Endocrine Test Prep Practice
Colloid
(1) a mixture in which the solute particles (usually proteins) do not settle out readily. (2) Substance in the thyroid gland containing thyroglobulin protein
Follicle
(1) ovarian structure consisting of a developing egg surrounded by one or more layers of follicle cells; (2) colloid-containing structure of the thyroid gland; (3) B cell-rich region in lymphoid tissue
Compare and contrast the effects of the two major pancreatic hormones.
The pancreas, located in the abdomen close to the stomach, is both an exocrine and an endocrine gland. The endocrine portion (pancreatic islets) releases insulin and glucagon and smaller amounts of other hormones to the blood. Glucagon, released by alpha cells when blood levels of glucose are low, stimulates the liver to release glucose to the blood. Insulin is released by beta cells when blood levels of glucose (and amino acids) are rising. It increases the rate of glucose uptake and metabolism by most body cells.
Triiodothyronine (T₃)
thyroid hormone; secretion and function similar to those of thyroxine (T₄)
Name the two major chemical classes of hormones. Which class consists entirely of lipid-soluble hormones? Name the only hormone in the other chemical class that is lipid-soluble.
The two major chemical classes of hormones are amino acid-based hormones and steroids. Steroids are all lipid soluble. Thyroid hormones are the only amino acid-based hormones that are lipid soluble.
Paracrine
A chemical messenger that acts locally within the same tissue and is rapidly destroyed. Examples are prostaglandins and nitric oxide
Androgen
A hormone such as testosterone that controls male secondary sex characteristics
Name the cells that release the thyroid hormone, parathyroid hormone, and calcitonin.
Thyroid follicular cells release thyroid hormone, parathyroid cells in the parathyroid gland release parathyroid hormone, and parafollicular (C) cells in the thyroid gland release calcitonin.
Follicle-Stimulating Hormone (FSH)
hormone produced by the anterior pituitary that stimulates ovarian follicle production in females and sperm production in males
Hypoglycemic
term used to describe hormones such as insulin that decrease blood glucose level
Thyroid Hormone (TH)
the major hormone secreted by thyroid follicles; stimulates enzymes concerned with glucose oxidation
Antagonist
(1) muscle that reverses, or opposes, the action of another muscle. (2) Hormone that opposes the action of another hormone
Follow the process of thyroxine formation and release.
Secretion of thyroid hormone, prompted by TSH, requires the follicular cells to take up the stored colloid and split the hormones from the colloid for release. Rising levels of thyroid hormone feed back to inhibit the anterior pituitary and hypothalamus. Most T₄ is converted to T₃ (a more active form) in the target tissues. These hormones act by turning on gene transcription and protein synthesis.
List the four anterior pituitary hormones that are tropic hormones and name their target glands.
LH and FSH are tropic hormones that act on the gonads, TSH is a tropic hormone that acts on the thyroid, and ACTH is a tropic hormone that acts on the adrenal cortex. (If you said growth hormone, that's also a good answer, as GH causes the liver to release IGFs might also be considered a tropic effect.)
Synthetic melatonin supplements are available, although their safety and efficiency have not been proven. What do you think they might be used for?
Melatonin is used by some individuals as a sleep aid, particularly to counter jet lag.
Briefly describe the importance of melatonin.
Melatonin, an amine hormone derived from serotonin. Melatonin concentrations in the blood rise and fall in a diurnal (daily) cycle. Peak levels occur during the night and make us drowsy, and lowest levels occur around noon. Recent evidence suggests that melatonin also controls the production of protective antioxidant and detoxification molecules within cells.
Describe how hormones are classified chemically.
Most hormones are steroids or amino acid-based. Most hormones are amino acid-based. Molecular size varies widely in this group - from simple amino acid derivatives (which include thyroxine constructed from the amino acid tyrosine and amines), to peptides (short chains of amino acids), to proteins (long polymers of amino acids). Steroid hormones are synthesized from cholesterol. Of the hormones produced by the major endocrine organs, only gonadal and adrenocortical hormones are steroids.
Indicate the general functions of parathyroid hormone.
