Exam 1 Flashcards
(101 cards)
1
Q
How do the response and signal compare in a negative feedback loop?
A
the response opposes the stimulus (decreases a variable when it gets too high; increases a variable when it gets too low)
2
Q
How do the response and signal compare in a positive feedback loop?
A
The response amplifies the signal/stimulus (ex. cervical stretch, oxytocin and uterine contractions= parturition)
3
Q
How does a positive feedback loop get shut off?
A
an outside factor is required (ex. delivery of baby in parturition stops the signal)
4
Q
What is the purpose of feedforward regulation?
A
anticipatory/proactive; does not require a deviation signal
Accelerates response and minimizes fluctuation (circadian rhythm, salivation)
5
Q
Which of the control mechanisms is a homeostatic reflex?
A
negative feedback
6
Q
Which control mechanism is explosive in nature?
A
positive feedback
7
Q
What is the mode of transmission of the endocrine system?
A
circulation
8
Q
How do hormones affect functions in their target cells?
A
regulate, NOT initiate
9
Q
What are the two post pit neuroendocrine hormones?
A
ADH and oxytocin
10
Q
What are the 6 anterior pit trophic hormones?
A
FSH, LH, ACTH, TSH, GH, PRL
11
Q
What are the 6 hypophysiotrophic hormones of the hypothalamus?
A
GnRH, GHRH, CRH, TRH, DA, SS
12
Q
What are the two types of tyrosine derivatives?
A
- Catecholamines (DA, Norepi, Epi in CNS/adrenal medulla) — exocytosis transport
- Iodothryonines — diffusion transport
13
Q
What are four places that steroid hormones are synthesized? What are they synthesized from?
A
- cholesterol
- adrenal cortex (aldosterone, cortisol, androstenedione)
- gonads (testosterone, estradiol, progesterone)
- placenta (progesterone, estrogens)
- kidney (calcitriol)
14
Q
How do steroid hormones behave in the body?
A
- lipophilic (diffuse easily in and out)
- bound to proteins in blood
- intracellular receptors
- can be administered orally
15
Q
What is another name for somatostatin?
A
GHIH - GH inhibiting hormone
16
Q
What are 3 glycoproteins and how do they differ?
A
LH, FSH, TSH - alpha subunits the same; beta subunits differ
17
Q
How do peptide hormones behave in the body?
A
- circulate unbound (except GH and IGF1)
- polar
- extracellular receptors
- syn as preprohormones/prohormones
- can be stored in cells as membrane bound granules
18
Q
Which two peptide hormones CANNOT circulate unbound?
A
GH and IGF1
19
Q
Which hormone type cannot be administered orally?
A
Peptide hormones
20
Q
What is the rate limiting enzyme in steroid hormone synthesis from cholesterol?
A
side-chain cleavage enzyme (P450scc) which converts cholesterol to pregnenolone
21
Q
What are the six major types of steroid hormones?
A
Vit D, progestin, mineralocorticoid, glucocorticoid, androgen, estrogen
22
Q
What are two special things about the free portion of hormones in circulation? (Catecholamines, peptides, proteins)
A
- biologically active
- controlled by homeostatic negative feedback control mechanism
23
Q
Where are hormone binding proteins synthesized? Purpose?
A
- liver
- hormone bound to BP’s is not available for metabolism, BUT serve as reservoir of readily-available hormone
24
Q
What happens to free hormone levels right after an increased in BP as in pregnancy? Later on?
A
- increased BP = increased bound hormone = decreased free hormone
- negative feedback loop regulation kicks in and results in an increase in total hormone and no change in free hormone
25
How do protein and peptide hormones transmit their signal inside a cell?
- hormones bind to extracellular receptor which induces a conformational change = signal
- change activates one or more intracellular 2nd messengers that bind effector proteins which result in hormone's action = SIGNAL TRANSDUCTION PATHWAY
26
What are 3 types of intracellular messengers?
- cyclic nucleotides: bind effector kinases
- ions: direct or indirect (calbindin) regulation of effector proteins
- Lipids: DAG activates protein kinase C; IP3 increases intracellular calcium; BOTH from phospholipase C activation
27
What are four protein hormone receptor types?
- receptors that gate channels
- receptors that activate enzymes (kinases and phosphatases)
- GPCR
- integrin receptors
28
What are two types of tyrosine kinases activated by protein hormone receptors?
- growth factor subtype: receptor is tyrosine kinase
| - cytokine subtype: receptor associated with JAK kinase
29
What are three G protein subtypes?
- Gs = stimulates adenylyl cyclase
- Gi = inhibits adenylyl cyclase
- Gq = activates phospholipase c
30
Why do steroid hormones act more slowly than protein hormones?
action requires genomic transcription and subsequent translational processes
31
What are steroid receptors? What superfamily do they belong to?
