Term
| What are the 3 types of cardiac muscle? |
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Definition
Atrial
Ventricular
Excitatory and Conductive |
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Term
| what ion channels does cardiac muscle have? |
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Definition
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Term
| why is the action potential of cardiac muscle so long and why does it have a plateau, where skeletal muscle does not? |
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Definition
AP of skeletal muscle is caused by sudden opeining of FAST Na channels, they close quickly and repolarization occurs.
Cardiac muscle, AP is caused by opening of the same fast Na channels AND slow Ca channels (Ca-Na channels)
-these are slower to open and remain open longer
large quantity of Ca and Na flows through to interior of cardiac muscle and this maintains a prolonged period of depolarization: CAUSING THE PLETEAU in AP
also, Ca ions that enter during plateau phase activate muscle contractile, Ca ions that cause skeletal muscle contraction are from sarcoplasmic reticulum
Another reason for diff:
immediately after onset on AP permeability of cardiac muscle membrane for K decreases ALOT, this does not occur in skeletal muscle (might results from excess Ca influx). Decreased permeability decreases outflux of K during AP plateau and prevents early return of AP voltage to resting level |
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Term
| what does the plateau in cardiac muscle cause in regards to ventricular contraction? |
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Definition
| ventric contraction lasts much longer than in skeletal muscle |
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Term
| cardiac wave forms: Sinus nodal fiber resting potential - not a flat line. Why? |
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Definition
| Sinus nodal fiber is leaky to Na and Ca ions and positive charges |
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Term
| Explain what happens in the diff phases of the cardiac AP |
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Definition
| Na channels open, Na moves into cell, increases membrane potential, depolarization. Plateau - slow opening of slow Na-Ca channels. Opening of K channels allows diffusion of large amounts of K out of fiber and returns membrane potential. |
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Term
Hemodynamics
Deoxygenated blood enters heart where?
Oxygenated blood enters heart where? |
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Definition
Deox blood enters Right atrium via Inf and Sup Vena cava
Ox enters Left Atrium via pulmonary veins
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Term
| Where does blood go after it enters the atria? |
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Definition
Blood in right atrium passes the Tricuspid valve to the right ventricle. then goes through the pulmonary valve to the pulmonary artery to the lungs (lowpressure)
blood in Left atrium passes through Bicuspid/mitral valve to the left ventricle
from here the blood flows through the aortic valve, to the aorta to the body (high pressure) |
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Term
| Why is the resting membrane potential of the Sinus nodal fiber between discharges -60 mv instead of -90 like ventricular fibers? |
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Definition
| cell membranes of sinus are naturally leaky to Na and Ca ions and these positive charges entering neutralize intracell negativity |
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Term
| what causes the AP in the sinus node fibers (atrial)? |
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Definition
| resting membrane potential only -55. Fast Na channels have already become inactivated. Only the slow Na-Ca channels can open and cause the AP. So the atrial nodal AP is slower to develop than the AP of ventricular muscle |
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Term
| Where is the SA node, AV node located? |
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Definition
SA: roof of rt atrium
AV: Floor of rt atrium |
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Term
| conduction of AP through cardiac muscle: slow. Rate of purkinje fiber conduction? |
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Definition
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Term
| how are AP spread cell to cell? |
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Definition
intercalated discs and gap junctions
gap jxn - protein pores in intercalated discs allows ions to flow from cell to cell |
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Term
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Definition
Skeletal
-Rapid rise caused by sudden opening of fast Na+ channels (close quickly)
-Repolarize quickly due to K+ efflux
Cardiac
-Rapid rise caused by fast Na channels and slow Ca channels
-Ca channels slower to open and remain open longer
-Prolonged period of depolarization causing a plateau
-Ca that enters initiates the contractile process
-little K efflux while Ca gates are open
-When Ca gates close, K efflux occurs to repolarize membrane |
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Term
Refractory Period
of ventricle?
Atria?
