A&P 2 Lab 9 Endocrine System

Which body system uses hormones released into the bloodstream to regulate distant target cells?

The endocrine system uses hormones released into blood capillaries to regulate target cells in distant tissues and organs.

How does an endocrine gland deliver its secretion to the rest of the body?

An endocrine gland is ductless and secretes hormones into interstitial fluid, where the hormones enter blood capillaries and travel through the bloodstream.

How does an exocrine gland deliver its secretion?

An exocrine gland releases secretions through ducts that carry the material to body surfaces or into cavities of hollow organs.

What feature separates endocrine glands from exocrine glands on a practical exam?

Endocrine glands lack ducts and release hormones into blood, while exocrine glands have ducts that carry secretions to a surface or cavity.

Why can an endocrine hormone affect a cell far away from the gland that secreted it?

Hormones circulate in the blood and only cells with the correct specific receptor respond to that hormone.

What is a target cell in endocrine physiology?

A target cell is a cell that has the specific receptor needed to bind a hormone and produce a response.

Can an endocrine target be an entire tissue or organ rather than a single cell?

Yes. A target of a hormone may be a single cell type, a tissue, or an entire organ that expresses the appropriate receptor.

What kinds of body processes are affected by hormones?

Hormones influence growth, development, metabolism, reproduction, fluid balance, electrolyte balance, immune activity, and many other body processes.

Which non-classic organs can produce hormones even though they are not usually listed as major endocrine glands?

The heart, stomach, kidneys, gonads, adipose tissue, and several other organs can produce hormones in addition to their primary functions.

What must happen before a hormone can change the activity of a target cell?

The hormone must bind to a specific receptor on or inside the target cell, triggering a cellular response.

Which endocrine gland secretes melatonin?

The pineal gland secretes melatonin.

What is the major function of melatonin?

Melatonin helps regulate circadian rhythms and promotes sleepiness, especially during darkness.

How does melatonin secretion change between day and night?

Melatonin secretion decreases during the day and increases at night.

Why does the pineal gland matter for sleep-wake cycles?

The pineal gland releases melatonin in response to darkness, helping coordinate the body's sleep-wake rhythm with the light-dark cycle.

A patient has increased sleepiness at night because of increased secretion from which gland?

Increased night-time melatonin from the pineal gland contributes to sleepiness.

Which brain region controls much of pituitary gland activity?

The hypothalamus controls much of pituitary gland activity through releasing hormones, inhibiting hormones, and direct neural connections.

What is the hypophysis?

The hypophysis is another name for the pituitary gland.

What are the two main lobes of the pituitary gland?

The two main lobes of the pituitary gland are the anterior pituitary, or adenohypophysis, and the posterior pituitary, or neurohypophysis.

How does the hypothalamus regulate the anterior pituitary?

The hypothalamus secretes releasing and inhibiting hormones into the hypothalamo-hypophyseal portal system, which carries them to the anterior pituitary.

How does the hypothalamus regulate the posterior pituitary?

Hypothalamic neurons send axons through the hypothalamo-hypophyseal tract to the posterior pituitary, where oxytocin and antidiuretic hormone are stored and released.

What is the hypothalamo-hypophyseal portal system?

The hypothalamo-hypophyseal portal system is a blood vessel network that carries hypothalamic releasing and inhibiting hormones directly to the anterior pituitary.

What is the hypothalamo-hypophyseal tract?

The hypothalamo-hypophyseal tract is a bundle of axons that carries neurosecretory signals from the hypothalamus to the posterior pituitary.

Which pituitary lobe is made of glandular endocrine tissue?

The anterior pituitary, or adenohypophysis, is made of glandular endocrine tissue and produces its own hormones.

Which pituitary lobe is neural tissue that stores hypothalamic hormones?

The posterior pituitary, or neurohypophysis, is neural tissue that stores and releases hormones made by hypothalamic neurons.

Which two hormones are released from the posterior pituitary?

The posterior pituitary releases antidiuretic hormone and oxytocin.

Where are antidiuretic hormone and oxytocin produced?

Antidiuretic hormone and oxytocin are produced by neurons in the hypothalamus and transported to the posterior pituitary for storage and release.

What is the full name of ADH?

ADH stands for antidiuretic hormone.

What is another name for antidiuretic hormone?

Antidiuretic hormone is also called vasopressin.

What does antidiuretic hormone do in the kidneys?

Antidiuretic hormone reduces urine output by increasing water reabsorption in the kidneys.

How can antidiuretic hormone affect blood pressure?

Antidiuretic hormone can help support blood pressure by increasing water retention and, at higher levels, causing vasoconstriction.

Which posterior pituitary hormone reduces urine volume?

Antidiuretic hormone reduces urine volume by promoting renal water reabsorption.

Which posterior pituitary hormone is important during labor?

Oxytocin is important during labor because it stimulates uterine contractions.

Which hormone causes milk let-down in lactating mothers?

Oxytocin causes milk let-down by stimulating contraction of myoepithelial cells around mammary glands.

What is the difference between milk production and milk let-down?

