Card Set Information
Fluid, neurons, cardiac cells
What is the distribution of fluid in the body?
What is a good index of ECF osmolarity?
: ECF osmolarity = 2*Na+(glucose/18)+(Urea/2.8).
What is the difference between mOsm/L and mM/L?
: concentration of particles
: concentration of molecules.
What is isotonic concentration?
300 mOsm/L (150mM/L Na).
What compartment of fluid enlarges/decreases with net changes in body fluid?
What can cause a loss of isotonic fluid?
What can cause a loss of hypotonic fluid (create hypertonic environment)?
what are the starling forces, what do they control?
Control "bulk flow"
: net movement in/out of capillaries.
What is the formula for fluid exchange?
Qf = k[(Ch+Io)-(Ih+Co)].
How do you calculate blood volume?
Blood volume= plasma volume/(1-Hct).
What are the two conditions for the development and maintenance of an edematous state?
Increase in starling forces with bulk flow into interstitium
Retention of Na and Water by kidneys.
What are the two types of edema?
: most common, responds to diuretics
: lymphedema, lymphatic obstruction (also myxedema: hyperthyroid states).
What is the most common form of pulmonary edema, first sign, confirmation?
Pulmonary Wedge pressure.
What are the most common causes of non-cardiogenic (permeability induced) pulmonary edema?
What forms in the absence of a functional epithelium?
Hyaline membranes, sheets of pink proteinacious material
(ARDS was also called hyaline membrane disease).
Definition of membrane conductance?
Number of channels open in a membrane.
What are the three main groups of channels?
What makes up the net force on an ion across a membrane?
What is the nernst equation?
What are the equilibrium potentials for Na, Cl, K?
Is a cell's resting membrane potential sensitive to K, why?
There are ungated potassium channels
Inreased extracellular conc
: decreased efflux, depolarization
Decreased extracellular conc
: increased efflux, hyperpolarization.
Is a cell's resting membrane potential sensitive to Na, why?
There are no ungated Na channels -- minimal to no Na conductance at resting conditions.
What causes the absolute (functional) refractory period what does it determine?
Voltage inactivation of Na Channels
Length determines frequency of APs.
What is the relative refractory period?
Greater stimulus than normal required to induce AP.
What are the three main factors that determine AP velocity?
Size of AP
Diameter of axon
What region of a neuron has the lowest threshold?
What are the channels found in cardiac cells?
Voltage Gated Na Channels (Fast)
Voltage Gated Ca Channels (Slow, L-type)
Voltage Gated Potassium Channels (2 types).
What are the two types of voltage gated potassium channels?
Inwardly Rectifying, iK1
Delayed Rectifying, iK.
What are the properties of the Inwardly Rectifying channels?
Open at rest
Close with depolarization
Remain closed during plateau
Open during repolarization.
Properties of Delayed Rectifying channels?
Opens with depolarization, closes once cell is repolarized
Slow to open (delayed).
What is the difference between fast and slow (cardiac) fibers?
Slow fibers lack fast channels
: Ventricular, Atrial, Purkinje fibers
: AV, SA nodal fibers.
What are the four phases of the ventricular AP, physio?
: Fast channels open (Na) -> Na influx -> rapid depolarization
: Slight repolarization - closure of Na channels and K current
: Plateau - L-type (Ca) channels open -> Ca influx -> iK1 channels close, preventing K efflux
: Repolarization - L-type Ca channels close, potassium channels open
: gK high - ungated potassium channels and iK1 channels open (delayed close slowly).
What three factors produce the pacemaker property of specialized cardiac cells?
: Funny current
Decreasing K conductance as iK channels close
Increasing Ca conductance near the end of prepotential (calcium T-channels).
What is If (funny current)?
Voltage gated Na channels that open when cell repolarizes, close when depolarizes.
What phases do SA cells have?
: slow channel L-type Ca influx
: rapid potassium efflux
: unstable, gradual depolarization.
What effect do sympathetics have on the pacemaker?
Slope of phase 4 increases
: increased funny current
Increased calcium current
increased potassium current.
What effect do parasympathetics have on the pacemaker?
Hyperpolarize by increasing potassium conductance
Decreased slope of phase 4
: decreased funny current.
What are the intrinsic rates of SA, AV, Purkinje cells?
The PR interval signifies, how long?
Atrial depolarization + conduction delay at AV node.
QRS duration, indication, prolonged?
: abnormal conduction through ventricles.
In what direction does ventricular depolarization occur, repolarization?
: Endocardium to epicardium
: Epicardium to endocardium.
What is first degree (partial block)?
Conduction slowed through AV node
What is second degree block?
Mobitz 1 (Wenckebach)
: progressively longer PR until dropped QRS
: dropped QRS after set of normal beats.
Third degree block?
No impulses from atria to ventricles
atria and ventricles beat independently
No correlation between P and QRS.
What is Wolff-Parkinson-White (WPW) syndrome?
Accessory pathway between atria and ventricles
: shortened PR, slurred R, widened QRS
may initiate a reentrant tachycardia.
Causes of left axis deviation?
Left heart enlargement
Conduction defects on left side
Right heart MI.
Causes of right axis deviation?
Right heart enlargement
Conduction defects on right side
Left heart MI.