Relative refactory? |
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Definition
Ventricle: .25 - about duraiton of plateau
Atria: .15
Relative refract period: Can get a premature beat here |
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Term
Excitation contraction coupling
AP passes over cardiac muscle membrane, AP spreads to interior of fiber along?
This causes?
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Definition
T tubules
T tubule APs act on the membrane of sarcoplasmic tubules to release Ca ions into muscle sarcoplasm from sarcoplasmic reticulum
Ca ions diffuse into myofibrils and catalyze chemical reactions that promot sliding of Actin and myosin filaments along one another
Differs from skeletal:
In additon to Ca ions that are released into the sarcoplasm from cisternae of SR, large quantity of extra Ca diffues into sarcoplasm from t tubles themselves at time of AP. Without extra Ca from t tubules the strenght of contraction would be reduced because SR of cardiac muscle is less well developed than that of skeletal and does not store enough Ca
T tubules also much larger
Strength of contraction also depends on [ ] of Ca in the ECF because T tubules pass directly through cell membrane into extracell spaces |
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Term
| Frank Starling mechanism. waht is it? |
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Definition
| intrinsic ability of heart to adapt to increasing volumes of inflowing blood. The greater the heart muscle is stretched during filling, the greaters is the force of contraction and the greater the quantity of blood pumped into the aorta. |
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Term
| the amount of blood pumped by the heart each minute is determined by the rate of ? called? |
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Definition
| blood flow into the heart from the veins - venous return |
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Term
| Sympathetic effect on heart |
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Definition
| increase HR, increase force of contraction, increase volume of blood pumped, increasing ejection pressure, increased CO |
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Term
Adrenergic Receptors and the Heart
What kinds of receptors for pacemaker cells? What mechanism opens Na and Ca channels?
this causes? |
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Definition
B1 adrenergic receptors
G protein mechanism
Increases diastolic depol
increases HR |
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Term
B1 adrenergic receptors of myocardial cells via G protein mech activates ?
This causes? |
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Definition
Ca channels
provides more Ca for stronger contraction |
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Term
| There are more ___ receptors than ___ on coronary arteries. |
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Definition
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Term
what do B2 receptors do? how?
What do alpha1 receptors do? |
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Definition
B2: smooth muscle relaxation (vasodilation)
does this by reducing sensitivity of myosin light chain kinase to Ca-Calmodulin complex
Alpha 1 in skin, GI and Kidney results in vasoconstriction by increase [Ca] in vascular smooth muscle |
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Term
Cholinergic Receptors
What receptors on pacemaker cells?
How do they act? results in? |
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Definition
M2 muscarinic receptors
directly open K channels which makes potential more negative
Reduction of HR |
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Term
| What happens with increased K levels? |
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Definition
Large increase: Heart becomes dilated, flaccid, slows HR, bradycardia (trouble repolarizing)
Small increase: Tachycardia - cells are more easily excited (potential is less negative, easier to reach threshold) |
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Term
| what happens with decreased K levels? |
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Definition
| cells will give up K (because ECF [ ] is low), inside of cell more negative, decreases excitability |
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Term
| what happens in the heart with excess Ca? |
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Definition
| decreases excitability (Ca binds to Na channels, more positive, Na can't move into cells, harder to excite) |
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Term
Heart Energy
Aerobic metabolism of ?
Does not tolerate anaerobic metabolism. Very sensitive to?
Oxygenated blood supplied via coronaries mostly during _________?
Venous return via ___ into right atrium |
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Definition
fatty acids and ketones
(some sugar)
Lactate
ventric diastole
coronary sinus |
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Term
| Does O2 or CO2 diffuse easier? |
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Definition
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Term
Diffusion of O2 from alveoli to pulmonary capillary blood
Why? |
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Definition
| PO2 of O2 in alveoli = 104, PO2 of venous blood = 40 (O2 removed going through tissues) |
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Term
Oxygenation during Exercise
During rest most perfusion happens where in lungs?
