Ch 16: The Endocrine System Flashcards
What is the basic characteristics of the endocrine?
- Acts with the nervous system
- Hormones are transported in the blood
- Response slower but longer lasting
What is endocrinology?
The study of hormones and endocrine organs
What does the endocrine control and integrates?
- Reproduction
- Growth and development
- Maintenance of electrolyte, water, and nutrient balance of blood
- Regulation of cellular metabolism and energy balance
- Mobilization of body defenses
What the difference between exocrine and endocrine glands?
- Exo: Nonhormal such as sweat and saliva have ducts
2. Endo: Produces hormone and lack 🦆
List the major endocrine organs and describe their body locations.
- Pituitary
- Thyroid
- Parathyroid
- Adrenal
- Pineal
- Hypothalalus
What is a hormone?
Long-distance chemical signals that travel in blood or lymph
What are autocrines?
Chemicals that exert effects on same cells that secrete them
What are paracrines?
Locally acting chemicals that affect cells other than those that secrete them
Out of hormones, autocrines, and paracrines, which are not part of the endocrine system?
Autocrine and paracrine are local chemical messengers
What are the 2 classes of hormones?
- Amino acid-based hormones
2. Steroids
What are examples of amino acid-based hormones?
Amino acid derivatives, peptides, and proteins
What are example of steroid hormones?
- Produced from cholestrol
2. Gonadal and adrenocortical hormones
What are target cells?
Tissues with receptors for specific hormone
Hormone action on target cells can cause?
- Alterations in plasma membrane permeability
- Membrane potential by oening or closing ion channels
- Stimulate synthesis of enzymes or other proteins
- Activate or deactivate enzymes
- Indoce secretory activity
- Stimulate mitosis
What would water soluble hormones achieve?
- Consist of all amino acid based hormones other than thyroid)
- Act on plasma membrane receptors via G proteins and secondary messengers
- Can’t enter the cell
What are some secondary messengers?
- cAMP
- cGMP
- PIP2
What is an example of a hormone acting on a receptor without the help of secondary messengers?
Insulin receptor is tyrosine kinase enzyme that autophosphorylates upon insulin binding.
What would lipid-soluble hormones achieve?
- Act on intracellular receptors that directly activate genes.
- Require a transport protein for transport in the watery environment of the blood.
- Can enter cell
Explain how hormone release is regulated.
- Blood levels of hormones are controlled by negative feedback system
- Blood levels have a narrow and desirable range
What are the 3 factors of target cell activation?
- Blood levels of hormones
- Relative number of receptors on or in target cells
- Affinity of binding between recpetor and hormone
What is up-regulation?
Target cells form more receptors in response to low hormone levels
What is down-regulation?
Target cells lose receptors in response to high hormone levels
Where are ACTH receptors found?
Certain cells of the adrenal cortex
Where are thyroxin receptors found?
Nearly all cells of body
What kind of stimulus would stimulate hormone release?
- Humoral
- Neural
- Hormonal
What happens as a result oh humoral stimuli?
Changing blood levels of ions and nutrients directly stimulating hormonal secretion
What is an example of humoral stimuli?
- Declining blood Ca2+ concentration stimulates parathyroid glands to secrete PTH.
- PTH causes Ca2+ concentrations to rise and stimulus is removed
What happens as a result of neural stimuli?
Nerve fibers stimulate hormone release
What is an example of neural stimuli?
Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines
What happens as a result of hormonal stimuli?
Hormones stimulate other endocrine organs to release hormones
What is an example of hormonal stimuli?
- Hypothalamic hormones stimulate release of anterior pituitary hormones.
- Anterior pituitary hormones stimulate targets to secrete still more hormones.
Describe the Hypothalamic-pituitary-target endocrine organ feedback loop
Hormones from final target organs inhibit release of anterior pituitary hormones
What overrides normal endocrine controls?
The nervous system
Where are hormones found?
- Circulating in the blood free or bound
2. Steroid and thyroid hormones are attached to the plasma membrane
How is a reflection of the concentration of circulating hormones?
- Rate of release
2. Speed of inactivation and remval from the body
How are hormones removed from the blood?
- Degrading enzymes
- Kidneys
- Liver
What is a half-life?
Time required for hormone’s blood level to decrease by half
What are the different types of onset action of hormone activity?
