ANS Flashcards
Gq receptor
↑ Phospholipase C → ↑ IP3, DAG, Ca2+
- A1
- M1, M3, M5
- V1
- H1
Gi receptor
↓ adenylate cyclase → ↓ cAMP
- A2
- M2, M4
- D2
Gs receptor
↑ adenylate cyclase → ↑ cAMP
- B1, B2
- D1
- V2
- H2
B1 receptor
- myocardium, conduction system → ↑ HR, contractility, conduction speed
- kidneys → renin release
B2 receptor
Bronchial tree → bronchodilation
Myocardial and skeletal muscle vascular beds → vasodilation
Ciliary muscle relaxes (far vision)
Gallbladder and ducts relax
Pancreas islet beta cells release MORE insulin
Liver ↑ serum glucose
Uterus relaxes
Bladder: destrusor relaxes
A1 receptor
Vasoconstriction (arteries > veins, but both)
EYES: radial muscle (iris) → contracts → MYDRIASIS
GI: sphincters contract
LIVER: serum glucose ↑
UTERUS: contracts
BLADDER: trigone + sphincter contract
Sweat glands ↑ secretion
A2 receptor
- vasoconstriction (veins > arteries, but both)
- Kidney: renal tubules → ADH inhibition → DIURESIS
- pancreas: Islet beta cells ↓ insulin release → hyperglycemia
- Salivary glands: dries out
- antishivering
- promotes platelet aggregation
SNS receptors in kidneys
A2 (renal tubules, diuresis via ADH inhibition)
B1 (↑ renin release)
DA receptors
-renal and mesenteric vasodilation
M2 receptors
-HEART: myocardium, conduction system: → ↓ HR, contractility
M3 receptor
BRONCHIAL TREE → bronchoconstriction
Phosphodiesterase III
- metabolizes cAMP to AMP which basically “turns off” a specific protein kinase, the cell is no longer instructed to perform that specific function.
- If you inhibit PDEIII, the “turn off” mechanism is inhibited and it indirectly ↑ cAMP, maintaining the protein kinases in the “turned on” state.
Lusitropy
Increasing the rate of relaxation by speeding up the return of calcium to the SR
Adrenal medulla
80% epi, 20% norepi
At rest secretes:
- 2mcg/kg/min epi
- 05mcg/kg/min norepi
Remember catecholamines in the bloodstream last 5-10X longer than they do in the synaptic cleft
Baroreceptor reflex monitoring locations and innervation: AFFERENT
- ) carotid sinus —> carotid sinus nerves (nerves of Hering) + CN IX (glossopharyngeal) converge to send afferent impulses to nucleus tractus solitarus in the medulla
- ) Transverse aortic arch sends afferent signal via vagus nerve.
Baroreceptor reflex location and innervation: EFFERENT
Vasomotor center in medulla and pons
Afferent traffic to nucleus tractus solitarus stimulates rostral ventrolateral medulla and intermediolateral nucleus.
SNS output is ↓ via inhibition of T1-T4 cardio accelerator nerves, neural network to vasculature, and at the same time a reciprocal rise in vagal tone. The net effect is ↓ HR, inotropy, and SVR.
Clinical examples of baroreceptor reflex
CEA: carotid sinus may cause bradycardia
Mediastinoscopy: pressure from scope on transverse aortic arch may cause bradycardia
Phenylephrine!
Drugs that preserve baroreceptor reflex
TPL, etomidate, hydralazine, SNP, NTG, norepi
ANS receptors: eye
A1: contraction radial muscle → mydriasis
B2: relaxation ciliary muscle → far vision
ANS receptors: pancreas
A2: ↓ insulin release
B2: ↑ insulin release
ANS receptors: liver
A1: ↑ serum glucose
B2: ↑ serum glucose
ANS receptors: uterus
A1: contraction
B2: relaxation
ANS receptors: bladder
A1: trigone + sphincter contraction (facilitates urination)
B2: detrustor relaxation (facilitates retention/storage)
Vasopressin receptors
V1: Gq
V2: Gs
Histamine receptors
H1: Gq
H2: Gs
How do preganglionic fibers get from spinal cord to SNS chain?
SNS preganglionic fibers exit SC via ventral nerve roots
Enter SNS chain via white rami
Steps of norepi synthesis
Tyrosine —(tyrosine hydroxylase) → DOPA → Dopamine → Norepi → Epi
Tyrosine hydroxylase is the rate limiting step
Where is the origin of efferent PNS pathways?
Craniosacral
- CN 3,7,9,10
- S2-S4
What drugs can be given to augment HR in a patient who got a heart transplant?
Epi, isoprel, glucagon
Glomus tumors
Originate from neural crest cells, tend to grow in neuroendocrine tissues that are near carotid, aorta, CN IX, and middle ear. Usually benign
→ release vasoactive substances HTN or hypo (NE, 5HT, histamine, bradykinin)
→ octreotide can be helpful for carcinoid-like sx
→ CN dysfunction (IX, X, XII) can ↑ aspiration risk, a/w obstruction
→ resection of a glomus that invaded IJ vein ↑ air embolism risk
Low, medium, and high dose epi compare/contrast
Low dose (0.01-0.03mcg/kg/min) → non selective beta. B1 ↑ HR/contractility, B2 → skeletal muscle vasodilation ↑ CO ↓ SVR
Intermediate dose (0.03-0.15mcg/kg/min) → mixed alpha beta
High dose (>0.15) → alpha prevails, BP ↑, tachyarrythmias
4 indications for isopreterenol
Chemical pacemaker if atropine not working
Heart transplant
Bronchoconstrition
Cor pulmonale
B1 selective drugs
Atenolol, Esmolol, Metoprolol, Bisoprolol Betaxolol
Non selective beta agonists
Propranolol, Labetolol, Carvedilol, Nadolol, Pindolol, Timolol
Alpha antagonists
Phenoxybenzamine: long acting nonselective noncompetitive antagonist A1+A1
Phentolamine: short acting nonselective competitive antagonist A1+A2
Prazosin selective A1 antagonist
