Endocrine System Overview and Hormone Chemistry
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Questions and Answers

Which type of hormones are synthesized from cholesterol?

  • Catecholamines
  • Steroid hormones (correct)
  • Peptide hormones
  • Monoamine hormones

What is the primary function of hormones in the endocrine system?

  • To generate electrical signals
  • To regulate body functions through chemical signals (correct)
  • To bind to tissues in the digestive system
  • To control muscle contractions directly

Where are the receptors for steroid hormones typically located?

  • In the bloodstream
  • In the plasma or nucleus of the cell (correct)
  • On the cell membrane
  • Outside the cell near the cell wall

Peptide hormones differ from steroid hormones in that they are:

<p>Water-soluble and typically bind to receptors on the cell membrane (D)</p> Signup and view all the answers

Which statement about catecholamines is true?

<p>They bind to receptors on the cell membrane (A)</p> Signup and view all the answers

What is the primary physiological effect of antidiuretic hormone (ADH)?

<p>Increases renal reabsorption of water (C)</p> Signup and view all the answers

Which hormone is responsible for uterine contractions during breeding and parturition?

<p>Oxytocin (B)</p> Signup and view all the answers

What condition is characterized by a deficiency of antidiuretic hormone (ADH)?

<p>Diabetes insipidus (D)</p> Signup and view all the answers

What hormone is produced by the follicle cells of the thyroid gland?

<p>Triiodothyronine (T3) (A)</p> Signup and view all the answers

Which of the following describes the function of thyroid hormone?

<p>Regulates developmental processes and metabolism (A)</p> Signup and view all the answers

What is the prognosis for a patient who requires lifelong levothyroxine treatment due to the inability to synthesize thyroid hormone?

<p>Excellent, with proper management (A)</p> Signup and view all the answers

Which hormone is responsible for stimulating the follicle to develop into the corpus luteum after ovulation?

<p>Luteinizing Hormone (LH) (B)</p> Signup and view all the answers

What is the effect of rising estrogen levels in relation to Follicle Stimulating Hormone (FSH) production?

<p>It decreases FSH production (A)</p> Signup and view all the answers

What role does Adrenocorticotropic Hormone (ACTH) play in the body's response to stress?

<p>It stimulates cortisol release (D)</p> Signup and view all the answers

Which of the following is NOT a clinical sign of thyroid hormone synthesis deficiency?

<p>Increased energy levels (C)</p> Signup and view all the answers

What does the negative feedback mechanism involving estrogen and FSH influence?

<p>Regulates the menstrual cycle (D)</p> Signup and view all the answers

Which hormone is primarily involved in stimulating spermatogenesis in males?

<p>Follicle Stimulating Hormone (FSH) (A)</p> Signup and view all the answers

What physiological effect does Melanocyte-Stimulating Hormone (MSH) have?

<p>Increases pigment production (D)</p> Signup and view all the answers

What is the primary role of calcitonin produced by the thyroid gland?

<p>Prevents hypercalcemia by depositing excess calcium in bones (C)</p> Signup and view all the answers

Which hormone is responsible for preventing hypocalcemia?

<p>Parathyroid hormone (PTH) (D)</p> Signup and view all the answers

What is the main function of glucocorticoids such as cortisol?

<p>Increase blood glucose levels (A)</p> Signup and view all the answers

Which hormone is primarily produced in the adrenal cortex and regulates sodium and potassium levels?

<p>Aldosterone (D)</p> Signup and view all the answers

Addison’s disease is characterized by a deficiency in which type of hormones?

<p>Glucocorticoids and mineralocorticoids (C)</p> Signup and view all the answers

Which of the following symptoms is associated with Addison's disease?

<p>Hypoglycemia (A)</p> Signup and view all the answers

Where are the adrenal glands located relative to the kidneys?

<p>Near the cranial ends of the kidneys (D)</p> Signup and view all the answers

Which of the following best describes the adrenal cortex?

<p>Originates from endocrine glandular tissue and produces multiple hormone types (D)</p> Signup and view all the answers

What hormone is primarily responsible for lowering blood glucose levels?

