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Endocrinology > Endocrine Hormones, Feedbacks, and Mechanisms > Flashcards

Endocrine Hormones, Feedbacks, and Mechanisms Flashcards

1
Q

Endocrine system definition

A

Intercellular communication network where hormones travel cell to cell thru the blood stream and regulate complex phenomena including stress, growth, electrolyte and fluid balance, and reproduction

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2
Q

Exocrine vs endocrine glands

A

Exocrine glands have ducts that carry secretions to the body surface or other organ cavity, endocrine are ductless and release hormone into tissue fluids with dense capillary networks (the bloodstream)

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3
Q

Autocrine signaling

A

Released by a cell to have local effects on the same cell type in which the chemical is released without being transported in the bloodstream

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4
Q

Paracrine signaling

A

Released by cells that affect other cell types locally without being transported in the bloodstream

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5
Q

Pheromones

A

Hormone like substances secreted into environment that modify behavior and physiology

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6
Q

Endocrine vs nervous system speed of response

A

Endocrine reacts very slowly (hormone release in seconds or over days and effects may continue for weeks with widespread affects on general organs) vs nervous system reacts rapidly (within 1-10 msec and stops quickly with very targeted and specific responses to one organ)

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7
Q

Example of steroids, peptides and glycoproteins, and monoamines

A
  • Sex hormones (derived from cholesterol)
  • ADH/vasopressin
  • Catecholamines (all tyrosine derived)
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8
Q

What 2 types of hormone must bind to transport proteins for transport because they are hydrophobic?

A

Steroid and thyroid hormones (half life increased when bound and protected from degrading enzymes and kidney filtration)

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9
Q

Monoamines and peptides are hydrophilic so they mix easily with…

A

….blood plasma in circulation without plasma carrier proteins

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10
Q

Nervous system and endocrine systems relationship and an example of this relationship

A

Interactions between allows for coordinated communication function to regulate several body systems
Ex) autonomic parasympathetic stimulation of the pancreas enhances insulin release

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11
Q

Elevated blood K+ stimulates the adrenal cortex to release ___ which causes ___ to promote excretion of K+ (and the retention of Na+)

A

Aldosterone, kidneys

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12
Q

Example of positive feedback loop in the body

A

In preovulation estrogen has a positive feedback effect on GnRH and LH release, which in turn increases estrogen release at least up until ovulation

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13
Q

What gland releases melatonin?

A

Pineal gland

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14
Q

What structure provides neural control of circadian rhythm?

A

Suprachiasmatic nucleus of the hypothalamus

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15
Q

Suprachiasmatic nucleus of hypothalamus and mechanism of action

A
  • Cluster of nerve cell bodies in the hypothalamus above optic chiasm that acts as the master biological clock serving as a pacemaker for body’s circadian rhythm
  • self induced firing establishes many inherent daily rhythms using clock protein release and accumulation until “critical mass” reached when transported back into nuclei blocking more production genetically resulting in levels gradually declining as degraded, removing inhibitory effects on the machinery. Then genes that are no longer blocked begin producing more proteins resetting the cycle
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16
Q

SCN of the hypothalamus works in conjunction with the ___ to synchronize various circadian rhythms and 24 hour daily cycle

A

pineal gland

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17
Q

Melatonin function

A

The “hormone of darkness”, released 10x more during darkness than in light from the pineal gland to help body system become entrained to light dark cues and therefore regulate sleep-wake cycle

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18
Q

Pituitary gland/hypophysis location, lobes

A
  • Housed in sella turcica of the sphenoid bone

- Anterior lobe (adenohypophysis) and posterior lobe (neurohypophysis)

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19
Q

Embryonic development of pituitary

A

A fusion of epithelial type tissue anteriorally and nervous tissue posteriorally

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20
Q

Anterior vs posterior lobe control of the pituitary

A
  • Anterior lobe is controlled thru hormones released and inhibited by the hypothalamus thru the hypophyseal portal system (microcirculation of blood vessels)
  • Posterior lobe is controlled thru neuroendocrine effects where hormones act on the hypothalamus and the posterior pituitary as an extension of the same tissue (bundles of neurons in the hypothalamo-hypophyseal tract signal down from the hypothalamus to cause release at the posterior pituitary)
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21
Q

Hypophyseal portal system

A

A series of 2 capillary beds, extending into the hypothalamus into the first capillary bed (the arcuate nucleus) which then extends to a second capillary bed at the anterior pituitary where hormones from the arcuate nucleus of the hypothalamus can have their action, before anterior pituitary hormones exit via the hypophyseal vein

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22
Q

2 hormones released from the posterior pituitary and where are they produced?

