Physiology of Autonomic Nervous System Flashcards
What are the components of the peripheral ANS?
Parasympathetic
Sympathetic
Enteric neurons
Visceral afferent fibers
The central ANS provides for homeostasis by what three routes?
- Controls viscera via its connections to preganglionic neurons that control teh heart, smooth muscle, and glands of the body through parasympathetic and sympathetic neurons
- Controls behaviors responsible for physical exchanges between the organism and environment via connecttions to motivational and somatic motor pathways
- Control of the endocrine system contributes to both of the foregoing control mechanism
Which systems are involved in appetitive behaviors?
-
Ingestive
- Eating and drinking
-
Excretory
- Micturition and defication
-
Reproductive
- Mating and parturition
Sympathetic efferents exit the CNS from the spinal cord between the ___ and ______ levels.
T1; L2
Organs of the _______ are inenrvated by prevertebral ganglia distal tot he spinal and paravertebral chain.
abdominal cavity
NOTE: Prevertebral ganglion are closer to target tissue, unpaired, and a short distance to travel to reach terminal ganglia (as opposed to paravertebral ganglia)
The sympathetic ganglia contain cell bodies of ________ (preganglionic/postganglionic) neurons that project to the target organs.
Postganglionic
Parasympathetic efferents exit the CNS via the cranial nerves or from the ________ spinal cord.
Sacral
In both divisions of parasympathetic, the CNS efferents in the ANS project to autonomic ganglia and are called __________ neurons.
Preganglionic
Where are the preganglionic and postganglionic sympathetics located respectively?
Preganglionic
- Intermediolateral cell colum in lamina 7
Postganglionic
- Paravertebral and Prevertebral
What si the course of preganglionic sympathetic neurons?
- Begin in intermediolateral cell column of lamina VII
- Project through the ipsilateral ventral root separating into the white ramus
- Synapse with postganglionic neurons
Paravertebral ganglion supply innervation to which structures?
- head
- thorax
- trunk
- limbs
- Blood vessels in muscles
- Sweat glands
- Erector pili mscles
What are the targets of the superior cervical ganglion?
Eyes
Salivary glands
Lacrimal glands
Blood vessels of the cranial muscles
Blood vessels of the brain
What are the targets of the middle cervical and stellate ganglion?
Heart
Lungs
Bronchi
Sympathetic preganglionic efferents can form synapses with what?
- In the paravertebral ganglia at the same level
- In the paravertebral ganglia at a different level
- In accessory sympathetic (prevertebral ganglia)
NOTE: Specialized sympathetic preganglionic neurons project to the adrenal medulla
What is the course of preganglionic fibers to reach prevertebral ganglion cells?
Preganglionic axons pass through the white rami, the chain ganglia, and the gray rami without synapsing to make contact with prevertebral ganglionic cells
What are the major prevertebral ganglion and what do they innervated?
Celiac (solar plexus)
- Stomach, foregut, liver, pancreas
Superior Mesenteric
- Midgut
Inferior mesenteric
- Hindgut and pelvic organs
Pelvic- hypogastric plexus
Urinary and genital tissues
The adrenal medulla is a ___________ ganglion containing postganglions.
Sympathetic prevertebral
________________ cells in the adrenal medulla behave like sympathetic postganglionic neurons, releasing epinerphrine (adrenaline) into the bloodstream.
Chromaffin
Where are parasympathetic ganglia located?
In or near their target organs, usually far from the spinal cord
Gray matter of which spinal cord segment provides parasympathetics?
S2-S4
Which parasympathetic nuclei are located in the brainstem? What is the function of each respectively?
Edinger- Westphal Nucleus
- Parasympathetic neurons travel in CN III and synapse onto postganglionic neurons in ciliary ganglion
- Innervates constrictor muscle of the pupil and ciliary muscle
Superior Salivatory Nucleus
- Parasympathetic neurons through a branch of CN VII to the pterygopalatine and submandibular ganglia
- Innervates lacrimal, submandibular and sublingual glands
Inferior Salivatory Nerve and Nucleus Ambiguus
- CN IX to the otic ganglion
- Innervates the parotid gland
About 75% of all parasympathetic nerve fibers are in the _______ nerve.
