Practice Test Flashcards
Receptors for ______________ reside in virtually all cells of the body.
Cortisol
Tyrosine is used to synthesize?
Thyroxine
A substance which is not an intracellular 2nd messenger is
adenylate cyclase.
Name 3 intracellular second messengers
C cyclic AMP.
D diacylglycerol (DAG).
C calcium-calmodulin.
A cytoplasmic enzyme which limits how long a target cell responds to a hormone is
phosphotase
In the follicle lumen of the thyroid gland the enzyme which couples two diiodothyronine molecules to form T4 is
thyroperoxidase
Thyroglobulin
contains many tyrosine molecules.
Of the hormones listed below which has the shortest half-life, i.e., is inactivated most quickly after it enters the blood?
epinepherine
Steroid hormones bind to plasma proteins which are synthesized in and secreted from the
liver hepatocytes
Cortisol is permissive for the ability of epinephrine to stimulate release of fatty acids from adipose tissue. A requirement of this response is
an exposure of the tissue for several hours to cortisol.
name three hormones secreted by the anterior pituitary
G growth hormone.
T thyroid stimulating hormone.
P prolactin.
name three hormones secreted by the hypothalamus
C corticotropin releasing hormone.
O oxytocin.
G gonadotropin releasing hormone
In negative feedback in the hypothalamic-pituitary-thyroid axis the hormone thyroxine feeds back to inhibit
both the anterior pituitary and the hypothalamus.
The cell bodies of neurons which synthesize and secrete antidiuretic hormone (ADH) have their nerve terminals (which release ADH) in the
posterior pituitary.
The total amount of fluid absorbed per day from the GI tract into the blood is about _________________ the amount of fluid ingested daily.
seven times
The amount of feces excreted per day is about _________________ the amount of food ingested daily.
one-tenth
The daily total amount of all secretions by GI exocrine tissues is about _________________ the total volume absorbed by the GI tract.
equal to
Choose the best answer regarding the role of the GI tract in bodily function.
a. The primary function of the GI tract is to provide nutrients and water for the nutrition of all of the cells of the body.
b. The GI tract plays a more important role than the kidneys or lungs in the homeostatic regulation of most blood plasma constituents.
c. The GI tract absorbs only about 50% of the nutrients present in the foods that we ingest.
d. The GI tract is a major route of excretion of toxins and waste products of metabolism.
a. The primary function of the GI tract is to provide nutrients and water for the nutrition of all of the cells of the body.
The active secretion of Cl- ions is an important mechanism by which several GI tract tissues move salt and water into the GI tract lumen. This involves
downhill leak of Cl- ions through ion channels in the luminal membrane into the luminal fluid.
the energy of ATP is utilized to export protons from a low concentration in the cytoplasm of the parietal cell to a high concentration in the pit lumen during the secretion of what?
During the secretion of hydrochloric acid by the parietal cells
The list of agents which stimulate the parietal cell to secrete HCl includes
HAG
H histamine.
A acetylcholine.
G gastrin.
controls exocrine secretions and smooth muscle motility in the GI tract.
The enteric nervous system (ENS)
Choose the statement which best describes the influence of the vagus nerve in influencing stomach function.
Stimulation of the vagus will cause gastric releasing peptide to be released in the vicinity of G cells in the gastric antrum, which respond by secreting gastrin into the blood.
During digestion of a meal gastric acid secretion will decline when
high acidity in the stomach lumen causes release of somatostatin.
high acidity in the lumen of the duodenum causes release of secretin.
the meal is largely digested and gastric filling declines
What is enhanced by activation of mechanoreceptors (stretch receptors) which communicate with nearby smooth muscle fibers controlled by the ENS?
Motility of the GI Tract
During swallowing of food
the upper esophageal sphincter relaxes as part of the swallowing reflex.
the bolus of food moves down the esophagus aided by peristalsis.
the lower esophageal sphincter relaxes before the bolus of food reaches it.
As food accumulates in the stomach during a meal
peristaltic contractions originate in the body of the stomach.
The migrating motility complex
is organized by the enteric nervous system in the lower stomach and small intestine.
The membrane of smooth muscle fibers in the gastric antrum
can be depolarized to a threshold value which causes action potentials to be generated.
Colonic mass movements
occur simultaneously with the gastroileal reflex.
advance the chyme toward the terminal colon.
may initiate the defecation reflex.
An exocrine secretion of sodium bicarbonate by the pancreas
contains HCO3- ions at a concentration 5 times greater than the plasma HCO3- concentration.
The list of enzymes secreted by the pancreas includes
CACE
C carboxypeptidase B
A amylase
CE cholesterol esterase
During the postabsorptive phase, when there is no chyme in the small intestine the gallbladder…..
the gallbladder is absorbing salts and water and concentrating bile salts, which remain in the gallbladder lumen.
Three functions attributable to cholecystokinin are
inhibition of gastric secretion.
relaxation of the sphincter of Oddi.
contraction of the gallbladder.
act as detergents in the intestinal lumen.
Bile Salt Molecules
During absorption of the digestion products of fat hydrolysis in the duodenal lumen
absorbed monoglycerides and fatty acids are synthesized into triglycerides using ATP.
The list of enzymes that are intrinsic membrane proteins embedded in the intestinal brush border membrane includes:
MED
M maltase
E enterokinase
D dextrinase
Chylomicrons do not contain
water-soluble vitamins.
Gastric hypersecretion of acid can cause
erosion of the duodenal mucosa and ulceration.
steatorrhea.
impaired digestion of dietary protein
The colonic absorptive mucosa differs from the small intestinal mucosa in that only the colonic mucosa
prevents absorbed Na+ ions from back-diffusing through the epithelium into the colonic lumen.
The colon is also referred to as the large intestine because
it has a wider diameter than the small intestine.
the duodenum influences the rate of gastric acid secretion by
- operating through the ENS to inhibit parietal cell secretion when the walls of the duodenum are distended
- releasing a hormone in response to luminal acidity which operates back upon the stomach to inhibit parietal cell acid secretion directly
- releasing a hormone in response to amino acids in the luminal chyme which reduces gastric acid secretion and the strength of gastric peristaltic contractions
steatorrhea or excessive fat in the stools may be due to
failure of pancreas to secrete NaHCO3
failure of pancreas to secrete lipase
failure of betalipoprotein synthesis by enterocytes
