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Endocrine/Repro > The Endocrine System (lecture 1) > Flashcards

The Endocrine System (lecture 1) Flashcards

1
Q

give 5 essential physiological processes regulated by hormone acton on target cells/tissues

A
  1. growth and development
  2. cellular metabolism and energy balance
  3. response to stress
  4. maintenance of electrolyte, water, and nutrient balance
  5. reproduction
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2
Q

give the 6 endocrine glands plus 6 organs that contain endocrine cells

A

glands:
1. pituitary
2. thyroid
3. parathyroid
4. adrenal
5. pancreas
6. gonads

organs with endocrine cells
1. adipose tissue (fat cells)
2. stomach and small intestines
3. heart
4. kidneys
5. liver
6. placenta (transient endocrine organ during pregnancy)

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3
Q

define endocrine glands; contrast to exocrine glands

A

endocrine glands perform ductless secretion of hormones that reach a target gland or tissue by the bloodstream, so these glands are well vascularized

exocrine glands secrete their products through a duct to reach their target

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4
Q

list and describe the 3 major classes of hormones

A
  1. peptide/protein: water-soluble/hydrophilic; act via membrane bound receptors
  2. steroid hormones: derived from cholesterol; lipid soluble/lipophilic, water INsoluble/hydrophobic; act via intracellular receptors
  3. tyrosine derivatives: derived from tyrosine or tryptophan; waster soluble/hydrophilic (THYROID HORMONE NOT WATER SOLUBLE THOUGH!!)
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5
Q

describe the key point regarding synthesis or protein/peptide hormones

A

involves transcription of DNA to RNA, then translation of mRNA to amino acid sequence, and then post-translational modifications, then packaging into vesicles for storage; all to say that hormone are NOT made quickly; synthesis takes time!! so most hormones are stored so they can be released quickly as needed

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6
Q

how are hormones released and why?

A

in a pulsatile manner to prevent saturation, down regulation of the receptor response, and desensitization to the hormone

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7
Q

what are the 3 types of hormone secretion rhythms? give examples of each

A
  1. circadian (day/night): cortisol, growth hormone, melatonin
  2. monthly or seasonal: gonadotropins during reproductive cycles
  3. developmental: puberty, menopause
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8
Q

describe the two modes of hormone transport

A
  1. hydrophobic hormones: steroids and thyroid hormone; bind to transport proteins (albumin, prealbumin, or specific hormone-binding proteins) in blood plasma to increase solubility, prolong half-life, and protect against enzyme degradation and kidney filtration; ONLY UNBOUND hormone can leave the capillary to reach the target cell
  2. hydrophilic hormones: peptides/proteins; mix easily/dissolve with blood plasma, then diffuse from capillaries to the interstitial fluid to reach target cells
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9
Q

describe regulation of circulating hormone levels

A
  1. hormone concentration in blood plasma are generally low
  2. physiologic concentration range of a hormone is regulated by the rate of its release and its half-life (rate of breakdown/clearance)
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10
Q

how is hormone secretion regulated? describe

A

by feedback mechanisms!

negative feedback control: limits responses

positive feedback control: amplifies responses

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11
Q

what controls the activity of the thyroid gland, the adrenal cortex, and the gonads?

A

the hypothalamic pituitary axis (HPA)

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12
Q

what 2 endocrine components are NOT regulated by the HPA? how are these regulated instead?

A
  1. endocrine pancreas
  2. parathyroid glands

these are instead controlled by feedback signals from the variable they control (like blood glucose in the pancreas or calcium in the parathyroid gland)

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13
Q

what is hormone specificity and mechanism of action dependent on? describe

A

dependent on the interaction with specific receptors ON target cells; only those cells that express specific hormone receptors are able to respond (target cells) and each target cell may express several receptor types (for several hormones)

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14
Q

describe hormone receptors

A

proteins or glycoproteins with a binding domain and a signal transducing domain

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15
Q

how do hormone receptors work? ABCs for ALL hormone receptor mechanism of action (3)

A

A: recognize and bind specific hormones (ligand)
B: undergo a conformational change when bound to the hormone
C: transduce a signal that promotes a cellular response

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16
Q

what are the 2 types of hormone receptors? what hormones do the bind? how do they work?

A
  1. membrane-bound: for hydrophilic/water-soluble hormones (proteins and peptide); hormone does NOT enter the cell (can’t pass through lipid bilary); instead binds to these membrane bound receptors on the cell surface
  2. intracellular: for hydrophobic/lipid-soluble hormones (steroids and thyroid hormones); these hormones must enter the cell and then bind to specific cytoplasmic or nuclear receptors
17
Q

describe the mechanisms of protein hormone action (2)

A

peptides and proteins interact with membrane-bound receptors, which have two main mechanisms of action:

  1. G-coupled protein second messengers: activate serine/threonine kinases through second messengers like cAMP
  2. tyrosine kinase: receptors with inherent tyrosine kinase activity or associated with intracellular molecules possessing tyrosine kinase activity
18
Q

what is the mechanism of steroid hormone action?

A
  1. steroid interact with cytoplasmic or nuclear receptors
  2. receptor binding to DNA regulatory site promotes gene activation
  3. this leads to protein synthesis
  4. new proteins promote one or more cellular responses
19
Q

summarize target cell hormone response

A
  1. the same hormone can promote different cellular responses in different target cell types
  2. hormone specificity is controlled by the receptor and its second messenger activation within the cell
20
Q

describe the 2 receptor responses to hormone stimulation

A
  1. priming effect: upregulation of receptor; hormone induces more of its own receptors in target cells, resulting in a greater response in the target cell
  2. desensitization: downregulation of receptor; constant exposure to a hormone attenuates this decrease in receptor numbers on targets; this decrease is usually avoided via the pulsatile hormone release
21
Q

describe hormone inactivation

A
  1. hormones must be inactivated once they exert their function
  2. inactivation in the metabolic conversion of a biologically active hormone to an inactive one (enzymatic degradation)
    2a. peripheral inactivation refers to degradation in blood or intracellular spaces, or the liver or kidneys
    2b. inactivation in target tissues occurs after the hormone has triggered a cellular response
  3. inactivation may involve either complete metabolism of the hormone (no byproduct in urine) or hormone modification
22
Q

what is metabolic clearance rate?

A

the volume of plasma cleared of a hormone per unit time; is inversely related to half-life

23
Q

what is half-life?

A

the time for a hormone to decrease concentration in the plasma by half

most peptide hormones: minutes to hours
steroids/thyroid hormones: days to weeks

24
Q

describe excretion/elimination of hormones (2)

A
  1. excreted by the liver into bile: steroids and thyroid hormones; long half life due to plasma protein binding
  2. excreted by the kidneys: amino acid based hormones with a short half life
25
Q

describe the 3 modes of endocrine disruption

A
  1. hormone excess/hyperfunction: due to hyperplasia of gland, hormone-producing tumors, or excessive stimulation of a gland
  2. hormone deficiency/hypofunction: due to congenital defects of gland/tissue, destruction of a tissue due to ischemia or inflammation or autoimmune reponse, or inactive hormones
  3. altered response of receptors:
    can have either a decreased/lack of response to the hormone due to reduced or no receptor expression in the cell or defects in receptors structure that limit hormone recognition or binding or
    excessive response to a hormone due to lack of receptor downregulation or constitutive receptor activation

Endocrine/Repro (31 decks)

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