ANS control of heart Flashcards
contractility
- alters tension development independent of fiber length
- increase in velocity of fiber shortening
- increase in pressure development
contractility is mediated by what ion
calcium
during sympathetic stimulation, what happens to contractility of heart
rates of pressure development and dissipation are increased (max pressure is higher; and pressure increases more quickly)
under normal circumstances, a single AP provides sufficient free cytoplasmic CA2+ to activate how many crossbridges
1/2 of them
*providing additional cytoplasmic CA2+ will result in additional force production
tension development in cardiac muscle is dependent on what ion concentration
calcium
function of digitalis and digoxin
- inhibits Na+K+ ATPase and therefore reverses the Na+/Ca2+ exchanger so that there is a higher intracellular Ca2+
- result: enhanves force of contraction (contractility)
parasympathetics have what response on contractility
a negative inotropic effect
catecholamines have what effect on contractility
a positive inotropic effect
how does heart rate affect inotropy
increases inotropy in a stepwise fashion (the “treppe” effect, Bowditch effect)
*inability of Na+/K+ ATPase to keep up with the influx of Na+, leading to accumulation of Ca2+ via the Na+/Ca2+ exchanger
parasympathetic nervous system innervates what parts of the heart
PNS (vagus nerve) primarily innervates SA and AV nodes
Sympathetic nervous system innervates what portions of the heart
- SA and AV nodes
- atrium
- ventricles
chronotropicity
heart rate
dromotropicity
conduction
SNS stimulation does what to heart
increases
- HR
- conduction
- contractility
*via adrenergic receptor subtype
PNS stimulation does what to the heart
decreases
- HR
- conduction
- contractility (minor)
*via muscarinic receptor subtype
PNS has what affect on SA node
- decreases rate of SA node depolarization
- increases permeability of SA node to K+
- hyperpolarizes SA node
- decreases inward movement of Na+ and Ca2+
SNS has what effect on SA node
- increases the rate of SA node depolarization
- increases inward movement of Na+ and Ca2+
in SA node slow action potential, when does Ca2+ T-type channel close, and Ca2+ L-type channel open
L-type Ca2+ current is not until threshold is reached
what is the maximum diastolic potential for SA slow action potential
-65mV
what is PNS effect on AV node
Ach decreases AV nodal conduction velocity (M2)
- increased permeability of AV node to K+
- slows AV node delay
- increases PR interval
What is SNS effect on nodal conduction
- increases T-type Ca2+ current
- decreases P-R interval
How does SNS enhance contractility
increased inward Ca2+ through L-type channels
In SNS innervation, contractility of the heart is increased; however, ventricular relaxation is also increased; What is this due to
relaxation increased due to stimulation of SERCA pump activity