Endocrinology Quiz: Hormones and Glands

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the main function of hormones bound to transport proteins?

They are immediately active upon secretion.

They remain in circulation longer. (correct)

They diffuse to target cells faster.

They are quickly broken down in the liver.

Which type of stimuli involves changes in the composition of extracellular fluid?

Humoral stimuli (correct)

Mechanical stimuli

Neural stimuli

Hormonal stimuli

What distinguishes the anterior and posterior lobes of the pituitary gland?

Their structural differences. (correct)

Their interaction with the hypothalamus.

Their location in the brain.

The types of hormones they secrete.

Which hormone is primarily responsible for stimulating the adrenal cortex?

Adrenocorticotropic hormone (ACTH) Signup and view all the answers

What is the primary role of the hypothalamus in endocrine control?

It regulates nervous and endocrine systems. Signup and view all the answers

What is significant about tropic hormones released by the anterior lobe of the pituitary gland?

They stimulate other endocrine glands. Signup and view all the answers

Which two capillary networks are part of the hypophyseal portal system?

Anterior and posterior capillaries Signup and view all the answers

Which hormone from the anterior lobe is involved in stimulating the production of sperm?

Follicle-stimulating hormone (FSH) Signup and view all the answers

What is the primary hormone secreted by alpha cells in pancreatic islets?

Glucagon Signup and view all the answers

Which cells in the body do not respond to insulin?

Neurons Signup and view all the answers

What is a common symptom of diabetes mellitus?

Polyuria Signup and view all the answers

How does the sympathetic nervous system affect insulin release?

It inhibits insulin release Signup and view all the answers

What condition is characterized by inadequate insulin production?

Type 1 diabetes Signup and view all the answers

Which of the following hormones directly increases blood glucose levels?

Glucagon Signup and view all the answers

What is the effect of parasympathetic stimulation on insulin release?

It enhances insulin release Signup and view all the answers

Which of the following best describes secondary endocrine organs?

Organs primarily involved in systems other than endocrine Signup and view all the answers

What is the primary hormone produced by parathyroid principal or chief cells?

Parathyroid hormone (PTH) Signup and view all the answers

What effect does aldosterone primarily have on the body?

Increases potassium excretion Signup and view all the answers

Which zone of the adrenal cortex produces androgens?

Zona reticularis Signup and view all the answers

What physiological function does the adrenal medulla primarily support?

Sympathetic response Signup and view all the answers

What triggers the secretion of glucocorticoids such as cortisol?

ACTH release from the pituitary gland Signup and view all the answers

What is one function of melatonin secreted by the pineal gland?

Influence timing of sexual maturation Signup and view all the answers

Which hormone is primarily responsible for reducing calcium excretion by the kidneys?

Parathyroid hormone (PTH) Signup and view all the answers

What is the primary effect of hypocalcemia on body physiology?

Increased sodium permeability of excitable membranes Signup and view all the answers

What major steroid hormone is produced in response to low blood pressure?

Aldosterone Signup and view all the answers

Which of the following hormones has anti-inflammatory properties?

Cortisol Signup and view all the answers

What is one of the primary roles of the corpus luteum following ovulation?

Releases a mixture of estrogens and progesterone Signup and view all the answers

Which hormone must be present for normal levels of GnRH and gonadotropin synthesis?

Leptin Signup and view all the answers

What type of hormonal interaction occurs when hormones have opposing effects?

Antagonistic effects Signup and view all the answers

What condition may arise from a lack of parathyroid hormone and calcitriol?

Rickets Signup and view all the answers

Which hormone is primarily responsible for muscular and skeletal development?

Growth hormone (GH) Signup and view all the answers

What is the net result when two hormones have synergistic effects?

They amplify each other's effects Signup and view all the answers

What is the role of insulin in growth?

Providing energy supply to growing cells Signup and view all the answers

What can result from low body fat in terms of reproductive health?

Delayed puberty and cessation of menstrual cycles Signup and view all the answers

Which of the following conditions can trigger stress?

Emotional responses like anxiety Signup and view all the answers

What is precocious puberty and how does it affect behavior?

Early release of sex hormones resulting in more aggressive behavior Signup and view all the answers

How do reproductive hormones typically change throughout adulthood?

