UNIT 2 ANS ✨ Flashcards
What are the 4 classifications of receptors?
Ion channel, GPCR, Enzyme-linked receptor, Intracellular receptor
What is signal transduction?
The process by which a cell converts an extracellular signal into an intracellular response.
Describe the general architecture of the G protein second messenger system.
1st msgr = extracellular signal
Receptor = responds to extracellular signal
G protein = turn on or off an effector
Effector = activates or inhibits the 2nd msgr
2nd msgr = primary intracellular signal
Cellular response = causes a physiological change
What second messenger system is associated with the alpha-1 receptor?
Gq > PLC > IP3, DAG, Ca++
What other receptors share a similar pathway with the alpha-1 receptor?
Histamine-2, Muscarinic-1
What second messenger system is associated with the alpha-2 receptor?
Gi > AC > ATP 🡪 cAMP
What other receptors share a similar pathway with the alpha-2 receptor?
Muscarinic-2, Dopamine-2 (presynaptic)
What second messenger system is associated with the beta-1 and beta-2 receptors?
Gs > AC > ATP 🡪 cAMP
What other receptors share a similar pathway with beta-1 and beta-2 receptors?
Histamine-2, Vasopressin-2 (renal), Dopamine-1 (postsynaptic)
Describe the autonomic innervation of the heart.
SNS: cardiac accelerator fibers arise from T1-4
PNS: Vagus nerve (CN X)
Describe the autonomic innervation of the bronchial tree.
Beta-2 receptors are NOT innervated! They respond to catecholamines either in the systemic circulation or in airway (inhaled).
What is the primary neurotransmitter of the SNS?
Norepinephrine (NE)
What are the 3 ways that NE can be removed from the synaptic cleft?
- Reuptake – into presynaptic neuron (accounts for 80%)
- Diffusion – away from synaptic cleft
- Reuptake – by extraneural tissue
What enzymes metabolize NE and epi?
- MAO – monoamine oxidase
- COMT – catechol-O-methyltransferase
What is the final metabolic byproduct of NE and epi?
VMA (vanillylmandelic acid) or 3-methoxy-4-hydroxymandelic acid
List the 3 types of cholinergic receptors.
- Nicotinic-M (muscle)
- Nicotinic-N (nerve)
- Muscarinic
Where are Nicotinic-M receptors found?
Neuromuscular junction (NMJ)
Where are Nicotinic-N receptors found?
- Preganglionic fibers at autonomic ganglia (SNS & PSNS)
- CNS
Where are Muscarinic receptors found?
Postganglionic PNS fibers at effector organs and CNS
What are the 5 components of the autonomic reflex arc?
Compare and contrast the architecture of the SNS & PSNS efferent pathways.
Both have pre- and post-ganglionic nerve fibers.
PSNS: Long, myelinated, B-fiber (Ach); Short, unmyelinated, C-fiber (Ach).
SNS: Short, myelinated, B-fiber (Ach); Long, unmyelinated, C-fiber (NE).
What is the origin of the efferent SNS pathways?
Thoracolumbar: T1-L3; cell bodies arise from the intermediolateral region of the SC.
What is the origin of the efferent PNS pathway?
CranioSacral: CN 3, 7, 9, 10 and S2-4.
Describe the innervation of the adrenal medulla.
No POST-ganglionic fibers; it is in direct communication with the bloodstream.
What is the treatment approach for managing a patient with pheochromocytoma?
ALPHA BLOCK BEFORE BETA BLOCK!
What is the transcellular K+ shift?
K+ 🡪 cells (ICF) = hypokalemia; K+ 🡪 ECF = hyperkalemia.
Describe the anatomy & physiology of the baroreceptor reflex.
Regulates short-term BP control; if BP ↑ = reflex ↓ HR, contractility, & SVR… and vice versa.
What is the primary determinant of cardiac output in the patient with a heart transplant?
Autonomic - intrinsic heart rate from the SA node.
What drugs can be used to augment HR in the patient with heart transplant?
EPI, isoproterenol, glucagon.
What are the anesthetic considerations for multiple system atrophy?
Autonomic dysfunction (orthostatic hypotension); treat hypotension with volume and direct acting sympathomimetics.
What effects does low dose epinephrine have?
NON-selective BETA effects predominate; beta1 ↑ HR, contractility; beta2 vasodilation in skeletal muscle.
What are the cardiovascular effects of isoproterenol?
↑ HR, contractility; ↓ SVR, ↓ DBP = ↓ coronary perfusion pressure.
List 4 clinical indications for isoproterenol.
- Bronchoconstriction
- Cor pulmonale
- Heart transplant pts
- Chemical pacemaker for bradycardia unresponsive to atropine
In what situations should ephedrine NOT be used to treat hypotension?
- Heart transplant pts
- Sepsis
- Risk of HTN crisis in pts on MAOI
- Conditions where ↑ HR or contractility is detrimental to hemodynamics.
How does vasopressin increase BP?
V1 = intense vasoconstriction; V2 = ↑ intravascular volume by stimulating aquaporins.
What is the best treatment for vasoplegic syndrome?
Vasopressin (0.5-1 units IVP f/b 0.03 u/min).
List 6 drugs that are selective for the Beta1 receptor.
- Atenolol
- Acebutolol
- Betaxolol
- Bisoprolol
- Esmolol
- Metoprolol
List 6 NON-selective beta antagonists.
- Carvedilol
- Labetalol
- Nadolol
- Pindolol
- Propranolol
- Timolol
What is the primary site of metabolism of commonly used beta blockers?
Liver.
What are 2 exceptions for the primary site of metabolism for beta blockers?
- Esmolol (RBC esterase’s)
- Atenolol (kidneys)
Which beta blockers have local anesthetic properties?
Propranolol and acebutolol.
What is intrinsic sympathomimetic activity?
Beta blockers that exert a partial-agonist effect while blocking other agonists.
List 3 alpha antagonists.
- Phenoxybenzamine
- Phentolamine
- Prazosin
What is the mechanism of action for phenoxybenzamine?
Long acting, non-selective, noncompetitive antagonist.
What is the mechanism of action for phentolamine?
Short acting, non-selective, competitive antagonist.
What is the mechanism of action for prazosin?
Selective, alpha-1 antagonist.
