closed system
no movement of mass across the system boundaries
open system
allows for exchange of mass across system boundaries
mass balance equation
acc = in - out + (gen - cons)
acc: rate of accumulation of mass
in: flow rate of mass into system
out: flow rate of mass out of the system
gen: rate of mass generation within system
cons: rate of mass consumption “
(gen - cons): net rate of mass production within system
homeostasis
maintenance of the conditions necessary for life
everything has certain ranges for normal function
NEGATIVE FEEDBACK - most important strategy
steady state
everything kept in functional state with feedback loops
everything happening simultaneously to maintain conditions
ex: body weight - steady when calorie intake and energy use are equal
equilibrium
a state in which opposing or influencing forces are perfectly balanced
will last forever with no outside forces
tidal volume
total forced inhalation and forced exhalation
ventilation
the exchange of air between alveolus and atmosphere
ventilation steps
1: inspiration
2: expiration
both are aided by action of set of muscles that increase and decrease volume in thorax
partial pressure
used to describe concentration of oxygen in gas
PO2 is the fraction of the pressure in the gas that is caused by oxygen
hemoglobin
allows blood to be a great oxygen carrier
can bind and carry 4 o2 molecules
when the hemoglobin binding sites are filled, blood is said to be saturated with o2
oxygen balance
assume steady state
assume no generation or consumption
2 out terms - oxygen leaves alveolus during expiration and oxygen lost to blood
carbon dioxide removal
one of the most important buffering systems - most co2 is converted into bicarbonate
buffer
chemical that when present absorbs H+ ions and causes a resist in pH (bicarbonate is a huge one in blood - level of co2 relates to local pH)
