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188 Cards in this Set

  • Front
  • Back
What are the three main muscle types in the heart?
1. Atrial muscle
2. Ventricular muscle
3. Specialized muscle
All muscle cells in the heart are what?
EXCITABLE!!!!1!11!!!
What does it mean for muscle cells to be excitable?
It means they can produce a brief, pulse-like change in their membrane potential and this AP can be conducted all over the heart simultaneously.
The SA nodal cells have a higher or lower resting potential? Why?
SA nodal cells have a HIGHER resting potential because of higher K+ conductance.
TRUE OR FALSE: SA nodal cells spontaneously generate action potentials.
TRUE!
Current flow is always taken as which direction?
Positive ion flow, outward flow being positive.
What kind of nerves alter the heart rate?
Autonomic nerves alter the heart rate by affecting the pacemaker potential.
What kind of stimulation accelerates the heart by increasing the slope of the pacemaker potential?
Sympathetic stimulation!
What are T-Type Ca2+ channels?
They are channels that have tiny conductances that transiently open
What are L-Type Ca2+ channels?
They are channels that have large conductances with long-lasting openings.
Which type of Ca2+ channels contribute the last third of the pacemaker potential?
T-Type!
What kind of stimulation slows the heart rate by decreasing the slope of the pacemaker potential?
Parasympathetic stimulation!
At phase 0 in the states of the Na+ channel during an action potential, depolarizations open what?
Depolarizations opens the activation gate, sodium conductance increases, and forms the upstroke.
At Phase 1 in the states of the Na+ channel during an action potential, what occurs?
Closure of the inactivation gate decreases sodium conductance and contributes to the notch repolarization
At Phase 2 in the states of the Na+ channel during an action potential, what occurs?
Time-dependent closure of the activation gate forms the closed but inactivatable state.
At Phase 3 in the states of the Na+ channel during an action potential, what occurs?
Activation gates open upon repolarization and resets the channel to its rest state.
At Phase 4 in the states of the Na+ channel during an action potential, what occurs?
Rest: activation gate closed, inactivation gate open (channel is closed but activatable)
What effect does epinephrine have on the cardiomyocite action potential?
It elevates the action potential plateau.
How does the action potential spread in the regions of ventricular cardiomyocytes?
APs spread passively through the gap junctions between cells.
What currents are responsible for the upstroke in the ventricular muscle cells?
Sodium current INTO the cell
During what part of the action potential do the Na channel inactivation gates close and activation gates open?
Activation gates are open and inactivation gates are closed during phase 1 (rapid repolarization).
What is the ECG?
A record of the electrical activity of the heart that is projected onto the surface of the body where it is measured by surface electrodes.
The heart muscle fibers act as what?
Electric dipoles!
The dipole moment is given as what?
p=q+d
What constitutes LEAD I?
Left arm - right arm
What constitutes LEAD II?
Left leg - right arm
What constitutes LEAD III?
Left leg - left arm
I + III = what?
II
Is convention - to + or + to -?
- to +!
If it is a closed circuit, vector addition should equal what?
0
The values of Leads I and III can be used to calculate what?
The electric dipole moment of the heart!
Sympathetic stimulation causes what to happen to the membrane channels?
Phosphorylation which results in depolarizations.
What is the Effective Refractory Period?
It corresponds to when an action potential will not have sufficient current to depolarize adjacent cells.
Cardiologists use ECGs for what 4 things?
1.Excitation of the pacemakers
2. Spread of activation from one region to another
3. Pathways by which wave of activation spreads
4. Basis of the action potential
What is Kirchhoff’s lead law of voltage?
Lead I + Lead III = Lead II
What causes the P-wave?
Atrial depolarization
What causes the QRS complex?
Ventricular depolarization
What causes the T wave?
Repolarization of the subepicardium before the subendocardium.
What is the epicardium?
The epicardium is the layer of cells on the outer surface of the heart
What is the endocardium?
The endocardium is the layer of cells lining the inner surface of the heart facing the blood.
