BIOC33H3 Lecture : Lecture 2

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beigewhale523

7 Mar 2011

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Ecg- measure of the surface electrical activity from the heart allowing to quantify heart rate and seeing how heart activity can change; looking at heart function and cardiovascular activity. 3 components of ecg (+/- deflection) are important because they tell us about the heart function. Electrical axis- heart depolarizes, electrical activity going off in all directions ultimately there is a mean axis at which the electrical activity flows and that axis which goes at about. 60 degrees from the middle of heart can shift left or right and shifting is important for determining heart disease. Ecg can also be used to determine heart rate : Arrhythmias: rhythm can be disrupted by processes that are atrial or ventricular in origin; Ventricular in origin, will be more problematic as compared to atrial. So we know that activity starts are sinoatrial node, goes to the intermodal pathways, then down to the atrioventricualr node, down the branch bundles and up to the purkinje fibres;

Related Questions

Heart function in frogs

1. what is the âtemporalâ relationship between the electrical activities (ECG) and the mechanical activities (ventricular contraction) in a frog heart?

In other words, do we expect to see the recordings of ventricular contraction preceded by the QRS complex on ECG recordings? Is there any other evidence that will show a cause-and-effect relationship between these two activities?)

2. why does the QRS complex appear first and then the ventricular contraction?)

3. what will happen to the heart rate and to the force of ventricular contraction when the temperature of the heart increases (20 to 30C) or decreases (20 to 10C)? What is the reasonable temperature coefficient (Q₁₀) for the heart rate or for the force of ventricular contraction?)

how does the temperature change affect these variables? Which chemical reactions are temperature-dependent during ventricular systole? For comparison, what is the temperature coefficient (Q₁₀) for a pure âphysicalâ reaction?)

4. describe the expected changes in the heart rate and the contraction force when an electrical stimulation is applied to the S-V node.)

how does this change come about? Explain the mechanisms for the heart function in terms of neurotransmitters and its effect on ion channels.

(b) What does the EKG measure? (c) What does each component of the EKG represent? (d) Can an EKG show ventricular contraction? Why or why not? (e) What would happen to the R-R interval during: i. bradychardia (decreased heart rate)? ii. tachychardia (increased heart rate)? (f) Why donât the electrical events of the EKG align exactly in time with the corresponding mechanical events?

Question 1

A moderate increase in extracellular potassium will

		Increase heart rate due to a more negative E_K
		Decrease heart rate due to a more negative E_K
		Increase heart rate due to a less negative E_K
		Decrease heart rate due to a less negative E_K

Question 2

Apply Atropin will directly

		Decrease parasympathetic innervation and increase heart rate
		Increase parasympathetic innervation and decrease heart rate
		Decrease sympathetic innervation and increase heart rate
		Increase sympathetic innervation and decrease heart rate

Frog ECG is recorded using

		An electrical stimulator
		Three wires including the one that is connected to the hook
		A force transducer
		Three wires and a force transducer

Question 4

How would you differentiate atrial contractions fromventricular contractions?

	A.	Observe the heart beating and tap the table to label it
	B.	From the size of the contractions
	C.	Correlate it with the electrical trace, if the electrical traceis typical.
	D.	Both A and C

Question 5

In this week's experiment, _________signal(s) will be recordedto study the frog cardiac functions.

		mechanical (contractile)
		electrical (ECG)
		both mechanical and electrical
		blood flow

Question 6

In this week's experiment, the heart is hooked at the________

		either atrium or ventricle
		ventricle
		atrium

		sympathetic/increase
		parasympathetic/decrease
		Sympathetic/decrease
		parasympathetic/increase

Question 8

The frog heart can be slowed or stopped by over stimulation ofthe vagus nerve. When apply ACh to the heart, if the frog heartstop beating, you should

		Wash the heart with warm Ringers
		Apply a few drops of Isuprel
		Massage the heart
		All of the above
		Observe the trace and do nothing

Question 9

The pacemaker in the frog heart is the __________ and thepacemaker in the mammalian heart is the ________

		AV, SA node
		SV, SA node
		SA, SV node
		SA, SA node

Question 10

Which of the following statements is TRUE regarding the frogheart

		There is no autorhythmic cells found in the frog ventricle.
		Oxygenated and deoxygenated blood are mixed completely insidethe frog ventricle
		There are two atria and two ventricles.
		Deoxygenated blood flows to the frog lungs and skin.

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BIOC33H3 Lecture : Lecture 2

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