<p>Insulin (D)</p> Signup and view all the answers

What is the primary role of glucagon in the body?

<p>Converts glycogen to glucose (C)</p> Signup and view all the answers

Which cells in the pancreas produce insulin?

<p>Beta cells (A)</p> Signup and view all the answers

What hormone is produced by interstitial cells in the testes?

<p>Testosterone (C)</p> Signup and view all the answers

What triggers the production of estrogens in the ovaries?

<p>Both FSH and LH (D)</p> Signup and view all the answers

What is the role of relaxin during pregnancy?

<p>Relaxes pelvic ligaments (A)</p> Signup and view all the answers

Which of the following hormones is NOT produced by the pancreas?

<p>Erythropoietin (C)</p> Signup and view all the answers

What is the primary function of progestins?

<p>Regulate the timing of the reproductive cycle (D)</p> Signup and view all the answers

Which hormone is responsible for stimulating gastric glands to secrete HCl?

<p>Gastrin (D)</p> Signup and view all the answers

What is the function of erythropoietin?

<p>Stimulates RBC production (A)</p> Signup and view all the answers

What is the primary function of negative feedback in hormone secretion?

<p>To decrease activity when hormone levels rise (A)</p> Signup and view all the answers

Which hormone is produced in the anterior pituitary?

<p>Growth hormone (D)</p> Signup and view all the answers

What triggers the release of prolactin?

<p>Teat stimulation (B)</p> Signup and view all the answers

What distinguishes the posterior pituitary from the anterior pituitary?

<p>It is derived from nervous tissue. (C)</p> Signup and view all the answers

Which of the following is NOT a hormone produced by the anterior pituitary?

<p>Antidiuretic hormone (C)</p> Signup and view all the answers

What function does thyroid-stimulating hormone (TSH) serve?

<p>Stimulates growth and development of the thyroid gland (D)</p> Signup and view all the answers

How do hormones travel from the hypothalamus to the anterior pituitary?

<p>Via a portal system of tiny vessels (C)</p> Signup and view all the answers

What is the consequence of positive feedback in hormone regulation?

<p>Can lead to uncontrolled upregulation (A)</p> Signup and view all the answers

What is the common clinical disease associated with excess growth hormone?

<p>Acromegaly (D)</p> Signup and view all the answers

What role does the adrenal gland medulla play in hormone secretion?

<p>Is controlled by the nervous system (C)</p> Signup and view all the answers

What is the effect of growth hormone on glucose metabolism?

<p>Inhibits glucose use by cells (D)</p> Signup and view all the answers

Where is the pituitary gland located?

<p>Ventral to the hypothalamus (D)</p> Signup and view all the answers

What is a possible diagnosis for someone with hypothyroidism?

<p>Autoimmune destruction of thyroid hormone-producing cells (D)</p> Signup and view all the answers

What distinguishes the anterior pituitary from the posterior pituitary?

<p>Contains releasing and inhibiting hormones (B)</p> Signup and view all the answers

Flashcards

Hormones

Chemical messengers produced in endocrine glands that travel through the bloodstream to target tissues, causing various effects in the body even in minute amounts.

Endocrine Glands

Organs or tissues that produce and secrete hormones into the bloodstream.

Peptide Hormones

Hormones made of chains of amino acids, soluble in water, with receptors on the cell membrane.

Steroid Hormones

Hormones derived from cholesterol, insoluble in water, requiring transport proteins in blood, and with receptors inside the target cells.

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Monoamine Hormones

Hormones derived from amino acids, with both hydrophilic and hydrophobic types, affecting different mechanisms and receptor locations.

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Feedback mechanism

A mechanism that regulates hormone secretion by either increasing or decreasing its production based on the current level of the hormone in the body.

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Negative feedback

The most common type of feedback mechanism, where an increase in hormone levels inhibits further production of that hormone.

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Positive feedback

A feedback mechanism where an increase in hormone levels stimulates further production of that hormone.

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Hypothalamus

A region in the brain that controls the pituitary gland and regulates various bodily functions like appetite, temperature, and sleep-wake cycles.

