Autonomic Nervous System (7) Flashcards
What kind of synapses do somatic motor neurons have? What kind of postsynaptic receptors?
Cholinergic (Ach); Nicotinic receptors (on the NMJ)
What is different about somatic motor system neurons, compared to autonomic efferent neurons?
Somatic motor neurons send their axons directly to their target organs (skeletal muscle), whereas autonomic nerves have two efferent neurons, the first of which synapses in a ganglia which then sends out the second (postganglionic) neuron.
What is the other term for the sympathetic NS?
Thoracolumbar
What is the other name for the parasympathetic NS?
Craniosacral
What is the only gland that receives direct, preganglionic innervation? What division of the ANS is responsible?
Adrenal gland; Sympathetic NS
Since it is a preganglionic nerve, it has cholinergic transmission (Ach); all preganglionics do
What is the pre-ganglionic NT for the sympathetic NS?
Acetylcholine
What is the postganglionic NT for sympathetic NS? What two exceptions and what is the NT for these?
Norepinephrine (NE);
Sweat glands and erector pili muscles are exceptions, these postganglionic sympathetic fibers use Ach
What NT is used by both preganglionic and post ganglionic parasympathetic neurons?
Acetylcholine (cholinergic)
Sympathetic discharge does what to pupils? Bronchi? HR and force of contraction? Blood vessels of skin and gut?
Dilates pupils
Dilates bronchi
Increases HR and force of contraction
Constricts vessels in skin and gut
What does sympathetic discharge do to pancreas? Adrenal glands?
Release of glucagon by pancreas ( also decreases insulin secretion
Release of Epi by adrenal glands (also NE)
What does parasympathetic discharge do to pupils? Bronchi? HR and force of contraction? Gastric vessels?
Constricts pupils
Constricts bronchi
Slows HR and force of contraction
Dilates gastric vessels (also stim. digestion)
What does parasympathetic discharge generally do to pancreas?
Increases release of both insulin and glucagon
Where in the spinal cord does sympathetic outflow originate? At what vertebral levels?
In the intermediolateral (lateral) horn of the spinal cord gray matter in vertebrae T1-L2.
The axons of the preganglionic sympathetic neurons exit the spinal cord via the _____ root.
Ventral (anterior) root
What structure conducts the preganglionic fibers of the sympathetic axons to the para vertebral chain ganglia?
White communicating rami (is lateral to the gray horn)
If a preganglionic sympathetic fiber synapses on a neuron within the paravertebral chain ganglia, by what structure does it leave the ganglia to send its axon back to the peripheral nerve?
Gray communicating ramus
What other two fates besides synapsing in a paravertebral ganglia may preganglionic sympathetic nerves in the ganglia have?
- May travel rostrally or causally in the chain before synapsing on a ganglion.
- May exit the chain to synapse in a more peripherally located prevertebral ganglion.
Which cranial nerves are involved as preganglionic parasympathetic neurons?
3, 7, 9, 10
Occulomotor, Facial, Glossopharyngeal, Vagus
What cranial nerve is the Edinger-Westphal nucleus associated with? What does it control?
Occulomotor n. (III); controls pupillary constriction
What peripheral ganglion does CN III’s preganglionic fibers synapse in?
Ciliary ganglion
Where on the brain is the Edinger-Westphal nucleus found?
In the midbrain
What two cranial nerves originate from the superior and inferior salivatory nuclei? Where in brain do the nuclei originate?
Facial n. (VII) and Glossopharyngeal n. (IX); these nuclei found in the upper medulla
What glands does parasympathetic outflow via Facial n. innervate? Parasympathetic outflow via Glossopharyngeal n.?
Facial - lacrimal and salivary glands
Glossopharyngeal - parotid gland
What two nuclei are associated with the vagus? Where do they both originate in the brain? (Is same place)
- Dorsal motor nucleus of the vagus
- Nucleus ambiguus
Both originate in the middle medulla
What do fibers in CN X do to the bronchial tree? Intestinal blood vessels? Peristalsis? HR?
Constrict bronchial tree
Dilate intestinal blood vessels
Increase peristalsis
Decrease HR
What ganglion do preganglionic parasympathetic fibers on CN VII headed for lacrimal glands first synapse in?
Pterygopalatine ganglion
What ganglion do preganglionic parasympathetic fibers on CN IX destined for parotid gland first synapse in?
