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2C1

2C1. Homeostasis, Negative feedback loops, Positive feedback loops, Temperature regulation . Homeostasis. As animals have evolved, specialization of body structures has increased For cells to function efficiently and interact properly, internal body conditions must be relatively constant

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2C1

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  1. 2C1 Homeostasis, Negative feedback loops, Positive feedback loops, Temperature regulation

  2. Homeostasis • As animals have evolved, specialization of body structures has increased • For cells to function efficiently and interact properly, internal body conditions must be relatively constant • The dynamic constancy of the internal environment is called homeostasis • It is essential for life

  3. Homeostasis • Negative feedback mechanisms • Changing conditions are detected by sensors (cells or membrane receptors) • Information is fed to an integrating center, also called comparator (brain, spinal cord, or endocrine gland) • Compares conditions to a set point • If conditions deviate too far from a set point, biochemical reactions are initiated to change conditions back toward the set point

  4. Homeostasis • Humans have set points for body temperature, blood glucose concentrations, electrolyte (ion) concentration, tendon tension, etc. • Integrating center is often a particular region of the brain or spinal cord • Effectors (muscles or glands) change the value of the condition in question back toward the set point value

  5. Homeostasis

  6. Homeostasis • Mammals and birds are endothermic • Maintain a relatively constant body temperature independent of the environmental temperature • Humans 37oC or 98.6oF • Changes in body temperature are detected by the hypothalamus in the brain

  7. Homeostasis • Negative feedback mechanisms often oppose each other to produce finer degree of control • Many internal factors are controlled by antagonistic effectors • Have “push–pull” action • Increasing activity of one effector is accompanied by decrease in the other

  8. Homeostasis • Antagonistic effectors are involved in the control of body temperature • If hypothalamus detects high temperature • Promotes heat dissipation via sweating and dilation of blood vessels in skin • If hypothalamus detects low temperature • Promotes heat conservation via shivering and constriction of blood vessels in skin

  9. Homeostasis

  10. Homeostasis • Positive feedback mechanisms • Enhance a change – not common • These do not in themselves maintain homeostasis • Important components of some physiological mechanisms • Blood clotting • Contraction of uterus during childbirth

  11. Homeostasis

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