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Pituitary gland

A gland located at the base of the brain that controls other endocrine glands and releases hormones that regulate growth, metabolism, and reproduction.

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Anterior pituitary

The front portion of the pituitary gland that secretes hormones like growth hormone, prolactin, and thyroid-stimulating hormone.

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Posterior pituitary

The back portion of the pituitary gland that stores and releases hormones like antidiuretic hormone (ADH) and oxytocin.

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Growth hormone (GH)

A hormone produced by the anterior pituitary that stimulates growth and tissue regeneration.

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Acromegaly

An abnormal condition caused by an overproduction of growth hormone by a tumor in the anterior pituitary, leading to excessive growth and physical changes.

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Prolactin

A hormone produced by the anterior pituitary that stimulates and maintains milk production in mammals.

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Thyroid-stimulating hormone (TSH)

A hormone produced by the anterior pituitary that stimulates the development and growth of the thyroid gland.

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Negative feedback mechanism

A type of feedback mechanism where a hormone's production is regulated by the level of another hormone.

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Thyroid hormone

A hormone produced by the thyroid gland. T3 and T4 are two types of thyroid hormones.

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Hypothyroidism

A condition where the thyroid gland isn't producing enough thyroid hormone, leading to slowed metabolism, weight gain, and fatigue.

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Adrenal hormones

Hormones produced in the adrenal gland, controlled by the nervous system, particularly the sympathetic nervous system, and are involved in the 'fight-or-flight' response.

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What is ACTH?

A hormone produced by the anterior pituitary gland, responsible for stimulating growth and development of the adrenal cortex. Also plays a role in stress response.

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Explain the negative feedback mechanism of ACTH.

A feedback mechanism where the production of cortisol (by the adrenal gland) inhibits the release of ACTH (from the pituitary gland). This helps regulate cortisol levels in the body.

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What is FSH?

A hormone produced by the anterior pituitary gland, responsible for stimulating growth and development of follicles in the ovaries and spermatogenesis in the testes.

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How does rising estrogen affect FSH and LH levels in females?

In females, rising estrogen levels (from FSH stimulation) inhibit FSH production while triggering LH production. This peak in LH leads to ovulation.

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What is LH?

A hormone produced by the anterior pituitary gland, responsible for triggering ovulation in females and stimulating testosterone production in males.

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What happens to the follicle after ovulation due to LH?

LH stimulates the ruptured follicle to become the corpus luteum, which produces progesterone.

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What is MSH?

A hormone produced by the anterior pituitary gland, thought to be involved in pigment production (melanin) by melanocytes. Its exact functions are still being researched.

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Describe hypothyroidism.

A condition where the body loses the ability to synthesize thyroid hormone. Symptoms include obesity, lethargy, and skin issues. Treatment involves lifelong thyroid hormone supplementation.

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Calcitonin

Hormone produced by the thyroid gland that lowers blood calcium levels by promoting calcium deposition into bones, inhibiting bone resorption, and decreasing calcium absorption from the gut.

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Parathyroid Hormone (PTH)

Hormone produced by the parathyroid glands that increases blood calcium levels by stimulating bone resorption, increasing calcium absorption from the gut, and reducing calcium excretion by the kidneys.

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Adrenal Glands

Paired endocrine glands located on top of the kidneys.

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Adrenal Cortex

Outer layer of the adrenal gland responsible for producing steroid hormones; composed of three layers

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Glucocorticoids

Steroid hormones produced by the adrenal cortex that regulate glucose metabolism, blood pressure, and the body's stress response.

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Mineralocorticoids

Steroid hormones produced by the adrenal cortex that regulate electrolyte balance, especially sodium and potassium.

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Addison's Disease

A rare condition caused by a deficiency in adrenal hormones, particularly cortisol and aldosterone.

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Cortisol

Adrenal hormone that helps regulate blood pressure and acts as a stress hormone, increasing glucose levels and reducing inflammation.

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What is Diabetes Insipidus?

ADH deficiency leads to excessive urine production (polyuria) and excessive thirst (polydipsia), mimicking diabetes. It can be treated by supplementing with ADH.

