Unit 2: Homeostasis (Lectures 1-2) Flashcards
What is homeostasis ?
The ability to maintain a steady state within a constantly changing environment
What are the 3 interdependent components of a homeostatic control mechanism ?
1) Receptor
2) Control centre
3) Effector
What is negative feedback ?
Anything that causes a change in direction opposite to that of the initial change. This returns it to its ‘ideal’ value
Are the majority of control mechanisms examples of positive or negative feedback ?
Negative
Give 3 examples of negative feedback mechanisms
- Control of blood sugar
- Regulation of temperature
- Blood pressure
What is positive feedback ?
When a result is to enhance or exaggerate the original stimulus so activity (output) is accelerated
What do positive feedback mechanisms usually control ?
Episodic (infrequent) events that do not require continuous adjustments
Give 3 examples of positive feedback
1) Blood clotting
2) Labour contractions
3) Urination
What is autoimmunity ?
An overreactive immune response of the body against substances and tissues that are normally present in the body
How can autoimmunity lead to illness ?
As the immune system attacks self cells
What is the major role of electrolytes in the extracellular fluid ?
To ensure that fluid levels inside and outside the cell are balanced
How can a cell adjust its fluid levels ?
By changing the concentration of electrolytes
What is the concentration of Na+ in the extracellular fluid ?
142 mEq/L
What is the concentration of Na+ in the intracellular fluid ?
10 mEq/L
What is osmolarity ?
The concentration of a solution expressed as the total number of solute particles PER LITRE of solvent (mOsm/L)
What is osmolality ?
The concentration of a solution expressed as the total number of solute particles PER KG of solvent (mOsm/kg H2O)
What is a measurement of plasma sodium below 142 called ?
Hyponatremia
What is the cause of hyponatremia ?
Excess water- over hydration
Loss of sodium- Dehydration
What is it called when the measurement of plasma sodium is above 142 ?
Hypernatremia
What is hypernatremia ?
Excess sodium- over hydration
Loss of water- dehydration
What is bicarbonate buffering ?
The regulation of CO2 by the lungs and HCO3- by the kidneys
What is compensation ?
The restoration of PH despite disturbed [HCO3-] or pCO2
What is correction ?
The restoration of normal PH , [HCO3-] and pCO2
