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Wk 3
The endocrine system
91
Medical
Undergraduate 1
08/05/2024

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Term
The endocrine system places ______ in systems that control the body
Definition
Second; nervous system is the fast-control system
Term
Hormones
Definition
Chemical messengers that are released into the blood
Term
Hormones control several major processes such as:
Definition
Reproduction, Growth and development, mobilization of body defenses, maintenance of much of homeostasis, and the regulation of metabolism
Term
Hormones are produced by:
Definition
Specialized cells that secrete them into extracellular fluids
Term
Blood transfers hormones to ______ and these regulate _______
Definition
target sites; the activity of other cells
Term
Endocrinology
Definition
The scientific study of hormones and endocrine organs
Term
Hormones are classified chemically as:
Definition
Amino acid-based, Steroid, or Prostaglandins
Term
Amino acid-based hormones include:
Definition
Proteins, peptides, and amines
Term
Steroid hormones are made from
Definition
Cholesterol
Term
Prostaglandins hormones are made from:
Definition
Highly active lipids that act as local hormones
Term
Hormones on target cells or organs
Definition
Hormones that affect only certain tissues or organs
Term
Target cells must have:
Definition
Specific protein receptors. These fit together like 2 pieces of a puzzle
Term
What does hormone binding do?
Definition
Alters the cellular activity
Term
A hormone's relationship to its target cells resembles:
Definition
That of an enzyme to its substrate.
Term
Typically, hormones have one or more of the following effects:
Definition

Change plasma membrane permeability or membrane potential by opening or closing ion channels

