2/2: Autonomic Nervous System Flashcards
What does the autonomic nervous system control?
Visceral functions of the boddy by monitoring (sensory) and adjusting (motor) activity of cardiac muscle, smooth muscle, glands and adipose tissue
What are the two divisions of the autonomic nervous system?
Sympathetic (SNS)
Parasympathetic (PNS)
Both systems of the autonomic nervous system are ________, ________ & ________, _________
Involuntary, excitatory & inhibitory, di-synaptic
Do the two autonomic systems oppose eachother when innervating the same tissue?
Yes
Each system is _______ active, but one system is usually predominant at ________
Tonically active; predominant at rest (PNS)
What is the sympathetic nervous system?
Fight or flight
The sympathetic nervous system can selectively activate what?
Effectors or elicit a mass discharge, especially during stress response
What is the hormone for the SNS?
Noraderenergic (NE)/adrenergic (EPI) at the target organ
- BUT cholinergic pre- to post ganglionic
What is the parasympathetic nervous system?
Rest and digest
Describe the control mechanisms of the PNS
Almost always specific, activating or inhibiting discrete targets
What hormone works with the PNS?
Cholinergic (ACH)
The actions of the SNS and PNS __________ one another
Antagonize
The PNS works with what areas of the body?
Craniosacral
- neurons leave from brain or sacral region
The SNS works with what areas of the body?
Thoracolumbar
- thoracic region or lumbar region is where the neurons enter or exit
Both the SNS and PNS have what kind of neurons?
Preganglionic nerouns
Where are the SNS and PNS preganglionic cell bodies located?
Lateral gray horn of the spinal cord (SNS) or motor nuclei of cranial nerves III, VII, IX, and X (PNS)
All preganglionic terminals release _______ that bind to _______ on the __________ neuron
ACh; nicotinic receptors (type N) (always excitatory -EPSP); postganglionic neuron
What kind of channels are nACh receptors and what are they selective for?
Ligand-gated ion channels (ionotropic); selective for both Na+ and K+
Where are postganglionic neuron cell bodies located?
Outside of the CNS
Where do preganglionic axons of the sympathetic NS exit and go?
Exit through a white ramus into one of the gangliaof the sympathetic chain
Once the sympathetic nervous system axons exit, the fibers will then do what?
- Synapse with postganglionic neurons at the ganglia
- Pass up or down the sympathetic chain, then synapse with a different ganglia
- pass through the chain and out a sympathetic nerve (Splanchnic) where it will synapse in a peripheral sympathetic canglion (celiac, superior mesenteric, or inferior mesenteric)
What is an exception of the places where a synapse can occur for the sympathetic nervous system?
Adrenal medulla
In all scenarios (besides adrenall medulla), where can a synapse occur for the SNS?
Sympathetic chain
Peripheral ganglion
What do almost all sympathetic postganglionic terminals release?
Norepinephrine (NE/adrenaline) at synapse with target cells
What does NE activate?
Alpha and beta receptors
What do most sympathetic post-ganglionic terminals release at sweat glands and what does this activate?
Release ACh at sweat glands to activate muscarinic receptors
Some skeletal muscle vasculature also works this way
What does the adrenal medulla secrete into the bloodstream?
Through chromaffin cells:
80% epinephrine (EPI/adrenaline)
20% NE
EPI and NE then circulate throughout the body and activate adrenergic receptors
How does the adrenal medulla catalyze the converstion of NE to EPI?
Through a specific enzyme
Describe how alpha and beta receptors work in the SNS?
Beta receptors work at low concentration (higher affinity)
Alpha receptors work at high concentrations (lower affinity)
What receptors is norepinephrine more potent to?
Alpha receptors compared to epinephrine
What does Alpha 1 receptor do?
Constricts smooth muscle because
Increase in IP3 = increase Ca = increae contraction
What does alpha 2 receptor do?
Blocks further NE release (presynaptic receptor) by decreasing cAMP
Describe how the catecholamine potency for beta receptors varies
Epi and NE have almost equal potency at Beta 1 receptors
Epi has a MUCh greater potency at Beta 2 receptors than NE
NE has slightly greater potency at Beta 3 receptors than EPI
What does beta 1 do?
Increase heart rate and contractility, increase lipolysis, increase renin secretion, increase protein content in saliva
What does beta 2 do?
Relax smooth muscle, release FA and glucose
Where is beta 3 doun?
Adipose tissue
What kind of beta is an epi pen?
Beta 2 because it dialates airways
What is the location of alpha 1 receptors?
Effector tissues; smooth muscle, glands
What is the function of an alpha 1 receptor?
Increases Ca2+, causes contraction, secretion
ex: blood vessels
Where is the location of alpha 2 receptors?
Nerve endings, some smooth muscle
What is the function of alpha 2 receptors?
Decrease transmitter release (nerves), causes contraction (muscle)
Where is the location of beta 1 receptors?
Cardiac muscle, juxtaglomerular apparatus
What is the function of beta 1 receptors?
Increase heart rate, increase force, increase renin release
What is the location of beta 2 receptors?
Smooth muscle, liver, heart
What is the function of beta 2 receptors?
Relax smooth muscle; increase glycogenolysis; increase heart rate, force
ex: blood vessels airways
What is the location of beta 3 receptors?
