Homeostasis/Cell membrane/Membrane Transport Flashcards
physiology
-study of the mechanical, physical and biochemical functions of living organisms
-the study of life
-2 MAIN APPROACHES:
-emphasis on purpose –> the WHY
-emphasis on mechanism –> the HOW
3 main functions of anatomical/physiological systems
1) facilitate the survival of the individual in its environment
2) facilitate the survival of the species
3) coordinate the functioning of the individuals anatomy/physiology systems
homeostasis
ability to maintain a stable internal environment in a changing outside world
ex: pH, volume and pressure, temperature
does homeostasis always strive for the same internal conditions (set points) in a given organism?
no. there are situations were the set points are shifting ie:
-puberty
-topor/hibernation
-sick –> fever is the new set point
pyrogens
what causes the rise in body temperature (fever)
exogenous pyrogens
from foreign substances (bacteria or viruses)
endogenous pyrogens
produced by immune cells in response to infection
to maintain homeostasis, control systems must be able to:
-DETECT deviations from normal
-INTEGRATE that info with other relevant info
-make the appropriate adjustments to RESTORE factor to desired value
negative feedback
-PRIMARY type of homeostatic control
-maintains stability by defending set points
-oppose the initial change
positive feedback
-doesn’t occur as often
-drives physiological values away from a set point —> initial change is AMPLIFIED
negative feedback examples
temperature regulation
-systems are limited in responses (only so much shivering and so much sweating one can do)
-overall gradual changes
hormone released by the hypothalamic-pituitary axis
-perceived info —> triggers response
sensor
monitors magnitude of a controlled variable and relays to the integrating center
integrator (control center)
compares sensor’s input with a set point
effector
receives information from the integrating center and responds accordingly
normal cortisol releasing pathway
1) hypothalamus - releases CRH (corticotropin releasing hormone)
2) anterior pituitary - releases ACTH
3) adrenal cortex - releases cortisol
primary hypoadrenocorticism
adrenal cortex does not release cortisol
result: no cortisol, elevated CRH and elevated ACTH
secondary adrenal deficiency
anterior pituitary does not release ACTH so adrenal cortex does not release cortisol
results: low cortisol, elevated CRH and low ACTH
ovulation positive feedback
1) hypothalamus - releases GnRH
2) anterior pituitary - releases FSH and LH
3) ovary - releases estrogen
negative feedback most of the cycle
positive feedback right before ovulation
parturition positive feedback
uterine contractions –> fetus pushes against cervix –> neuroendocrine reflex stimulates oxytocin release
stops once fetus leaves birth canal
homeostasis importance
1) redundancy: more vital, more likely to regulate
2) hierarchy and competition
3) adaptability
4) pathophysiology
composition of ECF and ICF fluids
HIGH ECF: Na, Cl, Ca
HIGH ICF: K
important: osmolarity is equal on both sides
what properties of particles influence whether they can permeate the cell membrane without assitance
-relative solubility of particle in lipid (ie: charge)
-size of the particle
passive transport
1) diffusion: movement of solutes across the lipid bilayer
2) osmosis: diffusion of water across the membrane
3) channel mediated: diffusion through a protein channel
4) facilitated diffusion: carrier mediated diffusion
active transport
primary and secondary —> moves solutes AGAINST a concentration gradient
ATP —> ADP + Pi
above shift causes a conformational change in the transport system
diffusion
depends on the random movement of molecules
-high to low concentration
-across a permeable membrane
-crucial to survival of every cell
glut 1
glucose uptake is required for cellular respiration
1) glucose binds to unbound protein
2) conformational change occurs
4) released to area of low concentration
channel mediated transport - gated ion channel
-open in response to stimulus
-allow many ions in at once
-specific to that ion (K+, Na+, etc)
primary active transport
-maintains gradients of Na and K
-utilizes ATP
-critical for survival
IMP: 3 Na OUT AND 2 K IN
secondary active transport - SGLT1
-atp not directly used
-energy is provided by Na+ gradient
-glucose is moved against a concentration gradient
aquaporins
-water is small enough to permeate the plasma membrane
-can allow flow of one billion water molecules per second
-the driving force for movement is the concentration gradient
osmolarity/osmolality
the total concentration of particles per amount of solution
what is tonicity?
the effect a solution has on cell volume which determines whether cell size remains the same, swells, or shrinks when a solution surrounds the cell
what is effective osmolarity?
the osmolarity of non-permeable particles in a solution
controls the actual movement of water
what are good osmometers?
erythrocytes (RBCs)
what can be used to check hydration status?
-skin turgor
-mucous membranes
-CRT
-eyes
-hematocrit: more quantifiable
what are hypotonic conditions?
when water flows INTO cells —> cells will swell
what are hypertonic conditions?
water diffuses OUT of cells —> cells will shrink
what is hematocrit?
the fraction of plasma occupied by RBCs after centrifugation
what proteins is plasma made of?
albumin and cholins
what are some basic principles of body water dynamics?
1) water shifts between compartments to maintain equality
2) electrolytes (ie: Na, K, etc) DO NOT CROSS cell membranes and are confined to the ECF
3) any loss or gain of water and/or electrolytes must occur in the ECF —> what we have access to
4) changes in TBW, total plasma protein and hematocrit may occur
what are some volume contraction examples?
diarrhea, water deprivation, adrenal insufficiency
what are some volume expansion examples?
infusion of isotonic NaCl, high water intake, SIADH
what happens to the ICF and ECF when you infuse saline (isotonic solution)?
-will have no effect on osmolarity
-may have changes to BP as there will be an increase in ECF volume
increase in TBW, decrease in protein plasma and hematocrit
what happens when there is a loss of isotonic solution (ie: diarrhea)?
-there will be a decrease in ECF volume
decrease in TBW, increase in protein plasma and hematocrit
what happens when there is a gain of hypotonic solution (ie: drinking large amounts of water)?
1) increase in ECF volume
2) decrease in ECF osmolarity
3) solution crosses semi-permeable barrier from ECF to ICF due to difference in osmolarity
4) increase in ICF volume
5) decrease in ICF osmolarity
increase in TBW, decrease in protein plasma and hematocrit
what happens when there is a loss of hypotonic solution (ie: water deprivation, sweating/panting)?
1) decrease in ECF volume
2) increase in ECF osmolarity
3) ICF solution crosses into ECF via semi permeable barrier
4) decrease in ICF volume
5) increase in ICF osmolarity
decrease in TBW, increase in protein plasma and hematocrit
what happens when there is a gain of sodium (ie: high NaCl intake) in the ECF?
1) increase in ECF osmolarity
2) solution crosses from ICF into ECF
3) increase in ECF volume
4) decrease in ICF volume
5) decrease in ICF osmolarity
TBW stays the same
decrease in protein plasma
MAJOR decrease in hematocrit