The parathyroid glands, located on the dorsal aspect of the thyroid gland, secrete parathyroid hormone (PTH), which increases blood calcium levels. It targets bone, the kidneys, and the small intestine (indirectly via vitamin D activation). PTH is the key hormone for calcium homeostasis.
Explain how hormone release is regulated.
The synthesis and release of most hormones are regulated by some type of negative feedback mechanism. In such a mechanism, some internal or external stimulus triggers hormone secretion. As levels of a hormone rise, it causes target organ effects, which then feed back to inhibit further hormone release. As a result, blood levels of many hormones vary only within a narrow range.
What is the major effect of thyroid hormone? Parathyroid hormone?? Calcitonin???
Thyroid hormone increases basal metabolic rate (and heat production) in the body. Parathyroid hormone increases blood Ca²⁺ levels in a variety of ways. Calcitonin at high (pharmacological) levels has a Ca²⁺ -lowering bone sparing effect. (At normal blood levels its effect in humans are negligible.)
Diabetes Mellitus (DM)
disease caused by deficient insulin release or by insulin resistance, leading to inability of the body cells to use carbohydrates
Diabetes Insipidus
disease characterized by passage of a large quantity of dilute urine plus intense thirst and dehydration caused by inadequate release of antidiuretic hormone (ADH)
Graves' Disease
disorder resulting from hyperactive thyroid gland
Endocrine Glands
ductless glands that empty their hormonal products directly into the blood
Renin
enzyme released by the kidneys that raises blood pressure by initiating the renin-angiotensin-aldosterone mechanism
Ketones (Ketone Bodies)
fatty acid metabolites; strong organic acids
Pancreas
gland located behind the stomach, between the spleen and the duodenum; produces both endocrine and exocrine secretions
Cortisol (Hydrocortisone)
glucocorticoid produced by the adrenal cortex
Gonadotropins
gonad-stimulating hormones produced by the anterior pituitary
Steroids
group of chemical substances including certain hormones and cholesterol; they are fat soluble and contain little oxygen
Glucagon
hormone formed by alpha cells of pancreatic islets; raises the glucose level of blood
Progesterone
hormone partly responsible for preparing the uterus for the fertilized ovum
Aldosterone
hormone produced by the adrenal cortex that regulates Na⁺; reabsorption and K⁺; secretion by the kidneys
Antidiuretic Hormone (ADH, also called Vasopressin)
hormone produced by the hypothalamus and released by the posterior pituitary; stimulates the kidneys to reabsorb more water, reducing urine volume
Parathyroid Hormone (PTH)
hormone released by the parathyroid glands that regulates blood calcium level
Calcitonin
hormone released by the thyroid. Lowers blood calcium levels only when present at high (therapeutic) levels
Oxytocin
hormone synthesized in the hypothalamus and secreted by the posterior pituitary; stimulates contraction of the uterus during childbirth and the ejection of milk during nursing
Growth Hormone (GH)
hormone that stimulates growth in general; produced in the anterior pituitary; also called somatotropin
Erythropoietin (EPO)
hormone that stimulates production of red blood cells
Adrenal Glands
hormone-producing glands located superior to the kidneys; each consists of medulla and cortex areas
Estrogens
hormones that stimulate female secondary sex characteristics; female sex hormones
Thyroxine (T₄)
iodine-containing hormone secreted by the thyroid gland; accelerates cellular metabolic rate in most body tissues
Thymus
lymphoid organ and endocrine gland active in immune response; site of maturation of T lymphocytes
Testosterone
male sex hormone produced by the testes; during puberty promotes virilization, and is necessary for normal sperm production
Hypothalamic-Hypophyseal Tract
nerve bundles that run through the infundibulum and connect the neurohypophysis and the hypothalamus
Posterior Pituitary
neural part of pituitary gland; part of the neurohypophysis
Pituitary Gland
neuroendocrine gland located beneath the brain that serves a variety of functions including regulation of gonads, thyroid, adrenal cortex, lactation, and water balance
Thyroid Gland
one of the largest of the body's endocrine glands; straddles the anterior trachea
Neurohypophysis
posterior pituitary plus infundibulum; portion of the pituitary gland derived from the brain
Gonad
primary reproductive organ; i.e., the testis of the male or the ovary of the female
Glucose
principal blood sugar; a hexose
Gonadocorticoids
sex hormones, primarily androgens, secreted by the adrenal cortex
Parathyroid Glands
small endocrine glands located on the posterior aspect of the thyroid gland
