9. Regulation of the CV System Flashcards
Decreased sensitivity also results in faster dissociation of ____ from TnC, thereby increasing lusitropy, which allows the heart to fill more quickly.
Ca2+
Stretch of the arterial cell wall where the baroreceptors sit activates _____ to cause depolarization and to trigger an AP.
mechanosensitive eNac Na+ channels
Phosphorylation of ____ decreases the Ca2+ sensitivity of TnC.
TnI
Where are baroreceptors located?
in the aortic arch and carotid sinus
- Ca++ channel - phosphorylation by PKA slows inactivation, increases Ca++ - increases ionotropy
L-type Ca++ channel (DHPR)
Block of β adrenergic receptors with propanolol _____ by inhibiting tonic sympathetic activity.
decreases heart rate
What produces cAMP?
adenylate cyclase
What is lusitropy?
myocardial/diastolic relaxation (the ability of the heart to relax)
In vascular smooth muscle cells, adenosine binds to _____.
A2 purinergic receptors
What is phospholambam?
- protein that PKA phosphorylates to remove - inhibits SERCA; remove for faster Ca++ into SR - increases inotropy and lusitropy - part of EC coupling
Parasympathetic Regulation of Chronotropy: ACh binds to the M2 muscarinic ACh receptor, activating Gi and inhibiting AdCy. The Beta-gamma subunits bind to ____ channel, which are K+ channels, causing _____ and decreased excitability of the cell to ____ the heart rate.
hyperpolarization; slow
The influx of Ca2+ through L-type Ca2+ channels triggers a larger Ca2+ release from the ___ via ryanodine receptors, a process termed Ca2+-induced Ca2+ release (CICR).
SR
What is an increase in HR in response to stretch called?
the Bainbridge Reflex
Name 3 ways the CNS controls the vasculature.
- sympathetic regulation 2. baroreceptor reflex 3. CNS control center
Block of _____ receptors with propanolol decreases heart rate by inhibiting tonic sympathetic activity.
β adrenergic
What is the Bainbridge Reflex?
an increase in HR in response to stretch
____ also phosphorylates ryanodine receptors, making them more sensitive to Ca2+, so that less trigger Ca2+ is needed to evoke Ca2+ release.
PKA
Decreased sensitivity also results in faster dissociation of Ca2+ from TnC, thereby increasing ____, which allows the heart to fill more quickly.
lusitropy
Low pressure baroreceptors in the atria and vena cavae mediate the ______.
Bainbridge Reflex
How is MLCK dephosphorylated?
by myosin light chain phosphatase (MLCP)
Name 3 families of G proteins involved in CV system function.
- Gs 2. Gi/o 3. Gq
How is cAMP’s role different in cardiac muscle vs smooth muscle?
in smooth muscle, cAMP causes relaxation
What is a Ryanodine Receptors (RyRs)?
- an intracellular calcium receptor - mediates Ca++ release from the SR (CICR) - a molecular target for sympathetic regulation of ino- and lustropy - its phosphorylation increases Ca++ sensiivity
In vascular smooth muscle cells, ____ binds to A2 purinergic receptors.
adenosine
Parasympathetic Regulation of Chronotropy: ACh binds to the M2 muscarinic ACh receptor, activating Gi and inhibiting AdCy. The Beta-gamma subunits bind to the GIRK channel, which are _____ channels, causing hyperpolarization and decreased excitability of the cell to slow the heart rate.
K+
What is the effect of muscarinic ACh receptor binding?
decrease chronotropy
L-type Ca2+ channels on the plasma membrane are activated by _____.
depolarization
Sympathetic Regulation of Chronotropy: NE binds to the Beta-adrenergic receptor, activating Gs and AdCy. The cAMP produced can then activate PKA, which then phosphorylates _____ or _____.
the L-type Ca++ channel or the RyR2
What does the brain do in response to baroreceptor firing?
slow heart rate and vasodilate BVs in an effort to decrease the BP
Stretch of the arterial cell wall where the baroreceptors sit activates mechanosensitive eNac Na+ channels to cause _____ and to trigger _____.
depolarization; an AP
What does MLCP stand for?
myosin light chain phosphatase
- an intracellular calcium receptor - mediates Ca++ release from the SR (CICR) - a molecular target for sympathetic regulation of ino- and lustropy - its phosphorylation by PKA increases Ca++ sensiivity
RyR2
How are smooth muscle cells different than striated muscle?
- they’re small and mononucleate 2. no sarcomeres 3. no striations 4. no troponin or tropomyosin 5. don’t require Ca++ release from SR 6. slower rate of contraction but can sustain it
What is inotropy?
contractility
SERCA removes ____ from cytosol following contraction (pumps it back into the _____).
Ca2+; sarcoplasmic reticulum (SR)
Name some of the CV GPCRs.
α & β adrenergic receptors, acetylcholine receptors, endothelin receptors, adenosine receptors, angiotensin II receptors
Sympathetic Regulation of Chronotropy: NE binds to the Beta-adrenergic receptor, activating Gs and AdCy. The cAMP produced can then directly act upon?
the HCN channel
What is troponin-I (TnI)?
- sarcomeric protein - phosphorylation by PKA decreases sensitivity Ca++ sensitivity of troponin-C - allows faster dissociation of Ca++ so faster filling = increased lusitropy
Parasympathetic Regulation of Chronotropy: ACh binds to the M2 muscarinic ACh receptor, activating Gi and inhibiting AdCy. The Beta-gamma subunits bind to the ____ channel, which are K+ channels, causing hyperpolarization and decreased excitability of the cell to slow the heart rate.
GIRK
____ are the most prevalent drug target.
GPCRs
Along with ____, TnI inhibits the interaction between actin and myosin in the absence of Ca2+.
tropomyosin
Where is the L-type Ca++ channel (DHPR) located?
on the T-tubule
Name 4 molecular targets for sympathetic regulation of inotropy and lusitropy.
- Phospholamban (PLB) 2. L-type Ca2+ channels (LTCCs) 3. Ryanodine Receptors (RyRs) 4. Troponin I (TnI)
What is inotropy?
strength of muscle contraction
Block of M2 muscarinic acetylcholine receptors with atropine _____ by inhibiting tonic parasympathetic activity.
increases heart rate
PLB is an inhibitor of ____.
SERCA
Faster Ca2+ reuptake has two effects on cardiac performance: 1) directly increases ____ and 2) increases inotropy by increasing SR Ca2+ load.
lusitropy
What do Beta-blockers treat?
arrhythmias, hypertension, cardioprotection post-MI
What does myosin light chain phosphatase (MLCP) do?
dephosphorylates MLCK to stop smooth muscle contraction
The baroreceptor cell axons project to the cardiovascular control center in the medulla of the brain via the _____ nerve or the _____ nerve.
glossopharyngeal; vagus