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MCAT Biology > Endocrine Organs and Hormones > Flashcards

Endocrine Organs and Hormones Flashcards

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1
Q

Hypothalamus

A
  • the bridge between the nervous and endocrine system
  • located in the forebrain above the pituitary gland and below the thalamus (hence the name hypothalamus)
  • some parts respond to increased in blood osmolarity
  • regulate appetite and satiety
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2
Q

Negative feedback

A
  • regulates the release of hormones by the hypothalamus
  • occurs when the final hormone (or product) of a pathway inhibits hormones (or enzymes) earlier in the pathway, maintaining homeostasis
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3
Q

Gonadotropin - releasing hormone (GnRH)

A

Promotes the release of follicle - stimulating hormone (FSH) and lutenizing hormone (LH)

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4
Q

Growth hormone - releasing hormone (GHRH)

A

Promotes the release of growth hormone

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5
Q

Thyroid - releasing hormone (TRH)

A

Promotes the release of thyroid - stimulating hormone (TSH)

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6
Q

Corticotropin - releasing factor (CRF)

A

promotes the release of thyroid stimulating hormone (TSH)

increases the level of cortisol being secreted into the blood

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7
Q

Prolactin - inhibiting factor (PIF or dopamine)

A

inhibits the release of prolactin
released by the hypothalamus
causes a decrease in prolactin secretion

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8
Q

Hypothalamus secretes compounds into the

A

hypophyseal portal system - which is a blood vessel system that directly connects the hypothalamus with the anterior pituitary

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9
Q

An alternative term for the pituitary is

A

Hypophysis

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10
Q

Hypothalamus releases what (5) hormones?

A
  1. Gonadotropin - releasing hormone (GnRH)
  2. Growth hormone - releasing hormone (GHRH)
  3. Thyroid - releasing hormone (TRH)
  4. Corticotropin - releasing factor (CRF)
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11
Q

Anterior pituitary releases what (7) hormones in response to the hypothalamus releasing hormones?

A
  1. Follicle - stimulating hormone (FSH) - tropic hormone
  2. Luteinizing hormone (LH) - tropic hormone
  3. Growth hormone (GH) - direct hormone
  4. Thyroid - stimulating hormone (TSH) - tropic hormone
  5. Adrenocorticotropic hormone (ACTH) - tropic hormone
  6. Prolactin - direct hormone
  7. Endorphines - direct hormone
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12
Q

Prolactin

A
  • promotes milk promotion
  • Secreted by the anterior pituitary
  • has a decrease in secretion when dopamine is released from the hypothalamus
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13
Q

Follicle - stimulating hormone (FSH)

A

promotes the development of ovarian follicles in females and spermatogenesis in males

acts on the gonads - testes and ovaries

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14
Q

Luteinizing hormone (LH)

A

promotes ovulation in females and testosterone production in males
acts on the gonads - testes and ovaries

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15
Q

Growth hormone (GH)

A
  • promotes growth of bone and muscle and shunts glucose to these tissues
  • It raises blood glucose concentrations
  • requires large quantities of glucose
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16
Q

Thyroid - stimulating hormone (TSH)

A

promotes synthesis and release of triiodothyronine and thyroxine from the thyroid

acts on the thyroid

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17
Q

Adrenocorticotropic hormone (ACTH)

A

promotes synthesis and release of glucocorticoids from the adrenal cortex

increases the level of cortisol being secreted into the blood

acts on the adrenal cortex

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18
Q

Endorphines

A

decreases perception of pain and cause euphoria

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19
Q

Anterior Pituitary

A

releases hormones in response to stimulation from the hypothalamus
4 Tropic hormones
3 Direct hormones

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20
Q

Hypothalamic (-) feedback mechanism

A

hypothalams – (CRF) –> Anterior Pituitary – (ACTH) –> Adrenal cortex – (cortisol) –>

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21
Q

Posterior pituitary releases two hormone produces in the hypothalamus:

A 
Antidiuretic Hormone (ADH ro Vasopressin)
Oxytocin
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22
Q

Oxytocin

A
  • Secreted during childbirth
  • Promotes milk ejection
  • Stimulates contractions during labor
  • Involved in bonding behavior
  • Has a positive feedback look loop, not negative… (the release of oxytocin promotes uterine contraction, which promotes more oxytocin release, which promotes stronger contractions, and so on)
  • Released by the Posterior pituitary
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23
Q

Antidiuretic Hormone (ADH ro Vasopressin)

A
  • increases reabsorption of water in the collecting ducts of the kidneys
  • secreted in response to low blood volume or increased blood osmolarity
  • increases blood volume
  • decreases blood osmolarity
  • Released by the Posterior pituitary
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24
Q

Follicle - stimulating hormone (FSH) and Luteinizing hormone (LH) is stimulated by the release of

A

Gonadotropin - releasing hormone (GnRH)

