Homeostasis Flashcards
What is Basal metabolic rate (BMR)?
the energy expenditure at rest (kcal/hr/sq meter body surface area). It is the largest proportion of our daily energy usage.
Define homeostasis
The maintenance of nearly constant conditions in the internal environment referred to as a STEADY STATE
Define steady state. Is it the same as equilibrium? If it is not the same how is it different?
Steady state: the maintenance of nearly constant conditions over time. It is not the same as equilibrium because it requires the input of energy while at equilibrium no energy is required.
Feedforward control
“anticipate” change and initiate the response loop before the change has occurred
A healthy young man requires ~30kcal/kg body weight to sustain daily resting metabolism. What is this called?
Resting Metabolic Rate (RMR) - throughout day, higher than BMR because of daily activity
What can increase BMR?
Arousal, fever, ingesting food, normal activity, and most profoundly by strenuous exercise.
What is the concept of mass balance?
Any substance taken in by the body = amount leaving body plus that removed by metabolism (system at steady state)
Define equilibrium
When a system’s solute concentrations and other parameters are constant in time without requiring the input of energy from metabolism or other sources
Positive feedback
Accelerates a process - output enhances response. Can be unstable
Good ex.: oxytocin released during childbirth to speed up contractions
Bad ex.: hypovolemic shock if 2L or more blood is lost
What does a high gain imply?
The system is better able to restore a controlled variable to its set point in response to perturbation.
How do you calculate gain?
Gain = Correction/Remaining Error
What is the primary extracellular electrolyte? What is the primary intracellular electrolyte?
Extracellular = Na. Intracellular = K. The sodium potassium ATPases keep this by pumping three Na out for every 2 K in.
What can decrease BMR?
Sleeping only
The degree of effectiveness with which a control system maintains constant conditions is determined by what?
The Gain of the negative feedback. The capacity of the system to restore a controlled variable to its set point after a perturbation is called the gain.
What can raise the RMR?
Increasing muscle mass, body size, hormones (thyroid hormone, growth hormone, testosterone, epi/norepi). (Poor nutrition lowers RMR)
