Term
| what is the normal sodium concentraion in major body fluids |
|
Definition
|
|
Term
|
Definition
| the loss of both water and sodium |
|
|
Term
| discuss how hyponatremia and hypernatremia affect salt appetite |
|
Definition
induced hyponatremia does not initiate salt appetite (though hyponatremia does boost salt appetite in hypervolemic rats)
hypernatremia does inhibit salt appetite |
|
|
Term
| is salt appetite a neural input |
|
Definition
| no, salt apetite develops too slowly to be a neural input |
|
|
Term
| Name three humoral signals that are released following hypovolemia |
|
Definition
AngII
Aldosterone
Oxytocin |
|
|
Term
| what G protein does the AT1 receptor couple to? what pathway does it activate? |
|
Definition
couples to Gq to stimulate PLC
activates MAP kinase pathway |
|
|
Term
AngII helps regulate water and salt intake. Describe the effects of:
injections of AngII directly into SFO and OVLT
|
|
Definition
| increases drinking behavior and salt appetite |
|
|
Term
| describe how AngII effects the posterier pituitary |
|
Definition
| AngII binds to AT1 receptors in CVOs and increases release of VP from posterior pituitary |
|
|
Term
| describe how AngII effects the anterior pituitary |
|
Definition
| AngII increases release of aldosterone from anterior pituitary: results in increased release of aldosterone from andrenal glands |
|
|
Term
| what effect does AngII have on the kidneys to modify release of renin |
|
Definition
| inhibits further release of renin (negative feedback mechanism) |
|
|
Term
| Explain how AngII promotes sodium retention by the kidneys |
|
Definition
| AngII binds to AT1 receptor in kidneys. activation of AT1 leads to increased activity of Na/H exhanger, an antiporter that allows sodium to enter cell from kidney tubule while excreting hydrogen ions |
|
|
Term
| what secretes aldosterone? |
|
Definition
|
|
Term
| what are main effects of aldosterone |
|
Definition
promotes sodium reabsorption by the kidneys
increases potassium excretion
increases water reabsorption through osmosis (as natural consequence of sodium reabsorption) |
|
|
Term
| what part of the kidney does aldosterone have the greatest effect? |
|
Definition
| distal tubules of the kidney |
|
|
Term
| what cells specifically in the kidney does aldosterone act on? how does aldosterone alter these cells transcription? |
|
Definition
| acts on tubular cells of kidney to increase tanscription of: sodium channels and Na/K ATPase |
|
|
Term
| what ther body tissues besides the kidneys does aldosterone effect in order to conserve the most sodium possible |
|
Definition
sweat glands
salivary glands
colon |
|
|
Term
| how does AngII effect the release of aldosterone? |
|
Definition
| increases the release of aldosterone from adrenal cortex |
|
|
Term
where is oxytocin produced and where is it released?
|
|
Definition
produced in magnocellular cells of the paraventricular nucleus (PVN) and supraoptic nucleus (SON)
Then released by the posterior pituitary |
|
|
Term
| what are the two 'classic' roles of oxytocin? |
|
Definition
inducing child birth
inducing lactation |
|
|
Term
| how does oxytocin affect salt appetite? |
|
Definition
| oxytocin is an inhibitory stimulus of salt appetite |
|
|
Term
| describe the relationship between salt intake and plasma oxytocin levels |
|
Definition
inverse relationship
increases in plasma osmolality stimulates pituitary and central release of oxytocin |
|
|
Term
| name two things that are caused by natriuretic peptides |
|
Definition
natriuresis- increased somdium excretion
diuresis- increased fluid excretion |
|
|
Term
| where is atrial natriuretic peptide (ANP) produced? |
|
Definition
| produced by smooth muscle cells in the heart atria |
|
|
Term
| where is B-type natriuretic peptide (BNP) produced? |
|
Definition
| produced predominantly by heart ventricles (especially left ventricle) |
|
|
Term
| Name three things that can stimulate the release of natriuretic peptides |
|
Definition
AngII
hypovolemia
Activation of the sympathetic nervous system (mediated by beta-adrenergic receptors) |
|
|
Term
| how does natriuretic peptide act on vasculature? |
|
Definition
|
|
Term
| how does natriuretic peptide act on the kidneys? |
|
Definition
increases glomelular filtration rate
increases excretion of sodium
decreases release of renin |
|
|
Term
| what is the local nervous system of the bowel called? |
|
Definition
|
|
Term
