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The Endocrine System Flashcards

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1
Q

What are hormones, and what secretes them?

A

Hormones are signaling molecules secreted directly into the bloodstream by glands.

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2
Q

What are the three types of hormones?

A

Peptides, steroids, amino acid derivatives

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3
Q

How are peptide hormones made?

A
  • cleaved from larger post-translational proteins

- Golgi modifies, activates, and directs them

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4
Q

How do peptide hormones work? Does the receptor type matter? What is this process called?

A
  • A signaling cascade
  • They are charged, so must bind to extracellular receptor
  • Acts as a first messenger, binds to a receptor and triggers a second signal, the second messenger
  • Receptor type determines what happens in the cell
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5
Q

What is amplification?

A
  • One hormone molecule binding to multiple receptors before being degraded
  • Or each receptor activates multiple enzymes, each creating lots of second messengers
  • Results in increased signal intensity
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6
Q

What are 3 common second messengers?

A

cAMP, IP3, calcium

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7
Q

Describe the activation of a G protein by a peptide hormone.

A
  • Peptide hormone binds to G protein-coupled receptor
  • Receptor is triggered to either activate or inhibit an adenylate cyclase
  • This enzyme will either raise or lower levels of cAMP
  • cAMP can then bind to intracellular targets (for example, protein kinase A, which phosphorylates transcription factors)
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8
Q

What are 2 differences between peptide and steroid hormones?

A
  • Peptide effects are rapid but short-lived, while steroids are slower but longer-lived
  • Peptides are water-soluble so can travel freely in bloodstream, steroids are lipid-soluble and must be carried by proteins in the blood
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9
Q

How are steroid hormones made? Which organs produce them?

A
  • Derived from cholesterol

- Produced by gonads and adrenal cortex

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10
Q

How do steroid hormones work?

A
  • Pass through the membrane, so receptors are intracellular or intranuclear
  • Bind to receptor and the whole complex undergoes conformational change
  • Receptor binds directly to DNA, either increasing or decreasing transcription
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11
Q

What is dimerization?

A

-A form of conformational change for steroid hormones, where two receptor-hormone complexes are paired

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12
Q

Are the proteins that carry steroid hormones through the bloodstream specific? Why do their concentrations matter?

A
  • Some are and some aren’t
  • Hormones aren’t active while attached to them, so levels of carrier proteins can change the levels of active hormones (like more carrier protein released, less hormone perceived by the body - a lot of it is bound to the proteins)
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13
Q

What are amino acid-derivative hormones made of?

A

1 or 2 AAs with additional modifications

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14
Q

Examples of amino acid-derivative hormones and how fast they act?

A
  • Epinephrine, norepinephrine - fast onset but short-lived
  • Triiodothyronine, thyroxine - slower but longer duration on metabolic rate
  • end in “in” or “ine” a lot
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15
Q

Examples of peptide hormones?

A

ADH, insulin

-end in “in” or “ine” a lot

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16
Q

Examples of steroid hormones?

A

Sex hormones

-end in “one” or “ol” or “oid” a lot

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17
Q

What are direct hormones?

A

Act directly on a target tissue

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18
Q

What are tropic hormones? Where are they usually secreted from?

A
  • Require an intermediary to act

- Brain and anterior pituitary gland

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19
Q

What does the hypothalamus do?

A
  • Regulates pituitary through tropic hormones
  • Portal system connects the organs
  • Receives input from lots of places
  • Regulates satiety, sleep-wake cycles, blood osmolarity
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20
Q

How is hypothalamus activity controlled?

A

Negative feedback

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21
Q

What is the system that connects the hypothalamus and the pituitary?

A

The hypophyseal portal system: blood vessels that connect the hypothalamus with the anterior pituitary gland
(hypophysis is an alternative name for pituitary)

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22
Q

What hormone does the anterior pituitary release in response to each of the following tropic hormones from the hypothalamus?

  1. GnRH
  2. GHRH
  3. TRH
  4. CRH
  5. PIF (dopamine)
A
  1. FSH and LH
  2. GH (growth)
  3. TSH (thyroid-stimulating)
  4. ACTH (adrenocorticotropic)
  5. Causes a decrease in prolactin
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23
Q

What are the axes? What is their function:?

A
  • HPX, hypothalamus-pituitary-target organ level

- Negative feedback system, where final secretion binds to receptors for it in hypo/pituitary to inhibit more secretion

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24
Q

What is the relationship between the hypothalamus and posterior pituitary? What does the posterior pituitary do?

A
  • Hypothalamus neurons send their axons into posterior pit

- Post pit can then release oxytocin and ADH

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25
Q

Which 4 tropic hormones does the ant pit make?

A
  1. FSH
  2. LH
  3. ACTH
  4. TSH
    FLAT
26
Q

Which 3 direct hormones does the ant pit make?

A
  1. Prolactin
  2. Endorphins
  3. GH (growth hormone)
    PEG
27
Q

When does lactation begin? What is the process of lactation hormonally?

