Chapter 18: Endocrine System

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Compare the Nervous system, and the Endocrine system.

Nervous: electrical signals, very fast, very short in duration, and targets specific areas
Endocrine: chemical messenger (hormone), slow, but long in duration, targets many regions of the body at once


What kind of feedback system controls the endocrine system?

A Negative feedback system.
-brings it back down to normal


What is a Hormone?

A mediator molecule released in one part of body to control another part (by binding to receptor cells)


What organs are apart of the endocrine system?

Hypothalamus, Thymus, Pancreas, Ovaries, Testes, Kidneys, Stomach, Liver, Small Intestine, Skin, Heart, Adipose and Placenta


Circulating Hormones

The most common kind of hormones; they pass into interstitial fluid and then blood; these hormones are inactivated by the liver
-They affect other parts of the body than that of which they are produced in (due to the travel in the interstitial fluid)


Local Hormones

Act on neighboring cells (paracrines) or on the same cell that secreted in (auocrines); these are inactivated quickly
-produced in the same part of the body that they affect


What are Lipid-soluble Hormones?

Include steroids, thyroid hormones and NO.
-Steroid Hormones: have a ringed nucleus and are derived from cholesterol
-Thyroid Hormones: (T3 and T4) are derived from iodine and the amino acid, tyrosine (thyroid will swell up without iodine)
-NO: (nitric oxide) a hormone and neurotransmitter


What are Water-soluble Hormones?

Include amine hormones, peptide hormones, and eicosanoid hormones
-Amines: formed from modified amino acids include epinephrine, norephinephrine, dopamine, histamine, serotonin, and melatonin
-Peptide hormones: amino acid polymers; they include ADH, oxytocin, and HGH, and insuline, and TSH
-Eicosanoid hormones: derived from arachidonic acid, a 20 carbon fatty acid, and include prostaglandins (local) and leukotrienes (circulating)


What are the actions of Lipid-soluble hormones?

-lipid-soluble hormones diffuse from the blood through interstitial fluid into cell
-in the target cell, they bind and activate membrane receptors which turn on or off SPECIFIC genes int he DNA
-DNA is transcribed; mRNA directs protein synthesis at ribosome
-new proteins alter the cell's activity and cause the response typical of the hormone

All of this cause something in te cell to change and alter the body in some way.


What are the actions of Water-soluble hormones?

-water-soluble hormones bind to integral transmembrane proteins in the plasma membrane because they are unable to pass through the membrane
-this action activates a number of enzymes inside the cell to accomplish the effects of the specific hormone

AKA: they will bind to the cell membrane, and will then produce a lot of enzymes that will do the job of the hormone


What is the Anterior Pituitary connected to?

the Hypothalamus (which is nervous tissue)
-the hypothalamus also regulates the anterior pituitary by releasing INHIBITING and RELEASING hormones, which reach the anterior pituitary via the hypophyseal portal system (part of circulatory system)


Where are the hormones secreted by the hypothalamus secreted from, and what do they do?

-They are secreted by neurosecretory cells near the optic chiasma of the brain
-They are INHIBITING and RELEASING hormones


What kind of hormones does the pituitary glad secrete?

-these affect specific glands that may then secrete something else.


Compare the Anterior Pituitary and the Posterior Pituitary

Anterior Pituitary:
-"master gland"
-produce and secrete hormones
Posterior Pituitary:
-produces NO hormones
-like a storage unit for the ones made by the hypothalamus (oxytocin and ADH)
- it stores and releases when the hypothalamus tell it to do so, but DOES NOT synthesize any hormones



Growth Hormone-Releasing Hormone
-stimulates release of growth hormone (HGH) by anterior pituitary



Growth Hormone Inhibiting Hormone
-inhibits release growth hormone by anterior pituitary
-inhibiting secretion of TSH by anterior pituitary



Thyrotropin-Releasing Hormone
-stimulates release TSH (thyroid stimulating hormone) by anterior pituitary



Gonadotropin Releasing Hormone
-stimulates release LH (luteinizing hormone) and FSH (follicle strimlating hormone) by anterior pituitary



Prolactin-Releasing Hormone
-stimulates secretion of Proactin



Prolactin-Inhibiting Hormone is Dopamine
-inhibits secretion prolactin by anterior pituitary



Corticotrophin-Releasing Hormone
-stimulates secretion of ACTH (adrenocorticotropic hormone), MSH (melanocyte-stimulating hormone) by the anterior pituitary


Describe the two hormones stored in the Posterior Pituitary.