- Some responses are immediate
- Some (steroid) are hours to days
- Some are activated by target cells
What happens when there is limited duration of action?
- 10 seconds to several hours
- Effects may diasppear as blood levels drop
- Some persist at low blood levels
What are the 3 interactions of hormones with target cells?
- Permissiveness
- Synergism
- Antagonism
What does it mean for a hormone to be permissible?
One hormone can’t exert its effects without another hormone being present
What does it mean for a hormone to be synergized?
More than one hormone produces same effects on target cells causing amplification
What does it mean for a hormone to be antagonistic?
One or more hormones oppose action of another hormone
What are the 2 lobes of the pituitary?
- Posterior: neural tissue
2. Anterior: glandular tissue
Describe the structure of the posterior pituitary
- Posterior pituitary and hypothalumus are neurally connected by the hypothalamic-hypophyseal tract
- Hypothalamus synthesizes oxytocin and antidiuretic hormone
- These hormones are stored in posterior pituitary
What are the functions of oxytocin release?
- Strong stimulant of uterine contraction
- Released during childbirth
- Hormonal trigger for milk ejection
- Acts as neurotransmitter in brain
What are the functions of ADH release?
- Inhibits or prevents uring formation
- Regulates water balance
- High concentrations of ADH cause vasocontriction
- Targets kidney tubules → reabsorb more water.
- Release also triggered by pain, low blood pressure, and drugs.
What occurs during diabetes insipidus?
ADH deficiency due to hypothalamus or posterior pituitary damage
Must keep well-hydrated
What occurs during syndrome of inappropriate ADH secretion (SIADH)?
- Retention of fluid, headache, disorientation
2. Fluid restriction, blood sodium level monitoring
How does the hypothalamus connect to the anterior pituitary?
Hypophyseal portal system
What is the purpose of the Hypophyseal portal system?
Carries releasing and inhibiting hormones to anterior pituitary to regulate hormone secretion
How is the anterior pituitary secretion regulated?
- 5 releasing and 2 inhibiting hormones in the hypothalamus stimulate/inhibit their secretion.
- Negative feedback via hormones released by target glands decreases secretion of three types of hormones
What are the hormones found in the anterior pituitary gland?
- Growth hormone (GH)
- Thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Follicle-stimulating hormone (FSH)
- Lutenizing hormone (LH)
- Prolactin (PRL)
Which hormone of the anterior pituitary gland does not activate cAMP?
GH
Which of the anterior pituitary hormone are tropic?
- TSH
- ACTH
- FSH
- LH
What is a tropic hormone?
Regulate secretory action of other endocrine glands
What is the function of GH?
Stimulates secretion of insulin-like growth factors (IGFs) that promote growth
How does GH directly affect metabolism?
Increases blood levels of fatty acids and glucose by glycogen breakdown (anti-insulin)
How does GH indirectly affect growth?
Mediates growth via growth-promoting proteins insulin-like growth factors (IGFs)
How are IGFs stimulated?
- Increased protein synthesis; cell growth and proliferation.
- Formation of collagen and deposition of bone matrix.
What are the target cells for GH?
Bone and skeletal muscle
How are GH chiefly regulated?
Hypothalamic hormones
What stimulates the release of GH?
GHRH
What inhibits the release of GH?
GHIH
What is ghrelin?
The hunger hormone that also stimulates GH release
What caused by the hypersecretion of GH?
- Adults: acromegaly
2. Children: gigantism
What caused by the hyposecretion of GH?
Pituitary dwarfism
What is the function of TSH?
Stimulates synthesis and secretion of thyroid hormones by the thyroid gland
What hormone activates the release of TSH?
Thyrotropin-releasing hormone
How is TSH inhibited?
Rising blood levels of thyroid hormon that act on pituitary and hypothalamus
What is the function of FSH?
Stimulates gamete production and Ovaries initiate development of oocytes; testes initiate development of spermatozoa
What is the function of LH?
Promotes production of gonadal hormones
How are gonadotropin release regulated?
- Triggered by gonadotropin-releasing hormone (GnRH) during and after puberty.
- Suppressed by gonadal hormones (feedback).
What is the function of PRL?
Stimulates breast growth, and development of the mammary glands
What regulates PRL release?
Prolactin-inhibting hormone (PIH) dopamine
What is caused when PRL is hypersecreted?