They generally remain the same Signup and view all the answers

Which part of the body's response is referred to as the general adaptation syndrome (GAS)?

The sequence of alarm, resistance, and exhaustion phases Signup and view all the answers

What role does the hypothalamus play in the context of hormones and behavior?

It is the main hormone regulator and monitor Signup and view all the answers

What is the primary function of antidiuretic hormone (ADH)?

To decrease water loss in the kidneys Signup and view all the answers

Which hormone is known for its role in stimulating contractions during childbirth?

Oxytocin (OXT) Signup and view all the answers

How does antidiuretic hormone (ADH) affect blood pressure?

It triggers vasoconstriction to increase blood pressure Signup and view all the answers

Which statement is true regarding thyroid hormones?

They are essential for normal development of various body systems Signup and view all the answers

What is the role of calcitonin (CT) in the body?

It inhibits osteoclasts in bone and stimulates calcium excretion by kidneys Signup and view all the answers

What is the difference between thyroxine (T4) and triiodothyronine (T3)?

T3 is more potent than T4 Signup and view all the answers

Which cells in the thyroid gland produce calcitonin?

Parafollicular cells (C Cells) Signup and view all the answers

What effect does hypercalcemia have on excitable tissues like muscles and nerves?

Decreases sodium permeability, making them less responsive Signup and view all the answers

What does TSH stimulate in the thyroid gland?

Release of thyroid hormones Signup and view all the answers

Where is the thyroid gland located in the human body?

Anterior to the trachea and inferior to the thyroid cartilage Signup and view all the answers

Study Notes

Chapter 10: The Endocrine System

The endocrine system maintains homeostasis through chemical messengers called hormones.
Hormones are released into the bloodstream and affect target cells with longer-lasting effects.
The nervous system, in contrast, is faster with specific destinations and shorter-lived effects.
Both systems use chemical messengers that bind to specific receptors on target cells.
Example chemical messengers: epinephrine (E) and norepinephrine (NE), which are also hormones when released from the adrenal medulla, and neurotransmitters when released across synapses.

Intercellular Communication

The endocrine and nervous systems coordinate distant communication.
The endocrine system is slower, releasing hormones into the bloodstream for longer-lasting effects on target cells.
The nervous system is faster, using neurotransmitters for specific and short-lived effects.
Both systems work together to maintain homeostasis.

The Endocrine System

Includes all endocrine cells and tissues.
Cells are glandular and secretory; secretions enter the extracellular fluid.
Local hormones, such as prostaglandins, affect adjacent cells.
Hormones act as chemical messengers, released in one tissue and transported by the bloodstream to target cells in other tissues.

Organs and Tissues of the Endocrine System

Hypothalamus produces ADH, oxytocin, and regulatory hormones.
Pineal gland secretes melatonin.
Pituitary gland (anterior lobe): ACTH, TSH, GH, PRL, FSH, LH, and MSH; posterior lobe: ADH and oxytocin.
Thyroid gland: thyroxine (T4), triiodothyronine (T3), and calcitonin (CT).
Adrenal glands (medulla): epinephrine (E) and norepinephrine (NE); (cortex): cortisol, corticosterone, aldosterone, androgens.
Pancreas (pancreatic islets): insulin and glucagon.
Ovaries: estrogens, progesterone, inhibin.
Testes: androgens (especially testosterone), inhibin.
Heart (secondary): ANP
Thymus: (undergoes atrophy in adulthood) thymosins
Adipose tissue: leptin
Digestive tract: various hormones for coordination, glucose metabolism and appetite.
Kidneys: erythropoietin (EPO), calcitriol

Three Groups of Hormones

Amino acid derivatives: Structurally similar to amino acids; include epinephrine, norepinephrine, thyroid hormones, and melatonin.
Peptide hormones: Consist of chains of amino acids; the largest class; include ADH, oxytocin, hypothalamic, pituitary, and pancreatic hormones.
Lipid derivatives:
Steroid hormones: Structurally similar to cholesterol, transported bound to plasma proteins; released by reproductive organs and adrenal glands.
Eicosanoids: Fatty acid-based, derived from arachidonic acid; coordinate local cellular functions and affect enzymatic processes (e.g., prostaglandins).

