Autonomic Nervous System and Saliva Flashcards
What branch of the autonomic nervous system is primarily in control of the gut?
the parasympathetic branch
What is the enteric nervous system?
the brain of the gut; intrinsic control of gut movement and secretion
What are the sensory cells in the enteric nervous sensitive to?
stretch, osmolarity, pH, fats, glucose, amino acid concentrations, and noxious toxins
What kind of impulses can the sensory cells of the enteric nervous system send?
afferent information
Where do the sensory cells of the enteric nervous system send afferent information to?
back to the neurons of the myenteric plexus and to the spinal cord/brain via autonomic nerves
What do the efferent neurons of the enteric nervous system control?
GI smooth muscle contractility, affect blood flow, secretory epithelium output, neuroendocrine cells, and immune cells
What do ENS effector cells make?
neurotransmitters
What controls the voluntary muscle of the GI tract?
voluntary muscle
What is the simple somatic motor reflex important for in GI physiology?
prehension, masticatin, deglutination, regurgitation, voluntary eructation, and defecation
What is rest and digest referring to?
the parasympathetic branch of the autonomic nervous system
What is fight or flight referring to?
the sympathetic branch of the autonomic nervous system
How many neurons does the parasympathetic and sympathetic system need to complete the efferent message?
two - preganglionic fiber and postganglionic fiber
Where are the preganglionic sympathetic nerve cell bodies located?
in the spinal cord from T2 to L3
What do axons of the preganglionic sympathetic nerve cell bodies exit the spinal cord via?
the sympathetic paravertebral chain
What are the two paths that the preganglionic sympathetic axons of the gut can take?
they can either enter the sympathetic chain and terminate where they meet the post ganglionic neuron, or they enter the white ramus and exit via a splanchnic nerve which terminates in a peripheral ganglia where they meet the post-ganglionic neuron
Where are the preganglionic parasympathetic nerve cell bodies located?
in the medulla or sacral spinal cord
What do the axons of the preganglionic parasympathetic nerve cell bodies leave via?
cranial nerves or sacral spinal nerves
Which cranial nerves do parasympathetic originate from?
CN III, VII, IX and X
What does the occulomotor nerve send parasympathetic fibers to?
the pupillary sphincters and ciliary body
What does the facial nerve send parasympathetic fibers to?
nasal, lacrimal, and mandibular glands
What does the glossopharyngeal nerve send parasympathetic fibers to?
the parotid gland and the posterior tongue
What does the vagus nerve send parasympathetic fibers to?
main inputs to visceral organs
What do the sacral segments of the spinal cord send parasympathetic fibers to?
the descending colon, rectum, bladder, and genitalia
How do the preganglionic axons of the vagus nerve travel to their target organs and what do they synapse with?
the preganglionic axon goes all the way to the organ, and within the gut it ends within the enteric nervous plexus and synapses with the post-ganglionic parasympathetic neurons that reside within
Define receptor.
specialized protein complex on outer surface of cells that recognizes a specific chemical which is known as the ligand for the receptor
Define agonist.
ligand that binds receptor and triggers action inside of the cell
Define antagonist.
ligand that binds receptor and blocks action inside the cell
What is the name of the receptor that recognizes acetylcholine released from preganglionic parasympathetic and sympathetic nerves?
nicotinic receptor
What can destroy ACH?
ACH-esterase
What can nicotinic receptors be blocked by?
curare (frog poison)
How do organophosphates affect ACH action?
they poison ACHesterase leading to prolonged action of acetylcholine
What are cholinergic nerves?
parasympathetic post-ganglionic nerves that release ACH
What is the name of the receptor that recognizes acetylcholine released from postganglionic parasympathetic nerves?
muscarinic receptor
What can block muscarinic receptors?
atropine or glycopyrolate
What are adrenergic nerves?
sympathetic post-ganglionic nerves that release norepinephrine
What does the adrenal gland mainly secrete?
epinephrine
What other things can sympathetic post-ganglionic fibers secrete?
neuropeptide Y, somatostatin, and even ACH
What is the norepinephrine released by sympathetic post-ganglionic nerves recognized by?
alpha or beta adrenergic receptors
What are the target cells for postganglionic sympathetic and parasympathetic fibers in the GI tract?
smooth muscle cells in GI wall, secretory epithelial cells, neuroendocrine cells within submucosa and mucosa, enteric nervous system cells
What is the function of the smooth muscle cells in the GI wall?
contractility and blood flow
What do the secretory epithelial cells of the GI tract secrete?