- intracellular receptors acting as transcription factors
| - nuclear receptor superfamily
32
What is the action of the hormone receptor complex?
- binds to specific DNA sequence = hormone response element
- binding alters rate of gene transcription
- can activate/repress transcription by recruiting co-activators or co-repressors
33
What is a major example of a negative feedback loop?
- Hypo-pit-target gland axis
34
How do changes in receptor sensitivity and response differ?
- response = change in receptor number
| - sensitivity = change in receptor affinity; less common
35
what are 3 endogenous hormone release patterns?
- diurnal
- ultradian: pulsatile release patterns prevent down-reg of receptors
- responses to specific stimuli
36
How does stress affect hormone levels?
Increases level of hormone/feedback set point but does not affect the diurnal/ultradian/circadian patterns of release
37
Where do axons and terminals of posterior pituitary originate?
hypothalamus via pituitary stalk - from oxy/ADH neurons of supraoptic and paraventricular nuclei via hypothalamohypophyseal tract
38
Post pit - where do hormones come from? blood supply? hormones are released where?
- hypothalamic neurons (post pit acts as storage site = Herring bodies)
- direct arterial blood supply
- releases into systemic circulation (detectable in peripheral blood)
39
What are the 3 families of hormones associated with the ant pit?
- glycoprotein family (TSH, FSH, LG)
- GH/prolactin family
- Proopiomelanocortin (POMC) family
40
What is POMC?
prohormone from which ACTH is cleaved
41
What controls the anterior pituitary?
hormone release controlled by hypothalamic releasing and inhibiting hormones that access ant pit via stalk portal capillaries (diffusion from secondary capillary plexus) -- hypo hormones not detectable in peripheral blood
42
How does GnRH affect ant pit hormones?
stimulates release of LH and FSH
43
How does GHIH affect ant pit hormones?
inhibits release of GH and TSH
44
How does TRH affect ant pit hormones?
stimulates release of TSH and PRL
45
How does dopamine affect ant pit hormones?
inhibits release of PRL
46
How does corticotropin releasing hormone affect ant pit hormones?
stimulates release of ACTH (from POMC family)
47
If hypothalamic control of ant pit is lost, what happens to hormone levels?
LH, FSH, TSH, GH, and ACTH decrease; PRL will increase (no longer inhibited by dopamine)
48
How does long-loop negative feedback control of HPA work?
Hormones produced by endocrine gland inhibit hypothalamic and ant pit hormone function
49
What is Kallmann's syndrome and what is it often associated with?
- Lack of GnRH neuron migration out of olfactory placodeand no GnRH
- deficiency of LH and FSH synthesis and secretion results in hypogonadism
- anosmia
50
Pathophysiology of Sheehan's syndrome?
portal caps operate at low pressure and thus are at risk for clotting/infarction under conditions of low BP - shock, hemorrhage
51
How do prolactin levels change in Sheehan's?
- initially increase due to lack of dopamine regulation
| - then levels drop when ant pit cells die
52
Tumors of pituitary commonly cause what type of visual deficit?
bitemporal hemi-anopsia
53
What type of injury can completely sever the pituitary stalk?
whiplash (ADH affected = diabetes insipidus; drink and pee a lot)
54
What is the importance of thyroid hormone in growth control?
essential for normal GH secretion and GH receptors; permissive to GH actions; important for CNS development
55
What is the importance of gonadal estrogen in growth of both sexes?
- pubertal growth spurt
| - epiphyseal closure
56
What is insulin's role in growth?
enhances growth and is required for normal growth
57
What is cortisol's role in growth?
increases GH release and is required for normal growth
58
What hormones control fetal growth?
insulin, other unknown factors
59
What hormones control juvenile growth?
GH, thyroid hormones, insulin, cortisol
60
What hormones control adolescent growth?
GH, sex steroids, thyroid hormones, insulin, cortisol
61
Why do diabetic mothers have larger infants?
Increased blood glucose increases insulin levels and insulin enhances growth/controls fetal growth
62
During what 2 periods are growth rates fastest?
- in utero
| - neonatal period (1st 2 years)
63
Plasma level increases in what 3 hormones cause the pubertal growth spurt?
- GH
- IGF1
- estrogens aromatized into androgens in boys and girls
64
When does rate of growth plateau?
high estrogen levels cause epiphyseal closure inat the end of puberty and growth plateaus in adulthood
65
What is the most abundant hormone in the ant pit?
GH, species specific, plasma concentrations vary throughout day
66
What circulating hormone can be used as a good indicator of growth rate?
circulating IGF levels in single samples
67
What is the GH receptor type?
tyrosine kinase receptor cytokine subtype (JAK-kinase-Stat TF)
68
What are the 4 direct actions of GH?
