Endocrine Organs and Hormones Flashcards
Hypothalamus
- the bridge between the nervous and endocrine system
- located in the forebrain above the pituitary gland and below the thalamus (hence the name hypothalamus)
- some parts respond to increased in blood osmolarity
- regulate appetite and satiety
Negative feedback
- regulates the release of hormones by the hypothalamus
- occurs when the final hormone (or product) of a pathway inhibits hormones (or enzymes) earlier in the pathway, maintaining homeostasis
Gonadotropin - releasing hormone (GnRH)
Promotes the release of follicle - stimulating hormone (FSH) and lutenizing hormone (LH)
Growth hormone - releasing hormone (GHRH)
Promotes the release of growth hormone
Thyroid - releasing hormone (TRH)
Promotes the release of thyroid - stimulating hormone (TSH)
Corticotropin - releasing factor (CRF)
promotes the release of thyroid stimulating hormone (TSH)
increases the level of cortisol being secreted into the blood
Prolactin - inhibiting factor (PIF or dopamine)
inhibits the release of prolactin
released by the hypothalamus
causes a decrease in prolactin secretion
Hypothalamus secretes compounds into the
hypophyseal portal system - which is a blood vessel system that directly connects the hypothalamus with the anterior pituitary
An alternative term for the pituitary is
Hypophysis
Hypothalamus releases what (5) hormones?
- Gonadotropin - releasing hormone (GnRH)
- Growth hormone - releasing hormone (GHRH)
- Thyroid - releasing hormone (TRH)
- Corticotropin - releasing factor (CRF)
Anterior pituitary releases what (7) hormones in response to the hypothalamus releasing hormones?
- Follicle - stimulating hormone (FSH) - tropic hormone
- Luteinizing hormone (LH) - tropic hormone
- Growth hormone (GH) - direct hormone
- Thyroid - stimulating hormone (TSH) - tropic hormone
- Adrenocorticotropic hormone (ACTH) - tropic hormone
- Prolactin - direct hormone
- Endorphines - direct hormone
Prolactin
- promotes milk promotion
- Secreted by the anterior pituitary
- has a decrease in secretion when dopamine is released from the hypothalamus
Follicle - stimulating hormone (FSH)
promotes the development of ovarian follicles in females and spermatogenesis in males
acts on the gonads - testes and ovaries
Luteinizing hormone (LH)
promotes ovulation in females and testosterone production in males
acts on the gonads - testes and ovaries
Growth hormone (GH)
- promotes growth of bone and muscle and shunts glucose to these tissues
- It raises blood glucose concentrations
- requires large quantities of glucose
Thyroid - stimulating hormone (TSH)
promotes synthesis and release of triiodothyronine and thyroxine from the thyroid
acts on the thyroid
Adrenocorticotropic hormone (ACTH)
promotes synthesis and release of glucocorticoids from the adrenal cortex
increases the level of cortisol being secreted into the blood
acts on the adrenal cortex
Endorphines
decreases perception of pain and cause euphoria
Anterior Pituitary
releases hormones in response to stimulation from the hypothalamus
4 Tropic hormones
3 Direct hormones
Hypothalamic (-) feedback mechanism
hypothalams – (CRF) –> Anterior Pituitary – (ACTH) –> Adrenal cortex – (cortisol) –>
Posterior pituitary releases two hormone produces in the hypothalamus:
Antidiuretic Hormone (ADH ro Vasopressin) Oxytocin
Oxytocin
- Secreted during childbirth
- Promotes milk ejection
- Stimulates contractions during labor
- Involved in bonding behavior
- Has a positive feedback look loop, not negative… (the release of oxytocin promotes uterine contraction, which promotes more oxytocin release, which promotes stronger contractions, and so on)
- Released by the Posterior pituitary
Antidiuretic Hormone (ADH ro Vasopressin)
- increases reabsorption of water in the collecting ducts of the kidneys
- secreted in response to low blood volume or increased blood osmolarity
- increases blood volume
- decreases blood osmolarity
- Released by the Posterior pituitary
Follicle - stimulating hormone (FSH) and Luteinizing hormone (LH) is stimulated by the release of
Gonadotropin - releasing hormone (GnRH)
Adrenocorticotropic hormone (ACTH) is stimulated by the release of
Corticotropin - releasing factor (CRF)
Thyroid - stimulating hormone (TSH) is stimulated by the release of
Thyroid - releasing hormone (TRH)
Growth hormone (GH) is stimulated by the release of
Growth hormone - releasing hormone (GHRH)
Thyroid is controlled by
the thyroid stimulating hormone
Thyroid has 2 major functions:
Setting basal metabolic rate and calcium homeostasis
Thyroid releases:
triiodothyronine (T3), thyrozine (T4) and calcitonin
triiodothyronine (T3) and thyrozine (T4)
- numbers 3 and 4 refers to the number of iodine atoms attached to the tyrosine
- produced by the iodination of the amino acid tyrosine int he follicular cells of the thyroid
- capable or resetting the basal metabolic rate of the body by making energy production more or less efficient, as well as altering the utilization of glucose and fatty acids
- increased amount of
Increased amount of T3 and T4 will lead to
cellular respiration
What prevents the excessive secretion of T3 and T4?
