Unit 1: cell biology, homeostasis, electrolytes Flashcards
Describe homeostasis
the maintenance of nearly constant conditions in the internal environment (ECF)
- Walter Cannon (1929)
“what goes in = what comes out” in a steady state; name examples of what “goes in” to a cell and what “comes out” of a cell to maintain homeostasis.
in: nutrients
out: energy and waste products
waste products can be: CO2, H+, solid waste, H2O, urea, and heat
explain how peripheral circulatory beds maintain homeostasis
they deliver only enough to meet tissue needs
increased metabolism > leads to a response in the CV system > increases blood flow to tissues/organs to meet O2 requirements
through arterioles, blood brings nutrients into the capillary bed, where O2 is exchanged to cells, and the venules bring blood back to the heart but also help to remove byproducts from blood
explain how the following organs maintain homeostasis:
2 hearts
lungs
GI system
kidneys
liver
peripheral vascular beds
L & R heart:
peripheral CV nutrients
O2 circulation to pulm system
lungs: regulate our O2 exchange/blood gas
GI system: replaces nutrients in the blood as they’re being consumed
kidneys: ECF buffering systems (pH)
liver: eliminates wastes/toxins through biliary system
peripheral vascular beds: moves around nutrients
What are 4 different ways the body uses a negative feedback loop to correct a drop in MAP
- increases sympathetic outflow
- decreases parasympathetic outflow
- increases vasopressin and ADH
- decreases ANP
all of these negative feedback systems will counteract the drop in MAP to bring the MAP back up
ANP - atrial natriuretic peptide - a hormone that helps regulate blood pressure by vasodilating vessels in response to atrial stretch due to hypervolemia
This feedback system is the most used in the body.
Negative Feedback System
List the steps for how negative feedback loops help the body maintain homeostasis?
- change/disturbance of homeostasis occurs
- regulatory mechanisms kick in
- body reacts to oppose/counteract the change
ex) increased CO2 leads to increased ventilation to decrease CO2
Explain how a Positive Feedback System responds to changes caused by select stimuli
positive feedback AMPLIFIES the changes
can be good or bad
bad = vicious cycles (pathologic positive feedback loops)
what 2 safety net features prevent physiologic positive feedback loops from progressing into vicious cycles
- checkpoints
- safety valves
explain how active labor is a physiologic positive feedback system
- labor causes the uterus to contract to push the fetus towards the cervix
- cervical stretch (change) causes a release of oxytocin into the bloodstream
- oxytocin causes the smooth muscle of the uterus to contract (amplified via the stretch of cervix)
- loop continues until it hits a “checkpoint” which, in this case, is birth
explain how the clotting cascade/platelet plug formation is a physiologic positive feedback loop
- injury to endothelial wall of a blood vessel occurs (change)
- clotting cascade initiates
- TXA2 (thromboxane 2; a potent platelet activator) initiates platelet aggregation to plug up vessel wall opening – amplification
- continues until reaches checkpoint (controlled bleeding)
name 6 pathologic positive feedback loops
sepsis/necrosis
severe acidosis
peripheral acidotic conditions
atherosclerotic plaque clotting
diabetic renal inflammation/hyperfiltration
severe hemorrhage
describe how sepsis/necrosis is a pathologic positive feedback loop
cellular death increased > wastes/toxins infiltrate neighboring healthy cells > increased cellular death
describe how severe acidosis is a positive feedback loop and what type of positive feedback loop is it?
in severe acidosis, pH is lowered, which decreases your respiratory drive, which further exacerbates CO2 retention and therefore continues to exacerbate acidotic state
pathologic positive feedback loop
describe how diabetic renal inflammation/hyperfiltration is a pathologic positive feedback loop
nephrons die off with aging > which in turn causes healthier nephrons to work harder > healthy nephrons age faster > increased nephron death
describe how severe hemorrhage is a pathologic positive feedback loop
decreased MAP d/t hypovolemia > decreased coronary blood flow > decreased CO > further decreases your MAP
compare and contrast compensated shock versus decompensated shock and how negative and positive feedback loops are integrated
in COMPENSATED shock, a negative feedback loop works well; compensatory mechanisms (fluid shifts) will help the body return to homeostasis
in severe hemorrhage (DECOMPENSATED shock), positive feedback leads to death: hypovolemia > decreased MAP > decreased coronary flow; less blood circulating > decreased CO > cellular death
too much blood loss too fast means that the negative feedback compensatory mechanisms will be outweighed by the positive feedback loop
describe the relationship between anesthesia and homeostasis
anesthetics can alter systems’ physiology (control systems usually in place go “offline” when anesthetics are administered)
also, changes in physiologic systems can alter anesthetic drug responses
cells are usually capable of replication; give 2 examples of some cells that have trouble with replication
neurons
cardiac cells
the cellular membrane contains a hydrophobic tail and a hydrophilic head; this is called a…
phospholipid bilayer
these types of compounds can pass easily through the phospholipid bilayer
charged compounds
the cytoplasm is 70-85% of this material
H2O
describe what the nucleus of a cell does
barrier to keep DNA packed, secured away from pathogens
the contents inside of a nucleus include the following:
nuclear membrane/nuclear envelope
nucleolus
nucleoplasm
chromatin material (DNA)
outside of a nucleus:
selective pores
endoplasmic reticulum
cytosol/cytoplasm
the nucleus has very selective pores to let specific material pass into and out of the nuclear membrane; name two of these materials.
steroids
RNA
which structure is an extension of the nuclear wall and produces fats, proteins, and calcium?