A
  • After expulsion of the placenta, when estrogen, progesterone, and dopamine levels drop, allowing for prolactin secretion
  • Newborn latches, causing activation of hypothalamus
  • Oxytocin released from post pit, causing contraction of smooth muscle in breast
  • Hypothalamus stops releasing dopamine into ant pit, allowing prolactin release, causing milk production
28
Q

How does GH work?

A
  • Prevents glucose uptake in tissues that aren’t growing
  • Stimulates breakdown of fatty acids
  • Increases availability of glucose overall for growth
29
Q

What problems can result from abnormal GH amounts?

A
  • Gigantism: too much GH before epiphyseal plates seal
  • Dwarfism: too little GH
  • Acromegaly: too much GH in adulthood, leading to only smaller bones growing too much (like hands, feet)
30
Q

When is ADH secreted?

A
  • in response to low blood volume or increased blood osmolarity
  • acts in kidney, where it increases the permeability of its collecting duct to water, so more water retention
31
Q

What causes oxytocin secretion? What type of feedback loop does it have?

A
  • Childbirth, suckling, bonding behavior

- Positive feedback loop that ends with birth

32
Q

What are T3 and T4 made of, what do they do, and where are they secreted from?

A
  • Produced by the iodination of tyrosine
  • Secreted from follicular cells in thyroid gland
  • Reset basal metabolic rate by controlling energy production efficiency and altering glucose/fatty acids
  • More T3/4 = more cellular respiration
33
Q

What problems can result from an abnormal thyroid?

A
  • Hypothyroidism: too little/none of thyroid hormone secreted; causes lethargy, slowed heart rate, weight gain, decreased body temp
  • Cretinism: deficiency in hormones can cause intellectual/development problems in kids
  • Hyperthyroidism: excess of thyroid hormone can cause tumor; weight loss, heat intolerance, fast breath and heart rate
34
Q

Where is calcitonin secreted from? What does it do?

A
  • C-cells (parafollicular cells) of thyroid produce calcitonin
  • Decreases plasma calcium by
    1. increasing Ca excretion from kidneys
    2. decreasing Ca absorption from gut
    3. Increasing storage of Ca in bone
  • Stimulated by lots of Ca in blood
35
Q

What are the parathyroid glands? What do they do?

A
  • 4 structures that sit on posterior surface of thyroid

- Produce PTH

36
Q

What does PTH do?

A
  • Antagonist to calcitonin, raising blood Ca levels (decreases Ca excretion by kidneys, increasing Ca absorption in gut, increases bone resorption)
  • Promotes phosphorus homeostasis (increases resorption of phosphate from bone, reduces reabsorption of phosphate in kidney - these cancel each other)
  • Activates Vitamin D for absorption
  • So overall effect is increase in blood Ca levels and little effect on phosphate
37
Q

Where are the adrenal glands located? What do they consist of?

A
  • On top of the kidneys

- Each gland has a cortex and a medulla with different functions

38
Q

What does the adrenal cortex secrete? What are the three classes these hormones fall into?

A

Secretes corticosteroids, which are steroid hormones that can be divided into three classes:

  1. Glucocorticoids
  2. Mineralocorticoids
  3. Cortical sex hormones
39
Q

What are glucocorticoids? What do they do? What are 2 examples? What hormone regulates them?

A
  • Steroid hormones (corticosteroids) from adrenal cortex
  • Regulate glucose levels
  • Ex: cortisol and cortisone
  • Raise blood glucose by increasing gluconeogenesis and decreasing protein synthesis
  • Can also decrease inflammation response
  • Cortisol is a stress hormone, released during times of stress
  • CRF from hypothalamus –> ACTH from pituitary –> glucorticoids
40
Q

What are mineralocorticoids? What do they do? What are examples?

A
  • Used in salt-water homeostasis in kidneys
  • Ex: aldosterone, which increases sodium reabsorption in kidney to increase water/blood volume and pressure (water follows salt, so plasma osmolarity stays constant)
  • Also decreases K and H ion reabsorption in kidneys so they are excreted in urine
41
Q

What system regulates aldosterone concentration?

A

Renin-angiotensin-aldosterone system:

  1. Decreased BP causes juxtaglomerular cells of kidney to secrete renin
  2. Renin cleaves an inactive angiotensinogen (plasma protein) to its active form, angiotensin I
  3. Angiotensin I is converted to angiotensin II by angiotensin-converting enzyme (ACE)
  4. Angiotensin II stimulates adrenal cortex to secrete aldosterone
  5. When BP is restored, there is a decreased drive to stimulate renin release.
42
Q

What are cortical sex hormones? What happens if there are disorders related to cortical sex hormones production?

