Physiology Flashcards
Hypokalemia
K+
Hyperkalemia - more of a concern- muscle weakness/paralysis. cardiac arrythmia - usually arises from kidney failure and inabilty to secrete K+ TOO MUCH Potassium
is when blood’s potassium levels are too low. Potassium is an important electrolyte for nerve and muscle cell functioning, especially for muscle cells in the heart. Your kidneys control your body’s potassium levels, allowing for excess potassium to leave the body through urine or sweat.
Plasma normal range?
It makes up about 55% of the body’s total blood volume.
3.5 - 5 to maintain membrane potential
??
electrogenic? producing a change in the electrical potential of a cell.
moving K+ out of cell, creates a charge imbalance “electrogenic”
receptor potential?
mechanosensors, olfactory receptors, photoreceptors
Plasma osmolalaity?
295-300 miile osmoles/KG
what human cells do not reproduce?
neurons, heart cells, skeletal muscle cells and red blood cells.
can smooth muscles reproduce?
Yes - Smooth cells have the greatest capacity to regenerate of all the muscle cell types. The smooth muscle cells themselves retain the ability to divide, and can increase in number this way. As well as this, new cells can be produced by the division of cells called pericytes that lie along some small blood vessels.
autocoids?
autocoids” are biological factors (molecules) which act like local hormones, have a brief duration, and act near their site of synthesis.
Paracrine signaling
is a form of cell signaling or cell-to-cell communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells.
operons?
An operon is made up of several structural genes arranged under a common promoter and regulated by a common operator. It is defined as a set of adjacent structural genes, plus the adjacent regulatory signals that affect transcription of the structural genes.
Signal transduction
(also known as cell signaling) is the transmission of molecular signals from a cell’s exterior to its interior. Signals received by cells must be transmitted effectively into the cell to ensure an appropriate response. This step is initiated by cell-surface receptors.
what’s in a cell? H2O
PMP
water - 2/3 of body’s water, and high in potassium, magnesium, phosphate
ecm? rich in?
1/3 water, large amounts of sodium, chloride, bicarbonate, oxygen, glucose, fatty acids, amino acids, carbon dioxide
body mass - % water?
60%
feedback system of body - 3 parts
receptor - reports to Central Control,
control center (brain or endocrine) evaluates and sends out orders,
effector - receives orders and complies
negative feedback in body
if something is excessive or deficient - attempts to return things to normal
positive feedback - leads to?
INstability - initiating change - ie blood clotting is good to stop a rupture, but it needs to stop or it can do bad things
cell membranes - allow lipid soluable substances to enter like?
CO2, O2, fatty acids, steriod hormones
keeps out water soluable - ions, glucose, amino acids
cell membrane made of mainly?
lipids and proteins - proteins fulfull many roles - trasnport, enzymes, hormones, antigens, ion and water channels, etc
amphipathic
glycerol backbone head, two fatty acid tails -
both hydro phillic and phobic
how does cholesterol affect cell membrane?
As temperature increases, so does phospholipid bilayer fluidity.
increases flex and stability, controls fluidity depending upon temperature -
Cholesterol reduces permeability of lipid membranes. … Cholesterol plays has a role in membrane fluidity but it’s most important function is in reducing the permeability of the cell membrane. Cholesterol helps to restrict the passage of molecules by increasing the packing of phospholipids.
protein components of cell membrane?
integral (channels, pores, transport proteins, receptoss G proteins)
peripheral - loosely attached to intra or extra cellular side by electrostatic interaction - not covalently bound
transport into/out of cell - 3 types
- bulk
endocytosis - pino, phago, receptor mediated
exocytosis
- passive - simple or facilitates (w carrier) NO ATP reqa
- Active - Uphill transport - needs energy - primary and secondary
pinocytosis - bring things into cell
vesicles formed -
via clathrin coating, latticework of actin and myosin - ATP and Ca++ required (to pinch)
both pinocytic and phagocytic vesilces may contain lysossomes and thus are
digestive organs of cells
phagocytosis
only some cells can do this - initiated when particle (bacterium) attached to antibody which is attached to outside of cell via opsonization - bring into cell, merge with lysosome - digest -
molecular gradients
outside cell - NA+, CL-
inside K+, PO4 (phosphate), proteins
diffusion - when stop?
how many kinds?
when dynamic equil reached - particular are uniform thruout
Simple and Facilitated
simple diffusion -
passes through pores or right thru membrane if lipid soluble -
down concentration gradient -
factors: concentration, velocity, kinetic movement, number and size of openings
typical lipid soluble molecules?