| The GI tract is approximately ___ meters (___ft) long |
|
Definition
|
|
Term
| what is the primary function of the GI tract |
|
Definition
| digestion and elimination of food |
|
|
Term
| what is another name for the GI tract? |
|
Definition
|
|
Term
| name four functions of the inner lining of the bowel |
|
Definition
digestion
absorption
fluid exchange
immune function
|
|
|
Term
| the swallowing reflex is controlled by what part of the brain |
|
Definition
|
|
Term
| what cells in the small intestine produce enzymes that aid in digestion |
|
Definition
|
|
Term
| what two organs produce/secrete digestive enzymes into the small intestine |
|
Definition
|
|
Term
| what is the major role of the large intestine |
|
Definition
| water absorption and storage of feces |
|
|
Term
| there are approximately ______ million nerve cells in the human ENS |
|
Definition
|
|
Term
| name the organs / tissues that are innervated by the ENS |
|
Definition
| esophagus, stomach, intestines, pancreas, gall bladder, and pancreato-billiary ducts |
|
|
Term
| Name the two main plexi of the ENS |
|
Definition
myenteric plexus
submucosal plexus |
|
|
Term
| what is the main function of the myenteric plexus |
|
Definition
|
|
Term
| what layer of the GI tract can the myenteric plexus be found? |
|
Definition
| between the longitudinal and circular muscle layers |
|
|
Term
| what layer of the GI tract can the submucosal plexs be found? |
|
Definition
| between the circular muscle and submucosa |
|
|
Term
| what parts of the GI tract is the submucosal plexus specific to? |
|
Definition
| small intestine and colon |
|
|
Term
| what are the effector cells of the myenteric plexus? |
|
Definition
| smooth muscle cells of longitudinal and circular muscles of GI tract |
|
|
Term
| what are the effector cells of the submucosal plexus? |
|
Definition
mucosal muscle cells (including secretory glands)
hormone secreting cells
mucosal and submucosal arterioles |
|
|
Term
| what is the main function of the submucosal plexus? |
|
Definition
|
|
Term
| The ENS contains thre types of neurons, name them. |
|
Definition
IPANs (intrinsic primary afferent neurons- sensory)
interneurons
motor neurons |
|
|
Term
| from what tissues do IPANs receive sensory information? |
|
Definition
| mucosa and smooth muscles |
|
|
Term
| name four kinds fo stimuli that can activate IPANs |
|
Definition
mechanical
thermal
osmotic
chemical |
|
|
Term
| IPANs are activated by 5-HT released by _______ cells |
|
Definition
| enterochromaffin cells (EC) |
|
|
Term
| 90% of the body's 5-HT is contained in the _____ cells of the gut mucosa. |
|
Definition
| enterochromaffin cells (EC) |
|
|
Term
| explain how mechanical pressure on the gut mucosa can initiate ENS reflexes |
|
Definition
| mechanical pressure on the apical end of enterochromaffin cells stimulates 5-HT release into gut wall, activating IPANs which initiate ENS reflex |
|
|
Term
| What is the predominant receptor found on IPANs that activate them? |
|
Definition
| 5-HT1p and 5-HT3 receptors |
|
|
Term
| When activated, what is the major neurotransmitter released by IPANs? How does it continue the signal initiated by the IPAN? |
|
Definition
ACh
ACh acts on nACh receptors on interneurons and motor neurons |
|
|
Term
| Where in the gut wall are interneurons of the ENS found? |
|
Definition
|
|
Term
| name the three types of interneurons of the ENS |
|
Definition
ascending
descending
intestinofugal |
|
|
Term
| what is the main function of ascending interneurons? |
|
Definition
| involved in excitatory motor reflexes |
|
|
Term
| what is the main function of descending interneurons? |
|
Definition
| involved in secretory reflexes and inhibitory motor reflexes |
|
|
Term
| what NT is released by ascending interneurons of the ENS? what does this NT then act on? |
|
Definition
| ACh that acts on nACh receptors on excitatory motor neurons |
|
|
Term
| what NT is released by descending interneurons of the ENS? what does this NT then act on? |
|
Definition
| release ACh with ATP or 5-HT as a co-transmitter onto secretomotor and inhibitory motor neurons |
|
|
Term
| what NT is released by intestinofugal interneurons of the ENS? what does this NT then act on? |
|
Definition
| Use ACh to signal sympathetic prevertebral ganglia |
|
|
Term
| what is the main function of intestinofugal interneurons of the ENS? |
|
Definition
involved in extraspinal intestino-intestinal relfexes.
