The heart Flashcards
Define the cardiac cycle
the sequence of events that occur within one full beat of the heart.
What is systole?
the contraction stage of the cardiac cycle
What is diastole?
the relaxation stage of the cardiac cycle
What does myogenic mean?
means muscle can contract and relax without receiving signals from the nervous system example - cardiac muscle
Describe the cardiac cycle stage 1
The sinoatrial node (SAN) sends out regular waves of electrical activity to the left & right atrial wall causing contraction.
Describe the cardiac cycle stage 2
The electrical waves are then passed onto the atrioventricular node (AVN), then to the bundle of His, with a slight delay.
Describe the cardiac cycle stage 3
The bundle of His splits into the Purkynge tissue, causing contraction of the left & right ventricles from the bottom up.
The rate at which the SAN fires is controlled …
unconsciously by the medulla oblongata in the autonomic nervous system
Heart response to High blood pressure, High blood O2, pH or low CO2
Medulla sends impulses along parasympathetic neurones, using acetylcholine to reduce the heart rate
Heart response to low blood pressure, High blood O2, pH or low CO2
Medulla sends impulses along sympathetic neurones, using noradrenaline to increase the heart rate
What receptor notices high or low blood pressure?
Baroreceptors in the aorta & carotid arteries
What receptor notices high or low blood O2, pH or high CO2?
Chemoreceptors in the aorta, carotid arteries & medulla
What do ECGs do?
detect the electrical signals through the skin
Features of an ECG
P wave shows atrial systole QRS complex shows ventricular contraction T wave shows diastole
Slow heart rate is called …
Bradycardia
