Overview of endocrine system Flashcards
What are the endocrine glands of the body?
1) Hypothalamus (The Master Gland)
2) Pituitary gland
3) Pineal gland
4) Thyroid gland
5) Parathyroid gland
6) Adrenal gland
7) GI-Tract
8) Gonads (ovaries and testes)
What is a hormone?
- It is a regulatory chemical that is secreted into the blood by ductless endocrine glands
- They produce an effect in the target organs that have their specific receptors
- They are essential in maintaining homeostasis (metabolism, growth and development, water and electrolyte balance, reproduction and behavior)
What are the different types of hormones?
1) Endocrine (hormone travels to the target organ)
2) Neuroendocrine (epinephrine, ADH, Oxytocin, norepinephrine, where the neurons release those hormones into the blood)
3) Paracrine (The cell releases hormones into the interstitium to affect nearby cells like estrogen)
4) Autocrine (Cells release the hormone into the interstitium but the effect is on the same cell like IL-1) “when a cell releases a hormone or signaling molecule that binds to receptors on its own surface”
What are the hormones that are secreted by the hypothalamus?
1) TRH (thyrotropin-releasing hormone)
2) CRH (Cortisol releasing hormone)
3) GnRH (Gonadotropin releasing hormone)
4) GHRH (Growth Hormone Releasing Hormone)
5) GHIH (Growth hormone inhibiting hormone)
What is the function of the hormones produced by the hypothalamus?
- It controls the release of the anterior pituitary hormones
What are the hormones that are secreted by the posterior pituitary?
1) Anti-Diuretic Hormone
2) Oxytocin
What are the hormones released by the anterior pituitary?
1) Thyroid stimulating hormone (TSH)
2) Adrenocorticotropic hormone (ACTH)
3) GH: Growth Hormone
4) FSH: Follicle Stimulating Hormone
5) LH: Leutinizing Hormone
6) PRL: Prolactin
What is the action of the thyroid-stimulating hormone?
It stimulates the secretion of T3 &T4
What is the action of the adrenocorticotropic hormone?
It stimulates the secretion of cortisol
What are the actions of the FSH?
It promoted follicular growth and sperm production
What is the action of the luteinizing hormone?
1) Ovulation
2) Testosterone Secretion
What does the pineal gland secrete?
Melatonin (control the biological rhythm of the body)
What does the thyroid gland secrete?
1) T3 & T4
2) Calcitonin
What is the action of T3 & T4?
It increases the metabolic rate, necessary for normal growth and nerve development
What is the action of calcitonin?
It decreases the plasma concentration of calcium
What are the hormones that are secreted by the adrenal cortex?
1) Aldosterone
2) Cortisol
3) Androgens
What is the action of aldosterone?
It increases the reabsorption of Na and secretion of K
What is the action of cortisol?
It increases the blood level of glucose
What is the action of the androgens?
It promotes axillary and pubic hair growth
What are the hormones that are secreted by the pancreas?
1) Insulin
2) Glucagon
3) Somatostatin
What is the action of somatostatin?
It inhibits the digestion and absorption of nutrients
What hormone is secreted by the parathyroid gland?
1)PTH: Parathyroid hormone
What is the action of the parathyroid hormone?
Counteracts (calcitonin) as it increases the plasma concentration of Ca+2, decreases plasma phosphate, and stimulate vitamin D activation
What are the hormones that are secreted by the ovaries?
1) Estrogen
2) Progesterone
FSH and LH are a type of which hormones?
Gonadotropins
What are the hormones that are secreted by the testes?
Testosterone
What hormones are secreted by the Kidneys?
1) Renin
2) Erythropoietin
What hormones are secreted by the stomach?
1) Ghrelin
2) Gastrin
What is the action of progesterone?
Prepares the body for pregnancy
What are the hormones that are secreted by the placenta?
1) Estrogen
2) Progesterone
- the above two prepare the breast and for maintaining the pregnancy
3) hCG (Maintains corpus luteum)
What is the action of estrogen?
It promotes the development of the follicle, secondary sex characteristics, uterine and breast growth, and the closure of the epiphyseal plate
What is the action of Ghrelin?
Stimulates appetite
What is the action of gastrin?
Controls motility and secretions
What are the hormones that are secreted by the small intestine?
1) CCK: Cholecystokinin
2) GIP: Gastric Inhibitory Polypeptide
3) Peptide YY3-36
What is the action of cholecystokinin?
Control the motility of the S.I and its secretions
What is the action of Gastric Inhibitory polypeptide (GIP)?
Stimulation of insulin
What is the action of polypeptide YY3-36
It suppresses the appetite (counteracts Ghrelin)
What hormone is secreted by the liver?
1) IGF-1: Insulin-Like growth factor
2) Hepcidin
3) Thrombopoietin
What is the action of the IGF-1?
pROMOTES GROWTH
What is the action of Hepcidin?
