Ninja Nerd - Endocrine

What are the two types of hormones?

Peptides and steroids

How do peptide hormones act on cells?

They act via secondary messenger systems.

What are the three main pathways for peptide hormones?

Gq pathway, Gs pathway, Gi pathway.

What is the source of steroid hormones?

They are derived from cholesterol.

Where do steroid hormones act within the cell?

On cytoplasmic or nuclear receptors.

What activates the Gs protein in the G-stimulatory pathway?

The addition of GTP after receptor activation.

What does adenylate cyclase do in the Gs pathway?

Converts ATP into cAMP.

What is the role of cAMP in the Gs pathway?

It activates protein kinase A (PKA).

What happens when a hormone binds to a Gq protein coupled receptor?

The Gq protein is activated and binds to phospholipase C.

What are the two fragments produced from PIP2 in the Gq pathway?

DAG and IP3.

What does IP3 do in the Gq pathway?

It binds to smooth ER receptors to release calcium into the cytoplasm.

What is the function of phosphodiesterase (PDE) in the G-inhibitory pathway?

It breaks down cAMP to inhibit its action.

What is the hypothalamic-pituitary axis?

The connection between the hypothalamus and the anterior and posterior pituitary.

What type of tissue makes up the posterior pituitary?

Nervous tissue.

What hormone does the supraoptic nucleus secrete?

Antidiuretic hormone (ADH).

What stimulates the secretion of ADH from the supraoptic nucleus?

Low blood pressure and high plasma osmolality.

What is the role of oxytocin during childbirth?

It stimulates uterine contractions.

What triggers the release of oxytocin from the paraventricular nucleus?

Stretch receptors in the uterus and suckling.

What is the function of GnRH in the female reproductive cycle?

Stimulates the anterior pituitary to secrete LH and FSH.

What are oogoniums converted to during childhood?

Primordial follicles.

What hormone stimulates the conversion of primary follicles to early secondary follicles?

FSH (Follicle Stimulating Hormone).

What is the zona pellucida?

A glycoprotein membrane that forms around the oocyte.

What is a Graafian follicle?

A late secondary follicle with a secondary oocyte stuck in metaphase 2.

What is the effect of estrogen secreted by granulosa cells during the mid-follicular phase?

It inhibits GnRH secretion.

What are the two stimuli for ADH secretion?

Low blood pressure and high blood osmolality.

What is the role of aquaporin-2 in the kidney?

Facilitates water reabsorption in response to ADH.

What is the role of aquaporin 2 in the collecting duct?

Aquaporin 2 allows water to enter the cell from the collecting duct.

How does vasopressin (ADH) affect blood pressure?

ADH increases blood pressure by promoting water reabsorption and causing vasoconstriction.

What condition is caused by low levels of ADH?

Diabetes insipidus.

What is the difference between central and nephrogenic diabetes insipidus?

Central DI is due to a problem with ADH secretion from the posterior pituitary, while nephrogenic DI is due to the kidneys not responding to ADH.

What are common symptoms of diabetes insipidus?

Polyuria (frequent urination) and polydipsia (excessive thirst).

What condition is characterized by excessive ADH secretion?

Syndrome of Inappropriate ADH (SIADH).

What are the effects of SIADH on blood composition?

It leads to diluted blood and dangerously low sodium levels.

What stimulates the secretion of growth hormone (GH)?

High amino acid levels, low glucose levels, low fatty acids, exercise, and some healthy stressors.

How does GH influence insulin-like growth factor-1 (IGF-1) production?

GH binds to liver receptors, activating a kinase that influences IGF-1 synthesis.

What is the function of IGF-1 in skeletal muscle?

It promotes protein synthesis and increases muscle size.

How does IGF-1 affect bone activity?

It increases osteoblast and osteoclast activity and stimulates endochondral ossification.

What is the role of prolactin in lactation?

Prolactin stimulates milk production in the alveolar cells of the breast.

What inhibits prolactin secretion?

Dopamine (prolactin inhibiting hormone) secreted by the arcuate nucleus.

What stimulates prolactin secretion?

Thyrotropin-releasing hormone (TRH) and estrogen.

What is the process of thyroid hormone synthesis?

TRH stimulates TSH release, which then stimulates thyroglobulin secretion and iodination in thyroid follicular cells.

What is thyroglobulin?

A precursor protein for T3 and T4 thyroid hormones.

How is iodide converted to iodine in thyroid hormone synthesis?

Thyroid peroxidase (TPO) oxidizes iodide to iodine.

What are the two forms of thyroid hormone produced from thyroglobulin?

T3 (triiodothyronine) and T4 (thyroxine).

How are T3 and T4 released into the bloodstream?

They are cleaved from thyroglobulin by lysosomal enzymes and exocytosed into blood plasma.

What is the role of 5' deiodinase?

It converts T4 into the active form T3 by removing an iodine atom.

What is the metabolic effect of T3 on cells?

It increases metabolic rate and heat production by stimulating Na+/K+ ATPase synthesis.

What is the significance of Na+/K+ ATPases in cellular metabolism?

They pump sodium out and potassium in, consuming ATP and increasing metabolic activity.

What triggers the release of TRH from the hypothalamus?

Low levels of thyroid hormones in the blood.

What is the function of the arcuate nucleus in hormonal regulation?

It secretes hormones that regulate the release of other hormones in the anterior pituitary.

