Circulation Of Blood Flashcards
What is the main function of the cardiovascular system?
To maintain an adaptable supply of blood to tissues to supply nutrients and signalling molecules and remove waste products.
This function is achieved through generating pressure differentials across tissues to enable capillary exchange.
What two major factors determine the flow of blood from A to B?
- Pressure difference between A and B (ΔP)
- Resistance to flow (R)
F= ΔP
——
R
Where higher pressure = faster flow
What is vascular resistance?
The opposition to blood flow due to friction between blood and vessel walls.
How does vessel radius affect blood flow?
Flow is proportional to the r^4 where r= vessel radius
small changes in arteriole diameter dramatically affect tissue blood flow.
What is the pressure gradient generated by the heart?
The contraction of the heart muscles generates a pressure gradient that moves blood through the circulation from heart → tissues → heart. (High to low pressure)
Elastic arteries (i.e aorta) act as “pressure reservoirs” to maintain blood flow during diastole
What are the systolic and diastolic pressures in a typical blood pressure reading?
Systolic Pressure: 120 mmHg
Diastolic Pressure: 70 mmHg (this is the minimum pressure in the artery)
What does the cardiac cycle consist of?
Dictates blood flow through the heart
A series of electrical and mechanical events determining blood flow through the heart and into the circulation during one heartbeat.
What is the role of the sinoatrial (SA) node in the cardiac conduction system?
It acts as the pacemaker, initiating the electrical impulses that trigger heart contractions.
What happens during isovolumic contraction?
Ventricles contract, AV valves close, and LV pressure rises without a change in volume.
True or False: The left side of the heart generates more pressure than the right side.
True
What is mean arterial pressure (MAP) and how is it calculated?
MAP = DBP + 1/3 Pulse pressure; calculated using diastolic blood pressure and pulse pressure.
What occurs during ventricular diastole?
Ventricles relax, aortic valve closes, and blood fills the ventricles.
What is the primary purpose of elastic arteries in the cardiovascular system?
To act as pressure reservoirs to maintain blood flow during diastole.
List the components of the cardiovascular system.
- Heart
- Blood Vessels
- Brain
- Adrenal Glands
- Kidney
What is haemodynamics?
The physics of blood flow: The flow (F) of blood from A to B is determined by 2 major factors
What factors affect the rate of blood flow?
- Pressure
- Vessel radius
- Vessel length
- Viscosity
- Vascular resistance
Name the vessels from the fastest to slowest rate of flow
- Elastic artery
- Muscular artery
- Arteriole
- Capillary
- Venule
- Vein
- Vena cava
How are blood pressure values measured?
Arterial pressure gradient, measured at brachial artery
Mean Arteriole pressure (MAP) = Diastolic blood pressure (DBP) + 1/3 pulse pressure (difference between systolic and diastolic pressure)
What is the cardiac conduction system?
A system that rapidly carries electrical impulses across the heart, initiating contraction/relaxation events
Describe the electrical events of the cardiac conduction system (7 marks)
- Sinoatrial (SA) node in the right atrium acts as pacemaker cells
- Causing spontaneous depolarisation
- Cell-to-cell conduction across the atria occurs (all depolarise) in 50 msec
- Impulse reaches Atrioventricular (AV) node where 100 msec delays occurs through the node to allow atrial contraction
- This slows conduction
- Impulse reaches Bundle of His where rapid conduction for coordinated ventricular contraction occurs
- Ventricular myocardium contraction
What is an ECG?
Detects electrical activity across the heart
It is an amalgamation of all the action potentials occurring in the heart
What is the P wave shown in an ECG?
Atrial systole
Atrial depolarisation = contraction (blood is squeezed into the ventricles)
What is the QRS complex shown in an ECG?
Ventricular Systole
Ventricular depolarisation = contraction
Atrial repolarisation = relaxation AT THE SAME TIME
What is the T wave shown in an ECG?
Ventricular Diastole
Ventricular repolarisation = relaxation
