Physiology Flashcards
Where in the cell is preproinsulin made?
Rough ER
Where is proinsulin stored?
Secretory granules
What conditions increase insulin and C-peptide?
Insulinoma an sulfonylurea use
Insulin and C-peptide are secreted in what amounts in relation to each other?
Equally
Insulin receptors have what type of enzymatic activity?
Tyrosine kinase activity
What does binding of insulin induce?
Glucose uptake and gene transcription
What are the effects of insulin on skeletal muscle and adipose tissue?
Increased glucose transport into those tissues
What are the effects of insulin on glycogen?
Increased glycogen synthesis and storage
What are the effects of insulin on triglycerides?
Increased triglyceride synthesis
What are the effects of insulin on sodium?
Increased sodium retention in kidneys
What are the effects of insulin on protein?
Increased protein synthesis in muscle
What are the effects of insulin on potassium?
Increased cellular uptake of potassium
What are the effects of insulin on glucagon?
Decreased glucagon release
What are the effects of insulin on lipolysis?
Decreased lipolysis in adipose tissue
What are the effects of insulin on the fetus?
None, cannot cross the placenta
Which GLUT transporter is insulin dependent?
GLUT4
Where are GLUT4 transporters found in the body?
Skeletal and adipose tissue
What activity can increase expression of GLUT4 transporters?
Exercise
What GLUT transporters are insulin independent?
GLUT1, GLUT 2, GLUT3, GLUT5
Where are GLUT1 transporters found in the body?
RBCs, brain, cornea, placenta
Which GLUT transporter is bidirectional?
GLUT2
Where are GLUT2 transporters found in the body?
B islet cells, liver, kidney, and small intestine
Where are GLUT3 transporters found in the body?
Brain and placenta
Where are GLUT5 transporters found in the body?
Spermatocytes and GI tract
Which GLUT transporter uptakes fructose
GLUT5
What molecule does the brain utilize for energy during starvation?
Ketones
What molecule does the brain normally use for energy?
Glucose
Why are RBCs only able to utilize glucose for energy?
They lack mitochondria for aerobic metabolism
What tissues are insulin-independent for glucose uptake?
Brain, RBCs, Intestine, Cornea, Kidney, Liver (BRICK L)
What is the major regulator of insulin release?
Glucose
What cell signaling molecule does insulin use in insulin-dependent glucose uptake?
Tyrosine kinase
What regulatory molecules are released after oral ingestion of glucose that stimulate insulin release?
Glucagon-like peptide (GLP-1) and glucose-dependent insulinotropic peptide (GIP)
What is the effect of GLP-1 and GIP on beta cells?
Increased beta cell sensitivity to glucose
Stimulation of which adrenergic receptors decreases insulin release?
Alpha-2
Stimulation of which adrenergic receptors increase insulin release
Beta-2
What is the effect of glucose entering a pancreatic beta cell?
Increased ATP from glucose metabolism
What is the affect of increased ATP in a pancreatic beta cell?
Increased ATP closes potassium channel
What is the affect of closing the potassium channel in a pancreatic beta cell?
Depolarization of the membrane
What is the affect of depolarization of the membrane in a pancreatic beta cell?
Opens voltage-gated calcium channels
What is the affect of increased calcium in a pancreatic beta cell?
Exocytosis of insulin granules
What cells of the pancreas make glucagon?
Alpha cells
What causes secretion of glucagon?
Hypoglycemia
What inhibits glucagon release?
Insulin, hyperglycemia and somatostatin
Gluconeogenesis and glycogenolysis are mediated by what hormone?
Glucagon
What effect does cortisol have on glucagon?
Permissive effect allowing glycogenolysis
Increased ketone production is caused by what hormone?
Glucagon
What hypothalamic hormone is decreased with chronic steroid use?
CRH
What pituitary hormones are increased by CRH?
ACTH, MSH, and B-endorphin
What hypothalamic hormone decreases release of prolactin?
Dopamine
What is the effect of some antipsychotics on dopamine release?
Decreased dopamine release causing hyperprolactinemia which leads to galactorrhea and amenorrhea, osteoporosis and hypogonadism
Regulates release of GH from anterior pituitary
GHRH
Regulates release of FSH and LH from anterior pituitary
Pulsatile GnRH
What is the effect of tonic release of GnRH?
Suppresses HPG axis, decreased LH and FSH release
What is the effect of pulsatile release of GnRH?
Leads to puberty and fertility, increased LH and FSH release
What suppresses release of GnRH?
Hyperprolactinemia
What is the function of prolactin?
Decrease GnRH release, promote milk production, decrease ovulation in women and spermatogenesis in men
What are the affects of a pituitary prolactinoma?
Amenorrhea, galactorrhea, osteoporosis, and hypogonadism
What is the affect of somatostatin on GH and TSH
Decreases release of GH and TSH
What is the analog of somatostatin used for?
Treat acromegaly
What is the somatostatin analog?
Ocreotide
Prolactin release is stimulated by what hypothalamic hormone?
TRH
What is the function of TRH?
Increase release of TSH and prolactin
What pathologic conditions increase TRH?
Primary and secondary hypothyroidism
What is the effect of increased TRH secretion as seen in primary and secondary hypothyroidism?
Increased prolactin secretion causing galactorrhea
Where is prolactin secreted from?
Mainly anterior pituitary
Prolactin is structurally homologous to what other hormone?
Growth Hormone (GH)
Libido is associated with excessive amounts of what anterior pituitary hormone?
Prolactin
What is the function of prolactin?
Milk production, inhibit ovulation and spermatogenesis
What hypothalamic hormone is inhibited by prolactin?
GnRH
What dopamine agonist can be used to treat prolactinoma and inhibit prolactin secretion?
Bromocriptine
What is the effect of antipsychotics and estrogens on prolactin secretion?
Stimulate production via dopamine antagonistic effects
How does prolactin inhibit its own secretion?
Increases dopamine release
How does dopamine inhibit prolactin secretion?
Tonic release of dopamine via tuberoinfundibular pathway of hypothalamus
What are the effects on TRH by increasing plasma T3/T4?
Decreased TRH
What are the effects of pregnancy on prolactin release?
Increases estrogen which stimulates prolactin release
What are the effects of spermatogenesis and ovulation on prolactin release?
Increase FSH and LH which inhibit prolactin release
What is the effect of progesterone on prolactin release?
Inhibits prolactin release
What is the effect of nipple stimulation on prolactin release?
Increases prolactin release
What is the effect of a crying baby or sight of a baby on prolactin release?
Inhibits higher cortical centers which inhibit hypothalamic release of dopamine and stimulate TRH release causing prolactin secretion
What is the effect of GH on insulin?
Increases insulin resistance
What hormone is released by liver vi GH stimulation?
IGF-1