homeostasis Flashcards
definition of steady state
maintenance of nearly constant conditions over time
definition of equilibrium
when a system’s solute concentrations and other parameters are constant in time without requiring an input of energy
what is Basal metabolic rate?
energy expenditure at rest
kcal/hr/sq meter body surface area
what value is usually less; basal metabolic rate or resting metabolic rate?
the basal metabolic rate because RMR includes various daily activities in its value
list 5 factors that can influence metabolic rate
gender age hormones temperature that you live in malnutrition
what is the primary intracellular fluid cation?
K+
what does mass balance for a system in steady state mean?
it means that any substance taken in by the body is nearly equal to the amount leaving the body plus that removed by metabolism
what is the primary extracellular fluid cation?
Na+
how is the difference between the intra and extracellular fluid cations maintained?
by the basolateral Na+/Ka+ ATPases which transport 3 Na+ molecules out of the cell in exchange for two K+ molecules transported into the cell
in the system level example of endocrine control over thyroid function, where does thyroid hormone negatively inhibit?
thyroid hormone negatively inhibits the anterior pituitary gland to prevent too much or too little TSH release
what is a system’s “gain”?
it is the capacity of the system to restore a controlled variable to its set point after a pertubation
what does a higher system gain imply?
a better ability to restore a controlled variable to its set point in response to a perturbation
give some examples of a USEFUL positive feedback systems?
- uterine contractions during birth
- blood clotting after vessel rupture
- estrogen effects on pituitary hypothalamus before ovulation
- generation of an all or none action potential via Na+ channel activation
- calcium inducted calcium release in the heart