Causes inappropriate lactation, lack of menses, infertility in females, and impotence in males
What is the function of ACTH?
Stimulates release of mineralocorticoid, glucocorticoid, and androgen hormones from the adrenal cortex
What hormone regulates ACTH release?
Hypothalamic corticotropin-releasing hormone (CRH)
What is the function of MSH?
Stimulate the production and release of melanin by melanocytes in skin and hair. MSH signals to the brain have effects on appetite and sexual arousal
What is the isthmus?
Two lateral lobes connected by median mass
What types of glycoprotein is produced by follicles?
Thyroglobulin
What is a colloid?
Fills lumen of follicles and is precursor of thyroid hormone
What do parafollicular cells produce?
Calcitonin
What is the difference between T4 and T3?
- T4 (thyroxine); has 2 tyrosine molecules + 4 bound iodine atoms
- T3 (triiodothyronine); has 2 tyrosines + 3 bound iodine atoms
What element is essential for TH synthesis?
Iodine
What are the functions of thyroid hormones?
- Major metabolic hormone
- Increases metabolic rate and heat production
- Regulation of tissue growth and development
- Maintenance of blood pressure
How are T3 and T4 transported?
Thyroxine-binding globulins (TBGs)
Describe the negative feedback regulation of TH release
- Rising TH levels provide negative feedback inhibition on release of TSH
- Hypothalamic thyrotropin-releasing hormone (TRH) can overcome negative feedback during pregnancy or exposure to cold
What is hyposecretion of TH in adults?
Myxedema, goiter if due to lack of iodinie
What is hyposecretion of TH in children?
Cretinism
What is hypersecretion of TH?
Grave’s disease
What cells would produce calcitonin?
Parafollicular (C) cells
What is the antagonist of PTH?
Calcitonin
What occurs when someone has high levels of calcitonin?
- Inhibits osteoclast activity and release of Ca2+ from bone matrix.
- Stimulates Ca2+ uptake and incorporation into bone matrix.
What is the most important hormone in Ca2+ homeostasis?
PTH
What cells secrete PTH?
Parathyroid cells
What are the functions of PTH?
- Stimulates osteoclasts to digest bone matrix and release Ca2+ to blood.
- Enhances reabsorption of Ca2+ by kidneys.
- Promotes activation of vitamin D (by kidneys); increases absorption of Ca2+ by intestinal mucosa.
Describe the negative feedback control of PTH?
- Hypocalcemia
- PTH increase from parathyroid gland causing osteoclast, Ca2+, and activation of Vitamin D increase
- Increase in Ca2+ in blood
What occurs during hyperparathyroidism?
- Caused by tumors
- Bones soften and deform
- Elevated Ca2+ depresses nervous system and contributes to formation of kidney stones
What occurs during hypoparathyroidism?
- Caused by gland trauma or removal, or dietary magnesium deficiency
- Tetany, respiratory paralysis, death
What is the difference between adrenal cortex and medulla?
Medulla: nervous tissue; part of sympathetic nervous system
Cortex: 3 layers of glandular tissue that synthesize and secrete corticosteroids
What are 3 layers of the adrenal cortex and what do they produce?
- Zona glomerulosa: mineralocorticoids
- Zona fasciculata: glucocorticoids
- Zona reticularis: gonadocorticoids
What is the primary functions of mineralocorticoids?
- Regulare electrolytes in ECF
- Importance of Na+: affects ECF volume, blood volume, blood pressure, levels of other ions
- Importance of K+: sets RMP of cells
What is considered the most potent mineralocorticoid?
Aldosterone
What does aldosterone stimulate?
Stimulates Na+ reabsorption and water retention by kidneys; elimination of K+.
What triggers aldosterone release?
- Decreasing blood volume and blood pressure.
2. Rising blood levels of K+.
Describe the Renin-Angiotensin-Aldosterone System (RAAS)
- Dehydration Na+ deficiency or hemmorhage
- Decreases in blood volume
- Decrease in blood pressure
- Juxtaglomerular cells of kidneys
- Increased renin
- Angiotensin is released by liver
- Renin converts angiotensin into Angiotensin II
- Angiotensin II is transferred to ACE
- ACE increases angiotensin II thats directed to the arterioles or adrenal cortex
- In the adrenal cortex increased aldosterone
- Increase Na+ and water reabsorption and increased secretion of K+ and H+ into urine
- Increased blood volume
- Vasoconstriction of arterioles and increased blood volume causes blood pressure increases
When would renin be released?