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What is Oxytocin?

A hormone produced in the hypothalamus and stored in the posterior pituitary gland. It stimulates uterine contractions during breeding and parturition, and milk let-down after stimulation of the teat by promoting contraction of myoepithelial cells in the alveoli.

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What is the thyroid gland's structure?

A butterfly-shaped gland located on either side of the larynx, connected by the isthmus. It contains thousands of follicles, spherical structures containing colloid (thyroid hormone precursor) and surrounded by simple cuboidal glandular cells.

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What are the thyroid hormones?

The thyroid produces two main hormones: T4 (tetraiodothyronine/thyroxine), the inactive reservoir form, and T3 (triiodothyronine), the active form. T4 is converted to T3 in the liver, kidneys, and muscles.

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Adrenaline and Noradrenaline

Hormones produced by the adrenal medulla, released in response to stress, increasing heart rate, cardiac output, and bronchodilation.

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Pancreatic Islets

The endocrine portion of the pancreas, containing specialized cells called islets of Langerhans, which produce hormones like insulin, glucagon, and somatostatin.

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Insulin

A hormone produced by beta cells in the pancreatic islets, responsible for lowering blood glucose levels by promoting glucose uptake and storage in cells.

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Glucagon

A hormone produced by alpha cells in the pancreatic islets, responsible for raising blood glucose levels by stimulating the liver to release stored glucose and promoting gluconeogenesis.

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Androgens

Hormones produced by the testes, primarily testosterone, responsible for male secondary sex characteristics, libido, spermatogenesis, and anabolism.

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Estrogens and Progestins

Hormones produced by the ovaries, primarily estrogens and progestins, regulating the female reproductive cycle and influencing secondary sex characteristics.

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Progesterone

A hormone produced by the corpus luteum in the ovaries, responsible for preparing the uterus for pregnancy and maintaining pregnancy.

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Relaxin

A hormone produced during late pregnancy, primarily by the placenta, responsible for relaxing pelvic ligaments and softening the cervix.

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Erythropoietin

A hormone produced by the kidneys, stimulating red blood cell production in the bone marrow.

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Gastrin

A hormone produced by the stomach, stimulating the gastric glands to secrete hydrochloric acid and digestive enzymes.

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Study Notes

Endocrine System Overview

  • The endocrine and nervous systems regulate body functions
  • Both use chemical messengers (hormones) to send signals
  • Hormones are produced in endocrine glands
  • Hormones travel through the bloodstream to target tissues
  • Minute amounts of hormones cause significant bodily changes

Hormone Chemistry

  • Peptide hormones: Chains of amino acids (few to 200+), water-soluble, receptors are on the cell membrane
  • Steroid hormones: Synthesized from cholesterol, lipid-soluble, receptors are inside the cell (in the cytoplasm or nucleus)
  • Monoamine hormones: Derived from amino acids, some are water-soluble (catecholamines), some are lipid-soluble (thyroid hormones), receptors are either on the cell membrane or inside the cell

Hormone Receptors

  • Cell membrane receptors: Hormones bind to receptors on the cell surface; suitable for water-soluble hormones
  • Intracellular receptors: Hormones enter the cell and bind to receptors inside the cell; suitable for lipid-soluble hormones

Control of Hormone Secretion

  • Negative feedback: Most common; hormone secretion decreases when hormone levels rise
  • Positive feedback: Hormone secretion increases when hormone levels rise
  • Adrenal gland medulla: An exception; it does not use positive or negative feedback; its secretion is regulated by the nervous system

