BIOL 252 Module 2
Heart
Pump
Maintain vital rhythm and stream
Myocardium = cardiac muscle tissue
Autorhythmycity = ability to initiate its very own electric impulses
Input from neurons or endocrine gadget
Myocardial Contractile Cells
99% of cells
Muscular contractions -> pump blood throughout frame
Myocardial Conducting Cells
1% of cells
Form conduction gadget
Purkinje cells = specialised engaging in cells (convey impulses thru ventricles)
Smaller than contractile
Structure of Cardiac Muscle Tissue
Cardiomyocytes = cardiac contractile cells
Shorter than skeletal muscle groups
Striations (light and darkish bands)
Myofibril (lengthy threads internal muscle cells)
Organized into sarcomeres (z-line to z-line)
Intercalated discs = bind cells together into one functional unit, desmosomes lock cells, gap
junctions allow ion passage
Sarcomere - z-line to z-line
Cardiac Muscle vs. Skeletal Muscle
T-tubules (extensions of sarcolemma and allow motion potentials): cardiac simplest at z-traces
and fewer, skeletal at junction of A and I band and more
Sarcoplasmic reticulum (specialised ER): cardiac fewer Ca ions and slower onset of contraction,
skeletal more CA ions and quicker onset of contraction
Cell additives (mitochondria and nucleus): cardiac 25% of volume and single/valuable nucleus,
skeletal fewer and hundreds of scattered nuclei
, Calcium Ions and the Heart
1. Slow Ca channels - refractory period
2. Combine with troponin for sarcomere shortening
-actin (thin) and myosin (thick)
three. Excitation-contraction coupling - movement potential/excitation reasons influx of Ca ions
and triggers contraction
4. Relaxation - decline in intracellular Ca, troponin returns to everyday and covers active web
sites
Excitation-Contraction Coupling Mechanism
Influx of Ca ions via voltage-gated ion channels
Muscles prompted to settlement
Elevated Ca stages -> bind to troponin on troponin-tropomyosin complex (actin filament)
Myosin head binds to open site -> move-bridges form -> power stroke -> pull actin to M line
H band gets smaller as actin slides over myosin
ATP needed to detach myosin heads
When Ca is bound, cycling keeps
Conduction System of the Heart
Separated embryonic heart cells can each generate their personal electrical impulse and cause
a contraction
When mixed, the cells set the tempo
Adult coronary heart cells preserve ability to generate own impulse (cardiac conduction device)
SA node = sinoatrial node
AV node = atrioventricular node
AV package = atrioventricular bundle
AV bundle branches
Purkinje cells
SA Node
In right atrium close to superior vena cava
Highest inherent price of depolarization -> pacemaker
Internodal pathways bring impulse to atria -> AV node
Connective tissue prevents impulse spreading to ventricles besides at AV node
50 ms
Muscular contraction of L and R atria -> blood to ventricles
AV Node
Inferior right atrium, proper facet
Heart
Pump
Maintain vital rhythm and stream
Myocardium = cardiac muscle tissue
Autorhythmycity = ability to initiate its very own electric impulses
Input from neurons or endocrine gadget
Myocardial Contractile Cells
99% of cells
Muscular contractions -> pump blood throughout frame
Myocardial Conducting Cells
1% of cells
Form conduction gadget
Purkinje cells = specialised engaging in cells (convey impulses thru ventricles)
Smaller than contractile
Structure of Cardiac Muscle Tissue
Cardiomyocytes = cardiac contractile cells
Shorter than skeletal muscle groups
Striations (light and darkish bands)
Myofibril (lengthy threads internal muscle cells)
Organized into sarcomeres (z-line to z-line)
Intercalated discs = bind cells together into one functional unit, desmosomes lock cells, gap
junctions allow ion passage
Sarcomere - z-line to z-line
Cardiac Muscle vs. Skeletal Muscle
T-tubules (extensions of sarcolemma and allow motion potentials): cardiac simplest at z-traces
and fewer, skeletal at junction of A and I band and more
Sarcoplasmic reticulum (specialised ER): cardiac fewer Ca ions and slower onset of contraction,
skeletal more CA ions and quicker onset of contraction
Cell additives (mitochondria and nucleus): cardiac 25% of volume and single/valuable nucleus,
skeletal fewer and hundreds of scattered nuclei
, Calcium Ions and the Heart
1. Slow Ca channels - refractory period
2. Combine with troponin for sarcomere shortening
-actin (thin) and myosin (thick)
three. Excitation-contraction coupling - movement potential/excitation reasons influx of Ca ions
and triggers contraction
4. Relaxation - decline in intracellular Ca, troponin returns to everyday and covers active web
sites
Excitation-Contraction Coupling Mechanism
Influx of Ca ions via voltage-gated ion channels
Muscles prompted to settlement
Elevated Ca stages -> bind to troponin on troponin-tropomyosin complex (actin filament)
Myosin head binds to open site -> move-bridges form -> power stroke -> pull actin to M line
H band gets smaller as actin slides over myosin
ATP needed to detach myosin heads
When Ca is bound, cycling keeps
Conduction System of the Heart
Separated embryonic heart cells can each generate their personal electrical impulse and cause
a contraction
When mixed, the cells set the tempo
Adult coronary heart cells preserve ability to generate own impulse (cardiac conduction device)
SA node = sinoatrial node
AV node = atrioventricular node
AV package = atrioventricular bundle
AV bundle branches
Purkinje cells
SA Node
In right atrium close to superior vena cava
Highest inherent price of depolarization -> pacemaker
Internodal pathways bring impulse to atria -> AV node
Connective tissue prevents impulse spreading to ventricles besides at AV node
50 ms
Muscular contraction of L and R atria -> blood to ventricles
AV Node
Inferior right atrium, proper facet