Low BP stimulates renal juxtaglomerular (JG) cells
What converts Angiotensin I to II?
Angiotensin converting enzyme (ACE)
What is the product for Angiotensin II?
Stimulates the adrenal cortex to secrete aldosterone
What are the mechanisms that influence aldosterone secretion?
- Renin-angiotensin-aldosterone mechanism: Decreased blood pressure stimulates kidneys to release renin → triggers formation of angiotensin II, a potent stimulator of aldosterone release
- Plasma concentration of K+: directly causes aldosterone release.
- ACTH: directly increases aldosterone during stress.
- Atrial natriuretic peptide (ANP): blocks renin and aldosterone secretion to decrease blood pressure.
What is aldosteronism?
- Hypersecretion due to adrenal tumors
- Hypertension and edema due to excessive Na+
- Excretion of K+ leading to abnormal function of neurones and muscles
What is the primary function of glucocorticoids?
- Keep blood glucose levels relatively constant
2. Maintain blood pressure by increasign action of vasoconstrictors
What are the glucocorticoid hormones?
- Cortisol
- Cortisone
- Corticosterone
What are the prime functions of cortisol?
- Prime metabolic effect is gluconeogenesis promoting the rise of blood glucose, fatty acids, and amino acids
- Enhances vasoconstriction → rise in blood pressure to quickly distribute nutrients to cells.
What is caused by hypersecretion of glucocorticoid?
Cushing’s syndrome
What is Cushing’s syndrome?
- Depresses cartilage and bone formation
- Inhibits inflammation
- Depresses immune system
- Disrupts cardiovascular, neural, and gastrointestinal function
What is caused by hyposecretion of glucocorticoid?
Addison’s disease
What is Addison’s disease?
- A deficiency in mineralocorticoids that causes decreases in glucose and Na+ levels
- Causes weight loss, sever dehydration, and hypotension
What are the contribution of gonadocorticoids?
- Onset of puberty.
- Appearance of secondary sex characteristics.
- Sex drive in women.
- Estrogens in postmenopausal women.
What is caused by hypersecrtion of gonadocorticoids?
Adrenogenital syndrome
How could adrenogenital syndrome effect males?
Reproductive organs mature; secondary sex characteristics emerge early.
How could adrenogenital syndrome effect females?
Beard, masculine pattern of body hair; clitoris resembles small penis
What are the effects of the adrenal medulla?
- Vasoconstriction
- Increased heart rate
- Increase blood glucose levels
- Blood diverted to brain, heart, and skeletal muscle
What cells synthesize epinephrine and norepinephrine?
Medullary chromaffin cells
What does epinephrine stimulate?
Metabolic activities, bronchial dilation, and blood flow to skeletal muscles and heart
What does the norepinephrine stimulate?
Peripheral vasoconstriction and blood pressure
What occur from the hypersecretion of adrenal catecholamines?
Hyperglycemia
What occur from the hyposecretion of adrenal catecholamines?
Nothing, adrenal catecholamines are not essential
What is the importance of the pineal gland?
Secretes melatonin
What does melatonin initiate?
- Timing of sexual maturation and puberty.
- Day/night cycles.
- Physiological processes that show rhythmic variations (body temperature, sleep, appetite).
- Production of antioxidant and detoxification molecules in cells.
Explain the differences between the exocrine and endocrine pancreas
- Acinar cells (exocrine) produce enzyme-rich juice for digestion.
- Pancreatic islets (islets of Langerhans) contain endocrine cells.
What is the difference between alpha and beta cells of the pancreas?
- Alpha: produce glucagon (hyperglycemic)
2. Beta: produce insulin (hypoglycemic)
What is the target cell for glucagon?
Liver
What are the effects of glucogon?
- Glycogenolysis – breakdown of glycogen to glucose.
- Gluconeogenesis – synthesis of glucose from lactic acid and noncarbohydrates.
- Release of glucose to blood
What are the effects of insulin?
- Lowers blood glucose levels by enhancing transport of glucose into fat and muscle cells and inhibiting glycogenolysis and gluconeogenesis
- Participates in neuronal development and learning and memory
How does insulin trigger enzymes in the cells?
- Increase glucose uptake (stored as glycogen in muscle).