It inhibits iron absorption into the blood
What is the action of Thrombopoietin?
It increases the platelet production
What hormone is secreted by the Skin?
Vitamin D
What hormone is secreted by the thymus?
Thymosin
What is the action of thymosin?
It enhances T-lymphocyte proliferation and function
What hormone is secreted by the heart?
ANP
What hormone is secreted by the adipose tissue?
Leptin
What is the action of Leptin?
It suppresses the appetite counteracting ghrelin, and acting along with peptide YY3-36
- IT ALSO HAVE A ROLE IN INITIATING PUBERTY
What is the chemical nature of the hormones?
1) Peptide and protein hormones
- > 100 amino acid = Proteins
- < 100 amino acids = Polypeptides
- Most hormones are proteins
2) Steroid Hormones
3) Amine Hormones
- We need to know which hormone is which, and for that, we will memorize the last two and whatever is left is a peptide/protein hormone
What are the characteristics of peptide and protein hormones?
1) They are synthesized as prohormones (allows them to be stored) which will then convert to prehormones which will convert to a hormone
2) They are stored in membrane-bound granules and released by exocytosis
3) They circulate in the blood unbound and they are relatively polar, with shorter half-lives as they can be degraded by enzymes found in the blood
4) Digested by the GI tract and thus they cannot be administered orally
5) They have a cell membrane receptor
What are the examples of steroid hormones?
- Monkeys Go South To Find Calcitriol
1) M: Mineralocorticoids (Aldosterone)
2) G: Glucocorticoids (Cortisol)
3) S: Sex hormones (Androgens)
4) T: Testosterone
5) F: Female hormones (Progesterone and estrogen)
6) C: Calcitriol
What are the characteristics of steroid hormones?
1) Derived from cholesterol (that are in the blood and intra-cellular)
2) Fat soluble, No cell receptor as they can cross the cell membrane, rather they have an Intracellular receptor
3) They are not stored in the endocrine gland like the peptide/protein
4) They are non-polar, and thus circulate as a protein-bound in blood meaning a longer half-life
5) It can be administered orally as they are absorbed by the GI
What are the amine hormones?
- Derived from tyrosine
1) T3 & T4 (not water soluble like steroids)
2) NE, & EPI (water-soluble like peptide and proteins)
What are the characteristics of the amine hormones?
1) Derived from tyrosine
2) Thyroid hormone is stored in thyroglobulin, released in the bloodstream and transported through the thyroxine-binding globulin
3) Cathecolamines are stored in vesicles and released by exocytosis, they are found in blood either conjugated or free
How are water-soluble hormones transported in the blood?
- Peptide and catecholamines (NE & EPI)
They are dissolved in the plasma and transported, they then reach the target tissues, diffuse out of the capillaries into the interstitium, and then the target cells
How are STEROID HORMONES TRANSPORTED IN THE BODY?
- Steroid and thyroid
They circulate in the blood as bound to plasma proteins (less than 10% exist free) they cannot diffuse easily out of the capillaries, and thus they are inactive until they dissociate from the plasma proteins
- Bound hormones serve as a reservoir and have a slow clearance
What controls the clearance rate of hormones?
1) Rate of hormone secretion into the blood
2) Rate of the removal of the hormone from the blood
What is meant by the metabolic clearance rate?
- The number of milliliters of plasma cleared of hormone per minute (rate of disappearance of the hormone from the plasma/concentration of hormone)
What are the different ways by which the hormones are cleared from the body?
1) Metabolic destruction
2) Binding with tissue
3) Excreted by the liver in bile
4) Excreted by the kidney in the urine
5) Degraded by blood enzymes
Describe the general anatomy of the pituitary
The hypothalamus is connected to the pituitary through the infundibulum
- We have an anterior pituitary which is derived from the adenohypophysis (pharyngeal epithelium)
- We have a posterior pituitary which is derived from the neurohypophysis (extension of the hypothalamus)
What is the relationship between the hypothalamus and the posterior pituitary gland (neurohypophysis)?
- The posterior pituitary does not synthesize hormones, but it stores and releases them (oxytocin & ADH) which are produced by the neurosecretory cells of the hypothalamus in the peraventricular and supraoptic nuclei
- These hormones are produced in the hypothalamus and travels along the axons reaching the axon terminal in the posterior pituitary where they are stored in the form of a vesicle until they are needed
Which nuclei produced oxytocin?
The paraventricular nuclei
Which nuclei produce ADH?
