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A&P Winter > 18. Endocrine System > Flashcards

18. Endocrine System Flashcards

1
Q

Endocrine System Features

A

Uses chemical messengers
uses “hormones”
slower delivery by blood
response is prolonged

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2
Q

Endocrine glands may be organized as - 3

A
  1. a discrete organ
    - pituitary, thyroid, parathyroid, adrenal glands
  2. a group of cells within another organ
    - hypothalamus, pancreas, ovary, testis
  3. individual cells within another organ
    - a) enteroendocrine cells in GIT
    - b) kidney - erythropoietin
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3
Q

Hormone

A

a molecule secreted by an endocrine gland that acts as a chemical messenger to regulate the functions of other cells in the body

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4
Q

Also two types of local hormones that do NOT enter the blood stream

A

A) Paracrine – act on neighboring cell

B) Autocrine – act on SAME cell that secreted them

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5
Q

Down/Up Regulation of Hormones

A

DOWN REGULATION: target cell ↓ # of receptors due to ↑ hormone concentration (target cells become less sensitive to hormone)
UP REGULATION: target cell ↑ # of receptors due to ↓ hormone concentration (target cells become more sensitive to hormone)

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6
Q

Hormones cause one or more of the following changes in the target cells

A
  1. stimulate protein synthesis
  2. change membrane properties
  3. activate or deactivate enzymes
  4. increase secretory activity
  5. stimulate mitosis
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7
Q

Target cell activation by hormone-receptor interaction depends upon: - 4

A
  1. blood level of the hormone
  2. relative # of receptors for that hormone on or in the target cells
  3. affinity (strength) of the bond between the hormone & receptor
  4. influences exerted by other hormones
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8
Q

Hormones can be classified as:

A

• Lipid or Water Soluble

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9
Q

Lipid soluble hormones

A

a) steroid hormones are derived from cholesterol – eg. aldosterone, cortisol, testosterone, estrogen, progesterone
b) thyroid hormones – eg. T3 and T4 (thyroxine)

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10
Q

Water-soluble hormones

A

a) amine hormones: eg - epinephrine
b) peptide hormones: eg – ADH, oxytocin
c) protein hormones: eg – human GH, FSH, LH, TSH, ACTH, prolactin, parathyroid, calcitonin, insulin, glucagon
d) circulate in blood in “free” form (not attached to other molecules)

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11
Q

Mechanism of Hormone Action: Lipid Soluble

A
  1. Diffuses into cell
  2. Bind to recptor –>complex binds to regulatory protein
  3. Activated receptor-hormone complex alters gene expression
  4. Newly formed mRNA directs the synthesis of proteins (DNA → mRNA → protein)
  5. New proteins alter cells activity
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12
Q

Mechanism of Hormone Action: Water-Soluble

A

can’t diffuse through the lipid bilayer

  1. Binding of hormone (1st messenger) to receptor-activated G protein which activates adenylyl cyclase
  2. Activated adenylyl cyclase converts APT–> cAMP
  3. cAMP is 2nd messenger to activate protein kinase
  4. Activated protein kininase phosphorylates cellular proteins
  5. Millions of phosphorylated proteins cause rxns that produce physiological responses
  6. Phosphodiesterase inactivates cAMP
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13
Q

Endocrine glands are stimulated to manufacture and release hormones by: 3

A

1) humoral stimuli – chemical changes in blood ion or nutrient levels
2) neural stimuli – nerve impulses can stimulate hormone release
3) hormonal stimuli – tropic hormones (from one endocrine gland) stimulate other endocrine glands

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14
Q

Hypothalamus

A

9 different hormones produced

  • 5 releasing hormones (stimulate anterior pituitary gland to secrete hormones)
  • 2 inhibitory hormones (suppress secretion of anterior pituitary hormones)
  • oxytocin hormone
  • antidiuretic hormone
  • RH/IH secreted into hypophyseal portal system to regulate ANTERIOR pituitary gland
  • ADH/oxytocin secreted into POSTERIOR pituitary gland
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15
Q

Pituitary Gland: Anterior lobe

A

Anterior lobe - glandular tissue, releases 6 hormones
> Growth hormone (GH) – stimulates growth of body cells and protein synthesis
> Thyroid stimulating hormone* (TSH) - stimulates thyroid gland to grow and synthesize/release thyroid hormones
> Follicle stimulating hormone* (FSH) – stimulates development of follicles in the ovary and sperm production in the testes
> Lutenizing hormone* (LH) – stimulates ovulation in ovary and testosterone production in testes
> Adrenocorticotropic hormone* (ACTH) – stimulates release of glucocorticoids from the adrenal gland cortex eg. cortisol
> Prolactin – stimulates milk production in mammary glands

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16
Q

Pituitary Gland: Posterior lobe

A

Posterior Lobe - neural tissue, stores 2 hormones
> Antidiuretic hormone (ADH) – increases water reabsorption in the kidney
> Oxytocin – stimulates contractions of the uterus and milk ejection in mammary glands

17
Q

Thyroid Gland

A
  • has follicles that contain colloid which is what thyroid hormone is derived from
  • Parafollicular produce calcitonin

Thyroid Hormones:
Hormone functions:
1. thyroxine (T4) – increases rate of metabolism
regulates growth & development

  1. calcitonin – ↓ blood calcium levels by inhibiting breakdown of bone (inhibit osteoclasts) and stimulating the deposition of calcium into bone matrix
18
Q

Parathyroid Gland

A

Produces parathyroid hormone (PTH): ↑ blood [Ca+2]
> stimulates release of calcium from bone by osteoclasts
> increases calcium absorption by the intestines
> increases calcium reabsorption by the kidneys

19
Q

Adrenal cortex

A

Outer Zone: (zona glomerulosa) Mineralocorticoids
> hormones affect mineral homeostasis
> aldosterone: increase blood levels of Na+/Ca2+, decreases K+

Middle Zone: (zona fasciculata) glucocorticoids
> regulating metabolism and resisting stress
> cortisol: increases blood glucose, fatty acids (lipolysis) and amino acids breakdown
> inhibits inflammation and the immune response

Inner Zone: (zona reticularis) Gonadocorticoids
> secretes weak androgens
> contributes to the onset of puberty

20
Q

Adrenal Medulla

A

epinephrine and norepinephrine (“fight-or-flight” response, SNS)
> increases HR & force of contraction
> increases BP due to vasoconstriction
> increases blood flow to skeletal muscle
> increase blood levels of glucose & fatty acids
> dilate airways in the lungs
> decreases blood flow to the GIT and decreases gut motility

21
Q

Pancreas

A
  • Endocrine = Islets of Langerhans
  • Regulation of blood glucose

Alpha Cells:
> produce glucagon
> response to low blood glucose (hypoglycemia)
> acts to ↑ blood glucose
> accelerates breakdown of glycogen to glucose in the liver

Beta Cells:
> produce insulin
> response to high blood glucose (hyperglycemia)
> acts to ↓ blood glucose levels
> increases transport of glucose into cells & increases the conversion of glucose into glycogen

A&P Winter (10 decks)

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