Homeostasis Flashcards
What is homeostasis
The maintenance of a “nearly constant” internal environment
What are tissues
Aggregates of cells with a particular function
What are organs
Specialised tissues plus connective tissues, served by nerves and blood vessels
What are systems
A group of integrated organs that collectively perform a function
What is the distribution of fluid into compartments
- 70% of fluid within cells - ICF
- 30% of fluid outside cells - ECF
How is homeostasis maintained
By control systems:
- Within cells - genetics
- Within/between tissues/organs/systems - nervous system, endocrine system
What is open loop
No feedback so could result in run away reactions
- Controller - controlled component - output
What are the types of control systems
- Open loop
- Closed loop
- Feedforward
What is closed loop
Output of the system feeds back and influences the controller
- Controller - controlled component - output - sensor - feedback - controller
What is feedforward
- Response is generated in anticipation of a change
- Precision of control depends on power and speed of response of controller and sensitivity of the sensor
What is gain
- It is the degree of effectiveness of a negative feedback control system
- Gain = correction/error
Describe the negative feedback control of arterial blood pressure
- Sensor - baroreceptors -stretch receptors in carotid arteries and aortic arch
- Control centre - solitary nucleus in medulla oblongata references set point and identifies change in blood pressure
- Effectors - heart and blood vessels respond
- Controlled variable - rise or fall in arterial blood pressure
Give examples of positive feedback
- Oxytocin induced uterine contractions in child birth
- Blood clotting
Give example of feed forward control
- Digestive system - sight or smell or thought of food induces a response in the GI tract so gut is prepared to mechanically and chemically digest and absorb the meal
