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SP MCAT Biology > Endocrine System > Flashcards

Endocrine System Flashcards

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1
Q

Glands

A

organs that secrete hormones

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2
Q

Hormones

A

signaling molecules that are secreted directly into the bloodstream to travel to target tissue

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3
Q

Peptide Hormones

A
  • made up of amino acids
  • derived from larger precursor polypeptides that are cleaved during posttranslational modifications
  • charged and cannot pass through plasma membrane so must bind to an extracellular receptor
  • considered a first messenger b/c it binds to a receptor and triggers the transmission of a second signal/messenger
  • effects are rapid but short-lived b/c act through transient second messenger systems
  • generally water soluble and can travel freely in bloodstream
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4
Q

Signaling Cascade

A

the connection between the hormone at the surface and the effect brought about by second messengers within the cell

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5
Q

List common second messengers (3)

A
  • cAMP
  • IP3
  • calcium
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6
Q

Steroid Hormones

A
  • derived from cholesterol
  • produced primarily by the gonads and adrenal cortex
  • nonpolar molecules that can easily cross plasma membrane
  • receptors are intracellular (in the cytosol) or intranuclear (in the nucleus) and after binding they form a hormone-receptor complex that binds to DNA to alter gene expression
  • effects of hormone are slower but last longer
  • cause alterations in amount of mRNA and protein present in cell
  • not water soluble so carried by proteins in bloodstream
  • includes: estrogen, testosterone, aldosterone, cortisol glucocorticoids
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7
Q

Dimerization

A

pairing of two receptor hormone complexes

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8
Q

Amino-Acid Derivative Hormones

A
  • includes: epinephrine, norepinephrine, triiodothyronine, thyroxine
  • catecholamines are a type of these
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9
Q

Catecholamines

A
  • includes: epinephrine, norepinephrine
  • bind to G protein coupled receptors
  • important in long-term stress responses
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10
Q

Direct Hormones

A

secreted and then act directly on a target tissue

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11
Q

Tropic Hormones

A
  • require an intermediary to act
  • do not cause a direct change in physiology of tissue but do stimulate production of another hormone by another endocrine gland that acts on the target tissue
  • originate in the brain and anterior pituitary gland
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12
Q

Hypothalamus

A
  • bridge between nervous and endocrine system
  • located in the forebrain directly above pituitary gland and below thalamus
  • regulates pituitary gland through tropic hormones via paracrine release of hormones into a portal system that connects the two organs
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13
Q

How does the hypothalamus interact with the anterior pituitary gland?

A
  • secretes compounds into the hypophyseal portal system (blood vessel that directly connects hypothalamus to anterior pituitary)
  • hormones can be found in appreciable concentrations in systemic circulation
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14
Q

List of hormones secreted by hypothalamus and response anterior pituitary hormones (4)

A
  • gonadotropin-releasing hormone (GnRH) -> follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
  • growth hormone-releasing hormone (GHRH) -> growth hormone (GH)
  • thyroid releasing hormone (TRH) -> thyroid stimulating hormone (TSH)
  • corticotropin-releasing factor (CRF) -> adrenocorticotropic hormone (ACTH)
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15
Q

What is different about Prolactin?

A
  • almost all other hormones cause an increase in anterior pituitary secretion but this hormone causes a decrease
  • prolactin-inhibitory factor (PIF) which is actually dopamine is released by hypothalamus and causes a decrease in prolactin secretion by the anterior pituitary
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16
Q

Posterior Pituitary Gland

A
  • neurons from hypothalamus send their axons down the pituitary stalk directly to this gland
  • essentially an extension of the hypothalamus
  • hormones released here: oxytocin, antidiuretic hormone/vasopressin
  • doesn’t synthesize any hormones itself, just stores them
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17
Q

Oxytocin

A
  • stimulates uterine contractions during labor and milk letdown during lactation
  • involved in bonding behavior with baby
  • positive feedback loop
  • source: hypothalamus (stored in posterior pituitary)
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18
Q

Antidiuretic Hormone (ADH)

A
  • increases reabsorption of water in collecting ducts of kidneys
  • secreted in response to increased plasma osmolarity or increased concentration of solutes within the blood
  • source: hypothalamus (stored in posterior pituitary)
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19
Q

List the 7 hormones that are synthesized/secreted by the anterior pituitary gland

A
  • FLAT PEG*
  • Follicle-stimulating hormone
  • Luteinizing hormone
  • Adrenocorticotropic hormone
  • Thyroid stimulating hormone
  • Prolactin
  • Endorphins
  • Growth hormone
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20
Q

What anterior pituitary hormones are tropic hormones?

A
  • FLAT*
  • Follicle-stimulating hormone
  • Luteinizing hormone
  • Adrenocorticotropic hormone
  • Thyroid stimulating hormone
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21
Q

What anterior pituitary hormones are direct hormones?