Otic ganglion
What ganglion do parasympathetic preganglionics destined for salivary glands first synapse in?
Submandibular ganglion
In addition to the cranial outflow, which vertebral levels also have exiting preganglionic sympathetic fibers?
S2-S4
Innervate descending and sigmoid colon, rectal and bladder sphincter muscles, prostate, and other genital organs
In the enteric NS, what does the myenteric plexus generally control?
Smooth muscle and therefore gut motility
Is the plexus between the longitudinal and circular SM layers; also called Auerbach’s
What does the submucal plexus (Meissner’s) primarily control?
Glandular secretions
What is the effector NT of gut motility?
Acetylcholine (parasympathetic postganglionics secrete it to increase motility; NE from sympathetics decrease motility, etc)
What is the role of the nucleus of the solitary tract in the control of autonomic function?
The sensory afferents reach the ANS via the nucleus of the solitary tract
What two brain structures regulate outflow (efferents) from the ANS?
Amygdala and hypothalamus
A lesion of the sympathetic fibers at any point from the ______ to the _____ nerve will cause a Horner’s syndrome on that side of the lesion.
Hypothalamus
Ciliary n.
What two clinical symptoms are associated with Horner’s syndrome?
- Ptosis (drooping eyelid)
2. Meiosis (small pupil)
How do sympathetics reach the eye after synapsing in the superior cervical ganglia?
Axons leaving the superior cervical ganglion travel through the carotid sheath and enter the cranium with the carotid artery. They then follow the short and long ciliary nerves to reach the tarsal muscles (eyelid) and the dilatory of the iris.
If the lesion causing a Horner’s syndrome is centrally located (within the brainstem or spinal cord) what clinical manifestation would be expected?
A loss of sweating on the entire side of body the lesion is located
If the lesion causing Horner’s were peripheral (i.e. at the nerve root or more distal) then where would sweating be lost?
Only on the face, head, and neck; all on the same side of the lesion
Where is the origin of the primary sympathetic neurons?
Hypothalamus
Which two cranial nerves provide information about blood pressure? Via what nucleus?
IX and X; via nucleus of the solitary tract
What three places is the nucleus solitarus (nucleus of the solitary tract) connected to via interneurons that can send out efferents to control HR and BP?
- Nucleus ambiguus
- Motor nucleus of the vagus
- Midbrain sympathetic neurons (rostral ventrolateral medulla)
Bladder fullness is sensed by mechanoreceptors in the bladder and transmitted to the spinal cord via what division of the ANS?
Parasympathetic
By what tracts does fullness in the body of the bladder get relayed to the thalamus/cortex?
Spinothalamic tracts
“Very fullness” sensed in the bladder trigone reach the thalamus/cortex via what structures?
Posterior columns
Why do children under three not have voluntary control of micturition?
Because the pontine micturition center reflexively empties the bladder
What portion of the brain develops after 3 years and exerts conscious control over bladder emptying?
Superior frontal gyrus (medial surface) ; (is still mediated by the pontine micturition center, which acts a a way station for the cortical voluntary control over contraction of the external urethral sphincter)
How does the sympathetic NS control urine retention?
- Causes relaxation of the bladder detrussor muscle (storage of urine in bladder)
- Contraction of the external urethral sphincter (also the internal, which is only present in males)
How does the pontine micturition center allow emptying of the bladder?
It stimulates the parasympathetic NS and inhibits the sympathetic NS. Also inhibits the voluntary control over the external sphincter
Which branch of the nervous system is responsible for a psychogenic or mental erection?
Sympathetics - fibers are usually inhibited by higher centers, but arousal can release the inhibition
What branch is responsible for erection due to physical stimulation? Which nerve carries the efferent sensory info?
Parasympathetics from sacral (S2-S4). Pudendal nerve carries the sensory info (also S2-S4)
What two responses are mediated by the parasympathetics in females?
Vaginal lubrication and engorgement of erectile tissue
What part of ejaculation is mediated by parasympathetics? Which part is mediated by sympathetics?
Seminal emission - parasympathetic
Expulsion of sperm - sympathetic
What is mydriasis?
Pupil dilation
What is miosis?
Pupil constriction
What is a drooping eyelid called?
Ptosis
What is sicca?
Dry eyes
What receptors generally constrict blood vessels? Which usually dilate?
Alpha receptors constrict
Beta receptors dilate
(Usually!)
