Endocrine System Flashcards

Flashcards about General Characteristics of Hormones and Hormonal Control Systems, The Hypothalamus and Pituitary Gland, The Thyroid Gland, The Endocrine Response to Stress ,Endocrine Control of Growth, Endocrine Control of Ca2+ Homeostasis

Endocrine glands

Ductless glands that secrete hormones.

Hormones

Chemical messengers that enter the blood and are carried from their site of secretion to the cells upon which they act.

Amine hormones

Derivatives of the amino acid tyrosine, including thyroid hormones and catecholamines.

Peptide and Protein Hormones

Hormones that are small or large polypeptides.

Steroid hormones

Hormones derived from cholesterol, such as those from the adrenal cortex and gonads.

Aldosterone, cortisol, corticosterone, dehydroepiandrosterone (DHEA), and androstenedione

The adrenal cortex secretes these five major hormones.

Mineralocorticoid

Steroid that affects salt balance.

Glucocorticoids

Steroids that affect glucose metabolism.

Androgens

Hormones like testosterone.

Ovaries

Secretes mainly estradiol and progesterone.

Testes

Secretes mainly testosterone.

Free (unbound) in plasma

Peptide and catecholamine hormone transport.

Protein-bound

Steroid and thyroid hormone transport.

Liver and kidneys

Major organs that metabolize or excrete hormones.

Up-regulation

Increase in the number of a hormone’s receptors in a cell.

Down-regulation

Decrease in the number of a hormone’s receptors in a cell.

Changes in the plasma concentrations of mineral ions or organic nutrients

One direct input that controls hormone secretion.

Neurotransmitters released from neurons ending on the endocrine cell

One direct input that controls hormone secretion.

Another hormone acting on the endocrine cell

One direct input that controls hormone secretion.

Primary hyposecretion

An endocrine gland secreting too little hormone because the gland is not functioning normally.

Secondary hyposecretion

The endocrine gland is not damaged but is receiving too little stimulation by its tropic hormone.

Primary hypersecretion

The gland is secreting too much of the hormone on its own.

Secondary hypersecretion

Excessive stimulation of the gland by its tropic hormone.

Hyporesponsiveness

The target cells do not respond normally to the hormone.

Hyperresponsiveness

Increased sensitivity to a stimulus

Anterior pituitary gland and posterior pituitary

The two lobes that primarily composes the pituitary gland.

Oxytocin

Hormone that stimulates contraction of smooth muscle cells in the breasts.

Vasopressin

Hormone that acts on smooth muscle cells around blood vessels to cause their contraction and also acts within the kidneys to decrease water excretion in the urine.

Hypophysiotropic hormones

Hormones that regulate anterior pituitary gland function.

Thyroid-stimulating hormone

Hormone that stimulates the thyroid to secrete thyroxine and triiodothyronine.

Adrenocorticotropic hormone

Hormone that stimulates the adrenal cortex to secrete cortisol.

Growth hormone

Hormone that stimulates the liver to secrete a growth-promoting peptide hormone known as insulin-like growth factor-1 (IGF-1).

Follicle-stimulating hormone and luteinizing hormone

Hormones that stimulate the gonads to secrete the sex hormones.

Prolactin

Hormone that stimulates development of the mammary glands during pregnancy and milk production when a woman is nursing.

Long-loop negative feedback

The target gland hormone exerts negative feedback on the secretion of the hypothalamic and/or anterior pituitary gland hormone in the pathway.

Short-loop negative feedback

A given anterior pituitary hormone inhibits the hypophysiotropic hormone(s) that control its secretion.

T4

Main secretory product of the thyroid gland.

T3

Active thyroid hormone; produced from T4 in target tissue.

Goiter

Enlarged thyroid from any cause.

Cortisol

Steroid hormone synthesized in the adrenal cortex.

Adrenal insufficiency

Inadequate production of cortisol.

Cushing’s syndrome

Chronically increased endogenous cortisol or taking exogenous glucocorticoid.

Vasopressin

Increased renal water retention (antidiuresis).

Epinephrine

From adrenal medulla in response to stimulation from the sympathetic nervous system increase heart rate and heart pumping strength, rate of breathing, shunting of blood to skeletal muscle, and energy sources in the blood

Norepinephrine

Primarily from sympathetic neuron terminals increase heart rate and heart pumping strength, rate of breathing, shunting of blood to skeletal muscle, and energy sources in the blood

Osteoblasts

Produce cartilage

Epiphyseal growth plates

Convert cartilage to bone

Growth hormone

Major stimulus of postnatal growth, stimulates the release of hepatic IGF-1, stimulates protein uptake and secretion is highest during puberty.

Thyroid hormone

Stimulates growth hormone synthesis and has many growth-promoting effects and essential for normal growth during childhood.

Insulin

Stimulates growth mainly during fetal life.

Testosterone and estrogen

Promote bone growth during puberty.

Cortisol

Inhibits growth

Bone mass and plasma Ca2+ concentration

Interaction of osteoblasts and osteoclasts determines these two things

Bone, the gastrointestinal tract, and the kidneys

are the primary sites of Ca2+ homeostasis.

Parathyroid hormone

Hormone that influences all effector sites by stimulating kidney reabsorption of Ca2+ Bone resorption: releases Ca2+ into the blood stimulates 1,25-dihydroxyvitamin D [1,25-(OH)2D] synthesis

Vitamin D

Released from skin cells into the blood, hydroxylated in the liver and then the kidneys.

Osteomalacia and rickets

Deficient bone mineralization caused by inadequate vitamin D intake.

