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42 Cards in this Set
- Front
- Back
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Intercalated discs |
o Desmosomes § Act as an anchor holding the cells together, keeps them adjacent |
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Gap junctions
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Have little pores that allow ions to get through |
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ions |
send a message |
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Autorhythmic |
auto means self, sets its own pace , can depolarize on their own |
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contractile |
they depolarize because their neighbor depolarizes |
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Electrical signal: Bachman’s bundle |
Highly conducted track |
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Sinoatrial node |
100 times a minute o depolarization § spread to adjacent cells |
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Atrioventricular node |
The track that connects the two is the INTERNODAL TRACTS
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0.1 second delay |
-how fast the conduction velocity goes -the bigger diameter vessel is faster - the anatomy of the fibers cause it to go veryslowly |
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Benefit of the slow spread at AV node? |
The need to contract so the message can contract
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Signal travels : |
Sinoatrial node --> atrioventricular node --> atrioventricular bundle --> right & left bundle branches--> subendocardial conducting network (Purkinje fibers) |
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Anatomy of theintrinsic conduction system showing the sequence of electrical excitation |
1. The sinoatrial (SA) node (pacemaker)generates impulses· 2. The impulses pause (0.1s) at theatrioventricular (AV) node · 3. The atrioventricular (AV) bundle connects theatria to the ventricles· 4. The bundle branches conduct the impulsesthrough the interventricular septum· 5. The subendocardial conducting networkdepolarizes the contractile cells of both ventricles |
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ECG example :(repolar/depolar) |
· Cardiac action potentials have a slightly different shape and Ca++ plays a role
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Cardiac actionpotentials: contractile cells |
1. Depolarization is due to Na+ influx through fast voltage-gated Na+ channels. § A positive feedback cycle rapidly opens many Na+ channels, reversing the membrane potential. § Channels inactivation ends this phase 2. Plateau phase is due to Ca2+ influx through slow Ca2+ channels § this keeps the cell depolarized because few K- channels are open. 3. Repolarization is due to Ca2+ channels inactivating and K+ channels opening. This allows K+ efflux, which brings the membrane potential back to its resting voltage |
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Pacemaker cells |
1. Pacemaker potential, this slow depolarization is due to both opening of Na+ channels and closing of K+ channels § notice that the membrane potential is never a flat line 2. Depolarization, the action potential begins when the pacemaker potential reaches threshold § depolarization is due to Ca2+ influx through Ca2+ 3. Repolarization is due to Ca2+ channels inactivating and K+ channels opening. This allows K- efflux, which brings the membrane potential back to its most negative voltage |
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Electrocardiogram (ECG or EKG) |
All action potentials at given time
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Three waves: |
-P wave § Depolarization SA node --> atria o -QRS complex § Ventricular depolarization and atrial repolarization -T wave § Ventricular repolarization |
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PQRST What is missing? |
Q is missing (dip before R)
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Electrical signal |
1. Atrial depolarization, initiated by the SA node, causes the P wave 2. With atrial depolarization complete, the impulse is delayed at the AV node 3. Ventricular depolarization begins at apex, causing the QRS complex. o Atrial repolarization occurs 4. Ventricular depolarization is complete 5. Ventricular repolarization begins at apex, causing the T wave 6. Ventricular repolarization is complete. |
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Mechanical events :the cardiac cycle |
Systole o Contraction Diastole o Relaxation Cardiac cycle o Blood flow through heart during one complete heartbeat o Atrial systole and diastoleà ventricular systole and diastole |
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Acids/baseshomeostasis: |
Acids/bases produced by the body
o Phosphoric acid, lactic acid, fatty acids § Things that make your tissue more acidic o Carbon dioxide forms carbonic acid o Ammonia/base |
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Three lines of defense: |
o Buffering of hydrogen ions (almost instant)
o Respiratory compensation (minutes) o Renal compensation (hours to days) |
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pH refresher |
· increase (H+) --> decrease pH
· decrease (H+) --> increase pH · a pH of 4 has ten times more hydrogen ions than a pH of 5 |
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Blood buffers: 1st line |
· three major chemical buffer systems
o bicarbonate buffer system: o Phosphate buffer system o Protein buffer system § Protein |
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Bohr effect |
oxygen binds to hemoglobin --> hydrogen ions are released |
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Buffers are: |
-molecules that react to prevent dramatic changes in hydrogen ion (H+) concentrations o Bind to H+ when pH drops o Release H+ when pH rises |
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Respiratory systemcontrols of acid-base balance: 2nd line of defense |
· Carbon dioxide --> bicarbonate ion and hydrogen ion
o Transported in the plasma · Increase (H+) --> more carbonic acid · Respiratory rate can rise and fall depending on changing blood pH o Hypoventilation will decrease pH o Hyperventilation will increase pH |
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RespiratoryCompensation: 2nd line of defense |
· Minutes
· Regulates pH by varying ventilation o Increase ventilation --> decrease CO2 --> decrease H+/ increase pH o Decrease ventilation --> increase CO2 --> increase H+/ decrease pH |
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Respiratory compensation for acidosis |
o Plasma pH decrease (acidity increase) --> Peripheral chemoreceptors --> Ventilation increase --> Plasma PCO2 decrease --> Plasma pH increase
§ Negative feedback |
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Renal compensationfrom respiratory acidosis· Respiratory acidosis: |
increased CO2 --> increase H+ --> decrease pH |
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Renal compensation: |
Increase H+ secretion
o Increase HCO3- reabsorption and synthesis |
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Renal compensationfrom respiratory alkalosis |
Decrease CO2 --> decrease H+ -> increase pH
· Renal compensation o Decrease H+ secretion o Decrease HCO3- reabsorption & synthesis o No effect on CO2 |
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Metabolic acidosis |
· Decrease pH through something other than carbon dioxide (usually low free bicarbonate)
o High protein diet o High fat diet o Heavy exercise o Severe diarrhea (loss of bicarbonate) -Renal dysfunction |
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compensation |
o Respiratory and renal
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Respiratory compensation |
o Increase ventilation --> decrease CO2
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· Renal compensation |
o Increase H+ secretion o Increase HCO3- reabsorption o Increase synthesis of new bicarbonate |
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Metabolic alkalosis |
· Increase pH through something other than dioxide (usually high free bicarbonate) · Excessive vomiting (loss of hydrogen ions) · Consumption of alkaline products (baking soda) · Renal dysfunction |
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o Metabolic alkalosis |
-Compensation : respiratory and renal
- Respiratory compensation is decrease ventilation à increase CO2 -Renal compensation --> decrease H+ secretion --> decrease HCO3- reabsorption --> decrease synthesis of new bicarbonate |
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What is the purpose of breathing in a paper bag to “calm down” |
· panic --> breathing heavy and/or fast --> hyperventilation --> respiratory alkalosis (hypocapnia= low levels of carbon dioxide in the plasma) o decrease CO2 (blood has less CO2) --> decrease H+ --> increase pH · each breath has more carbon dioxide entering my lungs o (CO2) bag > (CO2) air |
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Vasodilators |
· Metabolic o Increase O2 o Increase CO2 o Increase K+ · Neuronal o Sympathetic tone · Hormonal o Atrial natriuretic peptide |
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Intrinsic mechanisms (autoregulation) |
-Metabolic or myogenic controls - Distribute blood flow to individual organs and tissues as needed |
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Extrinsic mechanisms |
· Neuronal or hormonal controls · Maintain mean arterial pressure(MAP) · Redistribute blood during exercise and thermoregulation |