Prolactin promotes milk production, while oxytocin causes milk ejection or let-down.

Which anterior pituitary hormone stimulates the adrenal cortex?

Adrenocorticotropic hormone stimulates the adrenal cortex, especially cortisol release.

What is the full name of ACTH?

ACTH stands for adrenocorticotropic hormone.

What is the target gland of adrenocorticotropic hormone?

The target gland of adrenocorticotropic hormone is the adrenal cortex.

Which anterior pituitary hormone stimulates thyroid hormone production and release?

Thyroid-stimulating hormone stimulates the thyroid gland to produce and release thyroid hormone.

What is the full name of TSH?

TSH stands for thyroid-stimulating hormone.

Which anterior pituitary hormone stimulates growth of bones, cartilage, and muscle?

Growth hormone stimulates growth of bones, cartilage, and muscle.

Why do timing and amount of growth hormone matter?

The timing and amount of growth hormone release help determine body size because it drives growth of skeletal and soft tissues.

Which anterior pituitary hormone stimulates breast development and lactation?

Prolactin stimulates breast development and promotes and maintains lactation after childbirth.

What is the full name of PRL?

PRL stands for prolactin.

Which anterior pituitary hormone promotes ovarian follicle formation?

Follicle-stimulating hormone promotes formation of ovarian follicles and stimulates them to produce estrogen.

What is the full name of FSH?

FSH stands for follicle-stimulating hormone.

What is the role of follicle-stimulating hormone in males?

Follicle-stimulating hormone stimulates sperm development by acting on Sertoli cells in the testes.

Which anterior pituitary hormone initiates ovulation?

Luteinizing hormone initiates ovulation.

What is the full name of LH?

LH stands for luteinizing hormone.

How does luteinizing hormone affect the corpus luteum?

Luteinizing hormone helps maintain the corpus luteum after ovulation, supporting progesterone production.

How does luteinizing hormone affect males?

Luteinizing hormone stimulates Leydig cells in the testes to produce testosterone.

Which pituitary region produces melanocyte-stimulating hormone?

The intermediate lobe, considered part of the anterior pituitary, produces melanocyte-stimulating hormone.

What is the major effect of melanocyte-stimulating hormone?

Melanocyte-stimulating hormone can influence melanocytes and pigmentation, although its role is limited in adult humans compared with many other animals.

Which six major hormones are secreted by the anterior pituitary?

The six major anterior pituitary hormones are growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin.

Which anterior pituitary hormones are tropic hormones?

Thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, and luteinizing hormone are tropic hormones because they regulate other endocrine glands or endocrine cells.

Which anterior pituitary hormones are not primarily tropic hormones?

Growth hormone and prolactin are not primarily tropic hormones because they act more directly on tissues rather than mainly stimulating another endocrine gland.

What is a tropic hormone?

A tropic hormone is a hormone that stimulates another endocrine gland or endocrine cell population to grow, secrete hormones, or change activity.

Why is thyroid-stimulating hormone considered a tropic hormone?

Thyroid-stimulating hormone is tropic because it acts on the thyroid gland and stimulates thyroid hormone production and release.

Why is adrenocorticotropic hormone considered a tropic hormone?

Adrenocorticotropic hormone is tropic because it stimulates the adrenal cortex to secrete glucocorticoids such as cortisol.

Why are follicle-stimulating hormone and luteinizing hormone considered tropic hormones?

Follicle-stimulating hormone and luteinizing hormone are tropic because they stimulate the gonads to produce gametes and sex hormones.

What is negative feedback in endocrine regulation?

Negative feedback occurs when the final hormone or physiological effect reduces further hormone release from earlier steps in the pathway.

How does negative feedback prevent hormone levels from becoming too high?

Rising levels of a hormone signal the hypothalamus and pituitary to reduce stimulation, which lowers secretion from the target endocrine gland.

What is the hypothalamo-pituitary-adrenal axis?

The hypothalamo-pituitary-adrenal axis is the pathway in which hypothalamic corticotropin-releasing hormone stimulates pituitary ACTH release, and ACTH stimulates adrenal cortex cortisol secretion.

What is the negative feedback signal in the hypothalamo-pituitary-adrenal axis?

Cortisol provides negative feedback to the hypothalamus and anterior pituitary to reduce corticotropin-releasing hormone and ACTH secretion.

What is the hypothalamo-pituitary-thyroid axis?

The hypothalamo-pituitary-thyroid axis is the pathway in which hypothalamic thyrotropin-releasing hormone stimulates pituitary TSH release, and TSH stimulates thyroid hormone secretion.

What is the negative feedback signal in the hypothalamo-pituitary-thyroid axis?

Thyroid hormones, mainly T3 and T4, provide negative feedback to the hypothalamus and anterior pituitary to reduce TRH and TSH release.

What is the hypothalamo-pituitary-gonadal axis?

The hypothalamo-pituitary-gonadal axis is the pathway in which hypothalamic GnRH stimulates pituitary FSH and LH secretion, and those hormones regulate the ovaries or testes.

