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PHGY 216 Midterm Exam With Complete Solution
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PHGY 216 Midterm Exam WithComplete Solution
Hydrophilic Hormones? - Answer Unbound to carrier molecules
Most are peptides or proteins
What are the 2 kinds of amino hormones? - Answer Catecholamines - can be bound or
free, hydrophilic
Thyroid hormones - not hydrophilic
Peptide hormone synthesis - Answer 1. preprohormones synthesized by ER
2. preprohormones processed into active hormones and packaged into secretory
vesicles
3. secretion/exocytosis of vesicles with signal
Lipophilic Hormones? - Answer Include steroids and thyroid hormones. Not stored but
released when synthesized. Regulated by regulating synthesis
How do hormones interact with target cells? Hydrophilic vs Lipophilic? - Answer Only
free, unbound hormones can interact. Not an issue for hydrophilic and catecholamines
that re usually found in their unbound state. Lipophilic molecules are bounded to carrier
protein
Dynamic equilibrium, not 100% of steroid hormones bound to carrier molecule.
What happens after peptide hormones + catecholamines binds it receptor? - Answer
Peptide hormones + catecholamines activate second messenger system, amplify initial
signal.
cAMP: activates g protein, activates adenylyl cylcase molecules, converts atp to camp,
activate pka, phosphorylate and activate target protein
Ca2+: activate g protein, activate phospholipase c enzymes, convert pip2 to ip3, ip3
mobilizes intracellular ca2+, activates calmodulin, actives CaM kinase, phosphorylate
and activate target proteins
Lipophilic hormones and protein synthesis - Answer 1. free lipophilic hormone diffuse
across membrane, interact w intracellular receptors
2. HR binds to HRE within DNA
3. DNA binding activates genes, produces mRNA
4. mRNA leaves nucleus --> synthesis of proteins
,5. synthesized proteins lead to cellular response of hormone
Neural vs Endocrine control; characteristics vs response time vs number of targets? -
Answer Fast vs Slow
Brief vs long
one specific target vs many different targets
Describe the 2 lobes of the pituitary gland and their relationship to the hypothalamus -
Answer Posterior: neural like tissue, neurohypophysis. Connected to hypo by neural
pathway. Within hypothalamus, 2 clusters of neurons (supraoptic and paraventricular).
Axons from these nuclei project down stalk and terminate on blood vessels.
Anterior: glandular epithelial tissue, adenohypophysis. connected by
hypothalamic-hypophyseal portal system that carries regulatory hormones
What are the hormones of the posterior pituitary gland? - Answer Hormones synthesized
in neuron cell bodies, travel down axon. Neurons transmit action potential that cause
release of hormone-containing vesicles into the blood.
Vasopressin - ADH, enhance water retention by kidneys, contraction of arteriolar
smooth muscle
Oxytocin - stimulation contractions of uterine smooth muscle, promote milk ejection
What are the hormones of the anterior pituitary gland? - Answer 6 peptide hormones
1. GH (aka somatotropin)
2. TSH - thyroid hormone in thyroid gland
3. ACTH - stimulate secretion of cortisol by adrenal cortex
4. FSH - growth + dev of ovarian follicles in women, sperm in men
5. LH - ovulation and corpus luteum in women, testosterone in men
6. PRL (prolactin) - only one not tropic, enhance breast development and milk
production
how does the hypothalamic-hypophyseal portal system (HHPS) work? - Answer
hypophysiotropic hormones produced by neurosecretory neurons enter hypothalamic
capillaries. rejoin to form HHPS which branches into capillaries in anterior pituitary.
regulation of anterior pituitary secretion? - Answer TRH --> stimulate TSH + PRL
GnRH --> stimulate FSH + LH
GHIH --> inhibit GH and TSH
, CRH --> stimulate ACTH
GHRH --> GH
General chain of hormonal command? - Answer Neural +/or hormonal input -->
hypothalamic neurosecretory neuron --> hormone 1 --> anterior pituitary --> hormone 2
--> target endocrine gland --> hormone 3 (negative feedback) --> target cell -->
physiological effect
How are the 2 lobes of the thyroid gland connected? - Answer thin section - isthmus
What is the distinct organization of the thyroid gland? - Answer Follicular cells --> hollow
spheres
C cells secrete calcitonin
Colloid made of thyroglobulin where thyroid hormones are synthesized and stored,
unlike most lipophilic hormones
Describe the thyroid hormones - Answer T4 - 4 iodine molcules, 90% of thyroid
hormones secreted, must be converted into T3 in target tissues
T3 - 3 iodine
What is the important of iodine? - Answer Are the basic building blocks of tyrosine.
How are thyroid hormones synthesized and released? - Answer 1. Thyroglobulin
containing tyrosine is produced in ER-golgi, transported to colloid via exocytosis
2. Iodide taken up by follicular cells through process called iodide tapping. Driven
against conc gradient using Na+cotransporter
3. Iodide transferred into colloid
4. thyroid peroxidase converts iodide into iodine which attaches to thyroglobulin (iodide
organification)
5. MIT + DIT forms T3, DIT + DIT forms T4
6. Phagocytosis of thyroglobulin containing colloid, hormone-filled vesicle
lysosome fuse w vesicle, release all MIT, DIT, T3 and T4 from thyroglobulin
7. T3 T4 immediately cross plasma membrane to blood, bind to thyroid-binding globulin
What are the actions of thyroid hormones? - Answer Metabolic rate + heat production
Metabolism - breakdown of glycogen, degradation of protein
Sympathomimetic - increase # of catecholamine receptors
CV system - increase HR, CO, blood V and flow
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