Cardiovascular system Flashcards
Components of CV system
Heart, blood, vessels
Cardiac muscles
- Involuntarily myogenically stimulated
- Autorhythmic contractions (no neural input due to pacemaker)
- Striations with unique structure
- Wave like contractions to pump blood around body
- Functional syncytium (intercalated disks with gap junctions to allow coordinated contractions)
Diastolic
Relaxation phase (filling phase)
T wave to QRS
Normal - 75-85mmHg
62% of cardiac cycle duration
Systolic
Contraction phase (expel phase)
QRS to T wave
Normal - 110-130 mmHg
38% of cardiac cycle duration
AV node
Connects electrical systems of atrium and ventricles (stimulated by CNS)
40-60bpm with 0.13s delay
SA node
Natural pacemaker which works intrinsically
100-110bpm
Slowed by parasympathetic nervous system
Bundle of HIS
Bundle of specialised cardaic fibers, conduct electrical impulses from AV node to ventricles
30-40 bpm
Purkinje Fibers
Specialised nerve cells that transmit electrical signals to the ventricles from the bundle of HIS which allows for ventricles to contract
Parasympathetic nervous system
Decreases HR and contraction force through vagus nerve
- Neurotransmitter: Acetylcholine
Sympathetic nervous system
- Stimulated by stress – increase in HR and force of contraction
- Neurotransmitter: Adrenaline and Noradrenaline
Stroke volume
Volume of blood per contraction (ml)
- SV=EDV-ESV
EDV
End Diastolic Volume – Volume of blood in ventricle before contraction
ESV
End Systolic Volume – Volume of blood in ventricle after contraction
Cardiac output (Q):
Total volume of blood pumped by the left ventricle per minute
- Q = HR (fc) x SV
Ejection fraction
Proportion of blood ejected by left ventricle per beat
- EF = SV/EDV (averages 60%)
Mean arterial pressure
Average pressure exerted by the blood as it travels through arteries
- Vasoconstriction increases blood pressure and vasodilation reduces blood pressure
MAP equation
MAP = DBP + [0.333 x (SBP – DBP)]
Components of blood
55% plasma
45% formed elements
- >99% red blood cells
- <1% white blood cells and platelets
Heart adaptations after prolonged period of aerobic training programme
- Increased stroke volume
- Lower resting heart rate (bradycardia)
- Increased cardiac output during exercise
- Increased capillarisation of the myocardium
- Greater parasympathetic activity
Blood vessel adaptations after prolonged period of aerobic training programme
- Increased capillary density
- Improved endothelial function
- Reduced blood pressure
- Greater arterial elasticity
Blood adaptations after prolonged period of aerobic training programme
- Increased blood volume
- Higher haemoglobin levels
- Lower blood viscosity
- Increased oxygen extraction
P wave
- Atrial depolarisation (contraction)
- Typically proceeds atrial contraction
- Smooth, rounded waveform
QRS wave
- Ventricular depolarisation (contraction)
- Q wave: First wave deflection
- R wave: First positive deflection
- S wave: Negative deflection following the R wave
- Duration usually less than 0.12 seconds
T wave
- Ventricular repolarisation (relaxing)
- Typically follows the QRS complex
- Rounded wave with varying duration
