How Drugs Affect the ANS Flashcards
Describe typical sympathetic pre- and post-ganglionic neurons
Pre-ganglionic: short axon
Post-ganglionic: long axon
NE alpha-1 receptors associate with what G-protein receptor? What is the end effect of this?
Gq; influx of intracellular Ca++
NE alpha 2 associates with what G-protein receptor; what is the end effect of this?
Gi; decreased voltage-gated Ca2+ channels
NE beta 1-3 receptors associate with what G-protein receptor; what is the end effect of this?
Gs; increases cAMP
What is the preferential molecule for alpha 1 receptors, NE or EPI?
NE
What is the preferential molecule for alpha 2 receptors, NE or EPI?
It is equal
What is the preferential molecule for B1 receptors, NE or EPI?
They are equal
What is the preferential molecule for Beta 3 receptors, EPI or NE?
EPI >> NE
Where is norepinephrine produced in the body and what is its precursor?
the presynaptic terminal of the neuron; tyrosine
What happens if you activate Gq in a smooth muscle cell?
What happens if you activate Gs in a smooth muscle cell?
Relaxation
What happens if you activate Gi in a smooth muscle cell?
Contraction
Under what circumstances might it be advisable to administer a beta agonist to the airway?
asthma
What happens if you activate Gs in a cardiac muscle cell?
Contraction
What happen if you activate Gi in a cardiac muscle cell?
Decreased contraction
Compare and contrast Gq signaling in smooth muscle vs. cardiac muscle
Gq signaling stimulates contraction in smooth muscle and has unconventional cardioprotective effects in cardiac muscle
Compare and contrast Gs signaling in smooth muscle vs. cardiac muscle
Gs signaling stimulates relaxation in smooth muscle and contraction in cardiac muscle
Compare and contrast Gi signaling in smooth muscle vs. cardiac muscle
Gi signaling stimulates contraction in smooth muscle and decreases contraction in cardiac muscle
What happens if you activate Gi in a presynaptic terminal?
Describe cardiac tissue response to sympathetic stimulation
- Effects of EP and NE mediated primarily by B1 receptors
- symp stimulation increases ALL aspects of cardiac fxn
- SA node: incr rate (+ chronotropes)
- Ventricles/atria: incr contractility (+ inotropes)
- AV node: incr conduction velocity (+ dromotropes)
Describe blood vessel tissue response to sympathetic stimulation
- primary target: vascular smooth mm (VSM) cell
- typically a pressor response (incr MAP)
- alpha1 > VSM contraction > Incr resistance
- beta2 > VSM relaxation > decr resistance
-
alpha effect predominates in most tissues
- __except: sk mm, brain, large vv
What is the cardiovascular response to NE?
Parasympathetic activation > rapid homeostatic mechanism to decrease heart rate and blood pressure (baroreceptor reflex) via the vagus nn.
What is the eye tissue response to sympathetic stimulation?
- alpha1 > contracts radial mm = mydriasis (pupil dilation)
- beta2 > relaxes ciliary muscle = miosis (flattening of lens)
What is the lung tissue response to sympathetic stimulation?
- major effect = relaxation of bronchial smooth mm. via B2 receptor activation
- regulation of bronchial glandular secretions is species-dependent and variable
- beta2 > enhanced secretion
- alpha1 > reduced secretion (predominates)
What is the GI tract tissue response to sympathetic stimulation?
- generally inhibited by increased sympathetic tone
- beta2 > reduces motility by relaxing mm, reduces secretion
- alpha1 > constricts sphincters
What is the urinary bladder tissue response to sympathetic stimulation?
- complimentary effects lead to reduced urination
- alpha1 > constricts sphincter
What is the sweat glands response to sympathetic stimulation?
- symp postganglionic neurons are atypical as they are cholinergic (except in horses)
- release ACh onto mAChR
- horses exhibit “adrenergic sweating” (B2)