Hormone Action

Hormones alter operations in target cells by changing the types, activities, locations, or quantities of structural proteins and enzymes.
Sensitivity to a hormone depends on the presence or absence of hormone receptors on the target cell.
Receptors are on the plasma membrane or inside the cell.

Plasma Membrane Receptors

Required for hormones that are not lipid soluble (e.g., epinephrine, norepinephrine, peptide hormones, and eicosanoids).
Hormones cannot diffuse through the plasma membrane.
These hormones are first messengers that activate second messengers (e.g., cyclic AMP, calcium ions, cyclic GMP) in the cytoplasm.
Action is linked by a G protein, an enzyme complex.

Second Messenger Systems

A small number of hormone molecules can activate thousands of second messengers.
This process, called amplification, magnifies the effect of the hormone on the cell.
Examples of second messengers include cyclic AMP, calcium ions, and cyclic GMP.

Intracellular Receptors

Receptors are located inside the cytoplasm or nucleus.
Used for lipid-soluble hormones (e.g., thyroid and steroid hormones).
Hormones cross the plasma membrane.
The hormone-receptor complex activates or inactivates specific genes.
This alters the rate of mRNA transcription and changes the structure or function of the cell.

Hormone Secretion and Distribution

Hormones enter the bloodstream and are distributed to target cells throughout the body.
Freely circulating hormones have short lives and are deactivated through diffusion to target cells, absorption and breakdown in the liver and kidneys, and enzymatic breakdown in the plasma or interstitial fluid.
Hormones bound to transport proteins stay in circulation longer (steroid and thyroid hormones).

Control of Endocrine Activity

Hormonal secretion is based on three types of stimuli:
Humoral stimuli: Changes in the composition of the extracellular fluid (e.g., hormonal control of blood calcium levels).
Hormonal stimuli: Changes in circulating hormone levels.
Neural stimuli: Neural stimulation of a neuroglandular junction through neurotransmitters.

Hypothalamus and Endocrine Control

The hypothalamus provides the highest level of endocrine control.
Hypothalamic coordinating centers regulate nervous and endocrine systems through:
1. Production of ADH and oxytocin (OXT).
2. Secretion of regulatory hormones to control the activity of the anterior lobe of the pituitary gland.
3. Controlling sympathetic output to the adrenal medullae.

The Pituitary Gland

Also called the hypophysis.
Protected by the sella turcica.
Hangs from the hypothalamus by the infundibulum.
Anterior and posterior lobes have very different structures.
Secretes nine hormones, all unique peptides or small proteins, and all using a cAMP second messenger mechanism.

The Anterior Lobe of the Pituitary Gland

Contains endocrine cells surrounded by a complex capillary bed(part of the hypophyseal portal system).
Two capillary networks and the linking blood vessels are a portal system, named after their destinations.

The Hypophyseal Portal System

Regulatory hormones diffuse onto target cells in the anterior lobe.
Many of these hormones are tropic hormones targeting other endocrine glands.

The Seven Anterior Lobe Hormones

Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Prolactin (PRL)
Growth hormone (GH)
Melanocyte-stimulating hormone (MSH)

Thyroid-stimulating Hormone

Also called thyrotropin.
Released in response to thyrotropin-releasing hormone (TRH) from the hypothalamus.
Targets the thyroid gland.
Triggers the release of thyroid hormones.
Increased thyroid hormones decrease TRH and TSH secretion.

Adrenocorticotropic Hormone (ACTH)

Also called corticotropin.
Released in response to corticotropin-releasing hormone (CRH) from the hypothalamus.
Targets the adrenal cortex.
Stimulates secretion of glucocorticoids.
Increased glucocorticoids decrease ACTH and CRH.

Gonadotropins

Released in response to gonadotropin-releasing hormone (GnRH) from the hypothalamus.
Target the male and female gonads.
Include follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

Follicle-stimulating Hormone (FSH)

Promotes follicle development in females.
Promotes sperm production in males.
Cells of ovaries and testes produce inhibin, which inhibits FSH production through negative feedback.

