Cells of Multicellular Organisms

• • Cells of multicellular organisms are hierarchically organized into tissues:
• – Epithelial tissues – columnar, cuboidal, squamous
• – Connective tissues – fibrous, loose, cartilage & bone, blood
• – Muscle tissues – striated, smooth, cardiac
• – Nerve tissues – found throughout the body
• • Tissues are organized into organs
• • Organs are organized into organ systems
• • Organ systems are organized into individuals
• • Physiologically, multicellular organisms are synergisms (systems that are more than sum of their parts)
• • Tissues – organs
• • Organs – organ systems
• • Organ – individuals

Homeostasis

• Homeostasis (“steady state”)

• – Maintenance of nearly constant internal conditions
• – Snakes are cold-blooded (ectothermic or poikilothermic), heat & thus their body temperature is absorbed from environment
• – Humans are warm-blooded (endothermic or homeothermic), body temperature is generated internally

· Feedback Systems

• • Homeostasis is controlled by feedback
• • Feedback loops used by organisms to help maintain homeostasis & have 3 major components:

– Receptors - respond to various stimuli to which organism may be exposed
– Control center - decides to which stimuli organism should respond to & what is the right response
– Effectors - receive instructions from control center

• • Two kinds of feedback systems - positive & negative:

– Positive feedback enhances or intensifies a process

• Receptors, Control centers, & Effectors are also involved

– Negative feedback is used to

• Slow down, shut off, or reverse a physiological process &
• Return it to an optimal condition

·
Physiological Systems of Multicellular Animals

Digestion
• Regardless of how food is found, there is always a close relationship between structures used for nutrient acquisition & function

Respiratory Systems
• How do organisms obtain O2 & get rid of CO2? By diffusion

• As organisms became larger & bulkier, activity levels & energy requirements increased
• All of these systems share 2 characteristics:
– Extensive surface areas
– Thin, moist cell layers that facilitate diffusion

Circulatory System
• Circulatory system distributes acquired & processed nutrients throughout the body
•
Excretory System

• Maintaining Water Balance
• • Organisms cannot control amount of water in environment but they can control water in their internal environment
• • Proper concentrations of solutes & water in animal’s body – Fluids quite often differ from those in the environment
• Removing Metabolic Wastes
• • Cellular metabolism – Produces waste compounds that must be disposed of

Chemical Monitoring & Hormones

• • Hormones monitor & control functions

· – Happen slowly over a period of several days or weeks

· – Growth, maturity, reproduction

• Many hormones made by humans & other vertebrates

– Adrenaline, endorphins, insulin

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