The supraoptic nuclei
Describe the structure of the vascular link between the hypothalamus and the anterior pituitary
- Hypothalamic-Hypophyseal portal system (the way by which the anterior pituitary communicates with the hypothalamus)
1) The neurosecretory neurons in the hypothalamus secrete releasing and inhibiting hormones which will first reach the median eminence “connection between the base of the hypothalamus and the ant. pituitary” into the portal system
2) After it reaches the portal system it goes to the cells of the anterior pituitary, which will in turn respond to the hormonal stimulus
3) The produced hormone will then be carried by the capillaries of the anterior pituitary and into the systemic venous blood
- The major effect of the hormones produced by the hypothalamus on the ant. pituitary are stimulatory except for prolactin which is mainly inhibitory (Dopamine “pih”)
What are the hypothalamic and ant.pituitary hormones that control the breast?
- Hypothalamic hormones:
1) Dopamine (Prolactin Inhibitory Hormone)
2) Prolactin Releasing Hormone
- Anterior Pituitary:
1) Prolactin
What are the hypothalamic and ant.pituitary hormones that control the Thyroid gland?
- Hypothalamic hormones:
1) Thyrotropin-releasing hormone (stimulates the release of TSH and Prolactin)
- Anterior Pituitary:
1) Thyroid Stimulating Hormone
- The thyroid stimulating hormone will stimulate the thyroid gland to release T3 & T4
What are the hypothalamic and ant.pituitary hormones that control the adrenal cortex?
- Hypothalamic hormone
1) Corticotropic releasing hormone (CRH)
- Anterior pituitary hormone:
1) Adrenocorticotropic hormone (ACTH)
- ACTH will then stimulate the adrenal cortex to release cortisol
What are the hypothalamic and ant. pituitary hormones that control the Liver?
- Hypothalamic hormones
1) Growth Hormone Releasing Hormone
2) Growth Hormone Inhibitory Hormone
- Anterior pituitary:
- Growth Hormone
- GH will then go and act on the liver to release Insulin-Like growth factors
What are the hypothalamic and ant.pituitary hormones that control the endocrine cells of the gonads?
- Hypothalamic hormones
1) GnRH (Gonadotropin-releasing Hormone)
- Anterior pituitary
1) Follicle Stimulating Hormone (FSH “gonadotropin”)
2) Leutinizing Hormone (LH “gonadotropin”)
- These hormones will go into the endocrine cells of the gonads and release: 1) Androgens, 2) Estrogen and progesterone, which will go to the germ cells of the gonads
What is the function of TSH?
- TSH, AKA Thyrotropes
- It increases the metabolic rate by stimulating the release of T3 and T4 from the thyroid gland
What is the function of the ACTH?
- ACTH, AKA Corticotropes
- They stimulate the adrenal cortex to release cortisol, which has metabolic actions and responds to stress
What is the function of Somatotropes?
- Growth Hormone, AKA somatotropes
1) It will stimulate the liver to release IGF-1 which will stimulate the growth of the bone and soft tissues
2) It can stimulate and inhibit the adipose tissue, liver, and muscles, which will have a metabolic action
What is the function of Gonadotropes?
- Gonadotropes, AKA LH and FSH
- They will stimulate the gonads in males and females, stimulating the release of sex hormones and production of gamete
What is the function of lactotropes?
- Lactotropes, AKA Prolactin
- They will stimulate the mammary glands to produce milk, and grow in size
How is the hormone secretion regulated?
- To maintain a normal level of hormones, the secretion rate is adjusted either neurally (AP to adrenal medulla where it will secrete Epi and NE, or stress will release CRH which will release ACTH which will release Cortisol) or by feedback mechanisms
- The feedback mechanisms can either be negative or positive feedback and they are the most important ones for hormone regulation
- We also have a humoral mechanism where ion levels in the blood control the secretion of hormones (due to low Ca2+ in the blood the parathyroid gland will secrete PTH)
What is meant by negative feedback and what are its types?
- The response of a hormone action will directly or indirectly inhibit the further secretion of the hormone (self-limiting)
1) Long-loop feedback (hormones of the adrenals inhibiting the pituitary or the hypothalamus)
2) Short-loop feedback (hormones from the pituitary inhibiting the hypothalamus)
3) Ultrashort-loop feedback (hormone of the hypothalamus regulating itself)
What is meant by positive feedback?
When the response of a hormone causes more secretion of the hormone (self-augmented effect) like:
1) Dilation of the cervix during labor (oxytocin loop)
What are the different patterns of hormone secretions?
1) Continuous
- T3, T4 (Amine hormone)
- Very little variation throughout the day
2) Intermittent
- Glucocorticoid (Cortisol levels are highest during the morning)
- Gonadotropin (pulsatile release which is important for the release of LH and FSH, continuous administration of GnRH does not increase the production of LH and FSH)
- LH & FSH
- Their levels change without a biological clock
What is an acidophilic tumor?
- A tumor that originates from the somatotropes (GH) releasing lots of GH
- Called acidophilic as they can take acidic dye
