Flashcards in A&P Chapter 17 Endocrine System Deck (55):
Describe the Endocrine System, how does it affect the bodies tissues/cells?
The Endocrine system is comprised of ISOLATED organs and tissues which secrete chemical messengers (hormones) into the BLOOD which causes changes in cells and tissues (TARGETS) elsewhere in the body.
All cells are exposed to hormones but not all cells are affected by them, they MUST HAVE RECEPTOR SITES FOR A PARTICULAR HORMONE TO BE AFFECTED, THEY MUST BE A TARGET.
Explain how Endocrine glands communicate with cells/tissues.
Endocrine glands are DUCTLESS so they must secrete their hormones into rich networks of capillaries which then carry the hormone quickly through the blood to target cells/tissues.
What are the three major chemical groups of the Endocrine System?
Peptides, Amines and Steroids.
They are chains/rings of Amino Acids. Peptides are smaller than proteins. They have DISULFIED bonds affecting their 3-D shape (conformation)
Insulin, Oxytocin, and Antidiuretic Hormone are examples of Peptides.
They are SMALL molecules containing one or more amine group. An Amine group will be NH IF it's followed by a Carbon group or NH2 if it is not.
Epinephrine, Norepinephrine and Dopamine are all examples of Amines.
Steroids are formed from the lipid cholesterol by adding specific side chains.
Progesterone, Estradiol, Cortisol and Aldosterone are examples of Steroids.
Explain how the Nervous system and the Endocrine system are similar but different.
The nervous system uses Hormones for Neurotransmitters, they are released into the synaptic cleft and affect a target cell or neuron. This activation/stimulation happens in a fraction of a second and can be controlled VERY precisely, it's effect however is not very long lasting. The nervous system can be VERY targeted and affect a very precise area or cells.
The endocrine system secretes hormones into the blood stream where it is distributed throughout the body, it's effects can last over a much longer period of time and can affect large areas of the body. It is not as fast acting as the Nervous system and it is not always as precise with regards to it's ability to target specific cells/tissues.
The nervous system and endocrine system work together in some situations, the nervous system can begin affecting a target cell/tissue quickly while the endocrine system is preparing to affect the same cell/tissue over a longer period of time.
What changes can hormones produce?
They can stimulate or inhibit cell differentiation, cell division, protein synthesis and secretion. They can also activate or deactivate enzymes. They can also change the permeability of the plasma membrane.
What are the three types of receptors?
Transmembrane proteins: They travel all the way through the plasma membrane.
Glycoproteins: Carbohydrates attached to proteins in the plasma membrane.
Glycolipids: Carbohydrates attached to Lipids in the plasma membrane.
How can the effect of a hormone on a target cell be increased or decreased?
1. Changing the amount of Hormone in the bloodstream.
2. Changing the # of receptors which the target cells have for the hormone.
3. Changing the specificity and affinity which these receptors have for the hormone.
When a cell adds more receptors to it's plasma membrane in response to fewer hormone circulating in the blood stream to maintain the same affect on the cell.
When a cell removes receptors from it's plasma membrane in response to an increase in a hormone circulating in the blood stream to maintain the same effect on the cell.
What are the MAJOR Endocrine hormones?
Hypothalamus, Pituitary gland, Pineal gland, Thyroid gland, Parathyroid glands, Thymus gland, Adrenal glands, Pancreas and the Gonads (Ovaries and Testes)
Describe the Pituitary Gland
It's also known as the Hypophysis. It's located in the Sella Turcica of the Sphenoid bone. It has two developmentally AND functionally different parts both of which are under direct control from the Hypothalamus.
There is an ANTERIOR Pituitary (Adenohypophysis) gland and a POSTERIOR Pituitary Neurohypophysis gland.
The anterior pituitary is controlled by a portal system of capillaries while the posterior secretes hormones that arise as neurotransmitter from neurons originating in the Hypothalamus.
Describe the Anterior Pituitary Gland
Also called the Adenohypophysis. It did not originate as a part of the brain as the Posterior Pituitary did.
It is regulated by a portal system from the Hypothalamus, RELEASING FACTORS secreted from the hypothalamus travel through capillaries in the hypothalamus to capillaries in the Anterior pituitary gland causing a release of hormones by the Ant. pituitary.
It secretes 6 PEPTIDE hormones.
What is the portal system between the Hypothalamus and the Anterior Pituitary called?
The Hypothalamic-Hypophyseal Portal Vein.
What are the 6 Peptides secreted by the Anterior Pituitary gland?
Growth Hormone (GH)
Thyroid Stimulating Hormone (TSH)
Adrenocorticotropic Hormone (ACTH)
Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
What is the major function of Growth Hormone (GH)?
Stimulates the growth of many organs.
What is the major function of Thyroid Stimulating Hormone (TSH)?
Stimulates the Thyroid Gland to secrete its hormones.
What is the major function of Adrenocorticotropic Hormone (ACTH)?
Stimulates the adrenal cortex to secrete its hormones.
What is the major function of Prolactin (PRL)?
Stimulates the production of milk by mammary glands.
What is the major function of Follicle Stimulating Hormone (FSH)?
Stimulates the development of egg/sperm.
What is the major function of Luteinizing Hormone (LH)?
Stimulates the testes to produce testosterone and it stimulates the follicle of the ovary to change to the Corpus Luteum.