A
  • Oxytocin and ADH (vasopressin)

- Hypothalamus transported down posterior lobe by hypothalamo-hypophyseal tract

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23
Q

ADH/vasopressin mech of action

A
  • Hypothalamus detects increased osmolarity of blood thru osmoreceptors (indicating dehydration) or thru peripheral baroreceptors decreased firing (indicating lower blood pressure volume)
  • ADH released fro post. pituitary in response
  • H2O permeability of late distal tubule and collecting duct increased
  • constriction of vascular smooth muscle occurs
  • Fluid reabsorption by the kidneys and increased BP occurs
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24
Q

ADH/vasopressin and alcohol

A

ADH secretion is inhibited by alcohol causing production of large volume of dilute urine, will result in feeling dizzy and thirsty due to the drop in blood pressure and lack of fluid retention, respectively

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25
Q

Oxytocin uterine contraction pos. feedback mech of action

A
  • Labor begins,cervix of uterus is stretched
  • signal sent to hypothalamus causing posterior pituitary to release oxytocin
  • causes strong contraction of uterine smooth muscle
  • more signals sent to hypothalamus because of uterine stretching, repeating the cycle
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26
Q

Suckling reflex mech of action

A
  • suckling or other physiological stimuli (crying, etc) sends afferent fiber impulses to spinal cord and up to brain
  • hypothalamus triggered by dopamine levels dropping and releases oxytocin from posterior pituitary, anterior pituitary triggered to release prolactin (to produce more milk)
  • oxytocin stimulates contraction of smooth muscle around mammary ducts causing milk let down in response
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27
Q

Different levels of feedback loops (hypothalamic) (3)

A

Ultra short - within hypothalamus
Short - pituitary to hypothalamus
Long - target organ to hypothalamus and pituitary

28
Q

Growth hormone is also known as…

A

…somatotropin

29
Q

FSH impact in females vs males

A
  • Stimulates development of eggs and follicles

- stimulates testes and production of sperm

30
Q

LH impact on females vs males

A
  • Stimulates ovulation and corpus luteum to secrete progesterone and estrogen
  • stimulates interstitial cells of testes to secrete testosterone
31
Q

Growth hormone and IGF-1 functions (3)

A
  • Protein synthesis
  • enhance amino acid transport into cells
  • stimulate lipid metabolism
32
Q

Growth hormone release mech of action

A
  • Exercise/stress/fasting/sleep stimulate hypothalamus to increase GHRH secretion and decrease somatostatin secretion
  • This causes increased GH release from anterior pituitary
  • Plasma GH acts on the liver and other cells to increase IGF-1 secretion
  • these act on the muscles and other organs
  • these negatively inhibit further release of GHRH and GH in the hypothalamus and the anterior pituitary
33
Q

Acromegaly definition

A

Condition due to GH secreting pituitary adenoma that can lead to headache, visual distrubances, hyperglycemia, and increased lean body mass with thickening of bones and soft tissues

34
Q

Treatment for acromegaly (2)

A
  • Hypophysectomy

- irradiation of tumor

35
Q

Prolactin function and 3 things an excess of it can result in

A
  • Released from anterior pituitary and has trophic effects on the breast, inhibits GnRH and suppresses release of LH and FSH (inhibits ovulation and spermatogenesis)
  • when in excess can result in amenorrhea, infertility, or galactorrhea
36
Q

What inhibits release of prolactin, what enhances it?

A
  • Dopamine

- TSH

37
Q

Bromocriptine use in breast milk

A

Drug used for suppression of activity of prolactin in the case of a woman who does not want to produce breast milk

38
Q

ACTH release and function

A

Secretion from the anterior pituitary, increased by corticotropin releasing hormone (CRH) from the hypothalamus, stimulates release of cortisol from the adrenal cortex

39
Q

What stimulates release of FSH and LH?

A

GnRH release from hypothalamus

40
Q

LH for men is sometimes called….

A

….interstitial cell stimulating hormone

41
Q

Primary vs secondary endocrine disorders

A

Primary are due to dysfunction of target gland vs secondary are due to dysfunction of the pituitary gland or hypothalamus

42
Q

Primary vs secondary hyperthyroidism hormone levels

A

Primary sees increased T3/T4 with low TSH, while 2ndary sees increased T3/T4 with high TSH

43
Q

Cushings syndrome vs disease

A

-Syndrome is a problem with suppressed ACTH and elevated cortisol while disease is a problem at the level of the pituitary producing excess ACTH AND elevated cortisol (think primary vs secondary)

44
Q

3 common etiologies of hyperfunction endocrine disorders

A
  • autoimmune stimulation
  • secreting tumors
  • idiopathic
45
Q

5 common etiologies of hypofunction endocrine disorders

A
  • autoimmune inhibition
  • nonsecreting tumors
  • surgical removal
  • ischemia and infarct
  • receptor defects
46
Q

Treatment of hyperfunction endocrine disorders (3) vs hypofunction (1)

