Week 7. Examination Of Heart Pacemaker Activity And Vonduction System Flashcards
What is autorithmicity?
It is pacemaker+rhythmic contraction
What is Spontan diastolic depolarization (SDD)
=pacemaker potential (PP)
- base of pacemaker activity
- Normally stimulus developed in the SA. node(nomotopic pacemaker activity) then SDD
-Frequency of SDD is the highest in the SA node(about 95/min)
Special bundle-> rapid conduction
Atrial and ventricular bundles
AV node->slow conduction +Delay
Delay is important in normal ventricular filling
Conduction velocities from fastest to slow
Purkinje fiber->His bundle=L/R bundles branches->Atrial muscle->ventricle->AV node(delay)->SA node
Action potentials in the heart
Nodal tissue/ SA & AV node (pacemaker Ap)
- Non-selective cation channel-Mainly Na+ inflow ( slow diastolic depo.)
2.T type Ca2+ channel-Ca2+ inflow (early)
- L type Ca2+ channel-Ca2+ inflow (long lasting)
- Voltage gated K+ channel-K+ outflow (depolarization)
Action potential in the Atrial/Ventricular muscle
- Fast voltage gated Na+ channel- Na+ inflow
- Early K+ channel- k+ outflow(early repolarization )
- Voltage gated cl- inflow (early repolarization )
- L type ca2+ channel: Ca2+ inflow (Plateau phase)
- Late repolarization late K+ channels-K outflow
Absolute refractory period (ARP)
-heart is unexcitable
-during plateau phase
Defending function -> heart muscle cannot be tetanised
Relative refractory period (RRP)
- after ARP
- does not ans to stimuli arround threshold
- AP and contraction can be elicited by stimuli above threshold
Super normal phase(SNP)
- after RRP
- AP and contraction can be elicited by stimuli arround threshold
- in the short period after repolarization
Heart cycle: events during 1 heart beat
- duration: normally 0,8 sec
- systole: 1/3 heart cycle
- diastolic: 2/3 heart cycle
Work stations for electrophysiological registration
- Preparatum
- Mechanic-electrical transducer
3.Amplifier - Filter
5.AD converter - Computer
Application of extra stimuli in ventricular systolic and diastolic phase
- in ventricular systolic phase-> ES is ineffective because ARP
- in ventricular diastolic phase-> ES positive with compensatory phase
Result of continual stimulation of heart
Cannot be tetanised
Thermic stimuli of the heart
- Heat: SA node- HR increased, Ventricle- contraction force increased but HR no change
- Cool: opposite of 1. But in ventricle the HR no change as well
What is stannius- ligatures
1.binding of SA node
2. Binding of AV node
3. Cutting down of apex
Explain the 1. Ligature and why?
Heart stop for long time and then restart but with decreased HR. Because not only Sinus has pacemaker but also atrium
What is Bowditch All or nothing law
When stimuli reach the threshold the heart will totally contracts, the stimuli above the threshold the contacts force keep the same
Investigation of summation by 1 or 2 ligature
Stimulating with continual pulses under threshold but in creased the frequency then decreased we can see 1-1 single contraction
- Ligature
Apex is cutted down, no spontaneous contraction->ventricular working fiber have no pacemaker activity is by pinprick stimulate