Insulin Resistance
state in which a greater than normal amount of insulin is required to maintain normal glucose blood levels
Mineralocorticoid
steroid hormone of the adrenal cortex that regulates Na⁺; and K⁺; metabolism and fluid balance
Corticosteroid
steroid hormones released by the adrenal cortex
Hormones
steroidal or amino acid-based molecules released to the blood that act as chemical messengers to regulate specific body functions
Hyperglycemic
term used to describe hormones such as glucagon that elevate blood glucose level
Tropic Hormone (Tropin)
a hormone that regulates the secretory action of another endocrine organ
Prolactin (PRL)
adenohypophyseal hormone that stimulates the breasts to produce milk
Endocrine System
body system that includes internal organs that secrete hormones
Epinephrine
chief hormone produced by the adrenal medulla; also called adrenaline
Myxedema
condition resulting from underactive thyroid gland
Describe the two major mechanisms by which hormones bring about their effects on their target tissues.
All major hormones circulate to virtually all tissues, but a hormone influences the activity of only those tissue cells that have receptors for it. These cells are its target cells. Hormones bring about the characteristic effects by altering target cell activity. In other words, they increase or decrease the rates of normal cellular processes. The precise response depends on the target cell type. A hormone typically produces one or more of the following changes: - Alters plasma membrane permeability or membrane potential, or both, by opening or closing ion channels. - Stimulates synthesis of enzymes and other proteins within the cell. - Activates or deactivates enzymes. - Induces secretory activity. - Stimulates mitosis. In general, hormones act at receptors in one of two ways: - Water-soluble hormones (all amino acid-based hormones except thyroid hormone) act on receptors in the plasma membrane. These receptors are usually coupled via regulatory molecules called G proteins to one or more intracellular second messengers which mediate the target cell's response. - Lipid-soluble hormones (steroid and thyroid hormones) act on receptors inside the cell, which directly activate genes.
Diabetes mellitus and diabetes insipidus are both due to lack of a hormone. Which hormone causes which? What symptoms do they have in common?? What would you find in the urine of a patient with one but not the other???
Diabetes mellitus is due to a lack of insulin production or action, whereas diabetes insipidus is due to lack of ADH. Both conditions are characterized by production of copious amounts of urine. You would find glucose in the urine of a patient with diabetes mellitus, but not in the urine of a patient with diabetes insipidus.
Anita drank too much alcohol one night and suffered from a headache and nausea the next morning. What caused the "hangover" effects?
Drinking alcoholic beverages inhibits ADH secretion from the posterior pituitary and causes copious urine output and dehydration. The dehydration causes the hangover effects.
List the three classes of hormones released from the adrenal cortex, and for each, briefly state its major effect(s).
Glucocorticoids are stress hormones that, among many effects, increase blood glucose. Mineralocorticoids increase blood Na⁺ (and blood pressure) and decrease blood K⁺. Gonadocorticoids are male and female sex hormones that are thought to have a variety of effects (for example, contribute to onset of puberty, sec drive in women, pubic and axillary hair development in women).
List the major endocrine glands and describe their body locations.
Endocrine organs are ductless, well-vascularized glands that release hormones directly into the blood and lymph. They are small and widely separated in the body. The purely endocrine organs are the pituitary, thyroid, parathyroid, adrenal, and pineal glands. The hypothalamus is a neuroendocrine organ. The pancreas, gonads, and placenta also have endocrine tissue.
What are the three types of stimuli that control hormone release?
Hormone release can be triggered by humoral, neural, or hormonal stimuli.
Distinguish between hormones, paracrines, and autocrines.
Hormones are chemical messengers secretes by cells into the extracellular fluids. These messengers travel through the blood and regulate the metabolic function of other cells in the body. Autocrines are chemicals that exert their effects on the same cells that secrete them. For example, certain prostaglandins released by smooth muscle cells cause those smooth muscle cells to contract. Paracrines also act locally (within the same tissue) but affect cell types other than those releasing the paracrine chemicals.