What is subepicardium?
Subepicardium is a layer of cells adjacent to the epicardium layer.
What is Subendocardium?
Subendocardium is a layer of cells adjacent to the endocardium layer.
The largest depolarization in the heart defines what?
The MEAN electrical axis
What are the 4 assumptions with Einthoven's triangle?
1. hearts electrical activity can be represented as single dipole
2. heart is small compared to field (so heart is considered the center)
3. Thorax is a homogeneous conductor
4. Thorax is a sphere
What are 4 major differences between cardiac muscle and skeletal muscle?
1. Cardiac muscle fiber is smaller
2. Cardiac muscle have less nuclei
3. Cardiac muscle fibers often branch
4. Cardiac muscle has intercalated disks
Intercalated disks contain what three things?
1. Gap junctions
2. adherens junction
3. Desmosomes
TRUE OR FALSE: The strength of cardiac muscle contraction is regulated by recruitment and summation.
FALSE. Strength is NOT regulated.
In cardiac muscle, why are all cardiomyocytes activated for each heart beat?
Because the cells are electrically coupled: there is 100% recruitment at all times.
Why is it not possible to stimulate the cardiomyocytes for a second time during the heart beat?
Because the APs are so long.
What controls the actomyosin cross-bridge cycling?
Cytoplasmic Ca2+ concentrations
At low calcium concentrations, what is happening to the force or ATPase activity?
There is NO force or ATPase activity.
At high calcium concentrations, what is happening to the force and ATPase activity?
Force and ATPase activity is at its maximum
At steady state, force is proportional to what?
Proportional to the size of the Ca transient
When frequency increases, the next beat is stronger or weaker?
Weaker!
Why is the next beat after frequency increase weaker?
It is weaker because the RyR2 (ryanodine receptor 2) release channels are recovering from inactivation
In regards to the positive staircase, at the new steady-state, is force still proportional to the Ca transient?
Yes!
What are Ryanodine Receptors?
They form Ca channels across the SR membrane
Ca entry through what triggers SR Ca release?
Ca entry through the DHPR (dihydropyridine receptors) triggers SR Ca release.
The size of the sarcolemma Ca trigger and the amount of Ca stored in the SR determines what?
The size of the Ca transient!
Reuptake of Ca by the SR and sarcolemma extrusion of Ca cause what?
Relaxation!
Mitochondria can take up Ca through what mechanism?
Electrophoretic uniport
What regulates Cardiac Contractility?
1. size of the Ca transient
2. Sensitivity of the myofilaments to a given Ca transient
Sympathetic stimulation increases force by doing what?
Increasing the Ca transient!
What does the stretch of cardiac muscle do at short sarcomere lengths?
Stretch increases force by removing interfering overlap of the myofilaments and by increasing the Ca sensitivity.
The degree of filling of the heart strongly influences what?
Its force in contraction!
What happens if the heart overfills?
The active force would decrease and there would be no way to empty the heart!
Stretching increases what?
Stretching increases the fraction of active cross-bridges at any given Ca concentration.
The Ca transient can be altered by what 4 things?
1. Changing ECF Ca concentration
2. Altering Na-Ca exchange across membrane
3. increasing the heart rate
4. regulatory phosphorylation
Cardiac muscle normally operates on which limb of the length-tension curve?
Ascending limb!
What is Cardiac Output?
Average flow into the aorta. CO = SV X heart rate
Stroke volume is determined by what 3 things?
1. Preload
2. Aterload
3. Contractility
What is the preload?
Central venous pressure. It is the pressure load prior to contraction of the heart
What is the hearts contractility?
Its ability to produce force at any given stretch.
What is the afterload?
The afterload is the arterial pressure after contraction has begun.
The integral of the pressure-volume loop is what?
The Pressure-Volume Work!
Of the Pressure-Volume Loop, what is A (the lower left corner) on the graph (left ventricular pressure vs left ventricular volume)?
