Physiology Flashcards
(131 cards)
What are is the conduction system of the heart made up of?
specialised cardiac muscle fibres
Describe the flow of electrical signals
- The SA node spontaneously discharges an electrical impulse that triggers a wave of depolarisation down the heart
- Signals flow through internodal fibres from SA to AV node. The depolarisation contracts both atria.
- From the AV nodes, signals travel to the bundle of His, which then splits into the right and left bundles and into purkinje fibres
- Depolarisation of the ventricle muscle fibres results in the ventricle to contract.
What is the hierarchy of pacemakers
the pacemaker with the fastest rate of depolarisation sets the rhythm of the heart.
How does the atria function as a priming pump?
The atria contracts before the ventricles so that the ventricles may be fully filled before they contract.
What is the purpose of the fibrous ring?
How to ensure that the atria contract first.
The fibrous ring, together with the delay at the AV node ensures the atria contract first, fill the ventricles with blood, followed by the contraction of the ventricles.
Activation of the sympathetic nervous system results in …
the heart beating faster and harder.
Activation of the parasympathetic nervous system …
reduces the heart rate but does not affect the strength of cardiac contractions
What are the Factors Affecting Heart Rate DIRECTLY Through the SA Node?
What are the Factors Affecting Heart Rate through the Vasomotor Centre and Autonomic Nervous System
Describe the respective neurotransmitters, receptors and ionic changes for the sympathetic and parasympathetic systems
What gradients are involved in establishing resting membrane potential
Concentration gradient and electrical gradient
What is phase 2
This is phase 2 of the action potential, called as “plateau” phase. At this point the calcium influx (movement of positively charged ions into the cell) and the efflux of potassium from the cell balance each another, hence the action potential is “flat” at this point. These are the calcium ions that are responsible for causing the muscle fibre to contract
What is phase 0
voltage-gated sodium channels on the membrane of the ventricular muscle opens. When that happens, sodium, present in much higher concentrations outside the cell than in, rushes into the cell. The cell now becomes positive due to the entry of sodium.
What is phase 3
After a certain period, calcium ion influx stops. When this happens, and potassium continues to leave the cell, the cell continues to become more negative. This is phase 3 of the action potential, and the cell soon returns to its original resting membrane potential of -85 mV, while awaiting the next wave of depolarisation.
what is phase 1
To begin with, the outward rectifying potassium channels open. This is the initial repolarization, or phase 1. When potassium channels open, both the concentration gradient (potassium higher on the inside) together with the electrical gradient (because the cell is depolarised) both combine to push potassium out. So, the cell loses positive charges, and the inside of the cell becomes more negative.
Why are both pressure and flow are further regulated by the vascular system (especially the arterioles)?
so that optimal perfusion pressure and flow occur at the tissues.
What are examples of uncoordinated electrical activity?
ventricular tachycardia, ventricular fibrillation, atrial fibrillation and heart blocks.
How many electrodes are placed on the chest and limbs for an ECG recording?
10
What are the attributes of standard limb leads
What are the attributes of augmented limb leads
What are the attributes of precorial/ chest leads?
Describe the P wave
The P wave is the result of atrial depolarisation.
Describe QRS complex
The QRS complex is ventricular depolarisation. The Q wave results from the vector created when electrical signals depolarise the bundle of His. The R and S waves result from the depolarisation of the ventricles.
