After reading the blood circulatory system post, we should know how the heart works and which side pumps deoxygenated or oxygenated blood. In this IBDP Biology blog post, we will know:
- The control of heart beat
- Factors that influence the rate of heartbeat
Control of Heartbeat
The heart is made of cardiac muscle that beats by myogenic muscle contraction
This is regulated by SA node (pacemaker) controls the rate of the heart beat
SA node is made of myocytes (specialized muscle cells)
Excitation Wave:
1) Starts in the sinoatrial node in the top right concer of wall the right atrium
2) Spreads across to the right and left atrium causing atria to contract
3) Reaches atrioventricular node at the top of the septum (muscle in the middle speparating sides)
4) Carried by nerves down the septum to the ventricles and the base of the heart causing ventricles to contract
Factors that increase/decrease heart beat
Medulla (part of brain stem) which is connected to the spinal cord
Contains the nerve centres for respitory and cardiac systems and vomiting
Medulla: montiors the concentration of CO2 in the blood
When CO2 concentrations are too high Medulla sends a nerve impulse down the cardiac nerve
This nerve impulse acts on the SA node making the heart beat faster
When CO2 concentrations are too low Medulla sends a nerve impulse down the vagus nerve
This nerve impulse acts on the SA node making the heat beat slower
Adrenaline: Example of a hormone which are chemical messengers that travel in the blood
Adrenaline causes the SA node to fire more frequently during periods of excitement or stress
This causes the heart to beat faster to get sufficient energy and oxygen to the muscles this is a part of the "fight or flight" response
That's all! Well done!
Drafted by Venetia (Biology)
References:
- https://www.google.com/url?sa=i&url=http%3A%2F%2Fksuweb.kennesaw.edu%2F~jdirnber%2FBio2108%2FLecture%2FLecPhysio%2FPhysioCirculatory.html&psig=AOvVaw3bDdUl3Ey8vwPYZt46c4LK&ust=1625664797358000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCIC9iLnHzvECFQAAAAAdAAAAABAj
- https://www.google.com/url?sa=i&url=http%3A%2F%2Fib.bioninja.com.au%2Fstandard-level%2Ftopic-6-human-physiology%2F62-the-blood-system%2Fheart-rate.html&psig=AOvVaw0f9dx9qFFUlSyzYB857e5g&ust=1625664897874000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCPDJqunHzvECFQAAAAAdAAAAABAD