Homeostasis Flashcards
1
Q
cells in the primordial sea
A
- had to adapt
- semi permeable membrane facilitated process that provides nutrients
- damage to membrane impaired metabolic function and lead to death if homeostasis wasn’t restored
- in humans we use organ systems to create stable environment for cells
2
Q
mass balance
A
- for a system in steady state for metabolism:
- any substance taken in by the body is nearly equal to the amount leaving the body plus that removed by metabolism
- has a central compartment called the pool (ECF)
3
Q
BMR
A
- energy expidenture at rest (kcal/hr/sq meter body surface area)
- largest portion of daily energy usage
- metabolism is lowest during sleep and increases with arousal and fever, after ingestion of food and with normal activity
- 70 kg man needs 2100 kcal/day-which is the resting metabolic rate BMR is less than RMR
- RMR is 5% higher in men, declines during aging, increased by hormones, colder climate
- malnutrition decreases metabolic rate
4
Q
net fluid balance
A
-input = output
5
Q
ECF cation
A
sodium
6
Q
ICF cation
A
potassium
7
Q
sodium potassium ATPases
A
- 3 na out for 2 k in
- balance of pos and neg maintained in each compartment, but by different ions
8
Q
homeostasis is dynamic
A
- external conditions are far from constant, but physiological variables maintained in predictable range
- glucose rises in blood and are restored by insulin
9
Q
negative feedback
A
- stimulus on receptor
- afferent pathway goes to integrator which compares it to a set point
- efferent pathway goes to effector
- response occurs
-end products can be self regulators of molecular pathways
10
Q
feedforward control
A
- change with time is desirable
- anticipation
- heart rate and breathing increase in anticipation of exercise
11
Q
system neg feed back
A
- hypothalamus–>TRH–>ant pit–> TSH–>thyroid gland makes T4 and T3
- they negatively regulate ant pit
12
Q
gain of neg feedback
A
- correction divided by remaining error
- BP from 100-75 then back to 95
- correction is 20, error is 5
- bigger gain means bigger power
13
Q
neg feed back and bleeding
A
- recovery after 1 liter lost
- death by pos feedback after 2 L lost-neg feedback is overwhelmed
14
Q
useful pos feedback
A
-clotting and uterus