A
  • Secrete androgens and estrogens
  • Adrenal testosterone has a small role in men because testes already secrete a lot of androgens
  • But because the ovaries don’t secrete many androgens, females are very sensitive to disorders of cortical sex hormone production
  • Like an excess of androgen production in adrenal cortex would result in ambiguous/male genitalia in females
  • Same thing in men with excessive estrogen
43
Q

In summary, what are the 3 functions of the corticosteroids? (Hint: 3 S’s)

A
  1. Salt (mineralocorticoids)
  2. Sugar (glucocorticoids)
  3. Sex (cortical sex hormones)
44
Q

What does the adrenal medulla do? How does it secrete hormones?

A
  • Produces epinephrine and norepinephrine

- Specialized nerve cells secrete them directly into bloodstream

45
Q

What type of hormone is epinephrine/norepinephrine? What do they do to the body? What is their relationship to cortisol?

A
  • Amino acid derivative called catecholamines
  • Fight or flight response: increase basal metabolic rate, increase glucose breakdown, dilate bronchi, increase heart rate
  • Cortisol mediates long-term (slow) stress responses, while catecholamines control short-term (fast) stress responses
  • Cortisol also increases catecholamine synthesis
46
Q

Do the pancreas have exocrine or endocrine functions?

A

Both - exocrine means it secretes substances into ducts; endocrine means it secretes substances directly into bloodstream

47
Q

How is the endocrine component of the pancreas organized?

A
  • Hormone-producing cells grouped into clusters called islets of Langerhans throughout pancreas
  • Islets have three types of cells: alpha, beta, delta cells
  • Each cell secretes a different hormone: alpha-glucagon, beta-insulin, delta-somatostatin
48
Q

What is glucagon and what does it do?

A
  • Secreted by alpha cells in islets of Langerhans
  • Increases glucose production by triggering gluconeogenesis, glycogenolysis, degradation of protein and fat
  • Secreted because of low glucose levels but also certain GI hormones
49
Q

What is insulin and what does it do?

A
  • Secreted by beta cells in islets of Langerhans
  • Antagonistic to glucagon so secreted when blood glucose levels are high
  • Induces muscle and liver cells to take up glucose and store it as glycogen
  • Stimulates fat and protein synthesis
50
Q

What does an excess of insulin cause?

A

-Hypoglycemia: low blood glucose concentration

51
Q

What does an underproduction of insulin cause?

A

-Diabetes mellitus: hyperglycemia (too much blood glucose)

52
Q

Why do diabetics often report polyuria (increased urination) and polydipsia (increased thirst)?

A
  • Excessive glucose in kidneys will overwhelm their ability to reabsorb glucose, resulting in its presence in urine
  • As glucose can’t readily cross the cell membrane, its presence in the filtrate leads to excess of water and increase in urination/thirst
53
Q

What are the two types of diabetes?

A
  • Type I (insulin-dependent): autoimmune destruction of beta-cells of pancreas, resulting in low/absent insulin production; needs insulin injections for glucose uptake to avoid hyperglycemia
  • Type II (non-insulin-dependent): receptor-level resistance to the effects of insulin; partially inherited/partially environmental (high carb diets); take certain drugs
54
Q

What is somatostatin and what does it do?

A
  • Inhibits insulin and glucagon secretion
  • stimulated by high blood glucose and amino acid concentrations
  • Produced by pancreas
  • Also decreases growth hormone secretion
55
Q

What do gonadotropins cause their target organs to do?

A
  • Gonadotropins (LH and FSH) cause testes to secrete testosterone - sexual differentiation, secondary sex traits
  • Cause ovaries to secrete estrogen and progesterone
56
Q

What does the pineal gland do?

A
  • Secretes melatonin

- Involved in circadian rhythms, sleepiness

57
Q

Are there endocrine regions in the GI tract? If so, where?

A

Stomach and intestine; release hormones because of certain nutrients

58
Q

Summarize the 3 endocrine functions of the kidneys.

A
  • ADH increases water permeability in collecting duct
  • R-A-Aldo system increases Na/water reabsorption
  • Also produce erthyropoietin, which stimulates bone marrow to increase RBC production in response to low blood O2 levels
59
Q

What endocrine function does the heart have?

A
  • Releases ANP peptide to help salt and water balance
  • When cells in atria are stretched from excess blood volume, they release ANP
  • This promotes Na excretion and therefore increases urine volume
  • Antagonistic to aldosterone
60
Q

What endocrine function does the thymus have?

A
  • Behind sternum
  • Releases thymosin for proper T-cell development and differentiation
  • Thymus atrophies by adulthood
61
Q

Which 3 hormones are involved in water homeostasis? Where does each come from, and what effect does each have on blood volume and osmolarity?

A
  1. ADH: (posterior pituitary) increases BV and decreases BO
  2. Aldosterone (adrenal cortex): increases BV and has no effect on BO
  3. ANP (heart): decreases BV and has no effect on BO
62
Q

Which two hormones are involved in calcium synthesis? Where does each come from, and what effect do they have on blood Ca concentrations?

A
  1. Calcitonin: (C-cells of thyroid) decrease Ca levels

2. PTH: (parathyroid glands) increase Ca levels

Biology (14 decks)

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