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