Adipose cells
What is the function of beta 3 receptors?
Increase lipolysis
When adding epinephrine to local anesthetics, what does this cause? and how?
Vasoconstriction (via alpha 1 receptors) at the site of administration which decreases blood absorption and facilitates neuronal uptake, enhances quality of analgesia, prolongs duration of action and limits toxic side efects
- addition of EPI to lidocaine extends duration of anesthesia by at least 50%
What receptor does albuterol use and what does this do?
Beta 2 selective agonist
Used for asthma treatment because it causes bronchodilation
NE that is released by nerve terminals remains active for only a few seconds before:
- Diffusion away from synaptic cleft
- Reuptake by presynaptic terminal (cocaine blocks re-uptake)
- Destruction by the enzymes MonoAmine Oxidase (MAO) or Catechol-O-Methyl Transferase (COMT)
MAO inhibitors are a class of drugs used to treat what medical conditions? and what are their side effects?
Parkinson’s disease
Depression
Social anxiety
Side efects: xerostomia, nausea, b/c increase norepinephrine in salivary glands blocks the degredation of salivary glands
Does the PNS or SNS have longer preganglionic axons?
PNS
What do preganglionic termianls release that bind to nicotonic ACh receptors?
ACh
Preganglionic parasympathetic axons supply the face via what nerves?
Oculomotor (III)
Facial (VII)
Glassopharyngeal (IX)
Preganglionic sympathetic axons supply the thorax and upper abdomen via what nerve?
Vagus (X)
What areas of the spinal cord carry preganglionic parasympathetic axons to the pelvic viscera?
S2-S4
What do postganglionic parasympathetic varicosities release and bind to?
ACh that bind to muscarinic ACh receptors on target cells
What are the 3 things that muscarinic receptors (G-protein/metabotropic) do?
- Constrict smooth muscle
- Relax sphincters
- Stimulate glandular secretions
What are the actions of the PNS via muscarinic receptors?
(DUMBBLS)
Digestion
Urination
Miosis
Bronchoconstriction, Bradycardia
Lacrimation
Salivation
What is muscarinic receptor 1 associated with?
Stomach (secreitons and contraction)
Salivary glands (Inrease intracellular calcium)
What is M2 associated with?
Smooth muscle, myocardium, cardiac autorhythmic cells, CNS (decrease cAMP)
What is M3 associated with?
Exocrine glands (ex: salivary), smooth muscle, endothelium, sweat glands (sympathetic function) Increase intracellular Calcium
What is M4 associated with?
CNS, vagal nerve
Decrease cAMP
What is M5 associated with?
CNS
Increase intracellular Calcium
What do M1,3,5 have in common?
Similar g-protein coupling receptors (IP3)
All increase intracellular calcium levels
What do anticholinergic drugs do?
Inhibit the effects of ACh systemically (via muscarinic receptors)
What are side effects of anticholinergic drugs?
Xerostomia, constipation, ileus, nausea, vomiting
What can occur in patients taking anti-cholinesterases (treatment for alzheimers)?
Siallorhea (drooling)
What does binding of ACh to NM receptor elicit?
Contraction
What does release of ACh by the somatic motor neuron and activation of NM receptor stops cause?
Releaxation
In the PNS, what receptors constrict and relax the bladder?
M2 relax sphincter
M3 constricts detrusor (by increasing calcium)
In the SNS, what receptors constrict and relax the bladder?
alpha 1 constricts sphincter
beta 2 relaxes detrusor
In the SNS, what receptors constrict and relax the GI tract?
alpha 1 constricts
beta 2 relaxes (allows to stop movement of food in gut)
In the PNS, what receptors constrict and relax the GI tract?
M2 relaxes sphincter
M3 contracts muscle (allows more food along the gut)
In the PNS, what receptors stimulate watery secretion in salivary glands and why?
M1 and M3; due to contraction of myoepithelial cells and vasodilation
In the SNS, what receptors constrict and relax the salivary glands?
alpha 1 vasocontriction and secretion of concentrated saliva
beta 1 receptors stimulate secretion of protein
What does meth. act on and cause?
Methamphetamine acts on the α-adrenergic receptors of the vasculature
of the salivary glands, causing vasoconstriction and reducing salivary
flow, depriving the oral environment of saliva’s buffering activity to counteract acidity and prevent demineralization of enamel leading to “Meth Mouth”
In the SNS, what receptors constrict and relax the vascular smooth muscle/blood vessels?
alpha 1 vasoconstriction (decrease lumen size)
beta 2 vasodilation
Does the PNS regulate the diameter of most arterioles?
No; BUT the PNS (via ACH on Muscarinic Receptors) causes vasodilation of salivary gland arterioles,
which increases blood flow to the salivary glands for secretion of saliva. A few other arterioles that dilate
under PNS control include arterioles of the gastric and intestinal glands
In the PNS, what receptors are involved with the heart?
Predominant tone keeps HR
and conduction low (M2)
In the SNS, what receptors are involved with the heart?
B1 - increases HR and contractility
B2 - Coronary blood flow via vasodilation of coronary blood flow via vasodilation of coronary vessels
In the PNS, what receptors are involved with the lungs?
Predominant tone constricts bronchial smooth muscle (M3)
In the SNS, what receptors are involved with the lungs?
Relaxes bronchia muscle (B2)