- Catalyze glucose oxidation and ATP production.
- Convert glucose to fat (particularly in adipose tissue).
What factors inhibit insulin release?
- Elevated blood glucose levels.
2. Rising blood levels of amino acids and fatty acids. Acetylcholine/PNS
What factors inhibit insulin release?
Glucagon, epinephrine/SNS, growth hormone, thyroxine, glucocorticoids
What is caused from diabetes mellitus?
- Due to hyposecretion (type 1) or hypoactivity (type 2) of insulin.
- Glycosuria – glucose spilled into urine. Fats used for cellular fuel → lipidemia; if severe → ketones (ketone bodies) from fatty acid metabolism → ketonuria and ketoacidosis.
- Untreated ketoacidosis → hyperpnea; disrupted heart activity and O2 transport; depression of nervous system → coma and death possible.
What are the 3 cardinal signs of DM?
- Polyuria: huge urine output
- Polydipsia: excessive thirst
- Polyphagia: excessive hunger
What occurs during hyperinsulism?
- Excessive insulin secretion.
- Causes hypoglycemia.
- Low blood glucose levels.
- Anxiety, nervousness, disorientation, unconsciousness, even death.
- Treated by sugar ingestion
What produces steroid sex hormones?
Gonads
What do the ovaries produce?
Estrogen and progesterone
What is the purpose for estrogen?
- Maturation of reproductive organs.
- Appearance of secondary sexual characteristics.
- With progesterone, causes breast development and cyclic changes in uterine mucosa.
What does the placenta produce?
Estogen, progesterone, hCG
What is the purpose of testosterone?
- Initiates maturation of male reproductive organs.
- Causes appearance of male secondary sexual characteristics and sex drive.
- Necessary for normal sperm production.
- Maintains reproductive organs in functional state.
What is atrial natriuretic peptide (ANP)?
Decreases blood Na+ concentration therefore BP and blood volume
State the location of enteroendocrine cells.
GI tract
What kind of hormones are secreted by the enteroendocrine cells in the GI tract?
- Gastrin
- Secretin
- Cholecystokinin
- Serotonin
What is gastrin?
Stimulates the release of HCl
What is secretin?
Stimulates live and pancreas
What is cholecystokinin?
Stimulates pancreas, gallbladdeer, and hepatopancreatic sphincter
What is serotonin?
Acts as paracrine
What kind of hormones are secreted by the adipose tissue?
- Leptin
- Resistin
- Adiponectin
What does leptin secretion achieve?
Appetite control stimulating increased energy expenditure
What does resistin secretion achieve?
Insulin antagonist
What does adiponectin secretion achieve?
Enhances sensitivity to insulin
What kind of hormones are secreted by the kidney tissue?
- Erythropoietin: signals production of RBCs
2. Renin: initiates the renin-angiotensin-aldosterone mechanism
What kind of hormones are secreted by the thymus?
- Thymulin, thymopoietins, and thymosins.
- Involved in normal development of T lymphocytes in immune response.
- Classified as hormones; act as paracrines
What kind of hormones are secreted by the skeleton?
Osteocalcin: activates insulin
What kind of hormones are secreted by the skin?
Cholecalciferol: precursor of vitamin D
Describe the effects of aging on endocrine system function.
- GH levels decline: muscle atrophy
- TH levels decline: lowers basal metabolic rate increasing body weight
- PTH levels remain fairly constant with age
- Cortisol and aldosterone decline with age.
- Adrenal glands produce less cortisol and aldosterone.
- Pancreases releases insulin more slowly, and sensitivity to glucose declines
- Ovaries become unresponsive to gonadotropins
- Testosterone diminishes with age
Describe the general adaptation syndrome (GAS)
If stress is extreme, unusual, or long-lasting, normal mechanisms may not be enough
What is a stressor?
Any stimulus that produces a stress response
What is the alarm reaction?
- Short-lives “fight or flight” response of SNS
- Brings glucose and oxygen to the brain, lungs, and skeletal muscles.
- The RAAS is also activated to maintain blood volume and BP
What is the resistance reaction?
- Longer-lasting response initiated by hypothalamic releasing hormones
- High levels of cortisol and thyroid hormone assures that body tissues can sustain necessary metabolic needs.
What the exhaustion phase?
Body reserves become so depleted that they cannot sustain the resistance stage.
