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Human Systems > Frog Heart Stimulation > Flashcards

Frog Heart Stimulation Flashcards

1
Q

Explain why the heart continues to beat after destruction of the spinal cord.

A

Because the heart depends on respiratory movements, not the central nervous system. The heart is kept in Ringer’s solution which contains electrolytes.

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2
Q

Label this frog heart diagram.

A
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3
Q

Where is the ‘pacemaker’ located in the frog heart and human heart?

A

Frog heart - Sinus Venosus.

Human heart - SAN.

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4
Q

What three effects does adrenaline have on heart rate?

A
  1. Increases heart rate.
  2. Increases atrial force of contraction.
  3. Increases ventricular force of contraction.
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5
Q

What effect does adrenaline have on the pacemaker of the heart?

A

It increases the activity of the pacemaker.

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6
Q

What receptors on cardiac muscles does adrenaline act upon?

A

β1 – adrenoceptors.

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7
Q

How does Acetylcholine (ACh) affect heart rate and why?

A

It slows down heart rate because it stimulates parasympathetic nerve fibres and acts upon the sinus venosus. It also slows down atrial contraction, but ventricular contraction remains the same.

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8
Q

What receptors on cardiac muscles does Acetylcholine (ACh) act upon?

A

Muscarinic acetylcholine receptors.

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9
Q

What enzyme does Physostigmine inhibit?

A

Acetylcholinesterase.

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10
Q

What effect does Physostigmine have on the heart when it works independently?

A

It decreases the heart rate very slightly.

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11
Q

What effect does Physostigmine and Acetylcholine have on the heart when working together?

A

The heart rate decreases significantly.

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12
Q

Atropine is a competitve inhibitor for what receptor?

A

The Acetylcholine muscarinic acetylcholine receptor.

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13
Q

What effect does Atropine have on the heart when it works independently?

A

It increases heart rate slighlty.

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14
Q

What effect does Atropine and Acetylcholine have on the heart when working together?

A

It brings heart rate to a normal rate.

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15
Q

What effect does temperature have on the heart? Why?

A

As temperature increases, heart rate increases. This is due to enzymes having higher kinetic energy.

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16
Q

Define poikilothermic.

A

They are cold blooded organisms whose temperature varies with the temperature of its environment.

17
Q

Define refractory period.

A

The period during which a nerve or muscle is incapable of responding to stimulation, especially immediately following a previous stimulation.

18
Q

Define absolute refractory period.

A

There is a total inability to respond.

19
Q

Define relative refractory period.

A

There is a repsonse to very large stimuli.

20
Q

What effect does electrical conduction have during ventricular contraction?

A

There is no effect as the heart is in a refractory period.

21
Q

What effect does electrical conduction have during ventricular relaxation?

A

Ventricular contraction will take place once again.

22
Q

Define extra systole.

A

Where another ventricular contraction takes place in what is meant to be ventricular relaxation.

23
Q

Define compensatory pause.

A

A pause in the heartbeat following an extra systole that is long enough to compensate for the prematurity of the extra systole.

24
Q

Out of skeletal muscle and cardiac muscle, which has the longest refractory period?

A

Cardiac muscle.

25
Q

Stannius Ligature I is the ligature used between what parts of the frog heart? What is its purpose and what does it indicate?

A

The sinus venosus and atria. It blocks conduction between them and indicates the pacemaker lies in the sinus venosus.

26
Q

Stannius Ligature II is the ligature used between what parts of the frog heart? What is its purpose?

A

The atria and ventricle. It blocks conduction between them.

27
Q

When Stannius I is attached, what effect does it have on the heart?

A

It increases time between atrial contractions; thus slowing down heart rate.

28
Q

When Stannius II is attached, what effect does it have on the heart?

A

It stops the ventricles from contracting; however, the sinus venosus and atria continue to contract.

29
Q

Do the different chambers of the frog heart have their own inherent rhythms? If so, which ones?

A

Yes, the sinus venosus and the atria.

30
Q

The maximum rate of contraction is governed by the length of the refractory period. True or false?

A

True.

31
Q

What does double-pithing involve?

A

Destroying the brain and spinal cord so that it denerves the heart.

32
Q

What chemical makes the heart beat the slowest?

A

Acetylcholine and Physotigmine together.

33
Q

What chemical makes the heart beat the fastest?

A

Adrenaline.

Human Systems (17 decks)

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