Heart🫀 Flashcards
What is the heart?
Organ/muscles that pumps blood to all parts of the body
What controls the heart rate ?
Controlled by a group of pacemaker cells known as the Sinoatrial node (SAN), located in the right atrium.
How do SAN determine the heart rate?
SAN has an automatic rhythm of stimulation that determines the beat of the heart.
Can you explain in more depth how the SAN control heart rate?
-The SAN generates a wave of electrical activity that spreads across both atria - atria contract.
➔ A layer of non-conductive tissue prevents the wave crossing to the ventricles.
➔ Wave passes through a second group of cells called the atrioventricular node (AVN).
What the Avn and it is function?
conveys the electrical wave down between the ventricles through specialised muscle fibres called the bundle of His.
What is bundle of his?
conducts the wave through the septum to the base of the ventricles into the Purkinje fibres.
Wave is released to fibres, causing ventricles to contract.
What is cardiac cycle?and what is 2 main phases?
The cardiac cycle is a series of phases that occur each time the heart beats.
It occurs in two main phases:
◆ Diastole - relaxation of the heart
◆ Systole - contraction
What happens in diastole-relaxation?
—The atrial and ventricular walls are relaxed, allowing the pressure in the ventricles to decrease.
➔The ventricular pressure is also less than the pressure in the aorta/pulmonary artery, causing the semi-lunar valves to close - ‘dub’ sound.
➔ As blood returns to the atria from the vena cava and pulmonary vein.
➔ As the atria fill, the pressure in them rises.
➔ When the atrial pressure is greater than the
ventricular pressure, the atrioventricular valves open.
What happens in systole-contraction?
Systole - Contraction
➔Atrial Systole
➔The atria contract first simultaneously.
➔ This forces the remaining blood in the atria to be
forced down into the ventricles.
Ventricular Systole
➔ The ventricles contract after a short delay
➔This increases the pressure in them, forcing the
atrioventricular valves to close - ‘lub’ sound.
The other systole contraction?
Ventricular Systole
➔ The ventricles contract after a short delay
➔This increases the pressure in them, forcing the
atrioventricular valves to close - ‘lub’ sound.
➔ With the valves closed, the pressure increases further, causing the semi-lunar valves to open.
➔The blood is forced out into the arteries once the ventricular pressure exceeds the pressure in the arteries.
Tell me about the structure of the heart.
➔ The atrium are thin walled and elastic, stretching as it collects blood.
➔ The ventricle has a thicker muscular wall that allows it to contract strongly to pump blood long distances.
➔ The heart is a double pump:
• Left side pumps oxygenated blood to body
• Right side pumps deoxygenated blood to lungs
➔ Each side is separated by the septum, ensuring that the blood is unable to mix.
➔ The double pump is important as blood is returned to the heart to ensure the pressure is maintained to reach the rest of the body.
➔ The left ventricle has a thicker muscular wall to provide a stronger contraction to ensure enough pressure for the blood to reach the whole body.
What are heart valves and the 2 types?
➔ Between the atrium and ventricle are valves to prevent the backflow of blood into the atria when the ventricles contract.
1-Left atrioventricular (bicuspid) valve
2-Right atrioventricular (tricuspid) valve
What are semi-lunar valves?
Between the ventricles and the vessels that carry blood away from the heart are semi-lunar valves.
State the blood vessels,what they carry,from where to where?
Aorta
Oxygenated
Left ventricle
Body
Vena cava
Deoxygenated
Body
Right atrium
Pulmonary artery
Deoxygenated
Right ventricle
Lungs
Pulmonary vein
Oxygenated
Lungs
Left atrium
What are Coronary arteries?and what leads to blocked arteries?
➔ The heart is supplied by its own coronary arteries, which branch off the aorta .
➔ Blockages in these arteries leads to myocardial infarction as an area of the heart is deprived of oxygen and so these respiring cells die.
