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Microanatomy and Physiology of the heart (3 layers of the heart…
Microanatomy and Physiology of the heart
3 layers of the heart
myocardium
cardiac muscle tissue
striated
diad arrangement
centrally located nuceli
intercalated discs:
area where cells connect, contains
gap junctions
(uniform signal transduction),
desmosomes
, and
fascia adherens
capillaries
What would happen if the muscle tissue was replaced by fibrous (scar) tissue?
That could create an arrhythmia b/c the signal won't be coordinated
epicardium
= visceral pericardium
endocardium
epithelial tissue
areolar connective tissue
cell types in the heart
contractile cells (99%): myocardium
conducting cells (1%)
conducting system components
AV bundle
atrioventricular node
inter-nodal pathway (atrial conducting cells)
Sinoatrial node (SA) node:
under parasympathetic control
Bundle branches
Purkinje fibers
parasympathetic effects dominate in a healthy individual
nervous control
sym: neurotransmitter is NE, receptor is beta1
para: neurotransmitter is Ach, receptor is Muscarinic
action potentials
cardiac muscle cell
long refractory period:
gives the ventricles time to refill before contracting again
conducting cell
factors effecting HR
autonomic innervation
paras. neurons decrease HR
symp. neurons increase HR
bainbridge reflex:
increase venous return will increase HR
hormones
(conducting cells have receptors for these hormones on their membranes)
norepinephrine
thyroid hormone
epinephrine