O2, nitrogen, CO2, alcohol - dissolve directly in lipid bilayer - large amounts of of O2 transported this way - as if no membrane
water soluble molecules - need pores
Net diffusion - continues until become equal -
depends on -
size of concentration gradient,
partition coefficient?
diffusion coefficient
thickness of membrane
surface area available -
other factors - electrical gradient - if molecule is charged (if heading into an area with opposite charge - will go faster, more easily)
temperature
molecule mass (high mass - moves more slowly)
Membrane permeability
partition coefficient
Larger the number - the easier it gets thru
the greater the relative solubility in OIL - the higher the coefficient
non-polar solutes have higher values
Diffusion coefficient
Larger the number - the easier it gets thru
size of molecule vs. viscosity of medium -
small solute in nonviscous solution has a larger diffusion coefficient
thicker the membrane ?
greater the distance to travel - lower the rate of diffusion
greater the surface area?
easier, faster the diffusion
factors that increase permeability?
oil/water coefficient
radius (SIZE) of solute
Membrane thickness, viscosity of membrane
Fick’s Law of Diffusion
J=A/T x S x change ? P
Net diffusion
J = PA (Ca - Cb)
J - net rate
P - permeability
A - surface area
Ca concentration of solute 1
Cb - concentration of solute 2
osmolarity
number of particles into which a solute disassociates
does glucose disassociate?
No, so it’s osmolarity is 1 ?? IT is equal to its molarity
if a solute disassociates into more than one particle - then osmolarity =s molarity x number of particles - ie NaCL is 2 mOsml/lt
carrier mediated transport (all but simple diffusion)- 3 qualities
saturation
stereospecificity ?? L vs D
competition
is facilitated diffusion faster or slower than simple diffusions
at low solute concentrations - faster - but then levels off as binding sites become saturated -hence curves - vs simple just keeps going up
example of facilitated diffusion?
Glut 1 - RBC, BBB 2 - liver, pancreas, kidney 3 neurons 4 - fat, muscle - insulin 5 - testis and ?
Glut 4 transporter of glucose into skeletal muscles - glucose can be transferred as long as two things:
- glucose level higher in blood than ICF
- binding sites not saturated
does simple diffusion exhibit stereospecifity?
no - it allows both D and L to get thru - all others do NOT - only D is allowed to bind
three examples of primary active transport?
Na+ - K+ ATPase (all cells)
Ca2++ ATPase in sarcoplasmic and endoplasmic reticulum
H+K+ ATPase in gastric parietal cells
Na+-K+ pump
positivity continually pumped out - getting rid of positive NA+
“electrogenic”
cycles between E1 and E2 (E2 faces ECM) E1 requires ATP, not sure about E2
three sodium out, 2 potassium in - this is always happening and keeping the cells at these artificial levels (maintains concentration gradient) - ?? where does cell keep getting its sodium to kick out?
digitalis and ouabain- cardiac glycosides
inhibits NA+K+ pump - binds at E2 sites - stopping cycling
Cardiac glycosides are a class of organic compounds that increase the output force of the heart and increase its rate of contractions by acting on the cellular sodium-potassium ATPase pump.