Activate or inactivate enzymes

Stimulate or inhibit cell division

Promote or inhibit secretion of a product

Turn on or off transcription or certain genes

Term
Hormones act by 2 mechanisms
Definition
Direct gene activation, and second-messenger system
Term
Direct gene activation
Definition
Used by steroid hormones and thyroid hormone
Term
Second-messenger system
Definition
Used by protein and peptide hormones
Term
Steroid hormones diffuse through what?
Definition
The plasma membrane of target cells
Term
What does the hormone do as soon as it enters the cell?
Definition
It goes to and enters the nucleus
Term
Once inside the nucleus of a cell, the hormone does what?
Definition
It binds to a specific protein within the nucleus
Term
Hormone-receptor complex binds to:
Definition
Specific sites on the cell's DNA
Term
What must happen to transcribe messenger RNA?
Definition
Specific genes must be activated. after which new proteins are synthesized
Term
2nd messenger system: Hormone binds to a ____________ and then the activated receptor sets off a series of reactions that __________
Definition
membrane receptor; activates an enzyme
Term
2nd messenger system: Enzyme catalyzes a reaction that produces a second messenger molecule (known as ________________). This also oversees additional intracellular changes to promote __________
Definition
Such as cyclic AMP or cAMP; a specific response in the target cell
Term
Negative feedback
Definition
The way hormone levels in the blood are maintained
Term
A stimulus or low hormone levels in the blood will trigger:
Definition
The release of more hormone
Term
Hormone release stops once:
Definition
An appropriate level in the blood is reached
Term
Hormonal, humoral, and neural
Definition
The 3 major categories of stimuli that activate endocrine glands
Term
Hormonal stimuli
Definition
Most common category of stimulus; endocrine organs are activated by other hormones; some examples include the hormones of the hypothalamus which stimulate the anterior pituitary to secrete its hormones
Term
Humoral stimuli
Definition
Changing blood levels of certain ions and nutrients stimulate hormone release; Humoral indicates various body fluids, such as blood and bile; Some examples include 1) Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels or 2) insulin is produced in response to changing levels of blood glucose levels
Term
Neural stimuli
Definition
Nerve fibers stimulate hormone release; most are under the control of the sympathetic nervous system; examples include sympathetic stimulation of the adrenal medulla to release epinephrine and norepinephrine
Term
The major Endocrine organs are:
Definition
Hypothalamus, pituitary gland, pineal gland, Thyroid gland, parathyroid glands, thymus, Adrenal glands, the pancreas, and the Gonads (testes and ovaries)
Term
Glands that have purely endocrine functions are
Definition
Anterior pituitary, thyroid, adrenals and parathyroids
Term
Endocrine glands are ______ glands. Hormones are released into ________
Definition
Ductless; blood or lymphs
Term
Glands that are considered mixed glands have what functions?
Definition
Endocrine and exocrine function (pancreas or gonads)
Term
Pituitary gland
Definition
Pea-shaped gland that hangs by a stalk from the hypothalamus in the brain; Protected by the sell turcica of the sphenoid bone; has 2 functional lobes (anterior pituitary (glandular tissue) and posterior (nervous tissue)); often called the "master endocrine gland"
Term
Sella turcica
Definition
 a saddle-shaped depression in the body of the sphenoid bone
Term
Posterior pituitary
Definition
Does not make the hormones it releases; Stores hormones made by the hypothalamus
Term
2 hormones released by the posterior pituitary gland:
Definition
Oxytocin, and Antidiuretic hormones (ADH)
Term
Oxytocin
Definition
Stimulates contractions of the uterus during uterus during labor, sexual relations, and breastfeeding; Causes milk ejection (let-down reflex) in a breastfeeding woman
Term
What do antidiuretic hormone do?
Definition
Inhibits urine production by promoting water reabsorption by the kidneys; urine volume decreases, blood pressure increases; In large amounts, causes constriction of arterioles, leading to increased blood pressure (the reason why ADH is known as a vasopressin), Alcohol inhibits ADH secretion
Term
Tropic hormone
Definition
Stimulate the function in endocrine glands
Term
The 6 anterior hormones are divided into 2 types which are
Definition
2 which affect non-endocrine targets and 4 which do affect endocrine targets
Term
2 hormones that affect non-endocrine targets
Definition
Growth hormone and Prolactin
Term
The 4 tropic hormones are
Definition
Follicle-stimulating hormone, Luteinizing hormone, Thyrotropic hormone, and Adrenocorticotropic hormone
Term
All anterior pituitary hormones have these properties:
Definition
They are proteins (or peptides); Act through second-messenger systems are regulated by hormonal stimuli; are regulated mostly by negative feedback
Term
Growth hormone
Definition
General metabolic hormone; Major effects are directed to growth of skeletal muscles and long bones; Plays a role in determining final body size; causes amino acids to be built into proteins; Causes fats to be broken down for a source of energy
Term
Prolactin (PRL)
Definition
Stimulates and maintains milk production following childbirth; function in males is unknown
Term
Gonadotropic hormones
Definition
Regulate hormonal activity of the gonads with the follicle-stimulating hormone and the luteinizing hormone
Term
Follicle-stimulating hormone (FSH)
Definition
Stimulates follicle development in ovaries; Stimulates sperm development in testes
Term
Luteinizing hormone (LH)
Definition
Triggers ovulation of an egg in female production in males; Stimulates testosterone
Term
Thyrotropic hormone (TH) also called Thyroid-stimulating hormone (TSH)
Definition
Influences growth and activity of the thyroid gland
Term
Adrenocorticotropic hormone (ACTH)
Definition
Regulates endocrine activity of the adrenal cortex
Term
Pineal Gland
Definition
Hangs from the roof of the third ventricle of the brain; Secretes melatonin
Term
What connection to the body does melatonin play?
Definition
Believed to trigger the body's sleep/wake cycle; also thought to coordinate the hormones of fertility in humans and inhibit the reproduction system until maturity occurs
