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
What is glaucoma? What are some treatment strategies?
Increased intraocular pressure due to decreased aqueous outflow or increased aqueous production. Can be open or closed (iris pushed against cornea).
- Decrease aqueous production: sympathomimetics (alpha 1, alpha 2) causing vasoconstriction. Sympatholytics (beta 1, beta 2) causing decreased aqueous production.
- Open the angle: cause miosis to open the drainage angle. Parasympathomimetics (muscurinic) (causes pupillary constriction). Direct or indirect.
ANS - name the receptors found in this organ and their effects if stimulated:
Heart
- Beta 1 - increase HR, force of contraction
- M2 - decrease HR, and force of contraction (atrium).
ANS - name the receptors found in this organ and their effects if stimulated:
Blood vessels
- Alpha - Constriction of arterioles and veins.
- Beta 2 - dilation of arterioles in skeletal muscle, and dilation of veins
- M3 - dilation of arterioles in erectile tissue and salivary glands (and eye - aqueous humor production). No effect on veins.
ANS - name the receptors found in this organ and their effects if stimulated:
Viscera
- Alpha 1 - Decreased motility of GIT, contraction of bladder sphincter, contraction of uterus.
- Alpha 2 - Decreased motility of GIT, constriction of GIT sphincters, contraction of uterus
- Beta 2 - bronchodilation (indirect through circulating adrenaline), decreased GIT motility, relaxation of bladder wall
- M3 - bronchoconstriction, increased secretion in bronchi, increased motility of GIT, dilation of GIT sphincters, increased gastric acid secretion, contraction of bladder wall, bladder sphincter relaxation
ANS - name the receptors found in this organ and their effects if stimulated:
Male sex organ
- Alpha - ejaculation
- M3 - erection
ANS - name the receptors found in this organ and their effects if stimulated:
Eye
- Alpha - dilatation of pupil
- Beta - slight relaxation of cliary muscle
- M3 - constriction of pupil, contraction of ciliary muscle
ANS - name the receptors found in this organ and their effects if stimulated:
skin
- Alpha - piloerection
- sympathetic M3 - increased secretion of sweat glands
ANS - name the receptors found in this organ and their effects if stimulated:
salivary glands
- Alpha - increased secretion
- Beta - increased secretion
- M3 - increased secretion
ANS - name the receptors found in this organ and their effects if stimulated:
Kidney
- Beta 1 - increased Renin secretion
ANS - name the receptors found in this organ and their effects if stimulated:
Liver
- Alpha - glycogenolysis, gluconeogenesis
- Beta 2 - glycogenolysis, gluconeogenesis
In general, what are the main processes the ANS regulates?
- Contraction and relaxation of visceral and vascular smooth muscle
- All exocrine and certain endocrine secretions
- Heartbeat
- Energy metabolism (particularly in liver and skeletal muscle)
Name the outflow tracts of the parasympathetic nervous system.
- Cranial Outflow - cranial nerves destined for head, neck, thorax, abdominal viscera. The ganglia lie scattered in close relation to the target organs.
- Sacral Outflow - nerves destined for pelvic and abdominal viscera. The ganglia again lie scattered and in close relation to the target organs.
- The pelvic ganglia contain both sympathetic and parasympathetic nerves, and the two divisions are not anatomically distinct.
- Stimulation of the sacral outflow results in erection and is important in artificial insemination.
Name the outflow tracts of the Sympathetic nervous system.
- Paravertebral - bilateral on either side of the vertebral column. Nerve innervation to head, heart, lungs, blood vessels, sweat glands.
- Pre-vertebral - unpaired; on midline. Abdominal and pelvic viscera
- Terminal - adrenal medullas.
In some places the PNS and SNS produce opposing effects, other places they produce similar effects, and some where only one operates. Name some general areas of the body for these three categories.
- Opposing effects - visceral smooth muscle of GIT and bladder, heart
- Similar effects - salivary glands
- Single system innervation - sweat glands and most blood vessels (SNS). Ciliary muscle of the eye and bronchioles (PNS). These tissues have ways to modulate the single system innervation (bronchiole relaxation from circulating adrenaline or vascular relaxation via NO).