What happens to prolactin levels during breastfeeding?

Breastfeeding stimulates prolactin secretion to promote milk production.

How does estrogen affect prolactin secretion?

Estrogen can inhibit dopamine secretion, allowing for increased prolactin secretion.

What is the role of thyroid hormones in gluconeogenesis?

They stimulate gluconeogenesis in the liver, increasing blood glucose levels.

What is the effect of high estrogen levels on prolactin production?

High estrogen can stimulate prolactin production but inhibit its action in alveolar cells.

What effect does T3 have on metabolic rate?

Increases metabolic rate and heat production.

How does T3 affect mitochondria?

Regulates growth by increasing the number and size of mitochondria.

What is the role of T4 in the liver?

Converted to T3 by 5' deiodinase, triggering glycogen to glucose conversion.

What process does T3 stimulate to increase blood glucose levels?

Glycogenolysis and gluconeogenesis.

How does T3 affect LDL cholesterol levels?

Stimulates the synthesis of LDL receptors in the liver to decrease blood LDL levels.

What receptors does T4 stimulate in cardiac muscle cells?

Beta-1 adrenergic receptors.

What is the effect of T4 on heart rate?

Increases heart rate by enhancing action potentials from the SA and AV nodes.

What impact does thyroid hormone have on the Central Nervous System?

Increases dendrite growth, synapses, and myelination of axons.

How does thyroid hormone influence bone health?

Balances osteoblast and osteoclast activity, stimulating bone remodeling.

What role does thyroid hormone play in adipose tissue?

Stimulates lipolysis to break down triglycerides into fatty acids and glycerol.

What are the two processes of protein metabolism regulated by thyroid hormone?

Catabolism (breaking down proteins) and anabolism (building proteins).

How does thyroid hormone affect sweat glands?

Stimulates sweat release for cooling through evaporative cooling.

What is the effect of thyroid hormone on the GI tract?

Stimulates secretions and motility of smooth muscle cells.

Where is the parathyroid gland located?

On the posterior part of the thyroid gland.

What are the main cell types in the parathyroid gland?

Oxyphil cells and chief cells.

What hormone do chief cells produce?

Parathyroid hormone (PTH).

What triggers the release of PTH?

Low blood calcium levels.

What is the function of calcitonin?

Decreases blood calcium levels by inhibiting osteoclast activity.

How does PTH affect osteoclasts?

Stimulates osteoblasts to produce RANK-ligand, activating osteoclasts for bone resorption.

What is the role of vitamin D in calcium absorption?

Stimulates the synthesis of Ca2+ channel proteins in the GI tract.

What hormone is produced by the zona glomerulosa of the adrenal gland?

Aldosterone.

What triggers aldosterone secretion?

Low blood pressure and angiotensin II.

What is the pathway for converting cholesterol to aldosterone?

Cholesterol → Pregnenolone → Progesterone → 11-deoxycorticosterone → Corticosterone → Aldosterone.

What is the effect of PTH on the distal convoluted tubule?

Stimulates calcium reabsorption and phosphate secretion.

What is the role of renin in the aldosterone pathway?

Converts angiotensinogen to angiotensin I.

What enzyme converts angiotensin I to angiotensin II?

Angiotensin-converting enzyme (ACE).

What is the effect of high blood calcium on parafollicular cells?

Stimulates the production of calcitonin.

What triggers the synthesis of aldosterone?

Both angiotensin II and ACTH stimulate aldosterone synthesis.

What is the initial substrate for aldosterone synthesis?

Cholesterol

Which enzyme is primarily responsible for converting progesterone to 11-deoxycorticosterone?

21-hydroxylase

What are the humoral stimuli for aldosterone production?

Low blood sodium and high blood potassium levels.

What is the role of atrial natriuretic peptide (ANP) in aldosterone synthesis?

ANP inhibits aldosterone production.

How does aldosterone affect sodium levels in the blood?

Aldosterone increases sodium reabsorption, leading to higher blood sodium levels.

What is the effect of aldosterone on potassium levels?

Aldosterone promotes potassium excretion in urine.

Where is cortisol produced?

In the Zona Fasciculata of the adrenal cortex.

What hormone stimulates the release of ACTH from the anterior pituitary?

Corticotropin-releasing hormone (CRH)

What is the main function of cortisol in muscle tissue?

To stimulate protein catabolism, breaking down muscle proteins into amino acids.

What is the effect of cortisol on blood glucose levels?

Cortisol increases blood glucose levels by stimulating gluconeogenesis.

How does cortisol affect the immune system?

Cortisol inhibits immune cells, reducing inflammation.

What is the relationship between cortisol and stress?

Cortisol secretion is stimulated during stressful conditions.

What is the role of 21-hydroxylase in cortisol synthesis?

It catalyzes the conversion of 17-OH progesterone to 11-deoxycortisol.

What are gonadocorticoids and where are they produced?

Gonadocorticoids are sex hormones produced in the zona reticularis of the adrenal cortex.

What is the primary precursor for the synthesis of DHEA?

Pregnenolone

What are the effects of DHEA and androstenedione in males?

They stimulate hair growth and libido.

What is the primary function of the adrenal medulla?

To release catecholamines (epinephrine and norepinephrine) during stress.

What is the role of tyrosine in catecholamine synthesis?

Tyrosine is converted into L-Dopa, which is a precursor for dopamine, norepinephrine, and epinephrine.