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136 Cards in this Set

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What does the endocrine system do?
It interacts with the nervous system to coordinate and integrate the activity of body cells.
What are hormones?
Chemical messengers released into the blood by the endocrine system to influence metabolic activity.Usually long distance messengers
Endocrinology is the study of ________________?
The scientific study of hormones and the endocrine organs.
Processes controlled by hormones are?
reproduction, growth, development, body defenses, electrolyte balance, water balance, and cell metabolism
Exocrine glands
Produce nonhormonal substances such as sweat and saliva; have ducts which are routed to the membrane surface
Endocrine glands
"ductless glands"
produce hormones and lack ducts; release hormones into surrounding tissue fluid
Endocrine glands include these?
pituitary, thyroid, parathyroid, adrenal, pineal, thymus glands, pancreas, testes, ovaries
along with its neural functions produces and releases hormones, considered a neuroendocrine organ
Chemicals that exert their effects on the same cells that secret them ex. prostaglandins
also act locally but affect cell types other than those releasing the paracrine chemicals
Hormones are classifed into two groups
Amino based
Steroid based
Amino based hormones
Molecule sizes varies, from simple (amines and thyroxine), to peptide chains, and proteins
Steroid based hormones
Synthesized from cholesterol,
Only gonadal and adrenocortical hormones are steroid based
include leukotrienes and prostaglandins. Are biologically active lipids and are released by nearly all cell membranes. Do not fit the criteria for true hormones since they affect only nearby cells.
Are signaling chemicals that mediate inflammation and some allergic reactions.
Have multiple targets and effects, ranging from raising blood pressure, increasing uterine contractions, and enhancing clotting, and pain.
Target cells
Certain tissue cells that a given hormone influences- by altering that cell's activity by decreasing or increasing the rates of normal cellular processes
Cell responses to hormone stimulation may include?
Changes in membrane permeability, enzyme synthesis, activation, or inhibition, secretory activity, gene activation, and mitosis
How do water soluble (all amino based hormones except thyroid hormone) hormones work?
By acting on receptors in the plasma membrane via G proteins to one on more intracellular second messengers which mediate the cell's response
How do lipid soluble (steroid and thyroid hormones) work?
They act on intracellular receptors, directly activating genes- since these can enter the cell being lipids
Cyclic AMP Signaling Mechanism
1. The hormone (acting as the 1st messenger) binds to its receptor
2. Hormone binding causes the receptor to change shape, allowing it to bind to a nearby inactive G-protein
3. The activated G-protein moves along the membrane and binds to the effector enzyme adenylate cyclase
4. If activated, adenylate cyclase generates the second messenger cAMP from ATP
5. cAMP is free to diffuse within the cell triggers chemical reactions
Protein kinases
Enzymes that add a phosphate group to various proteins which activates some proteins and inhibits others
PIP- Calcium Signal Mechanism
Intracellular calcium ions act as the final mediator, involves phosphatidyl inositol.
Is an important second messenger system
How do steroid hormones affect cells?
They enter their target cells and effect responses by activating DNA, which initiates messenger RNA formation leading to protein synthesis
Target cell activation by hormone-receptor interaction depends on?
1. Blood levels of the hormones
2. Relative numbers of receptors for that hormone on or in the target cells
3. Affinity (strength) of the bond between the hormone and the receptor
Hormone receptors
Are dynamic structures. Changes in number and sensitivity of hormone receptors may occur in response to high or low levels of stimulating hormones
Target cells form more receptors in response to rising blood levels of the specific hormones to which they respond
Loss of receptors and prevents the target cells from overreacting to persistently high hormone levels
Concentration of a circulating hormone depends on?
