KINE 304 Lecture 3: Homeostasis
2 Mar 2017
School
Department
Course
Professor
Homeostasis / Control of Cells by Chemical
Messengers (Chps. 1, 5)
Homeostasis: maintenance of stable, or constant conditions in the internal environment
(underlying principle of physiology)
- Effective homeostatic control systems allow steady state
o *set point
- Steady state requires use of energy (unlike eqbm.)
- Generalizations
o Input = output
▪ Heat in heat out (sweat)
o Dependent upon balance of input and output, not magnitude
o Control systems cannot maintain complete constancy
o Each variable has normal range of values
o Homeostasis does not have an absolute number
- Virtually all homeostatic controls systems use negative feedback systems
- Most positive feedback systems exuberate original disturbance (oxytocin: birth)
Major Functional Homeostatic Systems
- Circulatory System
o No cell located 50 mm away from capillary
o Diffusion of almost any substance occurs within few seconds
o All blood pumped by heart traverses entire system once per min
- Respiratory System
o Acquires oxygen – releases CO2, maintains pH
- Gastrointestinal System
o Digest/absorbs food substances, releases waste products
- Hepatic System
o Degrades food substances, helps store excess; helps regulate iron stores in body
- Renal System
o Maintains homeostasis of water, ions, amino acids, glucose
▪ Glucose does not exit in urine
- Nervous System
o Senses changes in external and internal environment and stimulates proper
response
- Endocrine System
o Maintains homeostasis of food substrates ion, temperature, etc; allows
communication over distances
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Document Summary
Homeostasis: maintenance of stable, or constant conditions in the internal environment (underlying principle of physiology) Effective homeostatic control systems allow steady state: *set point. Steady state requires use of energy (unlike eqbm. ) Virtually all homeostatic controls systems use negative feedback systems. Most positive feedback systems exuberate original disturbance (oxytocin: birth) Circulatory system: no cell located 50 mm away from capillary, diffusion of almost any substance occurs within few seconds, all blood pumped by heart traverses entire system once per min. Respiratory system: acquires oxygen releases co2, maintains ph. Gastrointestinal system: digest/absorbs food substances, releases waste products. Hepatic system: degrades food substances, helps store excess; helps regulate iron stores in body. Renal system: maintains homeostasis of water, ions, amino acids, glucose, glucose does not exit in urine. Nervous system: senses changes in external and internal environment and stimulates proper response. Endocrine system: maintains homeostasis of food substrates ion, temperature, etc; allows communication over distances.
