homeostasis Flashcards
what is contained within the internal environment?
- nutrients
- oxygen
- waste
- carbon dioxide
define homeostasis
The various physiological arrangements that serve to restore the normal state once it has been disturbed.
what are examples of systems that interact with the external environment and expand energy?
- nervous system
- locomotor system
- reproductive system
what are examples of systems that interact with the internal environment and help to achieve homeostasis?
- cardiovascular system
- respiratory system
- excretory system
- alimentary system
what are examples of systems that control other systems?
- nervous systems
- endocrine systems
what are the 3 points that explain the importance of homeostasis?
- cells function most effectively under optimal environmental conditions
- basic cellular functions tend to alter their immediate environment
- homeostasis operates to correct any changes in the cellular environment
what is the optimum pH for pepsin?
pH 3
what is the optimum pH for trypsin?
pH 7
what are the two mechanisms of homeostasis control?
- feed back control
- feed forward control
what is negative feedback control?
- A change in a variable activates mechanisms that alter the level of that variable so as to counteract the change
- Tends to maintain the status quo
- Widely used in many physiological control systems
what is roughly the temperature of the oral cavity?
36.7
what is an example of negative feed back?
thermoregulation
describe an example of where homeostatic systems need to be adaptable
in many physiological systems, variables eg body temperature (circadian rhythm) alter during the 24hr cycle
what is feed forward control?
- This involves altering a behaviour before there is an obvious ‘error signal’
- Anticipatory action
- Stop eating before ‘full’
- Increasing heart rate, ventilation at onset of exercise
- Probably learned behaviours
what is positive feedback?
- A change in a variable activates mechanisms that alter the level of that variable so as to increase the change
- A small change is amplified and converted to a larger one
- Not used in homeostatic control
- Potentially disruptive (‘vicious circle’)
- Used in blood clotting, childbirth, action potentials
