Exam 2 - Medchem 753, Cardio Kioussi Flashcards
What is the leading killer in the US?
CVD, 50% of all deaths
Describe blood flow through the hearts chambers/valves
- Blood enters from superior vena cava/Inferior vena cava and enters into the right atrium. 2. Blood travels through the Tricupsid valve into the Right Ventricle. 3. Blood flows from right Ventricle through pulmonary valve to the Pulmonary artery 4. Blood flows from pulmonary artery to Lungs to Pulmonary veins 5. Blood flow from pulmonary veins into Left Atrium 6. Blood flows from left atrium through mitral (bicuspid) valve to the Left Ventricle. 7. Blood flows from Left ventricle through aortic valve into Aorta.
What outer fibrous layer surrounds the pericardial cavity? What is composed of?
The Parietal Pericardium - Areolar tissue - Epithelium - Dense fibrous layer
What is the space inside the parietal pericardium called?
Pericardial cavity
What is the layer deep to the pericardial cavity? What is it composed of?
Epicardium - Epithelium - Areolar tissue
What resides between the Epicardium and Endocardium?
Myocardium (Cardiac muscle tissue)
What is the innermost layer of the heart? What is it composed of?
Endocardium
- Areolar Tissue
- Endothelium
What are the fusions between cardiac muscle cells?
Intercalated disks
What is the role of gap junctions in cardiac muscle?
They allow electrical signals to pass rapidly form cell to cell
What are microfibrils?
Bundle of protein filaments
What fraction of cell volume do mitochondria occupy on a contractile cardiac fiber?
1/3
What is the function of Intercalated disks? What components allow them this function?
They allow the synchronized contraction of cardiac cells. They contain desmosomes that transfer force from cell to cell, and fasciae adherens which are ribbon like junctions stabilize the muscle
What two areas of the heart can initiate electrical activity?
Sinoatrial Node
Atrioventricular Node
What Node begins electrical activity of the heart?
Sinoatrial Node (pace maker)
What transmits electrical signal from SA node to AV node?
The internodal tract
Where can the electrical signal from the SA node also be sent?
To the Atria via Bachmann’s bundle, allows simultaneous depolarization of the atrias
What is the role of Purkinje Fibers?
to send nerve impulses to the cells in the ventricles of the heart and cause them to contract and pump blood either to the lungs or the rest of the body.
How is the electrical signal from the AV node directed?
It is directed towards the apex by the bundle branches, before coming back around by the way of the conduction pathways
Channel in which gates randomly alternate between open and closed positions
Leakage Channels
Channel in which they open in response to change in membrane potential
Voltage gated channels
Channels which open and close in response to specific chemical stimuli
Ligand Gated channels
Channels which open or close in response to mechanical action such as sensory receptors
Mechanically gated channels
Stages of Atrial/Ventricular Action Potential
4 - Resting Membrane (K leaks out)
0 - Threshold reached, Voltage gated Na open and sodium rushes in (Depolarizes)
1 - Sodium channels close, Voltage gated potassium channels open and potassium leaves cell (Repolarizes)
2 - Voltage gated Ca open and keeps the AP from rapidly repolarizing.
3 - Voltage gated Ca close, and cell begins to repolarize back to resting potential
4 - Voltage gated K close, Resting membrane.
What allows the depolarizing current to travel from contractile or autorhythmic cells?
Gap Junctions
Once a depolarizing current has entered a contractile cell, how does it travel along the cell?
The Plasma Membrane and T tubules
What happens once Ca channels on the plasma membrane and SR open?
The Ca influx induces Ca release from the SR
How do myosin-binding sites become exposed?
Ca binds to troponin, which causes tropomysin to pull and expose the myosin binding sites
Once muscle fiber contraction finishes, what happens to calcium?
Ca is actively transported back into SR and ECF
Once Ca leaves the SR and muscle fibers, what happens to the muscle fiber?
Tropomyosin reblocks myosin binding site and muscle fiber relaxes
Describe the phases of nodal action potential
4 - Spontaenous depolarization of pacemaker potential
0 - Depolarization phase continues, increase of Ca conductance
3 - Repolarization occurs, K channels open and L type Ca channels inactivate, (decline is long lasting)
4 - Spontaneous depolarization of pacemaker potential occurs
How does the Ventricular Action potential compare to the atrium’s action potential?
The Ventricle Action potential is longer lasting than the Atrium
What is the difference in membrane potential between Contractile myocardium and Autorhytmic myocardium?
Contractile = Stable @ -90mV
Autorhythmic = @ -60mV
What is the difference in events that lead to threshold potential in Contractile myocardium and Auto-rhythmic myocardium?
Contracile - Depolarization enters through gap junctions
Auto-Rhythmic - Na entry through If channel, and is reinforced by Ca entry
What is responsible for the rising phase of the action potential in contractile myocardium vs Autorhthmic myocardium?
Contractile - Na entry
Autorhythmic - Ca entry
What is responsible for the repolarization phase in Contractile myocardium vs Autorhymic myocardium?
Contractile - Extended plateau caused by Ca entry, and rapid phase caused by K efflux
Auto-rhythmic - Rapid repolarization by K efflux
What is the difference in the duration of the action potential in Contractile myocardium vs the autorhythmic myocardium?
Contractile - 200ms (extended)
Autorhythmic - ~150ms (variable)
What is the difference in the refractory period between Contracile Myocardium vs Autorhythmic myocardium?