A is when the mitral valve opens when atrial pressure exceeds intraventricular pressure
Of the Pressure-Volume Loop, what is B (the lower right corner) on the graph (left ventricular pressure vs left ventricular volume)?
B is when the mitral valve closes when contraction begins and pressure rises above atrial pressure
Of the Pressure-Volume Loop, what is C (the upper right corner) on the graph (left ventricular pressure vs left ventricular volume)?
C is when aortic valve opens when intraventricular pressure exceeds diastolic arterial pressure
Of the Pressure-Volume Loop, what is D (top middle between E and C) on the graph (left ventricular pressure vs left ventricular volume)?
D is the ejection of stroke volume of blood
Of the Pressure-Volume Loop, what is E (the high left corner) on the graph (left ventricular pressure vs left ventricular volume)?
Aortic valve closes when intraventricular pressure falls below arterial pressure
The total mechanical energy is the sum of what three energies?
1. Kinetic
2. Potential
3. Gravitational
What are the units of cardiac output?
Liters per minute.
What 5 things does Stroke Volume depends on?
1. heart size
2. contractility
3. duration of contraction
4. preload
5. afterload
What does the Frank-Starling Law of the Heart state?
States that increasing right arterial pressure increases the stroke volume of both ventricles.
What happens if the preload increases?
Increasing the preload increases the stroke volume!
What happens if the afterload is increased?
Increasing the afterload DECREASES the stroke volume!
What does the Ventricular Function curve show?
It shows the cardiac output of the heart when it is pumping against a constant arterial resistance and when HR when right atrial pressure is varied.
Sympathetic stimulation shifts isovolumetric systolic curve where?
Shifts the curve up and to the left!
What does Fick's Principle estimate?
It estimates cardiac output from O2 consumption!'
What is the simple mass balance equation that estimates the input and output of oxygen?
Qa[O2]a + Qo2 = Qv[O2]v
Positive ionotropic agents do what?
Increase cardiac contractility by shifting isovolumetric systolic curve up and to the left
What are the 4 functions of the vascular system?
1. Transforms pulsatile flow from the heart to more continuous flow (arteries)
2. Distributes the cardiac output to the tissues (arterioles)
3. Exchanges materials with the tissue (capillaries)
4. Provides a volume reservoir (veins)
What is Lateral Pressure?
Lateral pressure is pressure perpendicular to the flow
What is End Pressure?
Pressure that is same direction as flow.
Is compliance greater or lower in the veins than the arteries?
Compliance of veins is MUCH greater than compliance of arteries.
What does high compliance mean?
Stretches easily
Low compliance means what?
Means that adding small volumes markedly increases the pressure.
What is Systolic Pressure?
Highest pressure point in the artery
What is the Diastolic Pressure?
Lowest pressure point in the artery
What is the Dicrotic notch/incisura?
Brief rise in pressure during its fall in diastole that uccurs when the aortic valve snaps shut
What is Pulse Pressure?
It is the difference between systolic and diastolic pressure (normally 40 mmHg)
When does Pulse Pressure increase?
Increases with stroke volume and decreases in arterial compliance
What causes the arterial pressure pulse?
The hearts ejection of blood into the arterial tree
Diastolic pressure plus one-third pulse estimates what?
Estimates the mean arterial pressure!
What is the first Korotkoff Sound?
Corresponds to the point where cuff pressure is *just* lower than systolic pressure.
What does it mean when Korotkoff sounds disappear?
Disappearance corresponds to the point where cuff pressure is *just* lower than diastolic pressure.
What is Reynold's number?
Reynold's number is the point at which turbulent flow begins.
What are capillaries?
Capillaries are the smallest blood vessel that has walls that consist of a single layer of endothelial cells
What are the 6 conditions required for Poiseuille's law to be valid?
1. Fluid is newtonian
2. Flow is laminar
3. No slippage at the vascular wall
4. Flow is steady
5. Tube is cylindrical
6. Walls of the tube are rigid
What is the formula for Reynold's number?