A
  • PEG*
  • Prolactin
  • Endorphins
  • Growth hormone
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22
Q

Prolactin

A
  • stimulates milk production in the mammary glands

- release of dopamine from hypothalamus decreases its secretion from anterior pituitary

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23
Q

Growth Hormone

A
  • promotes growth of bone and muscle
  • prevents glucose uptake in tissues that aren’t growing and stimulates breakdown of fatty acids which increases availability of glucose overall allowing for muscle and bone to use it
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24
Q

Where does bone growth originate?

A

epiphyseal plates

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25
Q

What is the cause of gigantism?

A

excess GH release in childhood

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26
Q

What is the cause of dwarfism?

A

deficit in GH release during childhood

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27
Q

What is acromegaly?

A
  • when there is excess GH production in adults and they develop large hands + feet + head
  • occurs because small bones can still be affected by GH later in life whereas long bones cannot
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28
Q

Follicule Stimulating Hormone (FSH)

A
  • stimulates follicle maturation
  • stimulates spermatogenesis
  • source: anterior pituitary
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29
Q

Luteinizing Hormone (LH)

A
  • stimulates ovulation
  • stimulates testosterone synthesis
  • source: anterior pituitary
30
Q

Adrenocorticotropic Hormone (ACTH)

A
  • stimulates adrenal cortex to make and secrete glucocorticoids (anti-inflammatory)
  • source: anterior pituitary
31
Q

Thyroid-Stimulating Hormone (TSH)

A
  • stimulates the thyroid to produce thyroid hormones

- source: anterior pituitary

32
Q

Endorphins

A
  • inhibits the perception of pain in the brain

- source: anterior pituitary

33
Q

Thyroid

A
  • located on front surface of trachea

- two major functions: setting basal metabolic rate which is mediated by releasing T3 and T4; calcium homeostasis

34
Q

Triiodothyronine (T3)

A
  • 3 iodines attached to tyrosine
  • produced by iodination of tyrosine in the follicular cells of the thyroid
  • stimulates metabolic activity
  • source: thyroid
35
Q

Thyroxine (T4)

A
  • 4 iodines attached to tyrosine
  • produced by iodination of tyrosine in the follicular cells of the thyroid
  • stimulates metabolic activity
  • source: thyroid
36
Q

What happens when there are high levels of T3 and T4 secretion?

A

increased cellular respiration which causes greater amount of protein and fatty acid turnover

37
Q

Hypothyroidism

A
  • deficiency of iodine or inflammation of thyroid
  • characterized by lethargy, decreased body temperature, slowed respiration rate and heart rate, cold intolerance, weight gain
38
Q

Hyperthyroidism

A
  • excess thyroid hormone resulting from tumor or thyroid over stimulation
  • characterized by increased activity level, increased body temperature, increased respiration rate and heart rate, heat intolerance, weight loss
39
Q

Calcitonin

A
  • produced by C-Cells (parafollicular cells) in thyroid
  • decreases plasma Ca2+ levels in 3 ways: (1) increase Ca2+ excretion from kidneys (2) decrease Ca2+ absorption from gut (3) increase Ca2+ storage in bone
40
Q

Parathyroid Glands

A
  • produces parathyroid hormone

- 4 small structures that sit on posterior surface of thyroid

41
Q

Parathyroid Hormone (PTH)

A
  • produced by parathyroid gland
  • antagonist hormone to calcatonin
  • increases blood calcium levels by decreasing exrection of Ca2+ by kidneys, increasing absorption of Ca2+ in gut via vitamin D, and increases bone resorption
  • increases plasma Ca2+ levels lead to decreased secretion of this hormone
  • also affects phosphorous homeostasis by resorbing phosphate from bone and reducing reabsorption of phosphate in kidney (promoting excretion in urine)
42
Q

What are the important functions of calcium?

A
  • bone structure/strength
  • release of NTs from neurons
  • regulation of muscle contraction
  • cofactor in clotting of blood
  • cell movement
  • exocytosis of cellular materials
43
Q

Adrenal Cortex

A
  • located on top of kidneys
  • consists of a cortex and medulla
  • secrets 3 different classes of corticosteroids: glucocorticoids, mineralcorticoids, cortical sex hormones
44
Q

Glucocorticoids

A
  • regulate glucose levels
  • affects protein metabolism
  • increases blood glucose level and decreases protein synthesis
  • anti-inflammatory agent
  • includes cortisol ad cortisone
45
Q

Functions of Cortisol and Cortisone

A
  • raise blood glucose by increasing gluconeogenesis and decreasing protein synthesis
  • decrease inflammation and immunologic responses
46
Q