Contracile - long refractory period in which restting Na channels gates are delayed until the end of the AP
Autorhythmic - No refractory period
What electrical event is responsible for the P wave of an EKG?
Sinoatrial node depolarization
What electrical event is responsible for the QRS complex of an EKG?
Ventricular Repolarization
What electrical event is responsible for the T wave on an EKG?
Ventricular repolarization
What electrical event is responsible for tthe ST segment on an EKG?
The segment is seen due to the period during ventricular depolarization (plateau)
What event is responsible for the small u wave following the T wave on an EKG?
It is seen due to repolarization of the papillary muscle
What is the significance of the P-R interval?
It is the time taken from the first atrial depolarization to the first ventricular depolarization
What is the Q wave on an EKG?
The first downward deflection of the QRS, and may or may not be present/visible on an EKG
According to the Wiggers Diagram, when does ventricular pressure become greatest?
During Systole, prior to ejection into aorta
What happens when there is a change in the electrical activity of action potentials?
Cardiac Arrythmias
In a delay after depolarization, what occurs to action potential following 1st depolarization?
A new action potential appears qujickly after the first. This abnormal depolarization of cardiac myocytes can interrupt phase 2, phase 3, or phase 4 of the cardiac action potential
When does accelerated normal automaticity (reentry) occur?
Re-entry occurs when an action potential fails to extinguish itself and reactivates a region that has recovered from refractoriness
When do early after-depolarization often occur?
depolarizing shifts in the membrane potential can reactivate the L-type calcium channel, resulting in increased ICa,L that further depolarizes the membrane. This can continue to create a positive feedback loop.
DAD
Delayed afterdepolarization, spontanes release of calcium from the SR produces extra Ca removal from Na-ca exchanger, thich causes production of Na influx which depolarizes the cell
EAD
Early afterdepolarization, occurs due to interruption of phase 3 repolarization, where reactivation of Ca channels during AP prolongs it out further.
In Wolff-Parkinson-White Syndrome, What type of depolarization event occurs and how is it treated?
There is a premature atrial impulse which blocks in the acessory pathway, and on reaching the accessory pathway, the impulse re-enters the atrium, which then re-enters the ventricle via the AV node and becomes self-sustaining. This causes a short P-R interval which prolongs the QRS.
Treatment: Drugs that prolong refratoriness
What is the event when there is an obstruction of blood flow in the myocardium by partial or complete blockage of a coronary artery?
Myocardial Ischemia
A sudden severe blockage of coronary artery may lead to what event?
Myocardial Infarction
What types of events may lead to serious abnormal hearth arrhythmias?
Acidosis
Catecholamine release
Efflux of K from myocyte to ECS
Intracellular Ca accumulation
What is atherclerosis?
hardening and narrowing of the arteries
In acute ischemia, what is generally the cause of the event?
a mechanical or oxidative stress such as cell death which increases cytokine release resulting in inflammation and obstruction
in mild and severe ischemia, what happens to the threshold for AP?
The more severe the ischemia, the less negative the resting potential needed to reach threshold, and there is a delayed recovery period for AP depolarization.
What is the most common type of heart failure?
Enlargement, where the body tries to compensate fo heart’s reduced pumping ability by retaining salt and water to increase the amount of blood in bloodstream, which increases heart rate, and the size of the heart.
What are some common causes of fibrosis/heart failure?
- Changes in activity of some ion channels/ion transporters
- Increased sympathetic activity
- Mechanical stretch
- Electrolyte disturbances
Increasing the activity of delayed rectifier K channels has what effect on AP?
Shortens the AP
Decreasing the activity of delayed rectififier K channels does what to AP?
Prolongs the AP
The delayed inactivation of Na channels does what to AP?
Prolongs the AP
What is the type of heart rate defined by <60 beats/min
Bradycardia
What is the type of heart rate defined by >100 beats/min
Tachycardia
What heart arrhythmia occurs when there is an increased rate that arises in the ventricles?
Ventricular Tachycardia, (life threatening)
What is a Supra-ventricular arrhythmias?
An arrythmia that occurs above the ventricles
What is an atrial flutter?
A rapid regular beating of the atria
What is fibrillation?
A very rapid irregular beating of the atria or ventricles
What is a block arrhythmia?
A failure of heart conduction to occur
What non-pharmaceutical anti-arrhythmic interventions may be taken in the heart?
Cardioverter/defibrillator
Ectopic pacemaker
What are the Class I Anti-arrhythmic drugs and what subclasses are there?
Na Channel Antagonists (slow conduction velocity
1a: Intermediate rate
1b: Fast rate
1c: slow rate
What are the Class II anti-arrhythmic drugs?
B-adrenergic receptor antagonists (blunt sympathetic effects)
What are the Class III anti-arrhythmic drugs and what is there goal?
K channel antagonists (increase Action potential duration)
What are the Class IV antagonists and what is there goal?
Ca2+ channel antagonsits, affect the SA and AV nodes
What are the Class V anti-arrhythmic drugs?
Cl-channel antagonists
What are the disadvantages of anti-arrhythmic drugs?
Potential to be pro-arrhythmic
- Toxic
- Depress automaticity
- Depress conduction velocity
What are the advantages of anti-arrhythmic drugs?
They may be selective for abnormally fast heart rhythms