Luteinizing Hormone (LH)

Induces ovulation and estrogen and progesterone secretion in females.
In males, also known as interstitial cell-stimulating hormone (ICSH).
Stimulates interstitial cells/endocrine cells of the testes to produce androgens like testosterone.
Estrogens, progesterone, and androgens inhibit GnRH (thus decreasing LH levels).

Prolactin (PRL)

Released in response to prolactin-releasing factor (PRF) from the hypothalamus.
Targets female mammary glands.
With other hormones, stimulates mammary gland development.
During pregnancy and nursing, stimulates milk production.
Circulating PRL stimulates prolactin-inhibiting hormone (PIH) and inhibits PRF.

Growth Hormone (GH)

Also called human growth hormone (hGH) and somatotropin.
Regulated by growth hormone-releasing hormone (GH-RH) and growth hormone-inhibiting hormone (GH-IH) from the hypothalamus.
Stimulates cell growth and replication (especially of skeletal muscle and chondrocytes).
Indirect action: stimulates liver to release somatomedins (or insulin-like growth factors [IGFs]), triggering increased amino acid uptake and protein synthesis by cells after a meal.
Somatomedins stimulate GH-IH and inhibit GH-RH.

Direct Actions of Growth Hormone

In epithelial and connective tissues: Stimulates stem cell division and differentiation.
In adipose tissue: Stimulates breakdown of stored fats and releases fatty acids, a glucose-sparing effect.
In the liver: Stimulates breakdown of glycogen reserves and releases glucose into the bloodstream.

Melanocyte-stimulating Hormone (MSH)

Increases activity of melanocytes in skin to increase melanin production.
Appears to be non-functional in adults.

The Posterior Lobe of the Pituitary Gland

Contains axons from two groups of hypothalamic neurons.
Produces two hormones: antidiuretic hormone (ADH) and oxytocin (OXT).
Hormones are transported within the axons and then into capillaries of the posterior pituitary lobe.

Antidiuretic Hormone (ADH)

Also called vasopressin.
Released when body water is low.
Stimulated by an increase in the concentration of solutes in the blood or a decrease in blood volume and/or pressure.
Primary target is the kidney to decrease water loss.
Triggers vasoconstriction to increase blood pressure.

Oxytocin (OXT)

In women: Stimulates contraction of uterine muscles during labor and delivery, and contraction of cells surrounding milk secretory cells in mammary glands.
In men: Stimulates smooth muscle in walls of sperm duct.
In women: May stimulate smooth muscle contractions in the uterus and vagina, promoting sperm transport.

The Thyroid Gland

Located anterior to the trachea and inferior to the thyroid cartilage.
Has two lobes connected by an isthmus.
Contains many spherical thyroid follicles lined by simple cuboidal epithelium.
Follicles are filled with viscous colloid containing many proteins and thyroid hormones.

The Thyroid Follicles

Follicular cells make thyroid hormones and store them in colloid.
TSH causes thyroid hormone release.
Most thyroid hormones are transported bound to plasma proteins.
Derived from amino acid tyrosine and iodine.
Thyroxine (T4) has four iodine atoms; triiodothyronine (T3) has three.
T3 is more potent than T4.

The Effects of Thyroid Hormones

Affect nearly every cell in the body.
Increase the rate of ATP production in mitochondria.
Activate genes coding for enzymes involved in glycolysis and energy production.
Enzymes increase the rate of metabolism.
Calorigenic effect: Cell uses more energy, measured in calories, and heat is produced.
Important for the development of skeletal, muscular, and nervous systems.

The C Cells of the Thyroid Gland

Also called parafollicular cells; located between follicles.
Produce calcitonin (CT).
Stimulated by increases in plasma Ca2+.
Inhibits osteoclasts in bone.
Stimulates calcium excretion by kidneys.
Important for normal bone growth in children and during the last trimester of pregnancy.

Calcium Balance and Calcitonin

Hypercalcemia (high blood calcium level) results in decreased sodium permeability of excitable membranes and less responsive muscles and nerves.

The Parathyroid Glands

Two pairs of small glands embedded in the posterior surface of the thyroid gland.
Parathyroid principal, or chief, cells produce parathyroid hormone (PTH).
Stimulated by a decrease in plasma Ca2+.
Activates osteoclasts and inhibits osteoblasts in bone.
Reduces calcium excretion by kidneys.
Stimulates the kidneys to secrete calcitriol, increasing Ca2+ and PO43- absorption in the digestive tract.