When a part of the intestine becomes distended or its mucosa becomes excessively irritated, activity in other arts of the intestine is inhibited as long as the distension persists. |
|
|
Term
| what are the two kinds of myenteric motor neurons? |
|
Definition
ascending (excitatory) motor neurons
descending (inhibitory) motor neurons |
|
|
Term
| what is the main function of ascending myenteric motor neurons? |
|
Definition
| elicits contraction of smooth muscle |
|
|
Term
| what is the main function of descending myenteric motor neurons? |
|
Definition
| elicits relaxation of circular smooth muscle |
|
|
Term
what NTs are released by ascending myenteric motor neurons once activated?
|
|
Definition
|
|
Term
| what NTs are released by descending myenteric motor neurons once activated? |
|
Definition
| VIP(vasoactive intestinal peptide), nitric oxide, ATP |
|
|
Term
| what is the major function of submucosal motor neurons |
|
Definition
| elicit glandular secretion and vasodilation |
|
|
Term
| what cells are considered the 'pacemaker' cells of the ENS? |
|
Definition
| interstitial cells of Cajal (ICC) |
|
|
Term
| explain how interstitial cells of cajal function as a pacemaker for the ENS |
|
Definition
| ICCs in myenteric plexus generate slow waves, which modulate smooth muscle contractions |
|
|
Term
| what are the two main 5-HT receptors that are expressed on enteric neurons? |
|
Definition
|
|
Term
| what kind of receptor is the 5-HT3 receptor? What is its main function? |
|
Definition
ligand-gate ion channel- fast inward current activates IPANs.
activation of IPANs initiates nerve-induced contraction |
|
|
Term
| what kind of receptor is the 5-HT4 receptor? What is its main function? |
|
Definition
| G-coupled protein receptor - indirectly augments peristalic and secretomotor reflexes by increasing ACh release from cholinergic IPANs, interneurons, and motor neurons |
|
|
Term
| Name the two patterns of GI motility |
|
Definition
peristalsis
segmentation contractions |
|
|
Term
| describe the stimulus that will initiate peristaltic reflex. once initiated describe the cascade from stimulus to relfex. |
|
Definition
mechanical or chemical stimulation of mucosa will initiate reflex.
EC responds to distension to release 5-HT, which then activates IPANs. Excited IPANs release ACh onto acsending and descending interneurons, which will then cause contration on oral side of bolus and relaxation on aboral side of bolus.
|
|
|
Term
| Name 2 main goals of segmentation contractions |
|
Definition
mixes intestinal contents with digestive juices
brings mixture into contact with mucosa for absorption |
|
|
Term
| describe Hirschsprung's disease |
|
Definition
enlargement of the colon caused by bowel obstruction. starts at anus and progresses upward.
reflex arc for peristalsis no longer possible |
|
|
Term
| Explain a possible mechanism of pathology for Irritable Bowel Syndrome |
|
Definition
Decrease in EC cells' serotnin transporter (SERT), which leads to an excess of 5-HT
|
|
|
Term
| what is one possible treatment for IBS? |
|
Definition
intestinal anti-depressants
i.e. zofran, 5-HT antagonists |
|
|
