Cardiac System Flashcards
What is the conduction system simply?
Stimulation of the heart
What is the SA node?
Sino-Atrial Node
What is the AV-node?
Atrio-Ventricular Node
Put the steps of the conduction system in order
SA NODE
Impulse to left atrium
AV NODE
Bundle of His
Purkinje fibres
Where is and what does the AV node do?
Between right atria and ventricle receives signal from SA and relays to the bundle of his
Where is and what does the Bundle of His do?
Positioned in the septum, separates the signal into left and right
Where are and what do the purkinje fibres do?
Around the outside of the ventricles, they contract and spread the signal to every cell (all or none law) causes ventricular systole/ atrial diastole
What is the all or none law?
Nerves or muscle fibres react to a stimulus at any strength above the threshold the same, therefore it’ll respond completely or not at all
What is the medulla oblongata?
The cardiac control centre
What does the medulla do (neural control)?
It triggers either sympathetic or parasympathetic stimulation of the SA node
How does the medulla send parasympathetic stimulation?
Via the vagus nerve
How does the medulla send sympathetic stimulation?
Via the accelerator nerve
When would the stimulations be used?
Sympathetic - beginning of exercise to increase heart rate
Parasympathetic- end of exercise to decrease heart rate
How does the medulla know which one to use?
Chemoreceptors - Ph down acidity up = increase heart rate (via sympathetic) vice versa
Baroreceptors - detect blood pressure = if it goes up then sympathetic vice versa
Proprioceptors- the more change in muscular activity (lengthening) detected the more HR to power contractions with oxygenated blood (sympathetic) vice versa
What are the three controls and which one does sympathetic and parasympathetic fit into?
Neural control
And the other two are hormonal and intrinsic
What is hormonal control?
Release of adrenaline -> SA node stimulations greater contraction
What is intrinsic control?
Heart detects changes (temperature and contractility, more venous return -> heart stretches)
What are the three cardiac values and volumes?
Stroke Volume - 70ml
Heart rate - 70 bpm
Cardiac Output 4.9L/min
How do you work out Cardiac output?
SV x HR = Cardiac Output
What is SV?
The volume of blood leaving the left ventricle per minute
What is HR?
Amount of heart beats per minute
What are the approximate values for a 20 year old during maximal exercise?
140ml x 200bpm = 28L/min
100+ml usually
What are the three phases of the Cardiac Cycle for the atria?
Atrial diastole (atria fill)
Systole (atria empty ventricles fill)
Diastole (atria begin to fill again ventricles emptying)
What are the three phases of the Cardiac Cycle for the venticles?
End of systole (ventricles emptying, atria filling)
Diastole (atria empty, ventricles fill)
Systole (ventricles emptying atria begins to fill again)
