Cardiovascular System Flashcards
Define ‘systole’
Contraction of the heart
Define ‘diastole’
Relaxation of the heart
What is the pericardial sac?
The heart sits in the pericardial sac - the layer of tissue that protects the heart and allows it to move
How many steps are in the cardiac cycle?
6
State the Cardiac Cycle
Deoxygenated blood enters to right side of the heart through superior interior vena cava
Right Atrium contracts, blood flows from RA to RV, valves shuts to prevent back flow
Ventricle contracts, blood leaves through the pulmonary artery to lungs where it is oxygenated
Oxygenated blood return to the heart through pulmonary veins into left atrium
Left Atrium contract and blood goes to the left ventricle
Blood leaves through the aorta to the body
Define arteries
They carry blood away from the heart. Thick muscular walls to deal with higher blood pressure to pump blood to the body, with thin lumen (passageway)
Define veins
Carry blood to the heart. Thin walls, thick lumen (passageways), valves to prevent back flow of blood
How do you calculate Cardiac Output?
Stroke Volume x Heart Rate
What is stroke volume?
Amount of blood (mls) per beat
How is heart rate measured?
Beats per minute
What is Cardiac Output?
Amount of blood from the heart in 1 minute
What is the Conduction System?
A group of specialised cardiac muscles in the walls of the heart that send signal to the heart muscle causing it to contract
Name the 3 main components of the Conduction System?
- Sinoatrial node (SA Node)
- Atrioventricular Node (AV Node)
- Bundle of His
What’s the role of the Sinoatrial (SA) Node?
The main pacemaker of the heart situated near the vena cava
What’s the role of the Atrioventricular (AV) Node?
Serves as an electrical gateway to the ventricles and delays the electric impulses to the ventricles
Why does the AV Node delay electric impulses to the ventricles?
To ensure the atrium has projected all the blood into the ventricle before the ventricle contracts
How does the AV Node know when the delay of electric impulses is necessary?
AV Node receives signals from the SA Node to pass them onto the AV Bundle (of His)
What’s the role of Bundle of His?
It’s divided into left and right bundle branches which conduct impulses toward the apex of heart. The signals are then passed to the purkinje fibres, travelling upwards and spreading throughout the ventricle myocardium
What is an ECG?
Electrocardiogram. An ECG is a recording of all the action produced by the nodes and cells of the myocardium. Each wave of the ECG is a response to the cardiac electrical cycle.
What does the blood consist of?
55% Plasma
45% Formed elements
What does the 55% Plasma in the blood consist of?
90% water, salts, plasma proteins, nutrients, waste products of metabolism, respiratory gasses, hormones)
What are the 45% formed elements in blood?
erythrocytes, leukocytes, platelets
What 3 things trigger changes to this system during pregnancy?
- hormonal action
- mechanical actions as increased load/weight
- anatomical changes to the heart and it’s position
What happens to gaseous exchange levels in pregnancy and why?
HIGHER levels of gaseous exchange in lungs, in need of more oxygen for foetus and labour
Does oxygen consumption rise or fall? Why?
Rises due to increased body wight by approx 15% in pregnancy
In pregnancy, what does increased metabolic rate lead to?
Increased heat production
Is blood flow to skin membrane capillaries increased or decreased?
Increased
Increased red blood cells in pregnancy. What is the full term for this?
Erythropoiesis
Haemodynamic adjustments occurs in pregnancy. What does this entail?
haem = blood dynamic = forces involved in circulation
By how much does blood volume increase in pregnancy?
30-50%
What happens to blood viscosity in pregnancy? Why?
Decreases due to haemodilution (diluted)
Cardiac output decreases during pregnancy. True or False?
FALSE. It increases.
Blood pressure generally lowers in pregnancy. What else lowers in accordance with this?
Systemic vascular resistance
What is the key hormonal action of oestrogen in this system?
Stimulates angiogenesis (formation of new blood vessels and vascular beds)
What is angiogenesis?
Formation of new blood vessels and vascular beds
What is the key hormonal action of progesterone in this system?
Relaxes smooth muscle, causing pulmonary vasodilation and lowered peripheral resistance
What changes occur to the arteries in pregnancy?
Dramatic, systemic and pulmonary vasodilation to increase blood flow
What changes occur to the capillaries in pregnancy?
Increased permeability
What changes occur to the veins in pregnancy?
Vasodilation and impeded venous blood flow
What is normal range for heart rate?
60-100 bpm
What is amplitude? (heart rate)
A reflection of the pulse strength and elasticity of the arterial wall
Define tachycardia
Abnormally rapid heart rate
Define bradycardia
Abnormally slow heart rate
What changes happen to heart rate in pregnancy?
- Increases soon after implantation
- Increases 10-20bpm by 32 weeks, decline in 3rd trimester, returning to pre-pregnancy levels by term
In pregnancy the heart increases by how much and why?
10-15% because of increased cardiac output therefore increased muscle size since it’s working harder
What does increased levels of oestrogen do the the size and function of the heart?
Hypotrophy = increased size and function of cardiac muscle is stimulated by oestrogen
What changes are made to the location of the heart as uterus enlarges in pregnancy?
Displaced by elevation of the diaphragm and is rotated forwards and the the left
What changes are made to blood pressure in pregnancy?
Relatively unaffected. Hypotension can occur in early pregnancy. Little change in systolic level, diastolic can decreased in first 2 trimesters and return to pre-pregnant value by term
