Transport in Animals: The Heart Flashcards
(34 cards)
What is the function of the atria in the heart?
The atria act as thin-walled collection chambers, receiving blood before passing it to the ventricles.
Why do the atria have thin walls?
Because they only need to push blood a short distance into the ventricles.
Why is it important that the heart has two atria and two ventricles?
It allows for the separation of oxygenated and deoxygenated blood, maintaining efficient circulation.
What type of muscle makes up the heart?
The heart consists mainly of cardiac muscle, which contracts rhythmically without tiring.
What does myogenic contraction mean?
It means the heart initiates its own electrical impulses without requiring signals from the nervous or hormonal systems.
Why can the heart continue beating even after being removed from the body?
Because it has myogenic contraction, meaning it generates its own electrical impulses independently.
What structure in the heart initiates electrical impulses?
The Sinoatrial Node (SAN), located in the right atrium, acts as the pacemaker of the heart.
Why does cardiac muscle never tire?
Because it has a high density of mitochondria, ensuring a constant supply of ATP for contraction.
How does the heart receive oxygen and nutrients?
Through a rich blood supply from the coronary arteries, which deliver oxygenated blood to cardiac muscle.
What happens if the coronary arteries become blocked?
It reduces oxygen supply to the heart, leading to angina or a heart attack (myocardial infarction).
What is the function of the sinoatrial node (SAN)?
The SAN acts as the heart’s pacemaker, initiating a wave of electrical excitation that spreads across the atria, causing them to contract.
Why doesn’t the electrical impulse from the SAN pass directly to the ventricles?
Because there is non-conductive connective tissue between the atria and ventricles, preventing direct transmission.
Where does the impulse go after the SAN?
It reaches the atrioventricular node (AVN), located in the lower part of the right atrium.
Where does the impulse go after the SAN?
Why does the AVN introduce a delay?
The AVN delays transmission to ensure the atria fully contract before the ventricles, allowing efficient blood flow.
How does the impulse travel from the AVN to the ventricles?
➡️ The AVN sends the impulse down the Bundle of His, which runs through the septum to the apex of the heart.
What happens after the impulse reaches the apex?
The impulse spreads upward via the Purkinje fibres, causing the ventricles to contract from the bottom upwards.
Why is it important that the ventricles contract from the apex upwards?
his ensures blood is efficiently pushed up into the aorta and pulmonary artery, emptying the ventricles.
What is the correct order of electrical impulse transmission in the heart?
SAN → Atria contract → AVN (delay) → Bundle of His → Apex → Purkinje fibres → Ventricles contract
What is an ECG?
A trace of voltage changes in the heart, detected by electrodes on the skin, showing the heart’s electrical activity during a cardiac cycle.
What does the P wave represent?
Depolarisation of the atria due to electrical excitation from the sinoatrial node (SAN), causing atrial contraction.
Why is the P wave smaller than the QRS complex?
The atria have less muscle than the ventricles, so the electrical activity produces a smaller wave.
What is the PR interval?
The time between the start of the P wave and the start of the QRS complex.
What occurs during the PR Interval?
The time taken for the impulse to travel from the atria to the ventricles via the atrioventricular node (AVN).
What does the QRS complex represent?
Depolarisation and contraction of the ventricles.