- generally oppose insulin
| - increased lipolysis, gluconeogenesis, ketogenesis, and protein
69
What are the indirect actions of GH and how are they mediated?
- stimulate growth and protein synthesis in bone and splanchnic organs
- IGF1 (somatomedin C)
70
How does IGF1 regulate GH levels?
negative feedback control on hypothalamus and anterior pituitary
71
What five factors cause a responsive increase in GH levels?
- intense exercise
- hypoglycemia
- stress
- amino acids (Arginine)
- sleep rhythms
72
What type of dwarf results from decreased GH only?
sexual ateliotic dwarf
73
What type of dwarf results from a decrease in all anterior pituitary hormones?
panhypopituitary dwarf
74
What type of dwarf results from a defect in expression of GH receptors? GH and IGF1 levels?
- Laron dwarf
| - normal or high GH and LOW IGF-1
75
What type of dwarf results from a defect in IGF response to pubertal increase in GH? GH and IGF1 levels?
- African pygmy
| - normal GH and IGF1
76
What are the symptoms associated with decreasing GH with age?
- increased proportion of body fat
- decreased proportion of muscle
- muscle weakness and early exhaustion
77
What are 3 tests used for GH secretion?
- arginine
- dopamine
- insulin-induced hypoglycemia
78
How does excess GH affect blood glucose?
high GH --> increased blood glucose
- excess GH is diabetogenic
79
How does excess GH affect plasma IGF1 levels?
HIGH
80
Which two hormones bind to their hormone response element's on DNA to initiate transcription?
Vit D3 and Thyroid (gene transcription is repressed when hormones aren't bound)
81
What 3 hormones are secreted by the thyroid?
- calcitonin
- T4 thyroxine
- T3 triiodothyronine
82
Two Tx options for GH deficiency syndrome in children caused by hypothalamic defect?
- recomb hGH = somatropin, somatrem
| - synthetic GHRH = sermorelin acetate (less effective than somatropin)
83
AE's of using synthetic GHRH sermorelin acetate to tx GH deficiency syndrome in children caused by hypothalamic defect?
headache, dizziness, scoliosis due to rapid growth
84
Why must AR Laron syndrome be treated differently than typical GH deficiency?
GH resistant dwarfism
85
Tx for Laron syndrome? AE? Contra?
- mecasermin = IGF1
- intracranial hypertension
- cancer
86
What is the cause and Tx of GH deficiency syndrome in adults?
- defects in pit function (pit adenoma)
| - somatropin (not sermorelin bc it is GHRH and pit isn't working and can't make GH anyway)
87
AE's and contra in somatropin Tx in adults?
- arthralgia, myalgia, thirst, hunger headache
| - cancer
88
Three Tx options for GH excess?
- pit surgery
- octreotide/pasierotide = syn somatostatin analog
- pegvisomant = GH analog that binds receptor BUT w/ no dimerization/signaling (doesn't decrease GH levels)
89
AE's of synthetic somatostatins octreotide and pasireotide?
- GI, gallstones
| - liver tox, ACTH suppression
90
AE of GH analog pegvisomant?
reversible abnml liver f(x) test
91
Function and regulation of prolactin?
- stimulates breast development/lactation; inhibits gonadotropin secretion
- increased by TRH/suckling, decreased by dopamine
- no feedback control
92
Three causes of hyperprolactinemia?
- pit/hypo disorder (tumor)
- renal failure (dec PRL clearance)
- chest trauma (autonomic response)
93
Symptoms of hyperprolactinemia in men? Women?
- infertility, enlarged breasts, libido loss, impotence
| - infertility, amenorrhea, lactation in non-pregos
94
What is an example of a DA receptor agonist used to Tx hyperprolactinemia? AE's? Contra?
- bromocriptine (Parkinson's)
- NV, dizziness, insomnia
- uncontrolled hypertension
95
What are the 3 gonadotropins?
FSH, LH, placental chorionic gonadotropin
96
What drug can be used to treat steroid hormone excess conditions?
ketoconazole - inhibits steroid biosynthesis
97
FSH functions in men and women?
- stimulates spermatogenesis
| - stimulates follicle development
98
LH functions in men and women?
- increases testosterone secretion
| - stimulate mat. of follicle to corpus luteum; required for ovulation
99
Menotropins vs. urofollitropins?
- FSH and LH in urine from post-men women
| - purified FSH
100
Two AE's of tx of decreased gonadotropin production?
- multiple births
| - OHSS = ovarian hyperstimulation syndrome -- fluid in peritoneal cavity, pericardium, thorax
101
Population and caused of increased gonadotropin production?
- mostly males
| - constitutively active AD mutation of LH receptor
