Cardiac cycle Flashcards
What is diastole?
Relaxation, atria + ventricles fill with blood, vol of blood increases
What is systole?
Contraction, forces blood out of lungs, pressure increases, vol of blood decreases
Explain what happens during atrial systole:
- Atrium contracts
- AV vales open due to pressure being higher in atrium
What is AV valves?
Atrioventricular valves
What is ventricular systole?
- Ventricles contract
- AV valves close + SL valves open due to pressure being higher in ventricles than atrium
What are SL valves?
Semilunar valves
Explain what happens in diastole:
- Heart relaxes
- Atrium + ventricles fill with blood
- AVvalves open due to passive flow of blood due to lower pressure
- SL valves close
Explain what happens in the control of the cardiac cycle (before pause):
- Starts in sino-atrial node (SAN)
- Muscles contract when a signal called an action potential arrives. AP moves over atrium
- AP heads towards ventricles but stopped by band of non-conducting fibrous tissues
- Pause
Explain what happens in control of the cardiac cycle (after pause):
- AP directed through atrio-ventricular node (AVN) down the septum
- AP travels via the budle of his (made up of conductive fibres called purkyne fibres) to the apex of heart
- Bundle of his separates into 2 and purkyne fibres spread out through walls of ventricles
Why is the heart capable of beating without stimulation from the nervous system?
Has a myogenic system (i.e. has an ‘in built’ mechanism for initiating contraction of muscles)
What is intrinsic rhythmicity?
Ability of cells to beat together. Cells begin to beat in the embryo
What is the cardiovascular centre?
In the brain. If body requirements change, heart needs to soeed up or slow down
Controlled by nerves
Is AP a nerve impulse?
Yes
What is depolarisation?
Switching charge in nerve impulse, causes muscles to contract
What is the cardiac output?
The volume of blood pumped from each ventricle per min
How do you work out cardiac output?
Cardiac output (ml/min) = Stroke volume (ml/beat) x heart rate (beats/min)
If exercising, values increase since more blood + bests per min