mucous, enzymes, chloride secretion, and saliva
What are parasympathomimetic drugs?
parasympathetic agonists
What are some types of parasympathomimetic drugs?
nicotine, pilocarpine, and metacholine
What does nicotine do?
activates nicotinic receptors
What does pilocarpine and metacholine do?
activate muscarinic receptors
What are cholinesterase inhibitors?
organophosphates
What are some cholinesterase inhibitors?
neostigmine, pyridostigmine, ambenonium
What do cholinesterase inhibitors do?
potentiate the affect of acetylcholine on nicotinic receptors and muscarinic receptors
What are some anti-muscarinic drugs?
atropine, glycopyrolate, and scopolamine
What do anti-muscarinic drugs do?
block the effect of acetylcholine on target cells, slow the gut, stop saliva secretion, and increase heart rate
What are some sympathomimetic drugs?
phenylephrine, isoproterenol
What do sympathomimetic drugs do?
activate alpha or beta receptors
What is a sympathatic agonist drug?
propranolol
What do sympathetic agonists do?
block beta 1 and 2
What is in charge of the intrinsic control of the GI tract?
the enteric nervous system
What are the 2 parts of the enteric nervous system?
myenteric plexus and the submucosal plexus
What is in charge of the extrinsic conrol of the GI tract?
the autonomic nervous system
What does the parasympathetic control of the GI tract mainly do?
stimulates
What does the sympathetic control of the GI tract mainly do?
inhibits
Where is the enteric nervous system located?
in the gut wall submucosa and between the muscle layers from the esophagus to the anus
What is the enteric nervous system composed of?
cell bodies with axons, dendrites, and receptors
What does the enteric nervous system receive input from?
GI tract epithelial cells, sensory cells, other enteric nervous system neurons and the autonomic nervous system
Where is the myenteric plexus located?
from the esophagus to the anus between the longitudinal and circular smooth muscle layers
What is the function of the myenteric plexus?
it controls GI motility
What are the stimulatory influences of the myenteric plexus?
increase tonic contraction and contraction frequency/intensity
What are the inhibitory influences of the myenteric plexus?
decreased sphincter tone - pyloric sphincter, ileocecal sphincter, and lower esophageal sphincter
Where is the submucosal plexus located?
in the mucosal layer from the esophagus to the anus
What is the function of the submucosal plexus?
secretion by glands of the gut and epithelial cells of the gut, secretion of hormones by neuroendocrine cells, contraction of the muscularis mucosa to shorten or lengthen villi
Approximately how many liters of saliva does a 20 kg dog secrete?
.3 liters/day
Approximately how many liters of saliva does man secrete a day?
1.5 liters
Approximately how many liters of saliva does a cow secrete a day?
60-180 liters
What is the amount of saliva a cow secretes dependent on?
% forage indiet and moisture content of the diet
What are the two types of salivary secretions?
mucous and serous
Characterize mucous saliva secretion.
lubricating effect from mucin, hypotonic, poor buffer
Characterize serous saliva secretion.
watery with digestive enzymes, strongly buffered but still hypotonic
What is a major digestive enzyme in serous saliva?
amylase
What type of saliva does the parotid gland secrete?
serous saliva
What is the parotid salivary gland parasympathetically supported by?
the glossopharyngeal nerve
What type of saliva does the submaxillary salivary gland secrete?
both mucous and serous saliva
What is the submaxillary salivary gland parasympathetically supported by?
the facial nerve
What type of saliva does the sublingual salivary gland secrete?
mucous saliva
What is the sublingual salivary gland parasympathetically supported by?
the facial nerve
What is the function of saliva?
moisten and lubricate bolis, begin starch and fat digesiton, reduce osmolarity, buffer activity, and contains anti-bacterial substances
What is the pH of non-ruminant saliva?
7
What is the pH of ruminant saliva?
8.5
What is the function of saliva in ruminants?
buffer acids produced in the rumen
What is the secretion of the saliva dependent on in ruminants?
chewing action- the more chewing the more saliva (specifically the parotid gland)
What can salivary secretion be blocked by in all species?
atropine and glycopyrolate
What is slaframine slobbers?
Alkaloid made by black patch mold rhizoctonia leguminocola found in moldy legume haye (especially red clover) - has parasympathomimetic effects
What type of sympathetic receptors are on salivary glands?
adrenergic receptors
How can the sympathetic nervous system effect salivary secretions?
it can result in excessive salivation in some species or no secretions (cotton mouth) via circulating catecholamines from the adrenal gland
