2. Physiology Flashcards
What is the job of the cardiovascular system?
Transport of O2 and CO2 Nutrients Metabolites Hormones Heat
What controls the resistance to vascular beds?
Arterioles- elastic and have a contractile wall
As oppose to arteries which do not control vascular beds, they are more muscular in structure
How much blood is stored in the venous system?
75%- used as capacitance vessels
How do cardiac muscle cells communicate with one another?
Electrically connected via gap junctions
Physically connected by desmosomes
These form intercalated discs
What controls the strength of contraction of the heart?
Calcium as it does not fully saturate troponin.
How do pacemaker cells act a pacemaker?
They have unstable resting membrane potentials meaning they can spontaneously contract
How does potassium effect the heart?
Hyperkalemia- fibrillation and heart block
Hypokalemia-decreased heart rate and force of contraction
How does calcium effect the heart?
Hypercalceamia- increase HR and force of contraction
Hypocalcemia- decreased hr and force of contractions (calcium channel blockers)
Where are pacemaker cells found?
Sino-atrial node
Atrio ventrocular node
Bundle of His/Perkinje fibres
Explain the action potential of a pacemaker cell?
Sodium brings the cell to a threshold that opens the voltage gated calcium ion channels
This creates an action potential.
Potassium gated voltage channels occur at a higher level. This brings the voltage down and is the refractory period.
What limb lead is used to interpret ECG’s?
Why?
SLL II- follows the line of maximal depolorisation when looking at conduction to the left leg in respect to the right arm.
Explain the components of an ECG trace
P wave is caused by atrial depolorisation
QRS complex is caused by ventricular depolorisation
T wave is caused by ventricular repolorisation
What is the normal timings of an ECG trace
PR interval- 0.12-0.2 sec
QRS- 0.08s
QT interval- 0.42sec
What is the benefit of
- The augmented limb leads
- The precordial (chest) leads
augmented leads- gives you further information in the vertical plane
hows progression of the depolorisation on the front of the heart
How do you calculate the rate of an ECG
Count the R waves over 30 large boxes
What is this STEMI malarkey?
STEMI- ST elevated myocardial infarction- bad
NSTEMI- non ST elevated myocardial infarction
What is meant by S1 and S2?
S1- blood hits atrioventricular valves
S2- blood hits semilunar valves
What sound indicates mitral and tricuspid regurgitation or aortic/pulmonary stenosis
lub whoosh dub
What sound indicates stenosis of mitral/tricuspid or regurgitation through the aortic/pulmonary valve
lub dub whoosh
How does the sympathetic nervous system affect heart rate (be specific)
release noradrenlaine and adrenaline that acts on B1 receptors on the sinoatrial node
This increases heart rate
How does parasympathetic system affect heart rate?
Vagus nerve releases acetyl choline which acts upon muscarinic receptors
This decreases heart rate
How does end diastolic volume affect stroke volume?
Increases venous return therefore increasing stroke volume
How is stroke volume affected by peripheral resistance?
If peripheral resistance increased then contractility increased, reducing the capacity for stroke volume
What is stroke volume a synonym for?
Contractility
