Week 7. Examination Of Heart Pacemaker Activity And Vonduction System

Question 1

What is autorithmicity?

Answer 1

It is pacemaker+rhythmic contraction

Question 2

What is Spontan diastolic depolarization (SDD)

Answer 2

=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)

Question 3

Special bundle-> rapid conduction

Answer 3

Atrial and ventricular bundles

Question 4

AV node->slow conduction +Delay

Answer 4

Delay is important in normal ventricular filling

Question 5

Conduction velocities from fastest to slow

Answer 5

Purkinje fiber->His bundle=L/R bundles branches->Atrial muscle->ventricle->AV node(delay)->SA node

Question 6

Action potentials in the heart

Nodal tissue/ SA & AV node (pacemaker Ap)

Answer 6

1. Non-selective cation channel-Mainly Na+ inflow ( slow diastolic depo.)

2.T type Ca2+ channel-Ca2+ inflow (early)

3. L type Ca2+ channel-Ca2+ inflow (long lasting)
4. Voltage gated K+ channel-K+ outflow (depolarization)

Question 7

Action potential in the Atrial/Ventricular muscle

Answer 7

1. Fast voltage gated Na+ channel- Na+ inflow
2. Early K+ channel- k+ outflow(early repolarization )
3. Voltage gated cl- inflow (early repolarization )
4. L type ca2+ channel: Ca2+ inflow (Plateau phase)
5. Late repolarization late K+ channels-K outflow

Question 8

Absolute refractory period (ARP)

Answer 8

-heart is unexcitable
-during plateau phase
Defending function -> heart muscle cannot be tetanised

Question 9

Relative refractory period (RRP)

Answer 9

• after ARP
• does not ans to stimuli arround threshold
• AP and contraction can be elicited by stimuli above threshold

Question 10

Super normal phase(SNP)

Answer 10

• after RRP
• AP and contraction can be elicited by stimuli arround threshold
• in the short period after repolarization

Question 11

Heart cycle: events during 1 heart beat

Answer 11

• duration: normally 0,8 sec
• systole: 1/3 heart cycle
• diastolic: 2/3 heart cycle

Question 12

Work stations for electrophysiological registration

Answer 12

1. Preparatum
2. Mechanic-electrical transducer
   3.Amplifier
3. Filter
   5.AD converter
4. Computer

Question 13

Application of extra stimuli in ventricular systolic and diastolic phase

Answer 13

• in ventricular systolic phase-> ES is ineffective because ARP
• in ventricular diastolic phase-> ES positive with compensatory phase

Question 14

Result of continual stimulation of heart

Answer 14

Cannot be tetanised

Question 15

Thermic stimuli of the heart

Answer 15

1. Heat: SA node- HR increased, Ventricle- contraction force increased but HR no change
2. Cool: opposite of 1. But in ventricle the HR no change as well

Question 16

What is stannius- ligatures

Answer 16

1.binding of SA node
2. Binding of AV node
3. Cutting down of apex

Question 17

Explain the 1. Ligature and why?

Answer 17

Heart stop for long time and then restart but with decreased HR. Because not only Sinus has pacemaker but also atrium

Question 18

What is Bowditch All or nothing law

Answer 18

When stimuli reach the threshold the heart will totally contracts, the stimuli above the threshold the contacts force keep the same

Question 19

Investigation of summation by 1 or 2 ligature

Answer 19

Stimulating with continual pulses under threshold but in creased the frequency then decreased we can see 1-1 single contraction

Question 20

3. Ligature

Answer 20

Apex is cutted down, no spontaneous contraction->ventricular working fiber have no pacemaker activity is by pinprick stimulate