Endocrine System Flashcards by Leora Truong

Where do endocrine glands secrete hormones to?

-Directly into circulatory system

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Where do exocrine glands substances go?

-Transport by ducts

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What determines the specificty of hormonal action?

-Specific receptors on/in target cells

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What secretes adrenocortical steroids (corticosteroids)?

Adrenal cortex

- Stimulated by ACTH produced by anterior pituitary

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How do corticosteroids function?

-Determine which genes of target cell are transcribed and at what rate

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How are corticosteroids transported in bloodstream?

-Transcortins

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What are the 3 major classes of corticosteroids?

Glucocorticoids
Mineralocorticoids
Cortical sex hormones

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Glucocorticoids include…

Cortisol/Cortisone
Raise blood glucose levels (protein breakdown/ gluconeogenesis/ lower protein syn)
Increase plasma glucose levels
Release amino acids (skeletal muscle) and lipids (adipose)
Anti-inflammatory

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What is an example of mineralocorticoids?

Aldosterone - regulates plasma Na+/K+ levels
Active reabsorption of Na+/passive reabsorption of H2O
Increase blood volume/pressure

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What stimulates mineralocorticoids? Inhibits?

Angiotensin II

- ANP

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Where are most androgens produced in men?

-Testes

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What produces catecholamines?

Adrenal medulla

- E.g. Neurotransmitters: Epinephrine and Norepinephrine

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What are the effects of epinephrine?

Increase glycogen –> glucose (liver/muscle)
Increase basal metabolic rate
Dilate/constrict blood vessel (>blood flow to skeletal muscle/heart/brain)
Release lipids by adipose

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What connects the pituitary gland to hypothalamus?

-Infundibulum

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What regulates anterior pituitary gland secretions?

-Releasing hormones from hypothalamus

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What type of hormones does the anterior pituitary secrete?

-Direct and tropic hormones

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What are the direct hormones of the anterior pituitary?

Growth Hormone (GH, somatotropin)

- Prolactin

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What is acromegaly?

-Overproduction of GH in adults

What are the tropic hormones of the anterior pituitary?

Adrenocorticotropic hormone (ACTH)
Thyroid-Stimulating Hormone (TSH)
Luteinizing hormone (LH) - ovulation/corpus luteum or testes to produce testosterone
Follicle-Stimulating Hormone (FSH) -maturation of ovarian follicles/seminiferous tubules and sperm production
Melanocyte-stimulating Hormone (MSH) - darken frog
Endorphins - Neurotransmitters

What is the role of the posterior pituitary?

-Store/release peptide hormones, oxytocin and ADH

When is ADH released?

Plasma osmolarity increases (sense by osmoreceptors in hypothalamus)
Blood volume decreases (sense by baroreceptors in circulatory system)

What do the neurosecretory cells of the hypothalamus regulate? How?

Pituitary gland secretions by negative feedback

- Use of Inhibiting/releasing hormones

What does GnRH do?

-Stimulate anterior pituitary to secrete FSH/LH

How do releasing hormones function?

Secreted into hypothalamic-hypophyseal portal system

- Blood from capillary bed in hypothalamus –> portal vein –> anterior pituitary –> secondary capillary network

Neurosecretory cells in hypothalamus synthesize...

...oxytocin and ADH

How do hormones of hypothalamus reach posterior pituitary?

-Via hypothalmus axons

What are the thyroid hormones?

- Thyroxine (T4) and triiodothyronine (T3) | - Formed from glycoprotein thyroglobulin

Which thyroid hormone is more potent?

T3 (only 30% produced by thyroid vs 100% of T4)

How are T3 and T4 transported?

-Bound to plasma proteins

Hypothyroidism is characterized by...

- TH low - Slow HR/breathing, fatigue, cold, weight gain - Cretinism (young) retardation/short

Hyperthyroidism is characterized by...

- Overstimulated thyroid | - High metabolic rate, warmth, sweating, palpitations, weight loss, protruding eyes

What is the role of calcitonin?

- Decrease plasma Ca++ by inhibiting release from bone | - Antagonistic to parathyroid hormone

Why is the pancreas both endocrine and exocrine organ?

- Secreted digestive enzymes (exocrine) | - Islets of Langerhans (endocrine)

What do alpha cells produce/secrete?

- Glucagon - protein/fat degradation, glycogen --> glucose, gluconeogenesis - Increase blood glucose levels - Antagonistic to insulin

What do beta cells produce/secrete?

-Insulin - uptake glucose by muscle/adipose, store glucose as glycogen, synthesize fats from glucose, uptake aa

What does parathyroid hormone do?

- Regulate plasma Ca++ by increasing release from bone, decrease excretion by kidneys - Ca++ in bone bound to phosphorus so breakdown also increases phosphorus - Increase excretion of phosphorus in kidneys

What does renin do?

- Produced by kidneys - Enzyme converts plasma protein angiotensinogen to angiotensin I which is converted to angiotensin II stimulates secretion of aldosterone

What does EPO stimulate?

- Produced by kidneys | - Stimulates RBC production

What does the pineal gland secrete?

- Melatonin - May help regulate circadian rhythms - Antagonist to MSH in primitive vertebrates

Which type of hormone is first messenger?

- Peptide hormones | - Bind to specific receptors on surgace og target and trigger rxns

Where are steroid hormones produced?

-Testes, ovaries, placenta, adrenal cortex

Which hormones can cross the phospholipid bilayer?

- Steroid --> enter and target cells directly to bind receptor proteins in cytoplasm - Directly activates expression of certain genes

-What are some of the releasing hormones of the hypothalamus?

-GnRH, GHRH, CRF, Somatostatin (inhibits GH), dopamine (inhibits prolactin)