Vagus
Where are the cell bodies of the vagus nerve located?
Nucleus Ambiguus
- Activates striated muscles in the pharynx, larynx, and esophagus and slows the heart
Dorsal motor nucleus
- Initiates secretion of gastic acid, insulin and glucagon
Which structures receive parasympathetic innervation from the vagus nerve?
Viscera of the thorax and abdomen
Vagal afferent cell bodies are located in the __________ ganglion. What type of info is carried here?
Nodose
- Info about distention of hollow organs, blood gases, and body chemistry to the medulla
Sacral preganglionic cell columns control parasympathetic motor, vasomotor, and secretomotor functions to which structures?
Kidneys
Bladder
Transverse and distal colon
Reproductive organs
Nociceptive input from the left ventricle of the heart is referred to the left ___ to _______ dermatomes.
T1; T5
Both sympathetic and parasympathetic neurons release which neurotransmitter?
Acetylcholine
Acetylcholine acts at ______ receptors on the postganglionic neuron.
Nicotinic
*Excitatory
Which neurotransmitter is released by sympathetic postganglionic neurons?
Norepinephrine
NOTE: Norepinephrine acts through alpha and beta adrenergic rectors on target organs. Excitatory and inhibitory depending on target.
Parasympathetic postganglionic neurons release acetylcholine which acts through _____ receptors on target organs.
Muscarinic
*Excitatory and inhibitory depending on target
Postganglionic neurons release neurotransmitters from ______ instead of from axon terminal boutons.
Varicosities
*This bathes the target tissue in neurotransmitter
Nictotonic receptors are ligand-gated channels for _________ (slow/rapid) transmission.
Rapid
Post ganglionic parasympathetic neurons act through muscarinic ACh receptors on the postsynaptic membrane of the target cell, which are _______ (slow/rapid).
Slow (and prolonged)
What is the mechanism by which muscarinic receptors work to modulate K+ receptors?
- Muscaranic receptors (G protein coupled receptors)
- Stimulate the hydrolysis of phosphoinositide increasing [Ca2+]l and activate protein kinase C
- Inhibit adenylyl cyclase and thus decrease cAMP levels
- Directly modulate K+channels through G-protein beta-gamma complex
There are 5 types of muscuranic receptors. What are there functions respectively?
M1
- Found mediating slow EPSP at the ganglion in the postganglionic nerve, is common in exocrine glands and in the CNS
- Bound to G proteins of class Gq
M2
- Located in the heart
- Act to slow the heart rate down to normal sinus rhythm, by slowing the speed of depolarization.
- Act via a Gi type receptor, which causes a decrease in cAMP in the cell, inhibition of voltage-gated Ca2+ channels, and increasing efflux of K+, in general, leading to inhibitory-type effects.
M3
- Located in the smooth muscles of the blood vessels, as well as in the lungs.
- Gq-coupled
- Mediates an increase in intracellular calcium, it typically causes contraction of smooth muscle
- Increased synthesis of nitric oxide
M4
- Gi- coupled
- Located in CNS
- Decrease cAMP
M5
- Gq- coupled
What are the functions of the two types of norepinephrine receptors?
Alpha
- Contract smooth muscle
-
Types
- a1- blood vessels
- a2- presynaptic terminals
Beta
- Relaxes smooth muscle
-
Types
- B1- Heart
- B2- Bronchial muscle of the lungs
- B3- adipose
What are the effects of an a1 agonist?
Effective nasal decongestants because they cause contriction of blood vessels which reduces blood blow and results in shrinkage on the tissue
What effect would an a2 antagonist have?
Can be use to treat impotence (erectile dysfunction)
What effect would a B1 agonist have?
Increase cardiac output in congestive heart failure because B1 acts on the heart, causing relaxation, which will increase blood flow.
What effects would a B2 agonist have?
Used as bronchodilators in asthma and chronic lung disease
a1 antagonist may be used in cases of __________.
Hypertension
ATP works with norepinephrine to produce what actions?