Re = 2r(average velocity)density/viscosity
Blood pressure can be measured with what?
sphygmomanometer
What are the three types of Capillaries in order of abundance?
1. Continuous
2. Fenestrated
3. Discontinuous
Where are Continuous capillaries located?
Muscle, skin, lungs, fat, connective tissues and nervous tissue.
Where are Fenestrated capillaries located?
Kidneys, intestinal mucosa, exocrine glands, body of the eye.
Where are Discontinuous capillaries located?
Liver
Capillary exchange occurs through what three mechanisms?
1. Passive diffusion
2. Bulk flow of fluid
3. Transcytosis
What channel specifically allow water to pass through?
Aquaporins
At low flow, the diffusional transfer of solute is called what?
Flow limited
Where is gradient highest?
At high flows
To increase diffusional transfer, physiological systems can do what 3 things?
1. Increase blood flow
2. increase the gradient for diffusion
3. increase the effective area for diffusion
What is Solute Extraction?
Fraction of arteriolar that would be transferred across the capillary wall if the interstitial fluid concentration were 0. IT IS DEMENSIONLESS.
What is the Colloid Osmotic Pressure?
Pressure when solutes have the same concentration on both sides of the capillary makes no net osmotic pressure.
What are the 3 functions of the Lymphatic System?
1. Preservation of the circulatory volume
2. Absorption of nutrients
3. Defense against bacterial and viral invasion
Osmotic pressure only varies where?
In interstitial fluid!
What is Lymphedema?
A severe accumulation of massive amounts of protein-rich fluid in the tissues.
What are chylomicrons?
Chylomicrons are tiny globules of fat being transported by the lymph vessels.
What is Extrinsic Propulsion?
Propulsion caused by tissue movements and muscle activity
What is Intrinsic Propulsion?
Propulsion caused by rhythmic contractions of lymphatic smooth muscle.
Lymph must be pumped along the lymphatics by what two main mechanisms?
Extrinsic and Intrinsic propulsion
Lymph vessels posses what to ensure unidirectional flow from the tissues to circulation?
VALVES!
What decreases capillary pressure?
Vasoconstriction!
How does the body react to hemorrage?
By vasoconstriction mediated by the sympathetic nerves
What is vasoconstriction?
Constriction of the arteries and arterioles
What is venoconstriction?
Constriction of the veins
Increasing the arterial resistance does what to the capillary pressure towards the venous pressure?
Lowers the capillary pressure
Vascular smooth muscle contracts by the activation of what?
Myosin Light Chain Kinase!
What does MLCK do?
Myosin Light Chain Kinase phosphorylates regulatory light changes on myosin and activates contraction.
What does MLCP do?
Myosin Light Chane Phosphatase dephosphorylates myosin light chains and turns off contraction.
What is the outermost layer of the artery?
Tunica adventitia
What is the middle layer of the artery?
Tunica media
What is the innermost in the artery?
Tunic intima
What is Electromechanical coupling?
It involves the depolarization of the smooth muscle cell to open voltage gated Ca channels to allow influx of Ca.
Increased Ca concentration helps bind to what to activate the MLCK?
Calcium binds to calmodulin to activate MLCK.
What is Pharmacomechanical coupling?
Chemical signals (like norepinephrine) bind to receptors in the sarcolemma and activate signaling that eventually raises Ca concentration.
What is Ca Sensitization?
It is the increasing of myosin phosphorylation by inhibition of MLCP.
What 4 things make up the Intrinsic Control of Blood Vessel caliber?
1. Myogenic response
2. Endothelial secretion (NO, protacyclin, endothelin)
3. Metabolic control (adenosine, acid pH, K+)
4. Local paracrine secretion (epinephrine)
Which nervous system predominately controls the vascular system?
Sympathetic nervous system
What is metabolic hyperemia or functional hyperemia?
It is the increase of blood flow to regions of the brain when it is altered
What does Vasopressin (ADH - anti-diuretic hormone) do?
It constricts blood vessels
What does angiotensin II do?