Calcium Balance and PTH

Hypocalcemia (low blood calcium level) results in increased sodium permeability of excitable membranes, highly excitable spasmodic muscles and neurons, convulsions, or muscular spasms.
Parathyroid glands prevent hypocalcemia.

Hormones of the Thyroid and Parathyroid Glands

Table summarizing the hormones of thyroid and parathyroid glands, their targets, and hormonal effects.

The Adrenal Gland

Also called the suprarenal gland.
Yellow, pyramid-shaped; sits superiorly on the border of each kidney.
Two portions: adrenal cortex and adrenal medulla.

The Adrenal Cortex

Contains high levels of cholesterol and fatty acids.
Produces more than 24 steroid hormones called corticosteroids.
Essential for metabolic functions and life.
Transported in plasma bound to proteins.
Three zones produce three types:
Zona glomerulosa: Mineralocorticoids (e.g., aldosterone).
Zona fasciculata: Glucocorticoids (e.g., cortisol, corticosterone, cortisone).
Zona reticularis: Androgens.

Mineralocorticoids

Affect electrolyte balance in body fluids.
Aldosterone is the major mineralocorticoid.
Secreted in response to low plasma Na+, low blood pressure, high plasma K+, or the presence of angiotensin II.
Triggers the reabsorption of Na+ ions and the elimination of K+ ions.
Prevents loss of Na+ in urine, sweat, saliva, and digestive secretions.
Triggers secondary water reabsorption through osmosis.

Glucocorticoids

Affect glucose metabolism.
Most important are cortisol (hydrocortisone), corticosterone, and cortisone.
Secreted in response to ACTH.
Increase rates of glucose synthesis and glycogen formation. This results in an increase in blood glucose levels.
Also act as anti-inflammatory.

The Androgens

Small quantities produced in both males and females.
Some converted to estrogens in the plasma.
Stimulate development of pubic hair in boys and girls before puberty.
Not important in adult men but contribute to muscle mass, blood cell formation, and sexual drive in adult women.

The Adrenal Medulla

Highly vascular.
Contains cells similar to sympathetic ganglia and is innervated by preganglionic sympathetic fibers.
Two groups of secretory cells produce: epinephrine (E, or adrenaline) 75-80%, and norepinephrine (NE, or noradrenaline) 20-25%.
Hormones trigger metabolic changes to increase energy molecule availability and support/prolong the overall sympathetic response.

The Pineal Gland

Located on the posterior portion of the roof of the third ventricle.
Contains neurons, glial cells, and secretory cells that produce melatonin.
Rate of secretion affected by light and day-night cycles.
May influence the timing of sexual maturation.
May protect CNS neurons with antioxidant activity.
Plays a role in maintaining circadian rhythms (day-night cycles).

The Endocrine Pancreas

Pancreas lies between the stomach and proximal small intestine.
Contains both exocrine and endocrine cells.
Endocrine cells are located in pancreatic islets, or islets of Langerhans.
Account for only about 1% of all pancreatic cells.
Alpha cells secrete glucagon.
Beta cells secrete insulin.

Blood Glucose and Insulin

Increases in blood glucose levels activate beta cells to release more insulin, stimulating glucose uptake by cells (except neurons, red blood cells, and certain epithelial cells).
Increases rates of protein synthesis and fat storage, resulting in lower blood glucose levels.

Blood Glucose and Glucagon

Decreases in blood glucose levels activate alpha cells to release more glucagon.
Mobilizing energy reserves; glycogen in liver and muscles broken down to glucose; adipose tissue releases fatty acids.
Results in higher blood glucose levels.

Pancreatic Regulation of Blood Glucose

Insulin and glucagon secretion is independent of direct neural stimulus.
Indirectly affected by any hormone that influences blood glucose levels (e.g., cortisol, thyroid hormones).
Also affected by ANS activity: parasympathetic stimulation enhances insulin release, and sympathetic stimulation inhibits it.

