The heart Flashcards
(15 cards)
What does myogenic mean?
Beats with its own rhythm
What is the sinoatrial node (SAN)?
A patch of modified muscle cells in the wall of the right atrium
What does the SAN do?
Produces regular bursts of electrical impulse (waves of depolarisation) that spread through the walls of the atria, causing them to contract simultaneously
Why do the impulses from the SAN not pass directly to the ventricles?
As there is a band of non-conducting tissue separating the atria from the ventricles, but they reach the AVN
Where do the impulses travel after the AVN?
Through the Purkyne tissue in the Bundle of His, causing the ventricles to contract
What is the autonomic nervous system?
Part of the peripheral nervous system that regulates involuntary body functions
What are the 2 divisions of the autonomic nervous system?
- Sympathetic nervous system
2. Parasympathetic nervous system
What does the sympathetic system generally do?
Generally stimulates effectors and therefore speeds up activity, preparing for the fight or flight response
What does the parasympathetic system generally do?
Generally inhibits effectors and therefore slows down activity, conserving energy and replenishing reserves
What part of the brain controls the heart rate?
Cardiac centre of the medulla oblongata
What are the 2 cardiac centres of the medulla oblongata?
- Cardioacceleratory centre
2. Cardioinhibitory centre
Which centre speeds up the heart rate?
The cardioacceleratory centre
How does the cardioacceleratory centre increase the heart rate?
Sends a higher frequency of impulses via the sympathetic nervous system to the SAN causing the frequency of impulses from the SAN to increase
Which centre slows down the heart rate?
The cardioinhibitory centre
How does the cardioinhibitory centre decrease the heart rate?
Sends a higher frequency of impulses via the parasympathetic nervous system to the SAN causing the frequency of impulses from the SAN to decrease
