BIOC34H3 Lecture Notes - Vagus Nerve, Pilocarpine, Digitalis

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redcod59

7 Jul 2012

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Write a brief (no more than 100 words) introduction that describes the goal of the experiments performed in this lab. (2 marks) Heart rate is the number of heart beats per minute. The heart rate is based on the number of contractions of the ventricles in a certain period of time. Throughout this experiment, the frog heart will be put under various circumstances in order to see their effects on the heart rate. These circumstances include: electrical stimulations at different locations of one wave, constant electrical stimulation for a period of time, and the effects of various drugs, hormones and as well as temperature. The heart rate is expected to change accordingly in each situation due to underlying physiological mechanisms. Write a brief (no more than 300 words) methods section that describes the experiments performed in this lab. Describe the experimental preparation and the various manipulations that were performed. (3 marks)

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.

Effects of electrical stimulation of ventricle at various time points during a Frog cardiac cycle:

1. at which time points of the cardiac cycle can an electrical stimulation induce extra systole?

2. explain how the extra systole can appear during this manipulation in terms of the refractory period of the ventricular action potential.

3. Stannius ligature experiment: what will happen to the beating rate of the two atria (right and left) versus the ventricle during the ligature?)

4. explain how these changes occur in the beating rate during the stannius ligature.

5. now the heart is completely devoid of neural or hormonal input. What will happen to the beating rate of all three chambers? What about the chamberâs beating rate when they are surgically separated? explain possible mechanisms for the changes in the beating rate for each chamber.)

6. describe the effects of the following drugs on the heart rate and the force of ventricular contraction:
acetylcholine(1%), atropine (0.5%), Pilocarpine (2.5%), nicotine (0.2%), Epinephrine (0.1%), Isoproterenol (0.1%)

also, explain how each of the 6 chemicals above either mimic or inhibit the cardiac function

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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BIOC34H3 Lecture Notes - Vagus Nerve, Pilocarpine, Digitalis

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