Autotomic nervous system and the heart Flashcards
(14 cards)
What do sympathetic (accelerator) nerves supply in the heart?
Specific areas of the heart’s electrical system, atrial muscle, and ventricular myocardium
How do sympathetic nerves transmit commands?
By releasing norepinephrine
What effect does an accelerated heart rate have on the cardiac cycle?
Shortens all phases of the cardiac cycle
What happens if the ventricles do not fill completely?
- Less blood travels to the coronary arteries
- Less blood is pumped out of the ventricles
- CO decreases
- Signs of myocardial ischemia may appear
What is ischemia?
Anoxia caused by diminished blood flow to tissue, usually because of narrowing or occlusion of an artery
Which nerve fibers supply the SA node, atrial muscle, and AV junction of the heart?
Parasympathetic (inhibitory) nerve fibers via the vagus nerve
What is the primary function of parasympathetic nerve fibers in the heart?
Decreasing the heart rate
What are some ways the vagus nerve can be stimulated?
- Increasing pressure on the carotid sinus
- Straining or forced exhalation against a closed glottis (Valsalva maneuver)
- Distention of a hollow organ
What type of message travels down the vagus nerve to the SA node of the heart?
An electrical impulse
This impulse is critical for signaling heart activity.
What neurotransmitter is released at the SA node when stimulated by the vagus nerve?
Acetylcholine (ACh)
ACh plays a key role in regulating heart rate.
What effect does acetylcholine (ACh) have on the heart rate?
It signals the heart rate to decelerate
This process is part of the parasympathetic response.
Which node does acetylcholine (ACh) travel to after the SA node?
The AV node
This ensures the heart’s electrical signals are coordinated.
What enzyme is responsible for escorting acetylcholine (ACh) away?
Acetylcholinesterase (AChE)
AChE breaks down ACh to terminate its action.
What is atropine commonly used as?
A parasympathetic blocker
Atropine can increase heart rate by inhibiting the effects of ACh.
