The Cardio Vascular System - Cardiac Cycle, Sounds, Rhythms (w8) Flashcards
What is a systole ?
Heart contraction
What is a diastole ?
Heart relaxation
What are the three main phases to the cardiac cycle ?
1) ventricular filling
2) ventricular systole
3) early diastole
What happens during the ventricular ejection phase ?
The blood is ejected forcefully though the semi lunar valves, through aorta and pulmonary artery.
What causes the LUBb (s1) sound in the isovolumetric conraction phase of the cardiac cycle ?
The closure of the AV valves
What causes the DUBb (s2) sound in the isovolumetric contraction phase of the cardiac cycle ?
The closure of the SL valves
What is sound 3 in the early vertical area filling phase of the cardiac cycle caused by ?
Th tensing of the chordae tendineae and the atrioventricular ring.
Adults : ventricular systole failure, normal in children
What causes sound 4 in the atrial contraction phase of the cardiac cycle ?
The vibration of the ventricular wall, stiff verticle, hypertrophy or ischemic ventricle
What are the two main heart sounds ?
Sound 1 - LUBb
Sound 2 - DUBb
What happens at the (SA) Sino Atrial node (pace-maker) ?
- There is specialized electrically active myocardial tissue found in the atria. You can also find pacemaker cells in the right atrium which involuntarily generate pulses.
- spontaneous depolarization occurs around 90-100 times/min
- overall in generates electrical activity- impulse
What are contractile myocytes ?
Cardiac cells
What is vagus inner action responsible for ?
Reducing heart beat.
- is parasympathetic
- slows down SA and AV nodes
What do the SA node and AV act as ?
- SA = pacemaker
- AV = collecting node
What does sympathetic innervation do ?
Stimulated the AV and SA nodes
What is composition of cardiac muscle ?
-99% contractile
-1% autorhythmic cells
What happens at the gap junctions between cardiac muscle cells ?
Depolarization of the cells just to generate action potential and give stimulus for calcium to be released causing muscle contraction.
What occurs at the demosomes ?
They hold the muscle fibers together during muscle contraction
What are the 4 key properties of the cardiac muscle ?
1) auto-rhythmicity : ability to initiate heartbeat, consistent and continuous at regular pace without any external stimuli.
2) excitability : ability to respond to stimuli of adequate strength and duration (threshold or more) and the ability to generate and process action potentials.
3) conductivity : ability to conduct and transmit impulse through the cardiac tissue.
4) contractility : ability to contract in repose to a stimulation (mechanical)
Describe the excitation process of contraction coupling in contractile myocytes …
1)AP from adjacent cell excites myocytes and trigger membrane depolarisation in T-tubules.
2)Calcium enter the cells via voltage gated channel opens and calcium enters the cells
3)Calcium binds to Ryanodine receptor (RYR) and induce Calcium release from SR
4)Calcium binds to troponin and triggers acting-myosin complex and contraction
5)Calcium unbind from troponin and pumped back into SR
6)Calcium unbinding cause relaxation and excess Ca2+ exchanged with Na+
7)Na+ gradient is maintained by sodium-potassium- ATPase pump
During a sinus rhythm (ECG/EKG) what do the following equate to: p wave, QRS complex and T wave ?
P wave - atria depolarisation
QRS complex - ventricle depolarization
T wave - ventricle repolarisation
What is sinus bradycardia ?
When the hearty rate is less than 60bpm (not usually less than 40bpm)
- patients usually are asymptomatic and no treatment is required.
- can be caused by hypertension drug e.g. beta-blockers / calcium channel blocker (amlodapine)
- may also be seen in athletes and occur during sleep.
What is sinus tachycardia ?
Rate is > 100bpm, but not usually > 130bpm at rest
-Occurs normally in exercise / stress.
-Patient is usually asymptomatic.
-Hypovolaemia / underlying medical problems
What are conduction and contraction in cardiac cells coordinated by ?
Both mechanical and electrical activity.
