Lecture 3 Homeostatis

Organ system inter-relationship Necessary Life Functions Survival Needs Homeostasis Homeostasis control Mechanism

Organ Systems Interrelationships • The integumentary system protects the body from the external environment • Digestive and respiratory systems, in contact with the external environment, take in nutrients and oxygen. • Nutrients and oxygen are distributed by the blood • Metabolic wastes are eliminated by the urinary and respiratory systems

Necessary Life Functions • Maintain Boundaries • The internal environment remains distinct from the external environment, eg • Cellular Level – plasma membranes • Organism Level – skin

• Movement • Locomotion • Movement of substances

Necessary Life Functions • •

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Responsiveness Ability to sense changes in the environment and respond to them.

Digestion

Break-down and delivery of nutrients

• Metabolism – all the chemical reactions that occur within the body • Production of energy • Making body structures

Necessary Life Functions • Excretion

• Elimination of waste from metabolic reactions

• Reproduction • Production of future generation

• Growth • Increasing of cell size and number

Survival Needs • Nutrients • Chemicals for energy and cell building • Includes carbohydrates, proteins, lipids, vitamins, and minerals

• Oxygen • Required for metabolic reactions

Survival Needs • Water

• 60–80% of body weight • Provides necessary environment for metabolic reactions

• Stable body temperature • Necessary for metabolic reactions to occur at life sustaining rate

• Atmospheric pressure • Required for normal breathing and gas exchange in lungs

Homeostasis • Maintenance of a stable internal environment in an ever changing out side world • The internal environment of the body is in a dynamic state of equilibrium • Homeostasis must be maintained for normal body functioning and to sustain life • Homeostatic imbalance – a disturbance in homeostasis resulting in disease

Maintaining Homeostasis • The body communicates through neural and hormonal control systems to maintain homeostasis. • The three interdependent components of control mechanism include: 1. Receptor 2. Control Center 3. Effector

Maintaining Homeostasis 1- Receptor – Monitors the environment and responds to changes (stimuli)  2- Control center •Determines set point at which variable is maintained. •Analyzes information •Determines appropriate response 3- Effector •Provides a means for response to the stimulus

Maintaining Homeostasis

Feedback Mechanisms • Negative feedback • Positive feedback

• Negative feedback • Includes most homeostatic control mechanisms • Shuts off the original stimulus, or reduces its intensity • Works like a household thermostat

Negative feedback Most body systems regulate Via this mechanism, eg •Regulation of Blood Pressure •Removal of CO2 from body

Feedback Mechanisms • Positive feedback • Increases the original stimulus to push the variable farther • In the body this only occurs in blood clotting and birth of a baby

Positive feedback

Blood Clotting Cascade