Week 3 Cardiology Flashcards
Layers of Heart wall (innermost to outermost)
- Endocardium
- Myocardium
- Epicardium
- Visceral layer of serous pericardium
- Pericardial Cavitity
- Parietal layer of pericardium
- Fibrous pericardium
Fibrous pericardium
Outermost layer, strong connective tissuse
Serous pericardium
Consists of the partial and visceral pericardium
Epicardium is made of
Adipose tissues, nerves, blood vessels
Myocardium is made of
Cardiomyocytes, conducting system
Endocardium
Innermost layer of the heart wall, signed cell thick
Structure of cardiac Myocytes
- Sarcomeres (The fundamental contractile units within cardiomyocytes; separated by Z-lines)
- Intercalated Disks (Specialised cell junctions that facilitate electrical and mechanical coupling)
- Couplons (crucial for calculus signalling)
- Axial tubules (Intracellular tubles that assist in s=distrubuting calcium for excitation contraction coupling within mycotyes)
How do Cardiomyocytes contract
Calcium induced calcium release (CICR), whereby extracellaurlar calcium flux triggers release from the SR
Lipofuscin
-pigment composed of lipid contains residues from lysomal digestion
-functions as an indicator of oxidative stress and cellular senescence, associated with various cardiomyopathies and het failure
Twisting wringing motions of Cardiomyocytes
-arranged in a helical range ent around the heart —> efficient contraction during systole
-coordinated
Sacromere shortening mechanism
- ATP binds to ATP binding site and calcium bonds to troponin
- Tropomyosin elicits a conformational change
- Actin binds to actin binding site on myosin
- Actin pulls myosin towards the M-Line, the Z-disk moves towards the M line, muscle contracts and the sacromere shortens
Semi lunar valves
-Arotic and pulmonary
-rely on pressure gradients to open and close as they lack papillary muscles and Chordae Tendineae
Atrioventricular valves
-Tricuspid and mitral valves
-have papillary muscles and chordae tendineae to control valve function
-Papilarry muscles attached to the walls contract to pull on the tendineae, ensuring proper closure
-then during distole they relax, allowing valve to open
Mitral Valve: Location, No. of cusps, Systole, Diastole
Location: Between La and LV
No. Of cusps: 2
Systole: closed
Diastole: open
Aortic Valve: Location, No. of cusps, Systole, Diastole
Location: Between LV and Aorta
No. Of cusps: 3
Systole: open
Diastole: closed
Pulmonary Valve: Location, No. of cusps, Systole, Diastole
Location: Between RV & Pulmonary trunk
No. Of cusps: 3
Systole: open
Diastole: closed
Tricuspid Valve: Location, No. of cusps, Systole, Diastole
Location: Between RA & RV
No. Of cusps: 3
Systole: closed
Diastole: open
When does papillary muscle contraction occur re ventricular muscle contraction
Slightly before
S1 heart sound
Closure of AtrioVentricular
Start of systole
S2 Heart sound
Closure of Semilunar valves
Just before start of diastole
S3 Heart sound
Blood striking compliant ventricle
Indicates systolic heart failure or regurgitation
Occurs mid diastolic
S4 heart sound
Blood striking non-compliant ventricle
Indicates ventricular hypertrophy or aortic stenosis
Is late diastolic
Frank-Starling law
Increased cardiac preload will increase the stretch of the cardiac muscle (myocardial fibres) during diastole, thus increasing the force with which blood is ejected during systole.
Describe the effect of physiological stressors, such as exercise, on cardiac function and haemodynamics.
-Overall increase heart rate and stroke volume —> higher cardiac output
• Sympathetic nervous system (SNS) activation leads to increased myocardial contractility (positive inotropy)
and faster heart rate (positive chronotropy), resulting in more efficient circulation of oxygenated blood.
• Exercise further induces vasodilation in skeletal muscle arterioles, reducing systemic vascular resistance and
optimising tissue perfusion.
• The increased venous return during exercise augments end-diastolic volume (preload), which, according to the
Frank-Starling mechanism, further boosts stroke volume.