Term
Thyroid Gland
Definition
Found at the base of the throat, inferior to the Adam's apple; consists of 2 lobes and a connecting isthmus; Follicles are hollow structures that store colloidal material; Produces Thyroid hormone and Calcitonin
Term
Thyroid hormone
Definition
Major metabolic hormone; controls rate of oxidation of glucose to supply body heat and chemical energy; Needed for tissue growth and development; Composed of 2 active iodine-containing hormones: Thyroxine (T4) and Triiodothyronine (T3)
Term
Thyroxine (T4)
Definition
Secreted by thyroid follicles
Term
Triiodothyronine (T3)
Definition
Conversion of T4 at target tissues
Term
Calcitonin
Definition
Decreases blood calcium levels by causing calcium deposition on bone; Antagonistic to parathyroid hormone; Produced by parafollicular cells found between the follicles
Term
Parathyroid glands
Definition
Tiny masses on the posterior of the thyroid; Secret parathyroid hormone (PTH)
Term
Parathyroid hormone function is:
Definition
Most important regulator of calcium ion (Ca^2+) homeostasis of the blood; Stimulates osteoclasts to remove calcium from bone; hypercalcemic hormone (which increase blood calcium levels); and it stimulates the kidneys and intestine to absorb more calcium
Term
Thymus
Definition
Located in the upper thorax, posterior to the sternum; Largest in infants and children; decreases in size throughout adulthood; Produces a hormone call thymosin
Term
Thymosin hormone
Definition
Matures some types of white blood cells; Important in developing the immune system
Term
Adrenal Glands
Definition
Sit on top of the kidneys and are divided into two regions: The adrenal cortex and the Adrenal medulla
Term
Adrenal cortex
Definition
Outer glandular region has 3 layers that produce corticosteroids: the mineralocorticoids, the glucocorticoids, and the sex hormones
Term
Mineralocorticoids (mainly aldosterone)
Definition
Are secreted by the outermost layer of the adrenal cortex; regulates mineral (salt) content in blood, particularly sodium and potassium ions; regulates water and electrolyte balance; target organ is the kidney
Term
Glucocorticoids (including cortisone and cortisol)
Definition
Are secreted by the middle layer of the adrenal cortex; promotes normal cell metabolism; help resist long-term stressors by increasing blood glucose levels (hyperglycemic hormone); Anti-inflammatory properties; Released in response to increased blood levels of the ACTH
Term
Sex hormones
Definition
Are secreted by the innermost layer of the adrenal cortex; small amounts are made throughout life; most of the hormones produced are androgens (male sex hormones), but some estrogens (female sex hormones) are also formed
Term
Adrenal medulla
Definition
Inner neural tissue region; Produces 2 similar hormones (catecholamines) which are epinephrine (adrenaline) and Norepinephrine (noradrenaline); These hormones prepare the body to deal with short-term stress (Fight or flight)
Term
Release of aldosterone is stimulated by:
Definition
Humoral factors (fewer sodium ions or too many potassium ions in the blood); hormonal stimulation (ACTH); Renin and angiotensin II in response to a drop in blood pressure
Term
Aldosterone production is INHIBITED by
Definition
Atrial natriuretic peptide (ANP), a hormone produced by the heart when blood pressure is too high
Term
How is the body changed when epinephrine is flooded into it?
Definition
Heart rate increases, as well as blood pressure and blood glucose levels; It dilates small passageways of the lungs
Term
Pancreas
Definition
Located in the abdomen, close to the stomach; Mixed gland with both endocrine and exocrine functions
Term
The pancreatic islets (islets of Langerhans) produce hormones
Definition
Insulin (Which is produce by beta cells) and Glucagon (which is formed by alpha cells); These hormones are antagonists that maintain blood sugar homeostasis
Term
Insulin
Definition
Released when blood glucose levels are high; Increases the rate of glucose uptake and metabolism by body cells; Effects of chemical are hypoglycemic
Term
Glucagon
Definition
Released when blood glucose levels are low; Stimulates the liver to release glucose to blood, thus increasing blood glucose levels
Term
What do the Gonads produce?
Definition
Sex cells and sex hormones; Ovaries for females and testes for males
Term
Ovaries
Definition
Female gonads located in the pelvic cavity; produce eggs; produce 2 groups of steroid hormones specifically Estrogen and progesterone
Term
Testes
Definition
Male gonads suspended outside the pelvic cavity; produce sperm and androgens such as testosterone
Term
Estrogens
Definition
Stimulate the development of secondary female characteristics; Mature the female reproductive organs; When combined with progesterone, it promotes breast development and regulates the menstrual cycle
Term
Progesterone
Definition
Acts with estrogen to bring about the menstrual cycle; Helps in the implantation of an embryo in the uterus; Helps prepare breasts for lactation
Term
Testosterone does what?
Definition
Responsible for adult male secondary sex characteristics; Promotes growth and maturation of male reproductive system; Required for sperm cell production
Term
Which non-endocrine organs secrete hormones?
Definition
Stomach, small intestine, kidneys, and the heart
Term
Placenta
Definition
Produced hormones that maintain pregnancy; some hormones play a part in the delivery of the baby; produces human chorionic gonadotropin (hCG) in addition to estrogen, progesterone, and other hormones
Term
Human placental lactogen (hPL)
Definition
Prepares the breasts for lactation
Term
Relaxin hormone
Definition
Relaxes pelvic ligaments and pubic symphysis for childbirth
Term
In the absence of disease and before old age:
Definition
Efficiency of the endocrine system remains high
Term
Decreasing function of female ovaries at menopause leads to:
Definition
Symptoms such as osteoporosis, increased chance of heart disease, and possible mood changes
Term
People are more prone to ______________________ with the advancing of age and the slowing of the endocrine system
Definition
Diabetes mellitus, immune system depression, lower metabolic rate, and higher rates of cancer in some areas more than others
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