differentiation• Do all cells look alike?

• NO!!!• Do all cells have the

same functions?• NO!!!

• Cell Differentiation –Process by which

unspecialized cells (stem cells) develop into different cell forms and functions

How Do Cells Specialize Their How Do Cells Specialize Their Functions?Functions?

• Cells in multicellular organisms become specialized by turning ON or OFF different genes different parts of their DNA

Levels of OrganizationHow are living

things organized?

1. Chemical2. Cells3. Tissues4. Organs5. Systems6. Organism

Chemical Atoms, molecules, compounds

Cell Basic unit of living things

Tissue Similar cells doing specific function

Organ Similar tissues performing specific task

Organ System Organs working together

Organism All systems working together

• Tissues• groups of cells similar in structure and

perform common or related functions•Epithelial Tissue

• Skin, lining of tissues•Connective Tissue

• Blood, bones, cartilage•Muscle Tissue

• Smooth, striated, cardiac•Nervous Tissue•Nerves and fibers

Four Basic Types of Tissues

What is Homeostasis?• Process that occurs in ALL living

things• All organ systems work together

to achieve homeostasis• Definition:

– The ability of an organism to maintain its internal environment despite changes to its internal or external environment

http://balancewines.wordpress.com/2009/12/

Homeostasis in Animals• What do animals need to keep

constant/healthy?• Body cells work best if they have the correct

– Temperature– Water balance– Blood Pressure– Blood pH level– Glucose (sugar) levels– Oxygen and Carbon Dioxide Levels

• How does an organism respond to these changes? • 2 different pathways

» Negative or Positive Feedback

Negative Feedback1. Process that activates body to RESTORE

conditions to their ORIGINAL STATE2. Counteract further change in the same

direction–STOPS THE CHANGE!

3. It ensures that small changes don’t become too large

–MAINTAINS HOMEOSTASIS• EX: Thermoregulation, Blood sugar levels, Blood Calcium

level, O2/CO2 levels in blood

Positive Feedback1. Process that activates body to AMPLIFIES

original change2. CONTINUES more change in the same

direction–INCREASES the change!

3. Allows for small changes to become too large

–DOES NOT MAINTAINS HOMEOSTASIS• EX: Uterine contractions, Lactation, blood clotting

Homeostasis Control Systems• 3 components:

– Receptor– Control Center– Effector

• Receptor – detects a change in some

variable in the organism’s internal environment, such as a change in temperature

• control center – processes the information it

receives from the receptor and directs an appropriate response by the effector

HomeostasisExample: household thermostat

Whole control system is called a negative feedback system

Negative FeedbackExample #1: Thermoregulation in the body

What happens when you are too hot?

Sweat (liquid) turns to gas requires HEAT

Heat comes from your

body/skin skin cools

down

Negative FeedbackExample #1: Thermoregulation in the body

What happens when you are too cold?

“Goose Bumps” hairs trap a layer of air

next to skin warms by body heat

Air becomes an insulating layer

Called piloerection

Shivering Muscle movements

use ATP (energy) Breaking ATP

releases HEAT

Maintaining Body Temperature(Thermoregulation)

• Humans have a normal temperature of around 36.2 to 37.2 °C (98.6°F)

• If your body temperature goes above normal temperature likely suffering from infection– your body raises its

temperature to fight off the infection

• If your body goes below this range it indicates hypothermia.– could lead to cell damage

and possibly death.http://asimplebutimpossibletask.blogspot.com/

http://news.bbc.co.uk/2/shared/spl/hi/health/03/travel_health/diseases/html/sars.stm

Negative FeedbackExample #2: Regulating Blood Sugar (Glucose) Levels

Negative FeedbackExample #3: Regulating Calcium Levels in Blood

Why do you need calcium?

1)Carries messenges in body

1)Muscle contractions2)Nervous system homeostasis

1)Bone/teeth formation

2)Helps blood clotting

Holding Holding breath, breath, COCO2 2 levels levels

riserise

Control system Control system forces exhale, forces exhale, inhaleinhale

OO2 2 // COCO2 2 level level

returns to normalreturns to normal

Negative FeedbackExample #4:Regulating Oxygen and Carbon

Dioxide Levels in Blood

Positive FeedbackExample #1: Uterine Contractions

During childbirth…• Baby’s head PUSHES against sensors near opening of uterus •Oxytocin (hormone) is released stimulates uterine contractions• More contractions more oxytocin• ONLY STOPS when pushing STOPS

Positive FeedbackExample #2: Lactation (making milk)

•Suckling by baby stimulates brain to release hormone (prolactin) •Prolactin makes milk•More suckling by offspring (baby) more milk production

•Damaged blood vessel stimulates release of Damaged blood vessel stimulates release of clotting factors clotting factors Platelets build up at injured site •More chemicals released more platelets

•Platelets continue to pile up and until clot is formed•Finally, growth hormones stimulate cell Finally, growth hormones stimulate cell divisiondivision

  

platelets

fibrin

white blood cellred blood cell

blood vessel

clot

Positive Feedback Example #3: Blood Clotting

Homeostasis in Plants• What do plants need to keep

constant/healthy?• Plant cells work best if they have the correct

–Water– Sunlight–Oxygen and Carbon Dioxide Levels

Homeostasis in Plants

• What mechanisms for plants use to help maintain homeostasis? –Creates a waxy cuticle on leaves–Stores extra water–Opening/closing of stomata (pores in

leaves)–Bends towards light

Stoma OpenStoma Closed

Guard Cells

Stoma

CO2

O2 H2O

What goes in?

What goes out?

•What do plants use to control gas exchange?

•Guard Cells & Stoma

•Why do plants need to OPEN stomata?

•Photosynthesis

•Making food

•If the plant needs water for photosynthesis, why is water coming out of the stomata?

•Losing H20 helps get

H20 up plant against

gravity!!

Homeostasis in Plants Using Stomata

Stoma Open Stoma Closed

Guard Cells Guard Cells•Why would the plant close stomata using guard cells?

•Prevent excess water loss (conserve water)

•So what is the point of having stomata?

•Remove waste gas (O2)

•Take in gas (CO2) for photosynthesis

•Help move water up plant for photosynthesis

•Control water loss

Homeostasis in Plants Using Stomata

More Homeostasis in Plants• Stems bend towards

sunlight to maintain the amount of photosynthesis. –Called phototrophism

• Stems store extra water in a huge “pool” inside their cells–Called a central vacuole