What is the difference between a hormone and a paracrine?
Hormones are released into the blood and transported throughout the body, whereas paracrines act locally, generally within the same tissue.
List hormones produced by the adrenal gland, and cite their physiological effects.
The adrenal medulla produces catecholamines (epinephrine and norepinephrine) in response to sympathetic nervous system stimulation. Catecholamines enhance and prolong the fight-or-flight response to short-term stressors. Hypersecretion leads to symptoms typical of sympathetic nervous system overactivity.
List and describe the chief effects of anterior pituitary hormones.
The anterior pituitary has traditionally been called the "master endocrine gland" because many of the numerous hormones it produces regulate the activity of other endocrine glands. Researchers have identified six anterior pituitary hormones, all of them proteins - growth hormone, thyroid-stimulating hormone, adrenocortiotropic hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin. Four of the six anterior pituitary hormones are tropic hormones that regulate the function of other endocrine organs. Most anterior pituitary hormones exhibit a diurnal rhythm of release, which is subject to modification by stimuli influencing the hypothalamus. Growth hormone (GH) is an anabolic hormone that stimulates growth of all body tissues but especially skeletal muscle and bone. Thyroid-stimulating hormone (TSH) promotes normal development and activity of the thyroid gland. Adrenocortiotropic hormone (ACTH) stimulates the adrenal cortex to release corticosteroids. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) regulate the functions of the gonads in both sexes. FSH stimulates sex cell production; LH stimulates gonadal hormone production. Prolactin (PRL) promotes milk production in humans.
Describe structural and functional relationships between the hypothalamus and the pituitary gland.
The contrasting histology of the two pituitary lobes reflects the dual origin of this tiny gland. The posterior lobe is actually part of the brain. It derives from a downgrowth of hypothalamic tissue and maintains its neural connection with hypothalamus via a nerve bundle called the hypothalamic-hypophyseal tract.
For each of the following statements, indicate whether it applies more to the endocrine system or the nervous system: rapid, discrete responses, controls growth and development, and long-lasting responses.
The endocrine system is more closely associated with growth and development, and its responses tend to be long-lasting, whereas nervous system responses tend to be rapid and discrete.
Anterior Pituitary
The glandular part of the pituitary gland; see Adenohypophysis
Which of the two chemical classes of hormones do the gonadal hormones belong to? Which major endocrine gland secretes hormones of this same chemical class??
The gonadal hormones are steroid hormones. A major endocrine gland that also secretes steroid hormones is the adrenal cortex.
What is the key difference between the way the hypothalamus communicates with the anterior pituitary and the way it communicates with the posterior pituitary?
The hypothalamus communicates with the anterior pituitary via hormones released into a special portal system of blood vessels. In contrast, it communicates with the posterior pituitary via action potentials traveling down axons that connect the hypothalamus to the posterior pituitary.
Indicate important differences between hormonal and neural controls of body functioning.
The nervous system regulates the activity of muscles and glands via electrochemical impulses delivered by neurons, and those organs respond within milliseconds. The means of control and speed of the endocrine system are very different. The endocrine system influences metabolic activity by means of hormones.
Describe the functional roles of hormones of the testes, ovaries, and placenta.
The ovaries of the female, located in the pelvic cavity, release two main hormones. The ovarian follicles begin to secrete estrogens at puberty under the influence and FSH. Estrogens stimulate maturation of the female reproductive system and development of the secondary sex characteristics. Progesterone is released in response to high blood levels of LH. It works with estrogens in establishing the menstrual cycle. The testes of the male begin to produce testosterone at puberty in response to LH. Testosterone promotes maturation of the male reproductive organs, development of secondary sex characteristics, and production of sperm by the testes. The placenta produces hormones of pregnancy - estrogens, progesterones, and others.
Discuss the structure of the posterior pituitary, and describe the effects of the two hormones it releases.