Exercise: Hypoxia causes? |
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Definition
base of lungs
Vasoconstriction, blood shunts toward apex of lungs - more diffusion space
(During rest blood is oxygenated only a 1/3 of the way through the lungs) |
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Term
Changes in PO2
Systemic venous blood is oxygenated in the pulmonary capillaries. Why is the PO2 of arterial blood decreased a little bit? |
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Definition
Oxygenated blood is mixed with pulmonary shunt blood
Shunt blood is blood that was shunted past the gas exchange areas, so PO2 is only 40. When this blood mixes w/ oxygenated blood the PO2 falls to 95 |
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Term
| Oxygenated blood enters left heart and is pumped into the aorta and then to the body. What happens to the PO2? |
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Definition
| Interstitial fluid that surrounds the tissues cells is only 40, there is a large pressure diff. O2 diffuses rapidly from the capillayr blood into the tissues. Capillary PO2 falls to 40. So blood leaving tissues capillaries and entering the systemic veins is also 40. |
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Term
| What is the effect of Rate of Blood flow on PO2? |
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Definition
| if blood flow to a tissue is increased, greater quantities of O2 are transported into the tissue and tissue PO2 becomes higher. If blood flwo to tissue decreases, PO2 also decreases |
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Term
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Definition
O2 becomes H2O
-Food is stripped of H+ by dehydrogenases
-H+ is oxidized forming H2O
CO2 is relased from food substrate by decarboxylases
-dissolves into body fluids
-transported by blood to lungs |
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Term
PCO2- CO2 diffuses 20x more rapidly than O2
Diffusion of Co2 from peripheral tissue cells into Capillaries |
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Definition
Intracellular PCO2 46, Interstitial PCO2 45
CO2 diffuses from tissues into blood |
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Term
Alveolar CO2 Diffusion
Alveolar PCO2 = 40
Pulmonary PCO2 = 45 |
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Definition
| CO2 goes from blood to alveolus |
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Term
Effect of Blood flow and Metabolism on Peripheral PCO2
Decrease in blood from from normal to 1/4 normal does what to peripheral tissue PCO2?
Increasing blood flow to 6x normal decreases does what to interstitial CO2? |
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Definition
Increases tissue PCO2 to an elevated 60
Decreases interstitial PCO2 from 45 to 40 |
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Term
O2 transport
what is it bound to?
what is binding dependent on? |
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Definition
97% bound to Hgb
3 % dissolved in fluids
PO2 |
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Term
When PO2 is high, what happens with O2-Hgb binding?
When PO2 is low? |
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Definition
PO2 high - O2 binds with Hgb
Low - O2 is released from Hgb |
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Term
O2-Hgb Dissociation
Progressive increase in % of Hgb bound with O2 as ? Called? |
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Definition
blood PO2 increases
% saturation of Hgb |
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Term
O2 delivery
O2 sat vs O2 content. How is this not always equal? |
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Definition
you can have good O2 sat but low O2 content
it you only have a little bit of Hgb it doesn't take much O2 to saturate it! |
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Term
| What is offloading of O2 affected by? |
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Definition
Tissue O2
Tissue CO2
pH
temp
BPG |
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Term
| O2 delivery is relative to? |
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Definition
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Term
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Definition
| biphosphoglycerate - produced by RBCs to bump off O2 to be delivered |
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Term
Shifting Dissociation Curve
Right shift: Facilitates?
What happens to:
O2
CO2
pH
Temp
BPG |
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Definition
offloading of O2
Tissue O2 falls
Tissue CO2 risise
pH falls
increase in TEmp
increase in BPG |
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Term
shifting dissociation curve
Left Shift: facilitates:?
effects on:
pH
temp
BPG |
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Definition
O2-Hgb bonding
pH rises
temp decreases
decrease in BPG |
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Term
| Bohr Effect: what does it show? |
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Definition
| increased delivery of O2 to tissues when CO2 and H+ ions shift the O2-Hgb Dissociation Curve to the right |
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