Ca2++ ATPase pump
SERCA
most cells pump Ca out - 1 CA out for ATP used
sarcoplasmic and endoplasmic retic - pump 2 CA out for each ATP hydrolyzed
has an E1 and E2 site like NA/K pump -
H+/K+ parietal cells - and alpha-intercalated cells of renal collecting ducts -
Omeprazole - inhibits - reduces secretion of H+ for peptic ulcers
in stomach - pumps H+ from ICF of parietal cells into lumen - where acidifies
Secondary transport
transport of two or more solutes coupled - usually Na+ moves downhill and other solutes moves uphill - downhill provides the energy - ATP not used directly (Na+ to move downhill needs ATP??)
two types of secondary transport -
cotransport (symport)
countertransport (antiport or exchange)
cotransport example
glucose intestinal absorption - must bind to both glucose and Na+ simultaneously in the lumen of small intestine
countertransport example
GR - three positive charges move into cell in exchange for two positive out -
three NA+ enter, 2 Ca leave
electrogenic (producing a change in the electrical potential of a cell.)
Ca++ pumping out of cell in sarcoplasmic reticulum - must bind to both Ca and NA simultaneously to create transport
diabetes I example in book
GR - glucose NOT excreted thru urine - but is in diabetes - transporter not working, not reabosrbing glucose in Prox tubule -
insulin helps with reabsorption of glucose - but pt. lacking -
so more and more glucose is produced - and when levels high - are filtered in kidney -
and levels too high for capacity for Na+glucose transporter to transport all - so
excreted in urine
Note that if the solute is CHARGED - and coming into the cell - like an electrolyte or ion - two things may change
- net rate of diffusion will be changed depending upon the charges and how they add up
- diffusion potential
Osmosis
flow of water across semipermeable membrane beca of difference in solute concentration - occurs because of pressure difference
difference between osmosis and diffusion?
Diffusion - there is more water in one place than another
In diffusion, particles move from an area of higher concentration to one of lower concentration until equilibrium is reached. In osmosis, a semipermeable membrane is present, so only the solvent molecules are free to move to equalize concentration.
Osmosis and aquaporins
Vasopressin - Antidiuretic hormone
lots of AQP2 in kidney collecting ducts - vasopressin (hormone) increases water transport to inserting more AQP2 in apical plasma membrane
Nephrogenic diabetes - rare inherited, but can develop in people taking
LITHIUM
both conditions asso w/ lack of AQP2 in collecting ducts
kidney loses ability to reabsorb water properly - excessive loss of water - very dilute urine (polyuria)
amounts of solute expressed :
moles, equivalents, osmoles
CONcentrations of solute, expressed in
moles/Liter (millimoles mmol/L)
Equivalent/L, MilliEquivalent mEQ/L
Osmoles per liter (Osm/L), milliosmoles - mOsm/L
1 mole - vs an equivalent vs osmole
1 mole - 6x10(23)
Equivalent - amount of charged solute - numbers of charged solute multiplied by its valence
1 osmole - number of particles into which a solute dissociates
osmolarity vs osmolality
similar number - osmoLALITY is KG _note both lality and KG (v liter) come first in alphabet
Osmolality is what in ICF vs ECF?
SAME! 285 - 290 mOsm/Kg
typical plasma osmolarity is 295
Osmolarity?
A solution with low osmolarity has a greater number of water molecules relative to the number of solute particles; a solution with high osmolarity has fewer water molecules with respect to solute particles
Molarity (M)
is the amount of a substance in a certain volume of solution. Molarity is defined as the moles of a solute per liters of a solution. Molarity is also known as the molar concentration of a solution.
if solution doesn’t dissociate?
osmolarity = molarity
300 mM glucose - 300 mOsm
What are compounds that completely dissociate in water?
Substances that dissolve in water to yield ions are called electrolytes. Electrolytes may be covalent compounds that chemically react with water to produce ions (for example, acids and bases), or they may be ionic compounds that dissociate to yield their constituent cations and anions, when dissolved.
Osmolarity = g x C
osmolarity - concentration of particles
g - number of particles / mole
C - concentration
Isomotic solutions
solutions that have same calculated osmolarity
hyperosmotic - vs hypo
solution with higher osmolarity vs lower
Nernst potential - no net flow of ion from one side of membrane to another
Equilibrium refers to the fact that the net ion flux AT A PARTICULAR VOTAGE is zero.
the magnitude of the Nernst potential is determined by the ratio of the concentrations of that specific ion on the two sides of the membrane.
the reversal potential (also known as the Nernst potential) of an ion is the membrane potential at which there is no net (overall) flow of that particular ion from one side of the membrane to the other. … Equilibrium refers to the fact that the net ion flux at a particular voltage is zero.
nernst potential for sodium, potassium, calcium
intracellular vs extra concentrations
sodium +60
potassium -90
calcium +137
sodium 15
potassium 150
calcium 70
resting potentials of sodium, potassium, calcium
sodium -90
potassium
how do you calculate Nernst potential? aka reversal potential
The Nernst equation is often used to calculate the cell potential of an electrochemical cell at any given temperature, pressure, and reactant concentration.
