Control Of Heart Rate Flashcards
What is the autonomic nervous system?
A division of the nervous system that controls involuntary movement of cardiac/smooth muscles, glands
What is the autonomic nervous system divided into?
Sympathetic nervous system
Parasympathetic nervous system
Both include various neurones that control involuntary action of muscles and glands that works antagonistically against each other
Parasympathetic nervous system
Involving rest
Sympathetic nervous system
Involving fight/flight responses
What type of muscle is the heart composed of?
Cardiac muscle
Myogenic
Muscle contraction is initiated by the muscle itself instead of the neurone
Cardiac muscle is….
Myogenic
What is the main cause behind cardiac muscle contraction in the cardiac cycle?
A wave of electrical activity
What triggers the atria to contract in atrial systole?
SAN sends a wave of electrical activity across atria causing atrial contraction
What carries the wave of electrical activity across the atria?
Special cardiac muscle tissue
what prevents wave of electrical activity reaching ventricle?
Non conducting tissues between atria and ventricles stops wave of electrical activity passing down outer walls of ventricles
Why do we want to prevent wave of electrical activity immediately passing to ventricles?
Because we need a delay before the ventricles contract so blood can fill atria and Atrioventricular valves close
Prevents backflow of blood in ventricles
Where in the atria muscles does the wave of electrical activity join together?
In the Atrioventricular node (AVN)
What happens before AVN sends a wave of electrical activity?
AVN delays
Where does AVN send a wave of electrical activity down?
Down the bundle of His- down the apex of the heart
followed y purkyne tissue
What is the Bundle of His composed of
Purkyne tissue
How does the Bundle of His branch off?
Into individual Purkyne tissue that crawl up the sides of the ventricle walls
Wave of electrical activity up the purkyne tissue?
Causes ventricles to contract from the base up
What part of the brain controls how fast the heart rate is?
The medulla
Why would we need to increase heart rate?
During exercise to deliver oxygen and glucose faster to respiring muscles
Faster heart rate is a problem because,,,,
Leads to too high blood pressure which damages blood vessels
Lower heart rate is a problem because,,,,,,,,,,
Blood moves too slowly so not enough oxygen is delivered to tissues
Main theory on how the medulla can be stimulated to recognise when a faster heart rate is required?
By increasingaerobic respiration so increasing CO2 conc in blood so more dissolving in water in blood to produce a more acidic solution
To stimulate chemoreceptors, inverse for if a lower heart rate is required
What else can controlling heart rate lead to?
Changes in blood pressure
High heart rate leads to
High blood pressure since more blood is pumped per unit time
Low heart leads to
Low blood pressure since less blood is pumped per unit time
How does increase in respiration lead to increase in heart rate
Chemoreceptors in aorta detect rise in CO2 of blood
chemoreceptors send more impulses to medulla
Medulla sends more impulses to SAN;
By sympathetic neurones
