Activity 2: Examining the Effect of Vagus Nerve Stimulation

Which branch is more active @ rest?

parasympath

What are the 2 branches of the autonomic nervous system?

1. Sympathetic (fight or flight) 2. Parasympathetic (resting & digesting)

W/out the parasympathetic & sympathetic stimulation, the SA node generates AP over

100 times per min

What are 2 ways that the heart can overcome excessive vagal stimulation?

By using: 1. sympathetic reflexes 2. Purkinjie fibers

Which nerve carries signals to the heart?

Vagus nerve (cranial nerve X)

What is the sinoatrial node?

a cluster of autorhythmic cardiac cells found in the right atrial wall of the human heart.

Stimulation of the parasympathetic nervous system will:

decrease the heart rate w/out directly changing the force of contraction

Stimulation of the sympathetic nervous system will:

increase the rate & force of heart contractions

The vagus nerve carries:

signals that decrease the heart rate

Extreme vagus nerve stimulation affects the heart by:

stopping the heart completely

Vagal escape probably involves

sympathetic reflexes

What determines the heart rate and is considered the "pacemaker"

the SA node

What will happen if there is too much stimulation of the vagus nerve?

the heart will stop beating and after a short time, the ventricles will begin to beat again

The resting heart rate is ~70 beats/min which suggests that:

the parasympathetic nervous system has more control over the heart rate

Parasympathetic stimulation reaches the heart through:

vagus nerves

the sympathetic nervous system becomes more active:

when needed (during dire situations or excersie)

vagal escape?

when the heart resumes beating. This can be the result of sympathetic reflexes or inhibition of a rhythm by Purkinje fibers