Lecture 14 Flashcards
What percentage of deaths in the UK are cardiovascular-related?
One third
Approximately 180,000 people die from cardiovascular disease (CVD) annually in the UK.
How many deaths from coronary heart disease (CHD) occur annually in the UK?
82,000
Approximately 20% of male and 12% of female deaths are attributed to CHD.
What is the average number of heartbeats per day?
100,000
This results in pumping approximately 7,000 litres of blood per day.
What is the average weight range of the human heart?
200 to 425 grams
What is the cardiac output at rest?
5 L·min⁻¹
This is calculated using stroke volume and heart rate.
What is the stroke volume of the heart?
~70 mL·beat⁻¹
What is Starling’s Law of the Heart?
Energy of contraction is a function of the length of cardiac muscle fibres
It states that the output of two pumps in series must be equal.
What are the four main heart valves?
- Pulmonary valve
- Aortic valve
- Mitral valve
- Tricuspid valve
What is the role of heart valves?
Control blood flow
Valves open and close based on the pressure within the heart chambers.
What are the phases of the cardiac cycle?
- Systole: Ventricular contraction
- Diastole: Relaxation and filling of the heart
How long does diastole last at 70 beats per minute?
About 550 ms
What is the conduction pathway for a heartbeat?
- Sinoatrial (SA) node
- Atrioventricular (AV) node
- Bundle of His
- Purkinje fibres
Which node is known as the pacemaker of the heart?
Sinoatrial (SA) node
What is the primary ion responsible for pacemaker potential?
Calcium
Sodium also plays a role, but the pacemaker potential primarily depends on calcium.
What does the ECG record?
The spread of the heartbeat
It is used to diagnose cardiac disease.
What does the QT interval represent in an ECG?
Systole
What does the RR interval represent in an ECG?
Diastole
What is the average heart rate at rest?
70 beats·min⁻¹
What is the mean arterial pressure formula?
1/3 systole + 2/3 diastole
What structure connects myocytes electrically?
Intercalated disks
What prevents tetanus in cardiac muscle?
Long refractory period
True or False: The left side of the heart operates under lower pressure than the right side.
False
The left side operates under significantly higher pressure.
What is the role of the atrioventricular (AV) node in the conduction pathway?
It provides a pause before the signal travels to the ventricles
What is the role of calcium in cardiac muscle contraction?
Activates contraction by entering from intracellular stores and extracellular fluid