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25
Q

Adrenocorticotropic hormone (ACTH) is stimulated by the release of

A

Corticotropin - releasing factor (CRF)

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26
Q

Thyroid - stimulating hormone (TSH) is stimulated by the release of

A

Thyroid - releasing hormone (TRH)

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27
Q

Growth hormone (GH) is stimulated by the release of

A

Growth hormone - releasing hormone (GHRH)

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28
Q

Thyroid is controlled by

A

the thyroid stimulating hormone

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29
Q

Thyroid has 2 major functions:

A

Setting basal metabolic rate and calcium homeostasis

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30
Q

Thyroid releases:

A

triiodothyronine (T3), thyrozine (T4) and calcitonin

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31
Q

triiodothyronine (T3) and thyrozine (T4)

A
  • numbers 3 and 4 refers to the number of iodine atoms attached to the tyrosine
  • produced by the iodination of the amino acid tyrosine int he follicular cells of the thyroid
  • capable or resetting the basal metabolic rate of the body by making energy production more or less efficient, as well as altering the utilization of glucose and fatty acids
  • increased amount of
32
Q

Increased amount of T3 and T4 will lead to

A

cellular respiration

33
Q

What prevents the excessive secretion of T3 and T4?

A

negative feedback

34
Q

High plasma levels of thyroid hormones will lead to

A

decreased TSH and TRH synthesis

35
Q

Thyroid is located at:

A

the base of the neck in front of the trachea; t produces 3 key hormones

36
Q

Calcitonin

A
  • produced by parafollicular (C) cells
  • decreases plasma calcium concentration by (1)promoting calcium excretion in the kidneys, (2) decreasing the calcium absorption in the gut and (3) promoting calcium storage in the bone
37
Q

Hypothyroidism

A
  • caused by deficiency of iodine or inflammation of the thyroid
  • thyroid hormones are secreted in insufficient amounts of not at all
  • decreases body temp, slows down heart rate and respiratory, cold intolerance and weight gain
38
Q

Hyperthyroidism

A
  • an excess of thyroid hormone caused by a tumor or excess thyroid over stimulation
  • increased body temp, increased heart rate and respiratory, heat intolerance and weight loss
39
Q

C - cells

A
  • Produced by the follicular cells
  • produce calcitonin
  • decreases plasma calcium levels in 3 ways:
    increased calcium excretion from the kidneys
    decreased calcium absorption from the gut
    increased storage calcium in the bone
  • high levels of calcium in the blood stimulate secretion of calcium in the bone
40
Q

Important functions of calcium:

A
  • bone structure and strength
  • regulation of muscle contraction
  • clotting of blood (calcium is a cofactor(
41
Q

Parathyroid Hormone (PTH)

A
  • raises blood calcium levels
  • decreases excretion of calcium by the kidneys
  • increases absorption of calcium in the gut (via VitaminD)
  • increases bone resorption
  • subject to feedback inhibition
  • overall effect: increase blood calcium levels with little effect on phosphate
42
Q

As calcium levels INCREASE, PTH secretion is

A

DECREASED

43
Q

PTH activates which vitamin?

A

vitamin D

44
Q

Vitamin D is required for

A

the absorption of calcium and phosphate in the gut

45
Q

PTH increases calcium levels, while calcitonin (decreases/increases) calcium levels

A

decreases

46
Q

Adrenal Glands

A
  • located on top of the kidneys
  • consists of: a
    cortex and a medulla
47
Q

Adrenal Cortex secretes

A

corticosteroids

48
Q

Corticosteroids are divided into 3 classes:

A

glucocorticoids
mineralcorticoids
cortical sex hormones

49
Q

Glucocorticoids

A
  • steroid that regulates glucose levels
  • affect protein metabolism
  • 2 Glucocorticoids: cortisol and cortisone: both raise glucose levels, decrease inflammation an immunologic responses
  • Glucocorticoid release is under control of ACTH; CRF promotes the release of ACTH form the anterior pituitary
50
Q

Cortisol

A
  • is a Glucocorticoid
  • stress hormone
  • it is released in time of physical or emotional stress
  • increases blood sugar
51
Q

Mineralocorticoids

A
  • used in salt and water homeostatis
  • most profound effect are on the kidneys
  • Aldosterone is a mineralocorticoid; it increases sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron
52
Q

Aldosterone

A
  • a mineralocorticoid
  • increases sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron
  • decreases reabsorption of Potassium and Hydrogen ions, promoting excretion in the urine
  • under control of the Renin - Aniostensin - Aldosterone system
53
Q

Renin - Angiotensin - Aldosteron System

RAA system

A
  • Decrease in blood pressure causes the baroreceptors (juxtaglomerular cells) to secrete RENIN (enzyme)
  • Renin: cleaves an inactive plasma protein, angiotensiongen to its active form angiotensin 1
  • Antiotension 1 is then converted into Angeiotensin 2 by Antgiotensin converting enzyme (ACE) in the lungs
  • Antiotension 2 stimulates the adrenal cortex to secrete aldosterone
  • once blood pressure is restored, there is a decreased drive to stimulate renin release, therefore serving as a negative feedback
  • the goal of this is to raise blood pressure
54
Q

