ALL THINGS HEART <3 Flashcards
(51 cards)
What happens in the P,QRS and T wave?
P- atrial depolarisation
QRS- ventricular depolarisation
T- ventricular repolarisation
What are the 2 implications of long QT syndrome?
1.Triggered activity-
delay in repol means Na+ channels are activated again (after threshold reached) additional beat produced as a result, causing V.T and possible V.F
2.Re-entrant excitation
triggering of extra electrical activity in certain areas and time in the cardiac muscle- if the electrical activity backs up on itself- generates more A.Ps, causing V.T and possibly V.F
Symptoms of long QT
Syncope and palpitations
Treatment for long QT and its side effect
Beta blockers- atenolol etc. Can cause asthma, because it increases the risk of bronchoconstriction
What are the 3 main types of long QT and which channels are affected
LQT1- IKs, LQT2-IKr- both loss of function mutations, plateau is prolonged because not enough K+ is leaving the cell
LQT3-INa- gain of function mutation, Na+ channels open and don’t close, depol for longer
Symptoms for short QT
Syncope, palpitations and arrhythmias
What are the 2 types of short QT?
GoF- IKr,IKs and Ik1- too much K+ leaving the cell, repol too quick
LoF- Ica- channels open and close too early or don’t function normally
Treatments for short QT
Implanted defibrillator, K+ channel blockers may be effective
What are the 4 phases of the cardiac cycle?
- Inflow
- Isovolumetric contraction
- Outflow
- Isovolumetric relaxation
Brief summary of each phase
1-rapid ventricular filling diastasis atrial contraction 2-ventricles contract first heart sound 3-rapid ejection decreased ejection 4-dicrotic notch pressure in ventricles fall second heart sound
What is happening to the valved in each of these phases
1-opening of AV valves
2-closing of AV valves
3-opening of SL valves
4-closing of SL valves
Which factors affect how much tension the cardiac muscle can produce
- Preload- the initial sarcomere length (EDV)
2. Afterload- opposing force and arterial pressure creates the afterload
What is isotonic contraction?
Contraction of the cardiac muscle focuses only on afterload
What is contractility and what causes it to increase
It is the innate ability of the heart to contract. In general contractility increases when more cross bridges form per stimulus
NA causes an increase in maximum force and velocity. Reducing time between beats also increases contractility.
What is the Fick principle?
The O2 content of the pulmonary vein is derived from the pulmonary artery blood and O2 uptake across the lungs
How do you measure cardiac output to the lungs?
- O2 uptake rate by volume and O2 content of expired air
- O2 (PA)- a catheter
- O2 (PV)- peripheral arterial blood
Other ways of measuring cardiac output to the lungs
Indicator solution
Thermodilution
Ultrasound
What controls cardiac output?
Intrinsic- homeometric and heterometric
Extrinsic- parasympathetic- chronotropic (negative) and sympathetic- chronotropic and ionotropic (positive)
Humoral (positive)
Blood flow=?
difference in pressure/ resistance
Transmural pressure=?
Tension/radius
Compliance=?
change in volume/ change in pressure
What is the Windkessel effect?
The elastic nature of the arteries helping to dampen down large fluctuations in blood pressure- expand during systole, recoil during diastole
How is tissue fluid formed?
Formed through the balance of fluid being transferred between the capillaries and tissue
What forces balance- causing the net production of TF?
Hydrostatic pressure (favouring fluid out of the capillaries) Oncotic pressure (favouring fluid into the capillaries)