Its rate of release and the speed at which it is inactivated and removed from the body
Length of time for a hormone's blood level to be decreased by half. Water-soluble hormones exhibit the shortest half-lives
Situation when one hormone cannot exert its full effects without another hormone being present
Ex. Thyroid hormone is necessary for the timely development of reproductive structures along with the reprod. hormones
Situations when more than one hormone produces the same effects at the target cell and the combined effects are amplified
Ex. Glucagon and epinephrine cause the liver to release about 150% more when they act together
When one hormone opposes the action of another hormone
Ex. Insulin (lowers blood sugar)+ Glucagon (raises blood sugar)
Negative feedback system
Hormone secretion is triggered by some internal or external stimulation and as hormone levels rise, they cause target organ effects and inhibit further hormone release
Humoral Stimuli
Endocrine glands secrete their hormones in direct response to changing blood levels of certain critical ions and nutrients. The simplest of the endocrine control systems. Ex. PTH and calcium, insulin is also released in response to humoral stimuli
Neural Stimuli
Nerve fibers stimulate hormone release
Ex. SNS stimulation of the adrenal medulla to release norepinephrine and epinephrine during periods of stress
Hormonal Stimuli
Many endocrine glands release their hormones in response to hormones produced by other endocrine organs, the stimuli being hormonal stimuli
Ex. the hypothalamic-pituitary-target endocrine organ feedback loop p. 611
Nervous System Modulation
Both hormonal, humoral, and neural stimuli and feedback inhibition may be modified by the nervous system. Nervous system makes certain adjustments to maintain homeostasis by overriding endocrine controls
Pituitary Gland
located in sella turcica of the sphenoid bone, secretes at least 9 hormones, has two major lobes- one is neural the other is glandular
Posterior Pituitary
Composed of pituicytes (glia-like supporting cells and nerve fibers), releases neurohormones. Is a hormone storage area and not a true endocrine gland
hormones secreted by neurons
consists of the posterior lobe of the pituitary and the infundibulum
Anterior pituitary lobe
"adenohypophysis," composed of glandular tissue and it makes and releases a number of hormones
Hypothalamic-hypophyseal tract
a nerve bundle that runs through the infundibulum that connects the posterior lobe with the hypothalamus
Supraoptic and paraventricular nuclei
located in the hypothalamus, contain neurons that give rise to the hypothalamic-hypophyseal tract
What is the Primary capillary plexus?
located in the infundibulum, communicates inferiorly via the small hypophyseal portal veins with the secondary capillary plexus in the anterior lobe
Hypophyseal portal system
Consists of the primary and secondary capillary plexuses and the intervening hypophyseal portal veins
What does the hypothalamus do?
1. Regulates the hormonal output of the anterior pituitary via releasingand inhibiting hormones 2. Synthesizes two hormones that it exports to the posterior pituitary for storage and later release
Pro-opiomelanocortin (POMC)
an adenohypophyseal hormone, a large molecule that can be split enzymatically into one or more active hormones, the source of adrenocorticotropic hormone and melanocyte-stimulating hormone
Tropins or tropic hormones
includes 4 of the 6 anterior pituitary hormones- thyroid stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, and luteinizing hormone. They regulate the secretory action of the endocrine glands. All affect their target cells via a cyclic AMP second messenger system
Growth hormone (GH)
see p.618
anabolic hormone that stimulates growth of all body tissues especially skeletal and bone. GH mobilizes fats, stimulates protein synthesis, and inhibits glucose uptake and metabolism. Secretion is regulated by GH releasing hormone (GHRH) and GH inhibiting hormone (GHIH)
Hyposecretion of GH and Hypersecretion of GH results in what?
hypersecretion results in gigantism in kids and acromegaly in adults
hyposecretion in kids results in pituitary dwarfism
Thyroid-stimulating hormone (TSH)
chemical structure- glycoprotein, cell type- thyrotroph.