3 triggers of renin:

A
  1. decreased BP
  2. sympathetic Nerves
  3. low Sodium
55
Q

Cortical Sex Hormones

A
  • made by the adrenal glands

- consists of androgens and estrogens

56
Q

3 functions of the corticosteroids: (3 S’s)

A

Salt (mineralocorticoids)
Sugar (glucocorticoids)
Sex (cortical sex hormones)

57
Q

Adrenal Medula is responsible for which 2 sympathetic hormones:

A

epinephrine: causes a breakdown of glycogen to glucose
norepinephrine

Both:

  • fall under the category of catecholamines
  • increase heart rate
  • dilate the bronchi
  • alter blood flow to supply the system
58
Q

Pancreas

A
  • secrete both exocrine and endocrine functions
  • From an endocrine standpoint:
    small groups of hormone - producing cells are grouped together into islets of Lagerhands throughout the pancreas
59
Q

Islets of Lagerhands contain 3 distinct types of cells:

A

alpha cells - which secrets: glucagon
beta cells - which secretes: insulin
delta cells - which secretes: somatostatin

60
Q

Glucagon

A
  • secreted by alpha cells in the Islets of Lagerhands
  • secreted during times of fasting
  • Glucagon levels are high when glucose is gone
  • When blood glucose concentrations are high, glucagon release is inhibited
61
Q

Insulin

A
  • secreted by beta cells in the Islets of Lagerhands
  • antagonist of glycogen
  • secreted when blood glucose levels are high
  • induced muscle and liver cells to take up glucose and store it as glycogen for later use
  • because it is active when glucose levels are high, insulin stimulates anabolic processes such as fat and protein synthesis
62
Q

Polyuria

A

increase frequency of urination

found in diabetics

63
Q

Polydipsia

A

increased thirst

found in diabetics

64
Q

Two types of diabetes mellitus

A 
Type 1 (insulin dependent)
Type 2 (non insulin dependent)
65
Q

Type 1 Diabetes

A
  • (insulin dependent)
  • caused by autoimmune destruction of the beta cells of the - pancreas (beta cells secrete insulin)
  • produce little or no insulin because the majority of the B cells have been destroyed
  • require regular injection of insulin to prevent hyperglycemia and to permit entry of glucose into cells
66
Q

Type 2 Diabetes

A
  • (non insulin dependent)
  • result of receptor - level resistance of the effects of insulin
  • Type 2 diabetes mellitus is partially inherited and partially due to environmental factors (obesity, high carb diet)
67
Q

Hypoglycemia

A
  • caused by excess of insulin

- low blood glucose concentration

68
Q

Hyperglycemia

A
  • caused by not having enough insulin
  • high blood glucose concentration
  • can result in diabetes mellitus
69
Q

Somatostain

A
  • inhibitor of both insulin and glucagon secretion
  • high blood glucose and AA concentration stimulate its secretion
  • produced by the hypothalamus, where it function to decrease growth hormone secretion in addition to its effects on insulin and glucagon
70
Q

Gonads

A
  • Consist of the Testes and Ovaries
71
Q

Testes

A
  • part of the Gonads
  • secrete testosterone to response to stimulation by gonadotropins (LH and FSH)
  • Testosterone causes sexual differential of the male during gestation and promotes the development and maintenance of secondary sex characteristics of males (such as public hair and axillary, deepening of voice and muscle growth)
72
Q

Ovaries

A
  • part of the Gonads
  • secrete estrogen and progesterone to response to stimulation by gonadotropins (LH and FSH)
  • Estrogen is involved in development of the female reproductive system during gestation and also promotes the development and maintenance of secondary sex characteristics of males (such as public hair and axillary, breast growth and body fat redistribution)
  • Estrogen and Progesterone govern the menstrual cycle and pregnancy
73
Q

Pineal Gland

A
  • located deep within the brain
  • secretes hormone melatonin
  • involved in circadian rhythms
  • receives projections directly from the retina - but is not involved in vision
74
Q

Erythropoitein

A
  • produced by the kidneys
  • stimulates bone marrow to increase production of erythocytes (RBC’s)
  • secreted in response to low oxygen levels in the blood
75
Q

Atrial natriuretic peptide (ANP)

A
  • Hormone released by the heart
  • help regular said and water balance
  • is released when the cells in the atria are stretched from excess blood volume
  • promotes excretion of sodium and therefore increases urine volume
  • antagonistic to aldosterone because it lowers blood volume and blood pressure
76
Q

Thymosin

A
  • released by the thymus

- important for proper T - cell development and differentiation

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