Osteoporosis

Decreased bone density bone resorption exceeds formation.

Hypercalcemia and Primary hyperparathyroidism

Chronically elevated plasma Ca2+ concentration and produced and adenoma.

Hypocalcemia andPrimary hypoparathyroidism

Loss of parathyroid gland function causes decreased bone resorption of Ca2+ increased renal production of 1,25-(OH)2D.

Humoral hypercalcemia of malignancy

PTH-producing adenoma causes hypercalcemia by increasing bone resorption of Ca2+, increasing kidney reabsorption of Ca2+, and increasing kidney production of 1,25-(OH)2D, which increases Ca2+ absorption in the intestines.

secondary Hyperparathyroidism

PTH-producing adenoma causes long-term low plasma Ca2+.

acromegaly

Excess growth hormone and IGF- 1 concentrations in the blood.

Exocrine

Glands that secrete substances through ducts.

Endocrine

Glands that secrete hormones directly into the bloodstream, without ducts.

Adrenal glands

Two glands located above the kidneys, each with two main parts: the inner adrenal medulla and the surrounding adrenal cortex.

Adrenal medulla

The inner part of the adrenal gland that secretes catecholamines (epinephrine and norepinephrine).

Adrenal cortex

The outer part of the adrenal gland that secretes steroid hormones.

Amine hormones

A group of hormones derived from tyrosine, including thyroid hormones (produced by the thyroid gland), epinephrine/norepinephrine (produced by the adrenal medulla), and dopamine (produced by the hypothalamus).

The synthesis pathway involves:
Tyrosine \rightarrow L-Dopa \rightarrow Dopamine \rightarrow NE \rightarrow E (through PNMT).

Peptide hormones

Hormones that are synthesized as prohormones, packaged in the Golgi apparatus, and undergo post-translational modifications. They are soluble in plasma and bind to receptors in the plasma membrane. Removed quickly by the liver and kidneys by enzymes (minutes).

Steroid hormones

Hormones derived from cholesterol, produced by the adrenal cortex and gonads. They are not soluble and just bind in the plasma membrane. Removed slowly by glands and target cells (days). Receptors located in the cells.

Five major steroid hormones secreted by the adrenal cortex

Dehydroepiandrosterone (DHEA), Androstenedione, Cortisol, Corticosterone, Aldosterone (activates IP3 through Angiotensin II binding).

Aldosterone production

Occurs in the Zona Glomerulosa of the adrenal cortex.

Cortisol and androgens production

Occurs in the Zona Fasciculata of the adrenal cortex.

Androgens production

Occurs in the Zona Reticularis of the adrenal cortex.

Norepinephrine and epinephrine production

Occurs in the Medulla of the adrenal gland.

Hormone synthesis in testes

Cholesterol \rightarrow Androstenedione \rightarrow Testosterone. Testosterone is then secreted.

Hormone synthesis in ovaries

Androstenedione converts via aromatase \rightarrow estrone, Androstenedione converts via aromatase \rightarrow estradiol. Estrogens = estrone + estradiol.

Congenital Adrenal Hyperplasia

A condition characterized by excess virile androgens in females, stemming from the adrenal cortex.

Adrenal cortex hormones and their primary controls

• Aldosterone: controlled by angiotensin II (salt control)
• Cortisol
• Two androgens: DHEA, Androstenedione

Ovarian hormone secretion

• Women: estradiol
• Men: progesterone

Up-regulation

Increased sensitivity to a hormone due to an increase in receptor number on the target cell.

Down-regulation

Decreased sensitivity to a hormone due to a decrease in receptor number on the target cell.

Permissiveness

A hormonal interaction where one hormone must be present to amplify the signal of another (e.g., thyroid hormone being permissive of steroid hormones).

Inputs that control hormone secretion

• Changes in plasma concentration of ions or nutrients
• Neurotransmitters released from neurons
• Another hormone

Hormone Secretion Mechanisms

• Presence of an ion that stimulates the secretion of a hormone, leading to a cell response and feedback via the ion.
• Effects of peptide catecholamines influence enzyme activity, activity of Janus kinase, and G protein-coupled receptors with plasma membrane.
• Rapid (nongenomic) and slow (gene transcription) effects on the same target cell.

Tropic hormone

A hormone that regulates the secretion of another hormone.

Examples of hormone regulation

• Increased plasma glucose stimulates insulin secretion by pancreatic beta cells (negative feedback loop).
• Decreased plasma Ca^{2+} stimulates PTH secretion by the parathyroid hormone glands.

Hypothalamus's Role in Hormone Release

The hypothalamus can release hormones to the anterior pituitary and posterior pituitary, which then release hormones directly into the bloodstream.

Adrenal Medulla and Hormone Release

The adrenal medulla has a sympathetic ganglion that increases epinephrine and norepinephrine secretion.

Autonomic Neuron Hormone Release

Autonomic neurons release insulin and GI hormones.

Role of Median Eminence

The hypothalamus releases hormones in the median eminence to release tropic hormones.

Hyposecretion

Decreased hormone secretion.

Primary hyposecretion

A defect in the endocrine gland itself causes decreased hormone secretion.

Secondary hyposecretion

Decreased tropic hormone secretion causes decreased hormone secretion.

Hypersecretion

Increased hormone secretion, possibly due to a hormone-secreting cell tumor.

Primary hypersecretion

Increased hormone production is caused by the gland itself.

Secondary Hypersecretion

Too much tropic hormone causes and increased hormone secretion.

Hyporesponsiveness

Decreased responsiveness of target cells to a hormone.

Hyperresponsiveness

Increased responsiveness to a hormone.