Drugs affecting heart rate and arrhythmias/dysrhythmias Flashcards
Arrhythmia
Absence of rhythm
Dysrhythmia
Abnormal rhythm
What are the PSNS targets of the heart to control rate?
SA & AV nodes
What is the chemical transmitter for PSNS control of heart rate?
What is the pathway?
What is the target tissue receptor?
Acetylcholine
- Preganglionic (SC)
- ACh onto postganglionic nicitonic receptors
- ACh onto muscarinc receptors (M2, GPCR)
- decreased HR
Muscarinic receptor (SA)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/406/371/674/a_image_thumb.png?1659420609)
What does PSNS ACh stimulation do to heart rate?
Slows/bradycardia
ACh acts on M2R to decrease cAMP, opening K+ channels
K+ efflux slows Na+ and Ca2+ in, delays repolarization, tf takes longer for SA to reach threshold
**M2R is GPCR**
![](https://s3.amazonaws.com/brainscape-prod/system/cm/406/371/677/a_image_thumb.png?1659420659)
What does SNS NA(+Adr) stimulation do to heart rate?
Increases/tachycardia, +contractility
NA acts on B1-aR to increase cAMP, opens Ca2+ channels, Ca2+ influx
Ca2+ influx in Phase 4 depolarization increases slope @ SA & AV - tf reach threshold faster, +firing rate, +conduction (rate and rhythm)
*can trigger dysrhythmias*
**B1-aR is GPCR(stimulatory)**
![](https://s3.amazonaws.com/brainscape-prod/system/cm/406/371/678/a_image_thumb.png?1659420659)
Atropine
- Muscarinic antagonist
- PSNS: blocks muscR, +HR (~60bpm)
At rest, in normal healthy individuals, neural drive comes significantly from the
PSNS
What are the SNS targets of the control of heart rate?
innervates SA node
conducting tussue
myocardial cells
What is the chemical transmitter for SNS control of heart rate?
What’s the ganglionic pathway?
What is the target tissue receptor?
Noreadrenaline (+ circulating adrenaline)
- Preganglionic neurons release ACh onto NicR
- Postganglionic neurons release NA onto B-aR (B1, GPCR) and myocardial cells
- +HR, +contractility
- +circulating adrenaline also activates alpha and B-aRs, w/ different selectivity to
Beta-adrenoceptors
![](https://s3.amazonaws.com/brainscape-prod/system/cm/406/371/684/a_image_thumb.png?1659420609)
What are the primary ativations by the SNS and PSNS at the heart?
PSNS - rate
SNS - rate and contractility
Noreadrenaline
- SNS: at B-aR, +HR, +contractility
alpha-1 adrenergic receptors
In smooth muscle (skin, sphincters, kidney, brain, bladder/uterus)
mediate contraction
activation = vasoconstriction
alpha-2 adrenergic receptors
In brain and spinal cord
Vascular smooth muscle cells of certain blood vessels (skin arterioles, veins)
Binds NA from SNS postganglion and adrenaline from adrenal medulla
beta-1 adrenoceptors
Cardiac tissue, cerebral cortex, kidney
Increase CO (+HR at SA, +contractility)
+renin from juxtaglomerular cells
Lipolysis in adipose tissue
beta-2 adrenoceptors
Smooth muscle (bronchi, GIT, uterus)
blood vessels (vasodilation)
Heart (+contraction, +CO, +HR @SA +contractility)
Proranalol
- Beta blocker/antagonist
- SNS: -HR (~10bpm)