negative feedback
High plasma levels of thyroid hormones will lead to
decreased TSH and TRH synthesis
Thyroid is located at:
the base of the neck in front of the trachea; t produces 3 key hormones
Calcitonin
- produced by parafollicular (C) cells
- decreases plasma calcium concentration by (1)promoting calcium excretion in the kidneys, (2) decreasing the calcium absorption in the gut and (3) promoting calcium storage in the bone
Hypothyroidism
- caused by deficiency of iodine or inflammation of the thyroid
- thyroid hormones are secreted in insufficient amounts of not at all
- decreases body temp, slows down heart rate and respiratory, cold intolerance and weight gain
Hyperthyroidism
- an excess of thyroid hormone caused by a tumor or excess thyroid over stimulation
- increased body temp, increased heart rate and respiratory, heat intolerance and weight loss
C - cells
- Produced by the follicular cells
- produce calcitonin
- decreases plasma calcium levels in 3 ways:
increased calcium excretion from the kidneys
decreased calcium absorption from the gut
increased storage calcium in the bone - high levels of calcium in the blood stimulate secretion of calcium in the bone
Important functions of calcium:
- bone structure and strength
- regulation of muscle contraction
- clotting of blood (calcium is a cofactor(
Parathyroid Hormone (PTH)
- raises blood calcium levels
- decreases excretion of calcium by the kidneys
- increases absorption of calcium in the gut (via VitaminD)
- increases bone resorption
- subject to feedback inhibition
- overall effect: increase blood calcium levels with little effect on phosphate
As calcium levels INCREASE, PTH secretion is
DECREASED
PTH activates which vitamin?
vitamin D
Vitamin D is required for
the absorption of calcium and phosphate in the gut
PTH increases calcium levels, while calcitonin (decreases/increases) calcium levels
decreases
Adrenal Glands
- located on top of the kidneys
- consists of: a
cortex and a medulla
Adrenal Cortex secretes
corticosteroids
Corticosteroids are divided into 3 classes:
glucocorticoids
mineralcorticoids
cortical sex hormones
Glucocorticoids
- steroid that regulates glucose levels
- affect protein metabolism
- 2 Glucocorticoids: cortisol and cortisone: both raise glucose levels, decrease inflammation an immunologic responses
- Glucocorticoid release is under control of ACTH; CRF promotes the release of ACTH form the anterior pituitary
Cortisol
- is a Glucocorticoid
- stress hormone
- it is released in time of physical or emotional stress
- increases blood sugar
Mineralocorticoids
- used in salt and water homeostatis
- most profound effect are on the kidneys
- Aldosterone is a mineralocorticoid; it increases sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron
Aldosterone
- a mineralocorticoid
- increases sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron
- decreases reabsorption of Potassium and Hydrogen ions, promoting excretion in the urine
- under control of the Renin - Aniostensin - Aldosterone system
Renin - Angiotensin - Aldosteron System
RAA system
- Decrease in blood pressure causes the baroreceptors (juxtaglomerular cells) to secrete RENIN (enzyme)
- Renin: cleaves an inactive plasma protein, angiotensiongen to its active form angiotensin 1
- Antiotension 1 is then converted into Angeiotensin 2 by Antgiotensin converting enzyme (ACE) in the lungs
- Antiotension 2 stimulates the adrenal cortex to secrete aldosterone
- once blood pressure is restored, there is a decreased drive to stimulate renin release, therefore serving as a negative feedback
- the goal of this is to raise blood pressure
3 triggers of renin:
- decreased BP
- sympathetic Nerves
- low Sodium
Cortical Sex Hormones
- made by the adrenal glands
- consists of androgens and estrogens
3 functions of the corticosteroids: (3 S’s)
Salt (mineralocorticoids)
Sugar (glucocorticoids)
Sex (cortical sex hormones)
Adrenal Medula is responsible for which 2 sympathetic hormones:
