180 likes | 434 Views
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
E N D
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 • The dynamic constancy of the internal environment is called homeostasis • It is essential for life
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
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
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
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
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
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
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.