Exchange and transport - HEART STRUCTURE/CARDIAC CYCLE Flashcards
Describe the route of deoxygenated blood flow through the heart
- Vena cava
- Into the right atrium
- Tricuspid valve
- Right ventricle
- Pulmonary artery to lungs - becomes oxygenated.
Describe the route of oxygenated blood flow through the heart
- Pulmonary veins to heart
- Left atrium
- Bicuspid valve
- Left ventricle
- Aorta
Why is the left ventricular wall thicker?
To maintain a higher pressure as blood leaves the heart via the aorta to the whole body
What is the function of the coronary arteries and veins?
To supply the cardiac muscle cells with oxygen for respiration (ATP for muscle contraction) and remove waste products
What is the function of the papillary muscles and tendinous cords (tendons)?
(Tendons attach to the valves, papillary muscles attach to the tendons)
- Prevent the inversion and prolapse of the valves
- Keep the valves open correctly, to keep blood flowing in one direction
What is the function of the pericardium?
- Tissue that protects the heart from infection and other sources of disease
- Holds the heart in the chest wall
Suggest why it is important to prevent mixing of the blood in the two sides of the heart
- Prevent the mixing of oxygenated and deoxygenated blood
- Reduces concentration gradient - inhibits gas exchange at tissues
Why are valves important?
They prevent the unwanted backflow of blood
What are valves made of?
- Many flaps
- Made of tough but flexible, fibrous tissue
What causes valves to open?
- When the pressure is greater on the convex side
- Valves move apart to let blood through
What causes valves to close?
- When pressure is greater on the concave side
- Blood collects in the cusp
- Valves push together to prevent blood flow
In which direction does blood move? (Hint: pressure)
From high blood pressure to low blood pressure
What causes the ‘lub’ sound?
- Atrioventricular valves shutting
- Tricuspid/bicuspid valves
What causes the ‘dub’ sound?
- Semilunar valves shutting
What is atrial systole?
Atrial contraction
What is ventricular systole?
Ventricular contraction
What is diastole?
Filling of the atria with blood
Why is cardiac muscle described as being myogenic?
Can contract and relax without nervous external stimulation
What is the P wave?
- Impulses spreading across the atria
- Atrial systole
What is the QRS complex?
- Impulses spreading up through ventricles
- Ventricular systole
What is the T wave?
Recovery of ventricles during diastole
What is the function of the sinoatrial node?
- Pacemaker of the heart
- Generates electrical activity starting a heartbeat
What is the function of the atrioventricular node?
Delays spreading of electrical signal to allow the atria to fully contract and ventricles to fully fill
What is the function of the Bundle of His?
Electrical signal passes through to the bottom of the septum
What is the function of the Purkinje fibres?
Electrical impulse makes ventricles contract from the base up
What is the purpose of the autonomic nervous system?
Regulates involuntary physiologic processes such as:
- Heart rate
- Blood pressure
- Respiration
Where are chemoreceptors found?
In the carotid arteries
Describe the process of increasing heart rate if increased CO2 is detected in blood (5 marks)
- Blood pH lowered
- Chemoreceptors increase frequency of impulses to medulla oblongata
- Higher frequency of impulses to SA node via sympathetic nervous system
- SAN increases heart rate//increased blood flow
Describe the process occurring in the heart when blood pressure is higher than normal
- Pressure receptors transmit more nerve impulses to medulla oblongata
- Sends impulses via parasympathetic nervous system to SAN
- Decrease in heart rate
Describe the process occurring in the heart when blood pressure is lower than normal
- Pressure receptors transmit more impulses to medulla oblongata
- Sends impulses via sympathetic nervous system to SAN
- Increase in heart rate
