PHYS30001 Lecture Notes - Lecture 8: Genetic Predisposition, Unimodality, Catecholamine
enlargement of the heart
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Global = both right and left
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left ventricular
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right ventricular
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Definition
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parallels body growth
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doubles in size after 6 months
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triples in size after 1 year
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Timing
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from ovoid to spheroid in shape, because at birth both sides are similar size
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greater wall thickening
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RV: 2 to 20 ml
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LV: 2 to 40 ml
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greater increase in ventricular capacity
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greater change in left than right ventricle: pumps against greater resistance due to
longer circuit, requires greater pressure
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Characteristics - macroscopic
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myocardial cell division (hyperplasia) ceases after first few months: determined by a
genetic switch (thus after a heart attack, cardiomyocytes can't divide to regenerate lost
cells)
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increased fibre diameter: more sarcomeres
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RV: 10 to 16 μm
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LV: 10 to 20 μm
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further growth mostly through hypertrophy (cells get bigger)
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increased proportion of fibroendothelial cells (various fibro/endothelial cells: vessels,
matrix) that are not inhibited from replication: from 1:1 to 2.5:1 vs myocardial cells
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Characteristics - microscopic
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number of cells: determined by number of cells divisions in utero and first few months
of life
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growth hormone/IGF (insulin-like growth factor)
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thyroxine
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hypothalamic-pituitary axis: hormones that are vital to growth
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Controls
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body size (esp. lean body mass): body mass excluding fat (muscle and bone) correlates
with exercise
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blood pressure (esp. systolic, as it is the only pressure the heart sees): high BP > heart
must generate higher pressure
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angiotensin II and catecholamines: correlation is independent of the hormone's effect
on BP - result of trophic effect on smooth muscle and cardiomyocytes to help cope with
BP consequences of the hormone
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MZ twins are twice as genetically related as DZ twins, but also their life
experiences are much closer (enviro)
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family history - Heart size correlation between relatives
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Correlates
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Normal growth
8 Cardiac hypertrophy
Saturday, 15 August 2015
1:20 AM
Cardio Page 1
Document Summary
Global = both right and left left ventricular right ventricular. Timing parallels body growth doubles in size after 6 months triples in size after 1 year. Lv: 10 to 20 m increased proportion of fibroendothelial cells (various fibro/endothelial cells: vessels, matrix) that are not inhibited from replication: from 1:1 to 2. 5:1 vs myocardial cells. Controls number of cells: determined by number of cells divisions in utero and first few months of life hypothalamic-pituitary axis: hormones that are vital to growth. Bp consequences of the hormone family history - heart size correlation between relatives. Mz twins are twice as genetically related as dz twins, but also their life experiences are much closer (enviro) Cardio page 1 experiences are much closer (enviro) Left ventricular mass (g) in healthy young adults. Growth determinants extrinsic hemodynamic stroke volume systolic wave form: pump against greater pressure in arteries = greater pressure load non-hemodynamic. Genetic predisposition has additive effect with extrinsic determinants autocrine, paracrine.
