Lecture 11 - Excitation-contraction coupling Flashcards
chronotropy
pertaining to heart rate
SA node
dromotropy
pertaining to conduction
AV node + Purkinje fibers
myocardium
bathmotropy
pertaining to cell excitability
rhythms outside of SAN
Inotropy
pertains to contractility
myocardium (specifically ventricular)
lusitropy
pertain to relaxation
during contraction _____ moves closer to each other
Z-disc
describe excitation-contraction coupling in 7 steps
- Na+ entry
- depolarization
- calcium entry across channels
- release of calcium from the sarcoplasmic reticulum
- calcium binds to troponin
- tropomyosin moves
- actin-myosin interaction causes cell contraction
describe myocardial cell contraction in 10 steps
- cell depolarizes
- voltage change open long-lasting calcium channels
- extracellular calcium enters cell
- triggered calcium release from the sarcoplasmic reticulum via release channel
- increased systolic calcium
- calcium binds troponin and inhibition is removed
- ATP is hydrolyzed
- actin and myosin cross-bridge cycle
- sarcomere tenses and shortens leading to contraction
- calcium leaves cell and myocyte relaxes
what is the primary regulator of contraction
calcium availability
the inherent state of the actin-myosin interaction is called
contractility or inotropy
T/F: a positive inotrope or related stimulus increases the strength of myocardial contraction
TRUE
T/F: the sympathetic nervous system is activated by negative inotropy
FALSE
T/F: the parasympathetic nervous system is activated by negative inotropy
TRUE
what are examples of positive inotropic drugs
catecholamines, pimobendan
what are examples of negative inotropic drugs
CCB, Beta-blockers, anesthetics
summarize myocardial relaxation
- calcium removal or reuptake
- sodium-calcium exchanger
- two-way
what is SERCA
Sarcoplasmic reticulum ATPase
- pumps calcium into the SR
- phospholamban inhibits
summarize myocardial relaxation
- beta stimulation activates cAMP
- cAMP phosphorylates phospholamban
- SERCA activated
- improves calcium uptake and relaxation
what type of cell-to-cell junction is more prone to disease
desmosomes
what desmosomal protein has been found to decrease the transmittance of signals in diseases like boxer cardiomyopathy
striatin
what does the heart require energy for
- electrical activity
- contraction
- relaxation
- cell maintenance
what provides the most energy for the heart
beta-oxidation of fatty acids
mitochondrial myopathies occur when
metabolic pathways of energy production are abnormal or damaged
what determines myocardial oxygen consumption
- heart rate
- contractility
- systolic wall tension
