ANS Flashcards
What activities does the ANS control?
- Cardiovascular
- Respiration
- Endocrine secretion
- GI motility and secretion
- Reproductive and urogenital control
Name the divisions of the ANS, their neurotransmitters used, and their nerve fiber layout.
- Parasympathetic - rest/digest. Muscurinic and Nicotinic receptors using acetylcholine as a neurotransmitter. Long pre-ganglionic nerve fibers synapsing onto nicotinic receptors, and short post-ganglionic nerve fibers synapsing onto muscurinic receptors. More localized effect than SNS.
- Sympathetic - fight/fligh. Alpha and beta receptors using adrenaline/noradrenaline. Short pre-ganglionic nerve fibers synapsing onto nicotinic receptors (Ach as NT), and long post-ganglionic fibers synapsing onto adrenergic (alpha or beta) receptors. Innervation is more diffuse than with PNS (wider spreading effects).
What are some functions of the SNS?
- Bronchodilation
- Decreased GI motility
- Increased sphincter tone
- Glycogenolysis
- Gluconeogenesis
- Bladder wall distension, bladder neck constriction
What are some functions of the PNS?
- Decrease rate and force of contraction (atrial contraction) of heart
- Vasodilation - indirect effect through stimulation of NO release by Ach
- Increase GI motility and secretion
- Miosis (constriction of the pupil
- Bronchoconstriction, and increased secretion of mucous in resp tract
- Contraction of bladder wall, and relaxation of urethral sphincter
What kind of receptor does NA/A work on?
GPCR. alpha and beta
What are the different classifications of adrenoceptors?
- Alpha - 1, 2
- Beta - 1, 2, 3, 4
Where are alpha 1 receptors distributed?
- Vascular Smooth Muscle (constriction)
- Myocardium
- Bladder sphincter (contraction)
- Pupil (dilation - mydriasis)
- Uterine (contraction)
- GIT smooth muscle (decrease motility)
- Male sex organ (ejaculation)
- Salivary glands (secretion)
- Liver (glycogenolysis, gluconeogenesis)
Where are alpha 2 receptors distributed?
- Located pre-junctionally and inhibit NT release. alpha2a subtype
- Located post-junctionally in vascular smooth muscle (vasoconstriction). alpha2b subtype
- veins (vasoconstriction)
- GIT smooth muscle (decrease motility) (increase sphincter constriction).
- Uterus (contraction)
- Male sex organ (ejaculation)
- Pupil (dilation)
- Salivary gland (secretion)
- Liver (glycogenolysis, gluconeogenesis)
Where are beta 1 receptors distributed?
- Mainly in the heart (increased force of contraction, increased conduction, and increased rate of impulse formation)
- Kidney (renin secretion)
Where are beta 2 receptors distributed?
- Vascular smooth muscle (dilatation)
- Bronchodilation, and stabilization of respiratory mast cells (decreased secretion)
- GIT (decreased motility)
- Bladder wall (relaxation)
- Liver (glycogenolysis, gluconeogenesis)
Recap the alpha and beta 1 and 2 receptors. Name their general locations/actions.
- Alpha 1 - Increase IP3 and DAG, increasing [calcium]. Vasoconstriction, except in GIT
- Alpha 2 - Decrease adenylyl cyclase and cAMP. Presynaptic inhibition, contraction of VSM.
- Beta 1 - increase adenylyl cyclase and cAMP, increase [calcium]. Mainly in heart, increase HR, force of contraction, conductance.
- Beta 2 - increase or decrease cAMP. Relaxation of smooth muscle (bronchodilation, vasodilation in skeletal muscle)
What kind of receptor class are Nicotinic and Muscurinic receptors? What are the subtypes of these receptors?
- Nicotinic - ligand gated ion channel
- Muscurini - GPCR
- Nicotinic - Nm, Ng, Nn: skeletal muscule, ganglia, nervous system/brain
- Muscurinic - M1-M5
Are nicotinic receptors stimulatory or inhibitory?
Stimulatory
- Increase permeability to Na+ and K+
Are Muscurinic receptors stimulatory or inhibitory?
M1, M3, M5 are stimulatory.
M2, M4 are inhibitory.
- M1 - neural, gastric parietal cells.
- M2 - cardiac
- M3 - glandular, smooth muscle
- M4 - CNS
- M5 - CNS
What are some ways in which drugs can act indirectly?
- Sympathomimetics - displace NA/A
- Parasympathomimetics - acetylcholinesterases. displace ACh