Diabetes Mellitus

Faulty glucose metabolism causing buildup of glucose in blood and urine
Types: Type 1 (juvenile diabetes): inadequate insulin production; Type 2: insulin resistance.
Symptoms: Hyperglycemia, glycosuria, polyuria.

Secondary Endocrine Organs

Many organs release hormones, but their primary function is in another system
Examples include intestines, kidneys, heart, thymus, gonads, and adipose tissue.

The Intestines

Release local hormones that coordinate digestive activities and major control over digestive processes.
Can be influenced by ANS.

Hormones Released by the Kidneys

Calcitriol: Stimulated by PTH, increasing calcium and phosphate ion absorption from the digestive tract.
Erythropoietin (EPO): Stimulated by low oxygen levels in kidney tissues, increasing RBC production.
Renin: An enzyme that triggers the renin-angiotensin-aldosterone system, to increase blood pressure and blood volume.

The Heart

Endocrine cells in the right atrium respond to increased blood volume and release atrial natriuretic peptide (ANP).
ANP promotes Na+ and water loss, inhibits renin, ADH, and aldosterone release, and results in decreased blood pressure and blood volume.

The Thymus

Located deep to the sternum in the mediastinum.
Very active in early childhood; atrophies in adults.
Releases thymosins that aid in the development and maintenance of immune defenses.

The Gonads: The Testes

Interstitial endocrine cells produce androgens.
Most important is testosterone which promotes sperm production, maintains secretory glands of the male reproductive tract, determines secondary sex characteristics, stimulates protein synthesis in skeletal muscles.
Sperm production balance is maintained by inhibin secreted by nurse cells in the testes.

The Gonads: The Ovaries

Female sex cells (oocytes) are surrounded by follicles.
FSH triggers follicular cells to produce estrogens.
Estrogens support egg cell maturation, uterine lining growth, and have negative feedback on FSH.
Inhibin provides negative feedback on FSH.
Once a follicle releases an oocyte (ovulation), the corpus luteum is formed from remaining follicular cells.
Releases a mixture of estrogens and progesterone. This accelerates fertilized egg movement through the uterine tube, prepares the uterus for a developing embryo, and contributes to mammary gland enlargement.
All gonadal hormones are regulated by hormones from the anterior pituitary gland.

Hormones of the Reproductive System

Table summarizing the hormones of the reproductive system, their targets, and their effects.

Adipose Tissue

Produces peptide hormone leptin.
Provides negative feedback control of appetite by binding to hypothalamic neurons to trigger satiation (fullness) and appetite suppression.
Must be present for normal GnRH and gonadotropin synthesis.
Low body fat can result in late puberty and cessation of menstrual cycles.
Increased body fat can increase fertility.

Hormonal Interactions

Extracellular fluid contains mixtures of hormones that may have the same target, resulting in four possibilities:
- Antagonistic: (e.g., parathyroid hormone and calcitonin)
- Synergistic
- Permissive
- Integrative

Hormones and Growth

Six hormones required for normal growth:
1. Growth hormone (GH)
2. Thyroid hormones
3. Insulin
4. Parathyroid hormone (PTH)
5. Calcitriol
6. Reproductive hormones

Hormones and Stress

Stress is triggered by physical injury/illness, emotional responses (anxiety or depression), environmental conditions (extreme cold or heat), or metabolic conditions (acute starvation).
Stress triggers the general adaptation syndrome (GAS; or stress response).
- Three phases: alarm, resistance, exhaustion

Hormones and Behavior

The hypothalamus is the primary regulator and monitor of hormones.
Behavior is also affected by hormonal abnormalities (e.g., precocious puberty – early sex hormone release, resulting in aggressive and assertive behavior, hormone imbalances affecting CNS intellectual functions like learning, memory, and emotions).

Hormones and Aging

Most hormones generally stay the same in adulthood, but exceptions include reproductive hormones.
Changes in target organ receptors occur more often via reduced sensitivity.

An Overview of Some Important Endocrine Disorders

Tables summarizing important endocrine disorders, related symptoms, and tissue/hormonal effects.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on the functions of hormones, the structure of the pituitary gland, and the hypothalamus' role in endocrine control. This quiz covers key concepts related to hormone transport, signaling, and the hypophyseal portal system.