The posterior pituitary consists largely of axon terminals of hypothalamic neurons whose cell bodies are located in the supraoptic or paraventricular nuclei. These neurons synthesize one of two neurohormones in their cell bodies: Oxytocin or antidiuretic hormone (ADH). Oxytocin is a strong stimulant of uterine contraction, oxytocin is released in significantly higher amounts during childbirth and in nursing women. Diuresis is urine production, so an antidiuretic is a substance that inhibits or prevents urine formation. Antidiuretic hormone (ADH) prevents wide swings in water balance, helping the body avoid dehydration and water overload.
Which two endocrine glands are found in the neck?
The thyroid and parathyroid glands are found in the neck.
Describe the effects of the two groups of hormones produced by the thyroid gland.
The thyroid gland is located in the anterior neck. Thyroid follicles store colloid containing thyroglobulin, a glycoprotein from which thyroid hormone is derived. Thyroid hormone (TH) includes thyroxine (T₄) and triiodothyronine (T₃), which increase the rate of cellular metabolism. Consequently, oxygen use and heat production rise.
List three kinds of interaction of different hormones acting on the same target cell.
Understanding hormonal effects is a bit more complicated than you might expect because multiple hormones may act on the same target cells at the same time. There are three types of hormone interaction: - Permissiveness - is the situation in which one hormone cannot exert its full effects without another hormone being present. - Synergism - occurs when more than one hormone produces the same effects at the target cell and their combined effects are amplified. - Antagonism - occurs when one hormone opposes the actions of another hormone.
Consider the signaling mechanisms of water-soluble and lipid-soluble hormones. In each case, where are the receptors found and what is the final outcome?
Water-soluble hormones act on receptors in the plasma membrane coupled most often via regulatory molecules called G proteins to intracellular second messengers. Lipid-soluble hormones act on intracellular receptors, directly activating genes and stimulating synthesis of specific proteins.
You've just attended a football game with your friend Sharon, who is diabetic. While Sharon drank only one beer during the game, she is having trouble walking straight, her speech is slurred, and she is not making any sense. What does it mean when we say Sharon is diabetic? What is the most likely explanation for Sharon's current behavior?? How could you help her???
When we say Sharon is diabetic, this means that she has insufficient insulin action in her body. The most likely explanation for Sharon's behavior is that she has taken too much insulin and is experiencing hypoglycemia. You could help her by making sure she immediately ingests a sugary snack or drink.
Norepinephrine (NE)
a catecholamine neurotransmitter and adrenal medullary hormone, associated with sympathetic nervous system activation
Pharmacological Dose
a drug dose that is dramatically higher than normal levels of that substance (e.g., hormone) in the body
Physiological Dose
a drug dose that replicates normal levels of that substance (e.g., hormone) in the body. (Compare with Pharmacological dose.)
Atrial Natriuretic Peptide (ANP)
a hormone released by certain cells of the heart atria that reduces blood pressure and blood volume by inhibiting nearly all events that promote vasoconstriction and Na⁺; and water retention
Melatonin
a hormone secreted by the pineal gland; secretion peaks at night and helps set sleep-wake cycles; also a powerful antioxidant
Insulin
a hormone that enhances the carrier-mediated diffusion of glucose into tissue cells, thus lowering blood glucose levels
Pineal Gland (Body)
a hormone-secreting part of the diencephalon of the brain thought to be involved in setting the biological clock and influencing reproductive function
Angiotensin II
a potent vasoconstrictor activated by renin; also triggers release of aldosterone
Glucocorticoids
adrenal cortex hormones that increase blood glucose levels and aid the body in resisting long-term stressors
Luteininzing Hormone (LH)
anterior pituitary hormone that aids maturation of cells in the ovary and triggers ovulation in females. In males, causes the interstitial cells of the testis to produce testosterone
Adrenocorticotropic Hormone (ACTH)
anterior pituitary hormone that influences the activity of the adrenal cortex
Thyroid-Stimulating Hormone (TSH)
anterior pituitary hormone that regulates secretion of thyroid hormones
Adenohypophysis
anterior pituitary; the glandular part of the pituitary gland
Stressor
any stimulus that directly or indirectly causes the hypothalamus to initiate stress-reducing responses, such as the fight-or-flight response
