Week 5 - Heart Flashcards
Define cardiac output
Volume of blood ejected from the heart per minute
Cardiac Output calculation
Stroke Volume x Heart Rate
Average 70ml x 70bpm = ~4.9Lt
Stroke volume equation
End Diastolic Volume - End Systolic Volume
On average 130 - 60 = 70ml
Define diastole and EDV
Relaxation of the heart, ventricular filling.
End diastolic volume is ~130ml
Define systole and ESV
Contraction of the heart
End systolic volume is ~60ml
What does RBC transport around the body?
Lungs - O2, CO2
Liver - Bilirubin, Lactate
Kidneys - Urea
Other - Hormones, fatty acids, electrolytes, antibodies, WBCs, Cytokines
Two branches of left main coronary artery
Left circumflex artery, left anterior descending artery
Right and left atrial appendage
LAA and RAA serve as a reservoir for blood during cardiac cycle. Helps manage volume and pressure.
LAA is a common site for the formation of blood clots in patients with atrial fibrillation (Afib), a type of irregular heartbeat.
What substance is needed before a muscle contracts?
Calcium
First beat of the heart
S1 - mitrul and tricuspid valve closure for ventricular systole
S2 - semilunar valves closure
Two categories of arrhythmia
Bradyarrhythmia and tachyarrhythmia
Atrial fibrillation (AFib)
An irregular and often rapid heart rate
Atrial flutter (AFL)
The atria beat regularly but too fast, which results in atrial muscle contractions that are faster and out of sync with lower chambers or ventricles, of the heart.
Supraventricular tachcardia (SVT)
Rapid heartbeat caused by faulty electrical signals in the upper parts of heart.
Ventricular tachycardia
Abnormal electrical impulse that begins in the ventricles and causes irregular fast heartbeat
Ventricular fibrillation
Occurs when rapid and erratic electrical impulses cause the ventricles to quiver instead of pump blood properly.
Long QT syndrome (LQT)
Causes uncoordinated heartbeats which can lead to sudden, uncontrollable and dangerous arrythmias.
Bradycardia
Heart beats too slow
Ectopic beats
Extra heart beats that can arise from atria or ventricles.
Example of a reversible condition that might alter cardiac rhythm?
Emotions, exercise
Example of an irreversible condition that might alter cardiac rhythm?
Myocardial infarction (MI) or heart attack
This happens when there is a blockage in the coronary arteries that supply the heart.
Biological process of parasympathetic nervous system and heart rhythm
Acetylcholine (ACh) is released from Vagus Nerve affecting the SA and AV nodes.
ACh bind to muscarinic receptors on the cardiac pacemaker cells and conducting tissue.
Increase permeability to potassium ions (K+) and decrease in permeability of calcium ions (Ca2+). K+ leave cell, Ca2+ are blocked to enter.
Hyperpolarization occurs due to increased K+ leaving cell (makes cell more negatively charged). Decreased Ca2+ reduces rate of depolarization. Together they slow down the pace at which the SA node generates electrical impulses, thereby reducing the heart rate.
Parasympathetic also slows conduction through the AV node allowing for longer ventricular filling.
Biological process of sympathetic nervous system and heart rhythm
Norepinephrine released by heart nerve fibres and epinephrine released by the adrenal medulla. Both catecholamines bind to Beta-agonist (B1) adrenergic receptors on cardiac cells.
This activates to G proteins which leads to activation of adenylate cyclase.
Adenalate cyclase catalyzes the conversion of ATP to cyclic AMP (cAMP), which acts as a second messenger within cells.
cAMP activates protein kinase A (PKA), which phosphorylates various proteins within the cell.
PKA phosphorylates calcium channels keeping them open.
PKA also enhances calcium release from sarcoplasmic reticulum, and accelerates reuptake of calcium into sarcoplasmic reticulum to get ready for next contraction.
This enhances the depolarization process which increases heart rate.
Three factors that impact stroke volume
- Preload
- Contraction
- Afterload