This is done by simply dividing the current at each voltage by the driving force, which is the voltage minus the reversal potential (V − Vrev). Furthermore, reversal potential calculations can also signify how well the cell is voltage clamped
what does nernst equation compare?
find the what voltage is that can offset concentration gradient
where ions will flow when have both a chemical concentration gradient and an electrical concentration gradient - and predicts where the ions will flow
When can a second action potential be generated?
when inactivation gates of sodium channels begin to open up - in relative refractory period.
What is equilibrium potential?
net flow of zero ions because charge is balanced
Driving Force
Ions, atoms or molecules that have a charge, can be affected by an electrical driving force. This force across a cell membrane is expressed as the membrane potential. This potential results from an unequal distribution of charges across the membrane.
How is electrochemical driving force determined?
When an ion is not at its equilibrium, an electrochemical driving force (VDF) acts on the ion, causing the net movement of the ion across the membrane down its electrochemical gradient. The driving force is quantified by the difference between the membrane potential and the ion equilibrium potential (VDF = Vm − Veq.).
What is the equilibrium potential for K+?
K+ will be in electrochemical equilibrium when the cell is 90 mV lower than the extracellular environment.
K+ is a positively charged ion that has an intracellular concentration of 120 mM, an extracellular concentration of 4 mM, and an equilibrium potential of -90 mV; this means that K+ will be in electrochemical equilibrium when the cell is 90 mV lower than the extracellular environment.
The resting potential of a myelinated nerve fiber is primarily dependent on the concentration gradient of which of the following ions?
K+
what potassium disorder reduces the Na/K+ pump?
HYPOkalemia
digitalis also inhibits pump
The activity of the Na+-K+ pump is reduced in hypokalemia, not hyperkalemia.
Hypokalemia is when blood’s potassium levels are too low. Potassium is an important electrolyte for nerve and muscle cell functioning, especially for muscle cells in the heart. Your kidneys control your body’s potassium levels, allowing for excess potassium to leave the body through urine or sweat.
Resting potential - determined by concentrations between two sides
NOT by permeability?
In most neurons the resting potential has a value of approximately −70 mV. The resting potential is mostly determined by the concentrations of the ions in the fluids on both sides of the cell membrane and the ion transport proteins that are in the cell membrane
What is isotonic and hypertonic?
Hypertonic SUCKS
Water flows from hypo to hyper!
If a cell is placed in a hypertonic solution, water will leave the cell, and the cell will shrink. In an isotonic environment, the relative concentrations of solute and water are equal on both sides of the membrane. … When a cell is placed in a hypotonic environment, water will enter the cell, and the cell will swell.
is urea hypo or hypertonic?
Effective vs ineffective osmoles -
can they draw fluid across a membrane?
Effective - YES
Mannitol can draw CSF out of brain -
glucose, naCL also Effective
Ineffective - doesn’t cause water movement -
Hypo - RBCs will explode
An effective osmole is one that is UNABLE to cross from the Extracellular fluid (ECF) to the Intracellular fluid
- It will generate an osmotic force that draws fluid across a membrane.
- Effective osmoles include: NaCl, Glucose, Mannitol
- An ineffective osmole will contribute to total plasma osmolality but because it
can freely move from the ECF to ICF, it generates no osmotic pressure.
