Cardiovascular system: Initiation and regulation Flashcards
Where does the action potential start from?
The sinoatrial node
What action potential is produced by the SA node?
~1.5mV
How does the sinoatrial node control its depolarise?
It has an unstable resting potential
How do the myocytes of the atria, ventricle and conduction system have different action potentials from myocytes?
They all have the same initial depolarisation, however mysocytes in the heart have a plateau phase of depolarisation
What causes the plateau phase of depolarisation?
The inward movement of calcium ions
What does the calcium influx ensure?
It ensures that the AP lasts almost as long as the contract of the cell
What does the long plateau phase ensure?
The unidirectional excitation of the myocardium (i.e. muscles of the heart)
When does re-polarisation of the myocardial cells occur?
When the voltage dependent calcium channels inactivate
Label the diagram, what is this showing?
Showing an electrocardiogram (i.e. ECG)
What does an ECG show?
The electrical activity of the heart from the front (FYI electrical activity is different at different orientations)
What does the relative size of the ECG waves indicate about the heart?
The relative size of the heart
What creates the P wave? What does it cause?
the depolarisation of the atrium causes atrial systole
When there is a plateau in the ECG, what does this indicate?
Diastole of the entire heart (if there is any contraction in the heart then it causes an AP to be produced)
What creates the QRS complex? What does it cause?
The depolarisation of the ventricle causes ventricular systole
What causes the T wave?
The depolarisation of the ventricular myocytes
What part of the brain can influence the heart rate?
The cardiovascular centre
What parts of the brain connect to the cardiovascular system
Higher brain centres (i.e. cerebral cortex, limbic system, hypothalamus) and sensory receptors (proprioceptors, chemoreceptors and baroreceptors)
In what situations can the higher brain centres influence increased heart rate without exercise?
Stress, anxiety etc.
What do the proprioceptors monitor?
Monitor movement
Label the diagram, what is it showing?
It is showing how the heart delivers and receives information to and from the brain
What do the chemoreceptors monitor?
Monitor blood chemistry
What do the baroreceptors monitor?
Monitor blood pressure
What are the output nerves from the cardiovascular centre?
Sympathetic nerve and parasympathetic nerve
What does the sympathetic nerve do to the heart?
It cause an increase in the rate of spontaneous depolarisation in the SA and AV node increasing heart rate and it increase the contractility of the ventricles and atria
How is the sympathetic nerve able to cause its increase in heart activity?
It increases the amount of norepinephrine actin on ß1 receptors
What does the parasympathetic nerve do to the heart?
Decreases the rate of spontaneous depolarisation in the SA and AV node decreasing heart rate
How does the parasympathetic nerve cause the decrease in heart activity?
It lengthen the plateau period of depolarisation
What nerve runs into the heart from the cardiovascular centre?
The vagus nerve (contains the parasympathetic system FYI)
Where does the vagus nerve run through the body? What kind of nervous system is transferred in the vagus nerve?
Runs down next to the artery (not in the spinal cord)
The parasympathetic system
What is information coming into and out of the CNS called?
Into = Afferent information
Out = Efferent information
How is the sympathetic nerve connected to the heart?
It is connected to the heart b the cardiac accelerator nerve which runs through the spinal cord