Major Endocrine Glands

  • Hypothalamus: Regulates appetite, temperature, and sleep-wake cycles; connected to pituitary gland via a stalk
  • Pituitary gland: "Master gland"; located ventral to the hypothalamus.
    • Anterior Pituitary: Composed of endocrine tissue and produces several hormones (see details below).
  • Posterior Pituitary: Composed primarily of nervous tissue and stores hormones produced in the hypothalamus (see details below).
  • Pineal gland: Produces melatonin; influences wake-sleep cycles.
  • Thyroid gland: Located near the larynx, produces thyroid hormone and calcitonin
  • Parathyroid glands: Small nodules near the thyroid; produces parathyroid hormone (PTH), which regulates calcium levels
  • Adrenal glands: Located near the kidneys; comprised of an outer cortex and inner medulla, both producing various hormones.
    • Cortex: Produces steroid hormones (glucocorticoids, mineralocorticoids, sex hormones).
    • Medulla: Produces norepinephrine and epinephrine.
  • Pancreas: Produces digestive enzymes and hormones (glucagon, insulin, somatostatin).
    • Islets of Langerhans: Clusters of endocrine cells in the pancreas.
  • Gonads: Ovaries (female) and testes (male); produce sex hormones (estrogen, progesterone, testosterone).
  • Placenta: Produces hormones during pregnancy (e.g., chorionic gonadotropin, estrogen, progesterone, relaxin).
  • Thymus: Important in immune development, Produces thymosin and thymopoietin

Pituitary Gland Hormones (Anterior Pituitary)

  • Growth hormone (GH): Promotes growth and tissue regeneration, affects metabolism of macronutrients
  • Prolactin: Triggers and maintains lactation
  • Thyroid-stimulating hormone (TSH): Stimulates thyroid growth and development; regulated by negative feedback
  • Adrenocorticotropic hormone (ACTH): Stimulates growth and development of the adrenal cortex; regulated by negative feedback
  • Follicle-stimulating hormone (FSH): Stimulates follicle development in ovaries (female) and spermatogenesis in testes (male).
  • Luteinizing hormone (LH): Triggers ovulation and development of corpus luteum in ovaries (female), stimulates interstitial cells to produce testosterone in testes (male).
  • Melanocyte-stimulating hormone (MSH): Increases pigment production.

Pituitary Gland Hormones (Posterior Pituitary)

  • Antidiuretic hormone (ADH): Regulates water reabsorption in the kidneys.
  • Oxytocin: Stimulates uterine contractions during breeding and parturition, milk letdown, possible role in bonding.

Thyroid Gland Hormones

  • Thyroid hormone: Two forms (T4 and T3), regulates metabolism, body temperature, and growth.
  • Calcitonin: regulates blood calcium levels (opposite action of Parathyroid Hormone)

Parathyroid Hormone (PTH)

  • Regulates blood calcium levels
  • Prevents Hypocalcemia: Increases calcium levels when there is not enough.

Adrenal Gland Hormones

  • Corticosteroids (Cortex): Hormones that affect blood glucose, influence immune response, control the body's response to stress.
  • Mineralocorticoids: Regulate electrolytes (sodium, potassium, etc) in the body. Aldosterone is a mineralocorticoid.
  • Adrenal Medulla: Norepinephrine (primarily used in nervous system), epinephrine and their actions.
  • Sex Hormones: Small amounts in the adrenal cortex.

Pancreatic Islets of Langerhans

  • Glucagon: Raises blood glucose levels.
  • Insulin: Lowers blood glucose levels.
  • Somatostatin: Inhibits release of other pancreatic hormones.

Gonads Hormones

Testes

  • Testosterone: Development and maintenance of male secondary sex characteristics.
  • Spermatogenesis: Production of sperm.

Ovaries

  • Estrogens: Development and maintenance of female secondary sex characteristics, regulate the menstrual cycle.
  • Progestins: Regulate the menstrual cycle and prepare the uterus for pregnancy.
  • Relaxin: Important in late pregnancy for facilitating birth and loosening tissues.

Other hormone-producing organs

  • Kidneys (Erythropoietin)
  • Stomach (Gastrin)
  • Small Intestine (Secretin, Cholecystokinin)
  • Placenta (Chorionic gonadotropin, Estrogen, Progesterone, Relaxin)
  • Thymus (Thymosins/Thymopietin)
  • Pineal body (Melatonin)

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Description

Explore the intricacies of the endocrine system, including how it regulates body functions through hormones. Learn about different types of hormones such as peptide, steroid, and monoamine, as well as their respective receptors and actions within the body.

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