epinephrine: causes a breakdown of glycogen to glucose
norepinephrine
Both:
- fall under the category of catecholamines
- increase heart rate
- dilate the bronchi
- alter blood flow to supply the system
Pancreas
- secrete both exocrine and endocrine functions
- From an endocrine standpoint:
small groups of hormone - producing cells are grouped together into islets of Lagerhands throughout the pancreas
Islets of Lagerhands contain 3 distinct types of cells:
alpha cells - which secrets: glucagon
beta cells - which secretes: insulin
delta cells - which secretes: somatostatin
Glucagon
- secreted by alpha cells in the Islets of Lagerhands
- secreted during times of fasting
- Glucagon levels are high when glucose is gone
- When blood glucose concentrations are high, glucagon release is inhibited
Insulin
- secreted by beta cells in the Islets of Lagerhands
- antagonist of glycogen
- secreted when blood glucose levels are high
- induced muscle and liver cells to take up glucose and store it as glycogen for later use
- because it is active when glucose levels are high, insulin stimulates anabolic processes such as fat and protein synthesis
Polyuria
increase frequency of urination
found in diabetics
Polydipsia
increased thirst
found in diabetics
Two types of diabetes mellitus
Type 1 (insulin dependent) Type 2 (non insulin dependent)
Type 1 Diabetes
- (insulin dependent)
- caused by autoimmune destruction of the beta cells of the - pancreas (beta cells secrete insulin)
- produce little or no insulin because the majority of the B cells have been destroyed
- require regular injection of insulin to prevent hyperglycemia and to permit entry of glucose into cells
Type 2 Diabetes
- (non insulin dependent)
- result of receptor - level resistance of the effects of insulin
- Type 2 diabetes mellitus is partially inherited and partially due to environmental factors (obesity, high carb diet)
Hypoglycemia
- caused by excess of insulin
- low blood glucose concentration
Hyperglycemia
- caused by not having enough insulin
- high blood glucose concentration
- can result in diabetes mellitus
Somatostain
- inhibitor of both insulin and glucagon secretion
- high blood glucose and AA concentration stimulate its secretion
- produced by the hypothalamus, where it function to decrease growth hormone secretion in addition to its effects on insulin and glucagon
Gonads
- Consist of the Testes and Ovaries
Testes
- part of the Gonads
- secrete testosterone to response to stimulation by gonadotropins (LH and FSH)
- Testosterone causes sexual differential of the male during gestation and promotes the development and maintenance of secondary sex characteristics of males (such as public hair and axillary, deepening of voice and muscle growth)
Ovaries
- part of the Gonads
- secrete estrogen and progesterone to response to stimulation by gonadotropins (LH and FSH)
- Estrogen is involved in development of the female reproductive system during gestation and also promotes the development and maintenance of secondary sex characteristics of males (such as public hair and axillary, breast growth and body fat redistribution)
- Estrogen and Progesterone govern the menstrual cycle and pregnancy
Pineal Gland
- located deep within the brain
- secretes hormone melatonin
- involved in circadian rhythms
- receives projections directly from the retina - but is not involved in vision
Erythropoitein
- produced by the kidneys
- stimulates bone marrow to increase production of erythocytes (RBC’s)
- secreted in response to low oxygen levels in the blood
Atrial natriuretic peptide (ANP)
- Hormone released by the heart
- help regular said and water balance
- is released when the cells in the atria are stretched from excess blood volume
- promotes excretion of sodium and therefore increases urine volume
- antagonistic to aldosterone because it lowers blood volume and blood pressure
Thymosin
- released by the thymus
- important for proper T - cell development and differentiation