- Induces vascular constriction in vascular smooth muscle
- Activates purinoceptors (implicated in learning and memory, locomotor and feeding behavior, and sleep) on smooth muscle cells of blood vessels, urinary bladder and other visceral targets
- Via the P2x and P2y receptors: fast and slow excitation of smooth muscle in bladder, vas deferens and arteries
Neuropeptide Y works with ATP for ______.
vasoconstriction
- Stimulates arterial contraction and potentiates responses mediated by a1-adrenergic receptors
What are the major functions of nitric oxide?
- Relaxes vascualr smooth muscle
- Stimulates intracellular soluble guanylate cyclase
- Vasodialation, penile erection, urethral relaxation
Somatostatin works with norepinephrine to control ______ and __________.
Gut motility; secretion
_______ is the only brain site in a cloded efferent-afferent reflex loop with SNS and PNS.
Paraventricular nucleus
Tha paraventricular nucleus plays a role in what functions?
Feeding, thermoregulation, circadian rhythms, water balance, emotions, sexual drive, reproduction, and motivation
What are the stress hormones?
Cortisol (hypothalamus- pituatary-adrenal)
Norepinephrine and epinephrine (sympathetic nerve terminals and the adrenal medulla
the innervation of the small arteries and arterioles allows sympathetic stimulation to ________ (increase/decrease) resistance to blood flow and thereby to _______ (increase/decrease) rate of blood flow through the tissues.
Increase; decrease
Innervation of the large vessels, particularly of the veins, makes it possible for sympathetic stimulation to decrease the _____ of these vessels.
Volume
NOTE: This can push blood into the heart and thereby play a major role in regulation of hert pumping
The cardiac parasympathetic fibers originate in the ________, incells that lie in the dorsal motor nucleus of the vagus or in the nucleus ambiguus.
Medulla oblongata
The right and left vagus nerves are distributed to different cardiac structures. Where is each distributed and what does each stimulate?
Right vagus
- SA node and atrial muscle
- Stimulation of this nerve slows SA nodal firing and can even stop the firing for several seconds
Left vagus
- AV node and some ventricular muscle
- Inhibits AV conduction tissue to produce various degrees of AV block
For given levels of atrial pressure, the amount of blood pumped each minute (cardiac output) can be increased more than 100 percent by _________ stimulation.
Sympathetic
NOTE: The opposite is true for parasympathetic stimulation
Vagal fibers are distributed mainly to the ________.
Atria
*This explains the effect of vagal stimulation mainly to decrease heart rate rather than to decrease greatly the strength of heart contraction.
How does sympathetic stimulation affect calcium dynamics?
Alters intracellular calcium dynamics through a greater influx of calcium leading to plateu strengthening leading to increased cotnractility strength
Where are baroreceptors located?
Aortic arch and carotid sinuses
Baroreceptor respond to :
Vascular stretch and deformation induced by changes in arterial blood pressure
Autonomic Dyreflexia is a condition observed in about 85 percent of patients following spinal cord injury above ______.
C6.
What are the symptoms of autonomic dysreflexia?
Exaggerated autonomic reflexes, especially sudden dramatic increases in blood pressure are provoked by inappropriate stimuli, such as pressure on the bladder.
__________ is an autosomal recessive disorder in Askenazic Jews associated with decreased tearing and sensitivity to pain and absent fungiform papillae on the tongue.
Riley- Day Syndrome
NOTE: Episodic abdominal crises and fever are very common as is orthostatic hypotension
__________ is a progressive degenerative condition of unknown origin affecting cells of the central autonomic network in the brainstem, intermediolateral cell column, locus ceruleus, dorsal motor nucleus of the vagus, and other nuclei including the substantia nigra caudate nucleus, and cerebellum.
Shy-Drager Syndrome
NOTE: The presence of lewy bodies in many of these areas suggests this syndrome may be releated to Parkinson’s disease.
What is the hallmarksign of Shy-Drager syndrome?
Profound orthostatic hypotension without a compensatory increase in heart rate
What is the clinical use of pilocarpine?
Glaucoma (opens aqueous humor drainage pores)
What is the clinical use of neostigmine?
Myastenia gravis (increases availability of ACh)
What is the clinical use of albuterol?
Asthma (dilates bronchioles by binding to B2 receptors)
What is the clinical use of propranolol?
Hypertension (member of a class of drugs called beta-blocers that decrease heart rate and blood pressure