It constricts blood vessels, induces thirst, and releases ADH and aldosterone.
What 3 things increase renin release?
1. Renal sympathetic nerves
2. decreased distal tubular na+
3. Decreased afferent arteriolar pressure
Atrail Natriuretic Peptide opposes what system?
Renin-Angiotensin-aldosterone system (RAA)
What does Perfusion of tissues mean?
Means the blood flow through the tissue
What is the Total Peripheral Resistance?
It is the resistance of all arteries, arterioles, capillaries, venules, and veins that supply the tissues of the body.
What is the Mean Systemic Pressure?
It is the pressure that would be measured at all points in the systemic circulation if all inputs and outputs were stopped and pressure was the same everywhere.
What is the Stressed volume?
It is the added amount of blood needed to bring the pressure from 0 to the mean systemic pressure
What is the Unstressed volume?
It is the volume of blood that just fills the circulatory system with no pressure.
Vasoconstriction does what to the TPR?
Increases the resistance!
What does transfusion do for the value of the cardiac function curve and the atrial pressure?
Transfusion (addition of blood) will increase both the atrial pressure and cardiac output.
The Frank-Starling Law ofthe heart indicates that the increased filling pressure of the right heart results from what?
Increased cardiac input
What is the flow through the systemic circulation?
Q(veins) = Afterload - preload/total peripheral resistance
Venoconstriction does what to the mean systemic pressure?
Venoconstriction increases the mean systemic pressure!
In the vascular function curve, what does the knee represent?
The knee represents flow being 0 and the right atrial pressure is the mean systemic pressure.
At low right atrium pressures (below 0), what happens?
Veins collapse due to their lower luminal prussere
Is the mean systemic pressure affected by changes in the TPR?
NO.
What is Hemorrhage?
Is the loss of blood from the cardiovascular system.
Strenous exercise has what 4 major effects on the cardiovascular system?
1. Increased heart rate
2. Increased cardiac contractility
3. Vasoconstriction and vasodilation
4. Venoconstriction
Where does vasodilation occur during exercise?
The muscles!
Where does vasoconstriction occur during exercise?
In blood beds that are inessential to the immediate muscles being used.
What purpose does venoconstriction have during exercise?
It shifts the point at which the circulatory system fills with blood.
Arterial pressure is regulated by what three things?
1. cardiac contractility
2. vascular smooth muscle contractility
3. blood volume
What .3 mechanisms regulate arterial pressure?
1. Neurogenic mechanisms (fast)
2. Hormonal mechanisms (minutes to hours)
3. Intrinsic mechanisms (days to weeks)
What receptors sense blood pressure?
Baroreceptors in the carotid sinus and aortic arch sense blood pressure!
Which baroreceptors are more numerous?
Unmyelinated baroreceptor C fibers
What are Unmyelinated baroreceptor C fibers?
They are receptors with low conduction velocities but higher thresholds
At normal blood pressure, how many Baroreceptor C fibers are activated?
1/4
What is the Dynamic response?
A rapid burst of impulses
What are Baroreceptor A fibers?
They are large diameter, myelinated receptors that activate at normal blood pressures and at pressures slightly above normal.
Reduced sympathetic output to the vasculature causes what two things?
Causes vasodilation and a fall in the total peripheral resistance
What accelerates the heart faster than sympathetic stimulation?
Parasympathetic withdrawal!
Sympathetic stimulation of the heart is through what?
The rostral Ventrolateral medulla
What influences the heart rate?
Inspiration of air!
When blood pressure is high, the baroreceptor responds with how many impulses?
4
When blood pressure is low, the baroreceptor responds with how many impulses?
3
ADH and RAA shift the renal Function curve where?
To the right!
ANP shifts the Renal Function Curve where?
To the left!
What is the Respiratory Sinus Arrhythmia?
It is the effect where inspiration inhibits parasympathetic tone which accelerates the heart rate.
What secretes ADH?
The posterior pituitary gland in response to hypovolemia