Autonomic Nervous System Flashcards
What nucleus receives inputs from visceral afferents?
Nucleus of the solitary tract
What CNs control parasympathetic output?
CN III, VII, IX, and X
What results to autonomic regulation if there is a cervical spinal cord transection?
- Reticulospinal inputs to sympathetic output neurons is lost
- Reticulospinal inputs to sacral parasympathetic output neurons is lost.
- Results in loss of blood pressure control by sympathetic neurons and bladder control.
What largely regulates activity of sympathetic and parasympathetic output neurons?
Reticular formation, which integrates inputs from NTS, hypothalamus, and other areas.
What is the difference between the white and gray rami?
Preganglionic sympathetic fibers leave the spinal nerve (after exiting the ventral root) and pass through the white ramus into sympathetic ganglia chain.
Postganglionic sympathetic fibers arising from paravertebral ganglia pass back from sympathetic chain into spinal nerves through gray rami.
What are the two locations of the cell bodies of sympathetic postganglionic neurons?
Paravertebral ganglia and prevertebral ganglia (paravertebral are ganglia of sympathetic chain, prevertebral ganglia are ganglia of the periphery)
What is the importance of postganglionic sympathetic fibers in the skeletal nerves?
These fibers pass back from sympathetic chain into spinal nerves through gray rami, and travel to the body in skeletal nerves. These nerves innervate smooth muscle targets.
What are the 4 fates of the preganglionic sympathetic fibers after entering the ganglia?
- Synapse with postganglionic neurons in the ganglion it enters
- Pass up or down the chain and synapse with other ganglia
- Pass through the sympathetic nerves to terminate in the prevertebral ganglia
- Pass without synapsing all the way from the cell column of the spinal cord through the sympathetic nerves to the adrenal medulla.
What is the location of the parasympathetic preganglionic neurons?
Brainstem and sacral spinal cord. Vagus nerve contains 75% of all parasympathetic preganglionic axons
What are the targets of parasympathetic outflow of CN III?
Sphincter pupillae (pupillary constriction) and muscles of ciliary body (controlling the shape of the lens).
What are the targets of parasympathetic outflow of CN VII?
Salivary glands (except parotid) and lacrimal and nasal glands
What are the targets of parasympathetic outflow of CN IX?
Parotid gland
What are the targets of parasympathetic outflow of CN X?
Nearly all thoracic and abdominal viscera
What are the targets of parasympathetic outflow of the sacral spinal cord?
Distal colon, rectum, bladder, lower portion of ureters, external genitalia
What is the total synthetic pathway to make epinephrine? What degrades epinephrine?
Tyrosine -> L-dopa (via Tyrosine hydroxylase) -> dopamine (via DOPA decarboxylase) -> norepinephrine (via dopamine-beta hydroxylase) -> epinephrine (via PNMT). COMT degrades epinephrine (catechol-O-methyltransferase)
What type of ACh receptor is on autonomic ganglia?
A distinct subtype of nicotinic ACh
What is the sensitivity of alpha and beta receptors for epinephrine and norepinephrine?
Alpha1/2: NE > Epi
Beta 1: NE = Epi
Beta 2: Epi > NE
What sympathetic receptors are present over the heart’s conduction system?
Primarily beta-1 receptors
What does the eye’s radial muscle do and what is its sympathetic receptor?
When sympathetically activated on its alpha1 receptor, the muscle contracts which causes widening of the pupil
What eye muscle controlling pupil dilation is innervated by sympathetic inputs? parasympathetic inputs?
Sympathetic inputs are onto the radial muscle which widens pupil when the muscle contracts.
Parasympathetic inputs are onto the sphincter muscle which when it contracts causes closing of the pupil
What is the bidirectional control of the ciliary muscle of the eye?
Ciliary muscle controls the lens.
When acted on by sympth inputs to beta2 receptors, results in relaxation of muscle to flatten lens for far vision
When acted on by parasympth inputs, the muscle contracts to make lens more convex for near vision.
What sympathetic receptor is on the bronchial muscle?
Beta2, causing relaxation of muscle. Parasympathetic input causes contraction of the muscle
What autonomic control of skeletal muscle is there?
Only sympathetic control via beta2 receptors to increase contractility
What are the predominant inputs to sympathetic preganglionic neurons?
Comes from the brainstem, mainly areas of the reticular formation, and the hypothalamus.
Just rattle off everything you know about Viagra.
Viagra acts as an inhibitor of phosphodiesterase type 5 (PDE5). Blocking PDE5 increases the duration which NO is active in smooth muscle cells. NO acts on the smooth muscle of blood vessel walls to cause vasodilation. Parasympathetic innervation of the blood vessels in the genitalia results in release of NO, NO produces vasodilation by activating guanylate cyclase, increasing cGMP levels. cGMP pumps calcium out of smooth muscle, inhibiting interactions of actin and myosin and causing muscle relaxation.