Promotes normal development and activity of the thyroid gland. TRH (thyrotropin releasing hormone) stimulates release and negative feedback loop of TH inhibits it
Hyposecretion and Hypersecretion of TSH
Hyposecretion results in cretinism in kids and myxedema in adults, hypersecretion results in hyperthyroidism similar to Grave's disease
Adrenocorticotropic hormone (ACTH)
chemical structure- polypeptide of 39 amino acids
cell type- corticotroph
Stimulates the adrenal cortex to release corticosteriods. ACTH release is triggered by corticotropin-releasing hormone (CRH) and inhibited by rising glucocorticoid levels
include the follicle-stimulating hormone (FSH) and luteinizing hormone (LH). They regulate the function of the testes and ovaries. Stimulated by the gonadtropin-releasing hormone (GnRH) and gonadal hormones feed back to suppress FSH and LH release
Produced by the lactotrophs, stimulates milk production. Prolactin-inhibiting hormone (PIH) known to be dopamine prevents prolactin secretion, whereas, prolactin-releasing hormone (PRH) stimulates release
Posterior pituitary hormones
stored hormones are the antidiuretic hormone and oxytocin
a strong stimulant of uterine contractions and milk ejection in women, its release is mediated reflexively by the hypothalamus and represents a positive feedback mechanism
Antidiuretic hormone (ADH)

stored in posterior pituitary, stimulated by impulses from hypothalamic neurons in response to increased osmolality of blood or decreased blood volume. Inhibited by adequate hydration of the body and by alcohol. Major affect- the kidney
Hyper and hyposecretion of ADH
hyposecretion= diabetes insipidus
hypersecretion= syndrome of inappropriate ADH secretion (SIADH)
Thyroid gland
butterfly shaped, located in the anterior neck, on the trachea just inferior to the larynx. Isthmus connects the 2 lateral lobes. Largest pure endocrine gland in the body.
Thyroid follicles
Store colloid containing thyroglobulin, a glycoprotein from which thyroid hormone is derived
Thyroid hormone
consists of 2 iodine containing amine hormones (thyroxine T4) and triiodothyronine (T3, affects every cell in the body except for the adult brain, spleen, testes, uterus, and the thyroid gland itself.
Calorigenic effect
TH's effect of increasing basal metabolic rate and body heat production
Thyroid hormone effects
Maintains blood pressure, regulator of tissue growth and development, critical for normal skeletal and nervous system development and maturation and for reproductive capabilities
Thyroid hormone synthesis
Begin when TSH secreted by the anterior pituitary binds to follicle cell receptors
Steps of thyroid hormone synthesis
1. Formation and storage of thyroglobulin 2. Iodine trapping 3. Oxidation to iodine and iodination 4. Coupling of T2 and T1 5. Colloid endocytosis 6. Cleavage of the hormones for release
hypothyroid syndrome, "mucous swelling" results in a goiter if caused by a lack of iodine
a polypeptide hormone produced by the parafollicular or C cells of the thyroid gland, most important effect is to lower blood Ca 2+ levels, is a direct antagonist of the parathyroid hormone. It inhibits osteoclast activity and it stimulates Ca2+ uptake and incorporation into bone matrix
Parathyroid glands
Located on the dorsal aspect of the thyroid gland, they secrete parathyroid hormone (PTH) which causes an increase in blood calcium levels by targeting bone, the intestine, and the kidneys, is the antagonist to calcitonin
PTH release
Is triggered by falling blood calcium levels and is inhibited by rising calcium levels
Hypersecretion and hyposecretion of PTH
Hypersecretion= hypercalcemia and all its effects and in extreme bone wasting
Hyposecretion= leads to hypocalcemia, evidenced by tetany and respiratory paralysis
Adrenal glands
Pyramid shaped organs perched atop the kidneys also known as the suprarenal glands, consists of the inner adrenal medulla and the outer adrenal cortex
Steroid hormones that are synthesized from cholesterol by the adrenal cortex
Zona glomerulosa
outer layer of the adrenal cortex, Cell clusters that produce the mineralocorticoids are hormones that help control the balance of minerals and water in the blood
Zona fasciculata
middle layer of adrenal cortex, produce the metabolic hormones called glucocorticoids
Zona reticularis
innermost layer of adrenal cortex, produce small amounts of adrenal sex hormones or gonadocorticoids
Regulate the electrolyte (mineral salt)concentrations in extracellular fluids, particularly of Na and K
The most potent mineralcorticoids, and accounts for 95% of the mineralcorticoids produced. Reduces excretion of Na+ from the body and enhances Na+ reabsorption from sweat, saliva, and gastric juice
Releasing and inhibiting of aldosterone
stimulated by the renin-angiotensin mechanism, rising potassium ion or falling sodium levels in the blood, and ACTH. Aldosterone is inhibited by atrial natriuretic peptide
Hyper and hypo secretion of aldosterone
Hypersecretion results in aldosteronism which causes hypertension and edema due to excessive Na+ and water retention and accelerated excretion of potassium ions
Hyposecretion results in Addison's disease.
