Cardiac Output and Regulation of Function Flashcards
Define cardiac output
The rate at which a ventricle pumps blood
Define stroke volume
The volume of blood a ventricle pumps per contraction
CO = HR
Define heart rate
The number of contractions of a ventricle per minute = CO / SV
What is the autonomic nervous system split into
Divided into sympathetic and parasympathetic nervous system
Describe the sympathetic nervous system
- Only takes over in ‘fight or flight’ situations
- Thoracolumbar division of the autonomic nervous system - has paraspinal ganglia
- Neurotransmitter is noradrenaline
- AP, HR + CO increase
Describe the parasympathetic nervous system
- Regulates body’s normal resting state
- Craniosacral division of the autonomic nervous system
- Ganglia are present in and around the viscera
- Neurotransmitter is acetylcholine
- AP, HR + CO decrease
What effect does adrenaline have on heart rate
Stimulates more APs at the SAN, increases HR + velocities of APs
What effect do thyroid hormones, glucagon and insulin have on heart rate
- Increase the force of contraction
- Glucagon promotes an increase in HR
What is intrinsic control
Regulation of the heart by factors originating in the heart
What is extrinsic control
Regulation of the heart by factors outside of the heart
What is Starlings Law
When the rate of blood flow into the heart from the veins changes, the heart automatically adjusts its output to match the inflow
What is pre-load
Amount of blood that the heart receives and has to pump out during the next contraction
What is after-load
Resistance that the heart encounters as it works to push blood out into the arteries.
What is pre-load determined by
- Filling time - dependant on heart-rate
- Atrial pressure - dependent on venous return & force of atrial contraction