endoplasmic reticulum
differentiate granular (rough) ER vs smooth ER
granular (rough) ER: responsible for protein synthesis; transports proteins to be sent to golgi apparatus to be modified
smooth ER: no ribosomes are present; responsible for lipid production
describe the process of protein formation
- DNA transcription
- RNA transcribed and spliced
- mRNA leaves nucleus to cytosol
- ribosomal translation of mRNA into amino acids
- amino acids packaged and brought to rough ER (95% of protein synth occurs here) & sent to be modified at the golgi apparatus for post-translational processing
- proteins are sent to their specific sites to carry out their specific functions such as cell structure and cell enzymes (Na/K ATPase)
what is the role of the golgi apparatus
packaging/condensing proteins and post-translational processing; proteins are modified and sent out of the cell via secretory vessicles
describe what mitochondria do
mitochondria are the “powerhouse” of the cell; ATP production factory
describe the difference between lysosomes and peroxisomes
lysosomes:
use acidic conditions to digest/recycle cell content/proteins
peroxisomes:
use oxidative stress to destroy/process toxins in the cells; can also destroy proteins – mostly degrade toxins
what is unique about the nucleus in terms of barrier and protection?
the nucleus has a double phospholipid bilayer with highly selective pores on the nuclear membrane allowing only a few material to pass through into the nucleoplasm
how do water soluble materials get from one side of the cell wall to the other?
proteins – strings of amino acid structures; allows passage of charged molecules (such as potassium) through the selectivity filter of the pores in the cell wall
where do most proteins get made and what percentage is this?
where do the remaining % of proteins get made?
95% proteins made in R.E.R
5% in cytosol (most do not get packaged here)
why is it important for the chemistry of the water inside of a cell to be balanced?
homeostasis; acid/base balance
proton concentration
electrolyte concentration
give a few examples of some organelles
ex) peroxisomes
ex) mitochondria
ex) lysosomes
ex) golgi apparatus
ex) endoplasmic reticulum
not nucleus; it’s a membrane to protect genetic material
what is an enzyme?
typically are proteins that catalyze (speed up) a chemical reaction
ends in suffix “-ase”
ex) ATPase
describe what a sugar molecules role would be on a cellular wall
- identification (self vs non-self) (immune system)
- cell anchoring (to each other); “sticky”/adherence
- repelling negatively charged proteins (kidneys do this to prevent filtering out too many proteins)
filaments/proteins provide what function for a cell?
cellular structure; “skeleton”
describe how atherosclerotic plaque clotting is a pathologic positive feedback loop
plaque inside of a blood vessel > activated enzymes (clotting factors) act on other enzymes within clot itself > these enzymes act on unactivated enzymes in adjacent blood to accumulate more blood clotting > leading to infarct
decribe fats (lipids)
primarily found in cell wall (phosphlipid bilayer)
non-charged; found in oily substrates
ex)
lipid soluble compounds (cholesterol)
arachidonic acid (used to generate signaling compounds)
name 2 cell components responsible for motility structure
flagella – moves cell itself
cilia – moves other cellular components (ex. mucus)
describe genetic material in detail
most of our genetic material is found in the nucleus (DNA)
humans also inherit mitochondrial DNA from their mother; at least 20 different sets
describe secretory granules in detail
secretory granules/vesicles, found in specialized cells, empty other cellular material into environment around it
relate membrane components to anesthetic drugs
vast majority of anesthesia drugs dictate function at cell wall/membrane
describe ICF compartment calculations
inTRAcellular fluid
2/3 of TBW (in L)
ex) 70 kg male
42L = TBW
(2/3) x 42L = 28L ICF
describe ECF compartment calculations
extracellular fluid – fluid found outside the cells/in between cells
divides into two categories: plasma and ISF
ECF = 1/3 of TBW
ex) 70 kg male
TBW = 42L
(1/3) x 42L = 14 L ECF
describe plasma compartment calculations
plasma - found in entire CV system that doesn’t include the volume of any blood cells in the CV system
1/4-1/5 of ECF = plasma
ex) 70kg male, 42L TBW
ECF = 14L
so (1/5) x 14L = 2.8
or (1/4) x 14L = 3.5
therefore: 2.8-3.5 L = plasma
describe ISF compartment calculations
ISF - interstitial fluid (fluid found outside the CV system, that is not plasma “left over fluid”)
3/4 or 4/5 of ECF
ex) 70kg male, 42L TBW
ECF = 14L
so (4/5) x 14L = 11.2 L
or (3/4) x 14L = 10.5 L
therefore, ISF = 10.5 - 11.2L
- ISF can fluid shift to make up for volume loss in hemorrhage *
explain why a “steady state” is much different than equilibrium; what does “steady state” mean?
if the sodium concentration was in a state of equilibrium in the body (inside and outside the cell), our cells could not function properly; instead, they are in a “steady state” meaning sodium’s concentrations are tightly regulated in their respective compartments in and out of a cell
ex) external body temp vs internal body temp – if we were at an equilibrium state with our body temp, our organs and cells also would not be able to function
equilibrium = “equal”
differentiate capillary membrane vs cell membrane in terms of cellular body fluid compartments
capillary membrane: + separates plasma from ISF (separates CV system from interstitium)
+ fairly permeable; more porous than cell wall
+ tight enough to prevent plasma proteins from leaking out of CV system
cellular membrane/cell wall:
+ separates ICF from ECF
+ does not let charged compounds across membrane unless there is a channel/pump protein to let pass
TBW = ?
0.6 x body mass in kg
ex) 0.6 x 70kg = 42L TBW
2/3 of TBW = ?
ICF (intracellular fluid)
1/3 of TBW = ?
ECF (extracellular fluid)