Influence the energy metabolism of most body cells and help us to resist stressors. They keep blood sugar levels fairly constant, and maintain blood pressure by increasing the action of vasoconstrictors. Include cortisol, cortisone, and corticosterone. Only cortisol is secreted in significant amounts in humans. ACTH is the major stimulus for glucocorticoid release.
Cushing's syndrome
Most often caused by large doses of glucocorticoid drugs. Symptoms- hyperglycemia, losses in muscle and bone protein, water and salt retention, swollen face and buffalo hump.
Addison's disease
Major hyposecretory disease of the adrenal cortex, usually involves deficits in both glucocorticoids and mineralocorticoids
sex hormones, mainly androgens, are produced in small amounts throughout life
Adrenal medulla
Produces catecholamines (epinephrine and norepinephrine) in response to sympathetic nervous system stimulation. Its catecholamines enhance and prolong the fight or flight response to short term stressors. Hypersecretion leads to symptoms typical of sympathetic nervous system overactivity.
Mixed gland of both endocrine and exocrine gland cells, Acinar cells produce enzyme rich juice that is ducted into the small intestine during food digestion
Pancreatic islets (islets of Langerhans)
tiny cell clusters that produce pancreatic hormones. They contain two major types of hormone producing cells- alpha cells and beta cells
Alph and beta cells of the pancreas
Secrete glucagon and insulin appropriately during the fasting and fed states
Released by alpha cells,29 amino acid polypeptide, is a very potent hyperglycemic agent. Its major target is the liver where it promotes 1. Breakdown of glycogen to glucose
2. Synthesis of glucose from lactic acid and from noncarbohydrate molecules 3. Release of glucose to the blood by liver cells, which causes blood glucose levels to rise.
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. Hyposecretion of insulin results in diabetes mellitus. Symptoms are polyuria, polydipsia, and polyphagia.
A huge urine output that results in decreased blood volume and dehydration
Excessive thirst
Excessive hunger and food consumption
fatty acid metabolites, are organic acids. Blood pH drops when they accumulate in the blood= ketoacidosis
Produce steroid sex hormones, include the ovaries and testes
Produced in the ovaries, promote breast development, secondary sex characteristics, and cyclic changes in the uterine mucosa, work together with progesterone to establish the menstrual cycle
Produced by the testes, promotes maturation of the male reproductive organs, development of secondary sex characteristics, and production of sperm in the testes
Released in response to high blood levels of LH
Pineal Gland
Hangs from the roof of the third ventricle in the diencephalon. Its secretory cells are the pinealocytes. Secrete melatonin
Influences daily rhythms and may have an antigonadotropic effect in humans
Located in the upper thorax, declines in size and function as we age. Its hormones, thymosins, thymic factor, and thymopoietins, are important to the normal development of the immune response.
Other hormone producing structures
Heart- (atrial natriuretic peptide), gastrointestinal tract organs- (gastrin, secretin, and others), placenta- (estrogens and progesterones), kidneys (erythropoietin and renin), skin (cholecalciferol), and adipose tissue (leptin and resistin)
Endocrine glands origination
Are derived from all 3 germ layers. Those derived from mesoderm produce steroidal hormones, the others produce the amino acid- based hormones
The natural decrease in function of the female's ovaries during late middle age
Efficiency of endocrine glands as we age.