• A classic example of an ineffective osmoles are Urea, Ethanol
Reflection coefficient
varies from 1 to zero
zero - Zero osmatic pressure - membrane is freely permeable
(σ) - an index of the effectiveness of a solute in generating an osmotic driving force. of a solution to pull water across a biologic membrane. Example: Ethanol can accumulate in body fluids at sufficiently high concentrations to increase osmolality by 1/3, but it does not cause water movement.
two ineffective osmoles -
Zero reflection coefficient
do not pull water -
urea and ethanol
Transport of D- and L-glucose proceeds at the same rate down an electrochemical gradient by which of the following processes?
Only two types of transport occur “downhill”—simple and facilitated diffusion. If there is no stereospecificity for the D- or L-isomer, one can conclude that the transport is not carrier-mediated and, therefore, must be simple diffusion.
sodium potassium pump - 3 what are pumped out ?
3 sodium - so there!
How does the sodium calcium exchanger work?
three sodium ions are exchanged for each calcium,
The exact mechanism by which this exchanger works is unclear. It is known that calcium and sodium can move in either direction across the sarcolemma. Furthermore, three sodium ions are exchanged for each calcium, therefore a small (few millivolt) electrogenic potential is generated by this exchanger.
How is glucose taken up in the small intestine?
COTRANSPORT
The classical pathway of glucose absorption is across the intestinal brush-border membrane (BBM), which was predominantly mediated by SGLT1, a membrane protein that couples two molecules of Na+ together with one molecule of glucose.
How do you calculate partition coefficient?
A partition coefficient is the ratio of the concentration of a substance in one medium or phase (C1) to the concentration in a second phase (C2) when the two concentrations are at equilibrium; that is, partition coefficient = (C1/C2)equil.
water flows in which direction?
A hypotonic solution has a lower concentration of solutes than another solution.
from hypotonic to hypertonic
A 23-year-old man is brought to the Emergency Department after collapsing during basketball practice. On admission he is lethargic and appears confused. His coach reports that it was hot in the gym and he was drinking a lot of water during practice. An increase in which of the following is the most likely cause of his symptoms?
Drinking water after losing a significant volume
of water as sweat decreases the osmolality of the extracellular fluid
because the salt lost from the extracellular fluid in sweat is not replaced by
the ingested water. When the extracellular osmolality is decreased, water
flows from the extracellular to the intracellular body compartment, causing
intracellular volume to increase. The patient’s symptoms are caused by
swelling of the brain.
solute used to decrease intercranial pressure?
manitol
Mannitol, a hypertonic crystalloid solution, is commonly used to decrease brain water content and reduce intracranial pressure (ICP). Hypertonic saline solutions also decrease brain water and ICP while temporarily increasing systolic blood pressure and cardiac output.
If the extracellular K+ concentration is increased from 4 meq/L to 10 meq/L,
??
The membrane potential will become more negative
Inactivation of the sodium-potassium pump will cause
a. An increase in the intracellular volume
will allow Na ions to accumulate in the cell, as K ion will fall. So this creates a depolarization in the cell membrane.
Membrane excitability will be increased by the greatest amount by
a. Increasing extracellular Na+
The resting potential of a nerve membrane is primarily dependent on the concentration gradient of
a. Potassium
Which of the following statements best characterizes a molecule whose reflection coefficient to a membrane is zero?
It is as diffusible through the membrane as water - but will not pull water
Which of the following words or phrases is most closely associated with an end-plate potential at the neuromuscular junction?
b. Depolarization
In a nerve, the magnitude of the action potential overshoot is normally
a function of the
c. Extracellular sodium concentration
The amount of force produced by a skeletal muscle can be increased by
d. Decreasing the interval between contractions
The velocity of nerve conduction is increased with a decrease in the
Capacitance of the nerve fiber membrane
The rate of diffusion of a particle across a membrane will increase if
The lipid solubility of the particle increases
Periodic hyperkalemic paralysis is characterized by high potassium concentration and muscle weakness. Which of the following is likely to cause muscle weakness as a result of increased extracellular potassium concentration?
Inactivation of sodium channels in muscle cells
The flow of calcium into the cell is an important component of the upstroke phase of action potentials in
skeletal muscles
Which of the following will be less during the overshoot of an action potential than during the resting state?
Transference for potassium
Preventing the inactivation of sodium channels will decrease
c. The downstroke velocity of nerve cell action potentials