A
  • Surgical removal, blocking drugs, irradiation

- hormone therapy only one

47
Q

Thymus

A

Organ present at large size at birth in mediastinum superior to the heart that devolves after puberty and is responsible for hormone secretion that regulate development and later activation of T lymphocytes

48
Q

Thyroid gland definition and what does it produce and where (2)

A

-Largest endocrine organ with high rate of blood flow, has 2 lobes connected by an isthmus with follicular cells -T3 and T4 production in follicular cells (enhances bodies metabolic rate and O2 consumption, heat production, and increase heart rate and respiratory rate) and calcitonin in parafollicular cells (reduce ca2+ in blood)

49
Q

T3 vs T4

A

Most released from thyroid is T4, the only usable form in the body is T3 so it is converted in the body to its active form T3

50
Q

Synthesis of T3 and T4 mech of action

A
  • synthesis of thyroglobulin and exocytosis into follicle
  • active uptake of I- by follicle cells to colloid, activity increased by TSH
  • oxidation of I- to I2
  • I attaches to tyrosines on thyroglobulin
  • T3 and T4 formed
  • Endocytosis of colloid
  • Enzymatic removal of T3/4 from thyroglobulin by hydrolysis of peptide bond
  • Enters blood stream and binds to thyroid binding globulin (TBG)
51
Q

Excess iodine levels in bloodstream actually cause ___, caused by the ____ effect

A

decreased T3/T4 synthesis, the wolff-chaikoff effect

52
Q

Metabolic effects of thyroid hormone (4)

A
  • Thermogenesis (increased BMR and temp)
  • growth and development (particularly prenatal development of skeletal and CNS - cretinism without)
  • Cardiovascular increased HR and CO
  • Increased glucose absorption and metabolism
53
Q

Cretinism definition

A

Infantile low TH causing abnormal bone development, thickened facial features, low temp, lethargy, and brain damage

54
Q

Myxedema definition

A

Adult onset hypothyroidism causing sluggishness, sleepiness, weight gain, constipation, increased cold sensitivity and tissue swelling. IF severe and untreated can result in myxedema coma

55
Q

Endemic goiter cause

A

Due to dietary iodine deficiency resulting in low T3/4 and high TSH and an enlarged thyroid gland full of thyroglobulin not being used

56
Q

Toxic goiter (graves disease) and 2 signs of it

A
  • Development of autoantibodies against TSH receptors on the thyroid
  • elevated T3/4 and exopthalmos
57
Q

Hypoparathyroidism treatment and 1 severe complication of it

A
  • Surgical excision during thyroid surgery

- can result in fatal tetany in 3-4 days post op

58
Q

Important to refer patients in need of thyroidectomy to a specialist in the thyroid because need to…

A

…salvage the parathyroid

59
Q

Pancreas hormonal vs digestive function by mass

A

98% dedicated to exocrine digestion

60
Q

a cells vs B cells vs Delta cells of the pancreas

A
  • a cells release glucagon (low carb or fasting)
  • B cells release insulin (high carb to promote uptake into cells and stimulate glycogen synthesis)
  • Delta cells release somatostatin (secreted with rise in blood glucose and amino acids after meal to act paracrine modulating secretions of a and B cells)
61
Q

Hormones that raise blood glucose (5)

A
  • glucagon
  • epi/norepi
  • cortisol
  • Growth hormone
  • Thyroid hormone
62
Q

Insulin receptor definition and action upon binding insulin

A

Found on the target tissues for insulin, upon insulin binding causes tyrosine kinase to autophosphorylate the B subunits which then phosphorylate intracellular proteins to activate glucose transporters (GLUT4), glucose, K+, phosphate, and magnesium enter the cell

63
Q

Somatostatin (delta cells)

A

Produced by delta cells of the pancreas, essential in carb, fat, and protein metabolism and homeostasis of ingested nutrients, different from hypothalamic somatostatin which inhibits growth hormone release at the anterior pituitary

64
Q

Mineralcorticoids (aldosterone) is secreted from what part of adrenal cortex? What about glucocorticoids (cortisol)? What about androgens?

A
  • Zona glomerulosa
  • zona fasciulata
  • zona reticularis
65
Q

What time of day does blood cortisol peak and trough?

A

2-4am, 10pm-midnight

66
Q

Cortisol release mech of action

A
  • Stress or non stress neural inputs cause increased CRH release from hypothalamus
  • hypophyseal portal system takes that and releases ACTH from the anterior pituitary
  • This stimulates release of cortisol from the adrenal cortex
  • this acts at target cells for cortisol and has a negative impact on both CRH and ACTH release
67
Q

Actions of cortisol (4)

A
  • metabolism such as gluconeogenesis and mobilization of fat
  • increased muscle contractility and breakdown of muscle
  • bone and connective tissue sees decreased bone and collagen formation
  • inhibits immune system

Endocrinology (19 decks)

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