Oxytocin-OT: contraction of the uterus during delivery, ejection of milk from breasts
Antidiuretic-ADH; vasopressin: decreases urine protection; causes water retention; increase blood volume and blood pressure


What are the functions of the Thyroid hormones?

-regulating basal metabolism
-regulating body temperature

All of this is done through Follicles.


What are the two types of cells that are in the sacs of the Follicles that are apart of the Thyroid hormones?

Follicular: produce T4 and T3 (thyroid hormones). These help to regulate metabolism
Parafollicular: c cells, produce calcatonin which regulates calcium level homeostasis by decreasing the number and activity of osteoclasts thus decreasing Ca levels. (AKA: the production of calcitonin which lowers Ca levels in the blood)


Where is the Parathyroid Gland located?

On the posterior surface of the thyroid.


What cells produce Parathyroid Hormone (PTH)?

Chief Cells produce parathyroid hormone (PTH)


What are the function of the Parathyroid Gland?

-functions to increase number and activity of osteoclasts
-causes reabsorption of Ca+, HPO4-2 into blood from bones
-increases rate Ca+2, Mg+2 reabsorbed from urine to blood
-inhibits reabsorption HPO-2 from kidneys; it is excreted as an antagonist to calcitonin
-promotes fromation-calcitriol, an active form of vitamin D, which increases absorption Ca+2, Mg+2, HPO4-2 from GI tract


What is the outer region of the Adrenal gland called?

the Cortex


List the layers of the Adrenal glands from outermost to innermost.

Zona Glomerulosa
Zona Fasciculata
Zona Reticularis


What does the Zona Glomerulosa layer of the Adrenals secrete and what is this layer's purpose?

-it secrets mineralocorticoids
-Aldosterone: increase kidney reabsorption of Na+; water follows as well as Cl-, and HCO3-; increases excretion K+, H+ from kidneys (where salt goes, water follows)


What does the Zona Fasciculata layer of the Adrenals secrete and what is this layer's purpose?

-secretes glucocorticoids, cortisol, cortisone, and corticosterone
-regulates increased metabolism and resists stress; and has an anti-inflammatory effect and reduces immune response


What is the role of the Zona Reticularis region of the Adrenals?

-Androgens: male sex hormones
-dehydroepiandrosterone (DHEA) exerts mascullinizing effects


What is the inner region of the Adrenals?

the Medulla
-a modified sympathetic ganglion of the autonomic n.s.


Describe the cells, hormones, and the controls of the Medulla of the adrenals.

-Chromaffin cells are the hormone-producing cells
-Epinephrine and Norepinephrine (hormones) are produced in a rapid response (fight of flight)
-control: the Hypothalamus stimulates preganglionic neurons which stimulate chromaffin cells to secrete epinephrin and norepinephrine


What two functions of the Pancreas have?

Exocrine and endocrine functions


Name the four Pancreatic Islets.

-Alpha: secrete glucagons to raise blood glucose when it is low, by accelerating breakdown glycogen and fats into glucose
-Beta: secretes insulin to lower blood glucose when it is high, by accelerating transport glucose into cells; excess glucose converted to glycogen which is stored in the liver
-Delta: somatostatin; GHIH, which inhibits secretion insulin and glucagons; and inhibits absorption nutrients into GI tract
-F Cells: pancreatic polupeptide; inhibits secretion of somatostatin (GHIH); inhibits contraction of gall bladder; inhibits pancreatic digestive enzymes


What hormones do the Ovaries produce?

1) Estrogen and Progesterone: function to regulate reproductive cycle, maintain pregnancy, produces secondary sex characteristics
2) Relaxin: during pregnancy provides flexibility to pubis symphysis and causes dilation of the cervix
3) Inhibin: inhibits FSH (follicle stimulating hormone) from anterior pituitary AKA: stops production of eggs


What hormones do the Testes produce?

1) Tesosterone: functions in spermatogenesis, provides male secondary sexual characteristics
2) Inhibin: inhibits secretion of FSH AKA: stops the production of sperm


Describe where the Thymus is located and what is its function.

-the Thymus is located behind the sternum and between the lungs
-its function is Immunity
-the thymus gets smaller with age