NEED HELP WITH ALL TO SEE IF IM ON RIGHT TRACK. QUESTION 2-5 PLEASE 2. Relate th
ID: 3514834 • Letter: N
Question
NEED HELP WITH ALL TO SEE IF IM ON RIGHT TRACK. QUESTION 2-5 PLEASE
2. Relate the electrical events of the heart to the mechanical events of contraction. Describe the mechanical event of the heart during depolarization of each tissue in your answer listed above (there should be 6 structures). Some structures may have considerable overlap (e.g. SA node and internodal pathways both will correspond to atrial contraction). (15 pts)
Autorhythmic tissue
EKG representation
Mechanical event
EXAMPLE: SA Node
See beginning of the P wave
Atrial contraction
Internodal pathways
AV Node
Bundle of His
Left and right bundle branches
Purkinje fibers
3. Choose the autorhythmic tissue (use the list you created in question #1) responsible for each of the following events that promote cardiac efficiency: (14 pts)
Event
Tissue(s)
Atria fill ventricles
Delayed ventricular contraction to allow for complete ventricular filling
Septal contraction to provide scaffold for ventricular contraction
Contraction of the ventricular free-wall, from bottom to top
Contraction signal spreads rapidly into myocardium
4. Compare the mechanical events of a normal contraction to a premature ventricular contraction (PVC). List at least 4 events of the heart that are impaired when the heart contracts prematurely from an ectopic focus and explain why PVCs are hemodynamically inferior compared to a regularly routed contraction (12 pts)
5. Evaluate atrial fibrillation and the risk of stroke. Start by explaining the mechanical action of the atria during afib. What is happening to the blood inside the atria as they fibrillate? Describe the components of atrial fibrillation that put patients at higher risk for stroke and pulmonary embolus. (14 pts)
Autorhythmic tissue
EKG representation
Mechanical event
EXAMPLE: SA Node
See beginning of the P wave
Atrial contraction
Internodal pathways
AV Node
Bundle of His
Left and right bundle branches
Purkinje fibers
Explanation / Answer
ANSWER:3.AUTORHYTHMIC TISSUE:
DELAYED VENTRICULAR CONTRACTION
TO ALLOW FOR COMPLETE VENTRICULAR FILLING
SEPTAL CONTRACTION TO PROVIDE SCAFFOLD FOR
VENTRICULAR CONTRACTION
ANSWER:4.
VENTRICULAR CONTRACTION:If the ventricle is stimulated after the refractory period has passed,i.e., after the end of systole,it responds by contracting.
As the ventricles obeys All-or-None Law,it responds to the maximum of its ability if the stimulus is adequate.
The actual force of contraction depends on the extent to which the ventricles have recovered from their previous contraction and the degree of filling that has taken place.
PREMATURE CONTRACTION:
If the ventricle is stimulated early in diastole,the contraction it gives is feeble and may be insufficient to open the semilunar valves.
The premature beat then only gives rise to the heart sound and is not accompanied by atrial pulsation at the wrist.
If the ventricular premature contraction occurs later in the diastole,the ven
tricle may contract sufficiently forcibly to discharge its contents.
As the ventricle has not had the time to become completely filled ,the output during this premature beat is less than the normal,and the pulsation felt at the wrist is small.
The ECG features are the electrical record of the ectopic beat shows an abnormal ventricular complex which is not preceded by a P wave.The next P wave is generally burried within in this ventricular complex.The QRS is prolonged and abnormal in appearance.
ANSWER:5.ATRIAL FIBRILLATION:
Atria exhibit no co-ordinated contraction in atrial fibrillation.Most of the atrial muscle fibres are completely or partially refractory at any instant and the excitation wave takes an irregular sinous path.
The AV node is stimulated at irregular intervals and the ventricular beats become irregular.
Fibrillation commonly supervenes on flutter in diseased hearts and the atria may be excited as fast as 450 min.
The irregularity which is the condition superimposing on the ventricular rhythm is dangerous and this must be prevented either by
1.Direct electrical shock delivered to the chest wall,timed to fire at the peak of the R wave causing depolarization of the atria,thereby allowing the normal sinus rhythm to be restored .
2.Drug therapy such as DIGITALIS which acts on the ventricle rate and it lengthens the refractory period of transmission system of the AV node by reflexly increasing the vagal activity.
The ventricular muscle thereby receives a more regular transmission of impulses and can beat more slowly and powerfully.
In case of non treated atrial fibrillation , it causes pulmonary emboli which enters the ventricle and further in to the circulation ,the emboli dislodges and travels to the brain causing stroke or the emboli enters the coronary circulation leading to cardiac stroke as it blocks the coronary circulation,leading to decreased blood supply to the heart muscle.
In Atrial fibrillation there is no coordinated atrial contraction and therefore there is no P wave.
There are irregular electrical oscillations called fibrillation waves,which occur at a rate of 300-500 per min.
The bundle of His cannot conduct impulses at such high frequencies.
The QRS comples is irregular in time with a rate of about 150 per min.
EVENT TISSUES ATRIA FILL VENTRICLES BUNDLE OF HISDELAYED VENTRICULAR CONTRACTION
TO ALLOW FOR COMPLETE VENTRICULAR FILLING
ATRIOVENTRICULAR NODESEPTAL CONTRACTION TO PROVIDE SCAFFOLD FOR
VENTRICULAR CONTRACTION
CONTRACTION OF THE VENTRICULAR FREE WALL FROM BOTTOM TO TOP PURKINJEE FIBRES CONTRACTION SIGNAL SPREADS RAPIDLY IN TO MYOCARDIUM SINUATRIAL NODERelated Questions
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