Efficiency seems to decrease gradually, leading to increase in incidence of diabetes and a lower metabolic rate
The Endocrine System
Works with Nervous System
Lacks anatomical continuity
Weighs less than a pound
Anterior Pituitary
GH Growth Hormone
PRO Prolactin
TSH Throid Stimulating Horm.
ACTH Adrenocorticotropic Hor
FSH Follice Stimulating Horm
LH Luteinizing Hormone
ICSH Interstitial cell stimulating Horm
Posterior Pituitary
Hormones produce by Hypothalamus
Anitdiuretic hormone
Endocrine Glands
-No ducts
-They secrete directly into body fluid
-Hormones typically circulate throughout the body
-There are exceptions
Other organs with Endocrice functions
small intestine
Significant things controlled by hormones
stress reactions
fluid/electrolyte balance
cellular metabolism
endocrine messages are in the form of chemicals called hormone
hormon - to excite
Chemistry of Hormones
all are organic
2 chemical groups
-amino acids/proteins - some are simply altered amino acids(adrenalin and thyroxin) others aer short(ADH) or long(insulin chains of amino acids
-Steroids -all are similar complex ring forms made from cholesterol. All sex hormones and all products of the adrenal cortex
Target Cells
Cell that react and have specific receptors for specific hormones
Mechanisms of Hormone Action
A hormone typically brings about one or more of these effects
-permeability changes
-protein synthesis
-enzyme activation/suppression
Hormone levels are usually controlled by
Negative Feedback Mechanisms
Diabetes Insipidus
Diabetes mellitus(DM)
-endocrine disorder of most concern
-syndrome:hyperglycemia, ketoacidosis or coma
-maybe as many as 5% in USA have DM
-3rd on the list of killer diseases
complications of DM
atherosclerotic coronary
peripheral arterial disease
peripheral and autonomic neuropathies
-usually young
-usually thin
-most serious
-only 5-10% or total
-prone to ketosis, microangiopathy, gangrene, blindness, impotence
-maybe autoimmune due to viral induce changes or molecular mimicry
-insulin injections are vital
-Usually mature
-80% are obese
-causes are genetic and or obestiy
-diet, exercise and or oral hypoglycemics are treatment for NIDDM
IGT Imparied Glucose Tolerance
Usually not serious
has been called borderline latent, chemical, symptomless
Gestational Diabetes GDM
80% become NIDDM within 20 years
The concept of stress is somewhat intangible; it is however related to any deviation from homeostasis
Specific stimuli lead to specific response
In stress type reactions this does not hold true
GAS General Adaptation Syndrome
the same syndrome of responses may occur regardless of the stress or the term used to describe these reponses
Things to mention when talking to a person who is distressed, depressed, or displeased with life
-liking oneself - min guilt
-doing stimulating things
-knowing oneself
-need for secure niche
-be good to others
-intimate relationship
-appreciation of simple things
-planning and preparing
-have enjoyable work
-not fighting with inevitable
We all need some stress but too much may lead to ...
allergic reations
heart attacks
nervous break down
Fators that may influence how one reacts to stressors include
past experience
Measurable stress has been noted in
test pilots
persons on death row
students taking test
THe hypothalamus monitors the body for stressors. In response it activates to mechanisms
1-the alarm reaction
2-resistance reaction
THe alarm reaction
-involves the sympathetic nervous system and the adrenal medulla
-SNS immediately speeds things up
-adrenalin prolongs SNS responses
The resistance reaction
-slower and more prolonged
-CRH stimulates anterior pituitary A.P. releases ACTH
-ACTH stimulates adrenal cortex
-A.C. releases cortisol and aldosterone
-body is supportd for increased activity over a period of time
Exhaustion Stage
follows prolonged stress
the body cannot continue indefinitely to work at high stress capacity
-cortisol level may be depleted
hypokalemia may lead to cell death
-organs may fatigue and fail