What hormones provide feedback in the hypothalamo-pituitary-gonadal axis?

Estrogen, progesterone, testosterone, and inhibin provide feedback to regulate GnRH, FSH, and LH secretion.

How can a primary endocrine disorder be recognized?

A primary endocrine disorder begins in the target endocrine gland, so the target gland hormone is abnormal and the pituitary tropic hormone usually changes in the opposite direction because of feedback.

How can a secondary endocrine disorder be recognized?

A secondary endocrine disorder begins in the pituitary, so the pituitary tropic hormone is abnormal and the target gland hormone changes in the same direction.

What lab pattern suggests primary hypothyroidism?

Primary hypothyroidism typically shows low thyroid hormone with high thyroid-stimulating hormone because the pituitary is trying to stimulate a failing thyroid gland.

What lab pattern suggests secondary hypothyroidism?

Secondary hypothyroidism typically shows low thyroid hormone with low or inappropriately normal thyroid-stimulating hormone because the pituitary is not adequately stimulating the thyroid.

What lab pattern suggests primary adrenal insufficiency?

Primary adrenal insufficiency typically shows low cortisol with high adrenocorticotropic hormone because the pituitary is trying to stimulate a failing adrenal cortex.

What lab pattern suggests secondary adrenal insufficiency?

Secondary adrenal insufficiency typically shows low cortisol with low or inappropriately normal adrenocorticotropic hormone because pituitary stimulation is deficient.

Why are endocrine axes useful for interpreting hormone disorders?

Endocrine axes show which gland controls which target, making it possible to tell whether a problem is in the hypothalamus, pituitary, or target endocrine gland.

Which gland secretes thyroid hormone and calcitonin?

The thyroid gland secretes thyroid hormone from follicular cells and calcitonin from parafollicular cells.

What are the two major thyroid hormones?

The two major thyroid hormones are thyroxine, or T4, and triiodothyronine, or T3.

What is the main physiological role of thyroid hormone?

Thyroid hormone regulates the metabolic rate of the entire body and supports normal growth and nervous system development.

Why is thyroid hormone important during nervous system development?

Thyroid hormone is required for normal brain and nervous system development, especially during fetal life and early childhood.

Which thyroid cells produce colloid?

Follicular cells produce the colloid that contains precursors used to make thyroid hormone.

What is thyroid colloid?

Thyroid colloid is the protein-rich material inside thyroid follicles that contains thyroglobulin, a precursor used to synthesize thyroid hormones.

Which thyroid cells secrete calcitonin?

Parafollicular cells, also called C cells, secrete calcitonin.

What does calcitonin do to blood calcium levels?

Calcitonin lowers blood calcium levels by inhibiting bone resorption and reducing calcium release from bone.

What is bone resorption?

Bone resorption is the breakdown of bone matrix by osteoclasts, which releases calcium and phosphate into the blood.

Which hormone decreases bone resorption according to the endocrine material?

Calcitonin decreases bone resorption, which helps lower serum calcium levels.

Which small glands are usually found on the posterior surface of the thyroid?

The parathyroid glands are usually found on the posterior surface of the thyroid gland.

Which hormone is secreted by the parathyroid glands?

The parathyroid glands secrete parathyroid hormone.

What is the major function of parathyroid hormone?

Parathyroid hormone increases serum calcium levels and decreases serum phosphorus levels.

How does parathyroid hormone increase blood calcium?

Parathyroid hormone increases blood calcium by stimulating bone resorption, increasing kidney calcium reabsorption, and promoting calcitriol production that increases intestinal calcium absorption.

How does parathyroid hormone affect phosphate?

Parathyroid hormone decreases serum phosphate by increasing phosphate excretion by the kidneys.

How do calcitonin and parathyroid hormone differ?

Calcitonin lowers serum calcium, while parathyroid hormone raises serum calcium.

Which gland is active in young individuals and supports immunocompetency?

The thymus is active in young individuals and supports immune competence by promoting T cell maturation.

Which hormone produced by the thymus promotes T cell maturation?

Thymosin promotes maturation of T cells in the thymus.

Where do T cells begin before migrating to the thymus?

T cells originate from precursor cells in the bone marrow before migrating to the thymus for maturation.

Where do mature T cells travel after leaving the thymus?

Mature T cells migrate to lymph nodes and the spleen, where they perform immune functions.

Which heart chambers secrete natriuretic peptides when blood volume is high?

Cardiac muscle cells in the atria secrete natriuretic peptides when blood volume is elevated.

What are ANP and BNP?

ANP and BNP are natriuretic peptides released by the heart that promote sodium and water loss by the kidneys.

What does ANP stand for?

ANP stands for atrial natriuretic peptide.

What does BNP stand for?

BNP stands for B-type natriuretic peptide.

What is the kidney effect of ANP and BNP?

ANP and BNP act on the kidneys to increase loss of sodium ions and water, which helps lower blood volume and blood pressure.

Why does sodium loss cause water loss?

Water follows sodium osmotically, so increased sodium excretion pulls water into the urine.