Cardiovascular system Flashcards
(39 cards)
Explain the path of blood flow through the heart - the cardiac cycle
- Superior and inferior vena cava
- Right Atrium
- Tricuspid Valve
- Right Ventricle
- Pulmonary semilunar valve
- Pulmonary arteries
- Lungs
- Pulmonary veins (L+R)
- Left atrium
- Bicuspid valve
- Left ventricle
- Aortic semilunar valve
- Aorta
- Body: arteries -> capillaries -> veins
Electrical conduction pathway of the heart (6)
- Sinoatrial node
- internodal pathways
- AV node
- AV bundle of His
- bundle branches (R+L)
- perkinje fibres (R+L)
P-wave
atrial depolarisation (atrial repolarisation obscured by QRS complex)
PR interval (PQ)
time delay between atrial depolarisation and conduction through AV node for ventricular activation (0.12-0.2s)
QRS complex
ventricular depolarisation (0.06-0.1 sec)
ST segment
electrical plateau of ventricular activation
T Wave
ventricular repolarisation
Normal HR - how to find HR on ECG
60-100bpm
- number of QRS complexes in a 6 second strip x 10
Stroke Volume (SV) - definition and normal values, formula
amount of blood pumped out of each ventricle during a single beat
○ ~ 70-80ml @ rest
○ EDV - ESV = SV
Heart rate (HR) - definition and normal values, bradycardia, tachycardia
number of times the heart beats (per minute)
○ 60-100 bpm
○ Bradycardia = <60 bpm
○ Tachycardia = >100 bpm
Cardiac Output (CO) - definition and formula
the amount of blood pumped by each ventricle in 1 minute
○ CO (ml/min) = SV (ml/beat) x HR (beat/min)
The difference between resting and maximal CO is cardiac reserve
End Diastolic volume (EDV) - definition and normal value
amount of blood in each ventricle at the end of ventricular diastole (the beginning of ventricular systole)
~ 120ml @ rest
End Systolic Volume (ESV) - definition and normal value
amount of blood remaining in each ventricle at the end of ventricular systole (start of ventricular diastole)
○ ~ 50 ml @ rest
Ejection Fraction (EF) - definition and normal value
percentage of EDV ejected represented by SV i.e. SV/EDV (x100 to get %)
○ ~ 55-70%
○ Varies with changing demand
○ Represents the efficiency of the heart. A diseased heart will have a reduced EF
Preload - definition, how it affects CO
end-diastolic volume/pressure = stretch placed on myocardial fibres just before contraction
○ Greater the end-diastolic volume, the more ventricular muscle fibres are stretched (Frank Starling mechanism)
Affects CO:
- Preload too low => amount of blood available to pump out is decreased => SV decreased -> CO decreased
- Preload too high and ventricles stretched out => reduced SV -> reduced CO
Afterload - definition, how it affects CO
resistance to ventricular contraction
Affects CO:
- Increased Afterload => increased demands of the heart
Blood Pressure (BP) - definition, SBP, DBP definition, normal BP, hypertension, folrmula
Pressure the blood exerts against the inner wall of the blood vessels
○ Systolic BP (SBP) - ‘high’ pressure in arterial system
○ Diastolic BP (DBP) - ‘low’ pressure in arterial system
○ Normal arterial BP = 120/80
○ Hypertension = >140/90
○ BP = CO x TPR
Pulse pressure
Pulse Pressure = SBP - DBP
Mean arterial pressure (MAP)
- DBP +1/3 pulse pressure
- Average driving pressure propelling blood from LV to RA
What are the (2) determinants of blood flow rate? How do they affect blood flow?
- Driving pressure - Flow is directly proportional to gradient pressure; blood flow increases when pressure increases and vice versa
- Vascular resistance - Flow is inversely proportional to resistance; as resistance increases, blood flow decreases
What are the determinants of vascular resistance? How do they affect resistance?
- Length of blood vessels - longer blood vessel = more resistance
- Radius/diameter of the blood vessels (physiological) - smaller radius/diameter = more resistance
- viscosity of blood - thicker blood = harder to pump -> increases vascular resistance
What causes BP changes (3)?
Occur in response to:
- baroreceptors and chemoreceptors in the arteries (short term regulation )
- renin-angiotensin system (long term regulation)
- the kidneys (long term regulation)
What are the short term regulators of BP?
define short term and list methods (sensor, control, effectors)
short term = regulation of minute to minute changes in arterial pressure due to e.g. postural changes or manoeuvres
methods:
- sensors: aortic and carotid baroreceptors via vagus and GP nerves. Sense change -> alert cardiac control centre
- control: cardiovascular control centre in the medulla oblongata regulates CV activity through nervous and endocrine systems
- vasomotor centre = changes arterial diameter of;
- skeletal muscle arterioles -> vasodilation
- visceral arterioles -> vasoconstriction
- cardio-accelerator centre = increased HR and contractility
- cardio-inhibitor centre = decreased HR and contractility - effectors: sympathetic nerves to heart and blood vessels, vagus nerve, vasomotor nerves
- endocrine influence: threat/stress -> sympathetic NS stimulation -> adrenaline & noradrenaline -> increased BP and HR
What are the long term regulators of BP?
define long term and list methods
Long term = regulating overall arterial bp over time, involving endocrine and renal systems
Controls: (low bp) -> Renin-angiotensin-aldosterone system -> increased total circulating blood volume -> increased BP