Mineralcorticoids

A
  • used in salt and water homeostasis mostly at kidneys

- includes aldosterone

47
Q

Aldosterone

A
  • leads to increased Na+ reabsorption in distal convoluted tubule and collecting duct
  • water follows Na+ cations into bloodstream which increases blood volume and pressure while keeping plasma osmolarity unchanged
  • leads to decreased reabsorption of K+ and H+ ions in distal convoluted tubule and collecting duct which promotes their secretion in urine
  • primarily under the control of the renin-angiotensin-aldosterone system
48
Q

Cortical Sex Hormones

A

includes androgens and estrogens

49
Q

Functions of the Corticosteroids

A
  • SALT, SUGAR, SEX – the deeper you go the better it gets*
  • SALT: mineralcorticoids
  • SUGAR: glucocorticoids
  • SEX: cortical sex hormones
50
Q

Adrenal Medulla

A
  • derivative of the nervous system
  • produces the sympathetic hormones epinephrine and norepinephrine which can be directly secreted into the circulatory system
51
Q

Epinephrine

A
  • increases breakdown of glycogen to glucose (glycogenolysis) in the liver and muscle
  • increase basal metabolic rate
52
Q

Functions of Epinephrine and Norepinephrine

A
  • increased heart rate
  • dilate bronchi
  • alter blood flow to supply systems used in sympathetic response – vasodilation of blood vessels leading to skeletal muscle + heart + brain + lungs
  • increases blood glucose level
53
Q

Cortisol increases the synthesis of ____

A

catecholamines

54
Q

Pancreas

A
  • contains islets of langerhans which contain 3 distinct groups of hormone producing cells – alpha, beta, delta
  • secretes 3 hormones: glucagon, insulin, somatostatin
55
Q

What hormone is secreted by the alpha cells in the pancreas?

A

glucagon

56
Q

What hormone is secreted by the beta cells in the pancreas?

A

insulin

57
Q

What hormone is secreted by the delta cells in the pancreas?

A

somatostatin

58
Q

Glucagon

A
  • secreted during fasting when glucose levels are low
  • secretion stimulates degradation of protein and fat, glycogen to glucose in liver, and production of new glucose via gluconeogenesis
  • increases blood glucose concentrations
59
Q

What two GI hormones stimulate alpha cells to release glucagon?

A
  • cholecystokinin

- gastrin

60
Q

Insulin

A
  • antagonist to glucagon
  • secreted when blood glucose levels are high
  • induces muscle and liver cells to take up glucose and store it as glycogen
  • stimulates anabolic processes like fat and protein synthesis
  • decreases blood glucose concentrations
61
Q

Hypoglycemia

A
  • occurs when insulin is present in excess

- characterized by low blood glucose concentrations in blood

62
Q

Diabetes Mellitus

A
  • underproduction/insufficient secretion/insensitivity to insulin
  • characterized by hyperglycemia (excess glucose in blood)
  • individuals with this have increased glucose in filtrate which leads to excess excretion of water and increased urine volume
  • have increased frequency of urination (polyuria) and increased thirst (polydipsia)
63
Q

Type I Diabetes

A
  • insulin-dependent
  • caused by autoimmune destruction of beta cells in pancreas so produce little to no insulin
  • require regular injections of insulin to permit hyperglycemia and permit entry of glucose into cells
64
Q

Type II Diabetes

A
  • non-insulin-dependent
  • result of receptor-level resistance to effects of insulin
  • partially inherited and partially due to environmental factors (high carb diet and obesity)
65
Q

Somatostatin

A
  • inhibitor of both insulin and glucagon secretion
  • stimulated by increased blood glucose and amino acid concentrations
  • also produced by hypothalamus where it functions in decreasing growth hormone secretion
66
Q

Testes (Gonads)

A

secrete testosterone in response to stimulation by gonadotropins (LH and FSH)

67
Q

Ovaries (Gonads)

A
  • secrete estrogen and progesterone in response to FSH and LH
  • estrogen maintains female secondary sex characteristics
  • progesterone promotes growth/maintenance of endometrium
68
Q

Pineal Gland

A
  • located deep within the brain

- receives projections directly from retina but not involved in vision so is likely responding to light intensity

69
Q

Melatonin

A
  • secreted by the pineal gland

- involved in circadian rhythms

70
Q

Erythropoietin

A
  • produced in kidneys
  • stimulates bone marrow to increase production of erthrocytes (RBCs)
  • secreted when there are low levels of oxygen in blood
71
Q

Atrial Natriuretic Peptide (ANP)

A
  • released from heart
  • involved in osmoregulation and vasodilation
  • helps regulate salt and water balance
  • released when cells in atria are stretched from excess blood volume
  • promotes excretion of Na+ so increases urine volume
  • antagonist to aldosterone because it lowers blood volume and pressure while having no effect on blood osmolarity
72
Q

Thymosin

A
  • released from the thymus (located behind sternum)

- important in proper T Cell development and differentiation

SP MCAT Biology (21 decks)

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