Describe the Posterior Pituitary Gland:
Also known as the Neurohypophysis. It secreted 2 Peptide Hormones but unlike the Anterior Pituitary gland its hormones are really neurotransmitter that gets released from the axons of neurons that originate in the hypothalamus and run through the hypothalamic-hypophyseal tract to the posterior pituitary gland.
The axons end in the posterior pituitary gland and release their hormone into the capillaries found there.
What are the Hormones secreted by the Posterior Pituitary gland?
Oxytocin (OT) and Antidiuretic Hormone (ADH)
What is the major function of Oxytocin (OT)?
It stimulates the contraction of smooth muscle in breasts (for lactation) and uterus (to aid in labor).
It is also associated with orgasm, love and emotions.
What is the major function of Antidiuretic Hormone (ADH)?
It increases the absorption of water in the kidneys to concentrate urine and decrease it's volume. Ultimatly it changes the permeability of the cells in renal ducts.
Diabetes Insipitus results from a lack of ADH which results in no control over the permeability which results in over urination and dehydration.
Describe the Thyroid gland:
It's located in the neck anterior to the trachea.
It secretes 2 similar AMINE hormones and 1 Peptide Hormone.
Triiodothyronine and Tertraiodothyronine are the AMINE hormones and Calcitonin is the Peptide Hormone.
The secretory cells for T3 and T4 are arranged in hollow spheres called FOLLICLES, they are stimulated by THYROID STIMULATING HORMONE from the ANTERIOR PITUITARY.
The cells that secrete Calcitonin are regulated by the concentration of Calcium in the blood.
What are the major functions of Triiodothyronine (T3) and Tetraiodonthyronine (T4)?
They increase the metabolic rate of cells throughout the body by stimulating energy production by the mitochondria of the cells.
What are the major functions of Calcitonin (CT)?
It stimulates Osteoblast activity resulting in the additional storage of calcium in the extracellular matrix of bone thus LOWERING the calcium level in the blood.
It also inhibits Osteoclast activity thus preventing calcium from being reintroduced into the blood stream and overall helping to keep the blood calcium level low.
Describe the Parathyroid Glands:
Four-Eight small glands on the POSTERIOR surface of the Thyroid gland.
They secrete 1 Peptide hormone called Parathyroid Hormone (PTH).
What is the major function of Parathyroid Hormone (PTH)?
Parathyroid Hormone increases the concentration of calcium in the blood.
It stimulates osteocytes and osteoclasts to reabsorb calcium from the deposited bone matrix thus raising levels in the blood.
It also inhibits the Kidneys from losing calcium through the urine.
Describe the Adrenal Glands:
They are located in the abdomen superior to the kidneys.
Each Adrenal Gland is actually TWO distinct glands. The outer gland is called the adrenal cortex and it completely surrounds the inner gland called the Adrenal Medulla.
Describe the Adrenal Medulla
It is actually a ganglion (collection of neural cell bodies or somas) of the sympathetic division of the autonomic nervous system. There are no axons off these cell bodies instead the neurotransmitters are released into capillaries.
The secretory cells of the Medulla are stimulated by PRE-GANGLIONIC sympathetic neurons and they secrete 2 related AMINE hormones called Catecholamines they are Epinephrine and Norepinephrine.
Since Epinephrine and Norepinephrine are the neurotransmitters normally secreted by the POST-Ganglionic neurons of the sympathetic division they produce all of the effects of sympathetic nerve stimulation on various organs. This results in a 2 phased stimulation, sympathetic neurons stimulate target cells and then the Medulla of the Adrenal glands secrets the hormone over a longer time frame.
Describe the Adrenal Cortex
It secrets more than twenty different steroid hormones collectively called the CORTICOSTEROIDS.
The secretory cells of the cortex are arranged in three concentric layers, each layer produces a specific GROUP of CORTICOSTEROIDS.
From superficial to deep they are the Zona glomerulosa, the Zona fasciculate and the Zona reticularis.
What are the three layers of the Adrenal Cortex (Starting Deep to Superficial) and what group of hormones do they secrete?
Zona Reticularis: Gonadocorticoids
Zona Fasciculata: Glucocorticoids
Zona Glomerulosa: Mineralocorticoids
Describe Gonadocorticoids, Where are they secreted?
They are sex hormones which supplement those secreted by the testes and ovaries. They produce Androgens (Male Hormones) and some Estrogens and Progesterone (Female Hormones). The most common is Dehydroepiaandrosterone and Testosterone.
They are secreted by cells in the Zona Reticularis layer of the Adrenal Cortex.
Describe Glucocorticoids, Where are they secreted?
They regulate metabolism in many cells by: A. Stimulating the Breakdown of Fat. B. Stimulating the Breakdown of Proteins and C. Increasing the concentrations of fatty acids, amino acids and glucose in the blood (A direct result of A and B). They also stimulate the REPAIR OF DAMAGED TISSUES.
The most common Glucocorticoids are Cortisol and Corticosterone. Cortizone is a hormone made in the lab which is more potent than these.
They are secreted from cells in the Zona Fasciculata of the Adrenal Cortex.
Describe Mineralocorticoids, Where are they secreted?
They regulate concentrations of various minerals, ions and electrolytes in the blood by controlling their retention and removal by the kidneys.
The Most common Mineralocorticoid is Aldosterone which regulates Na+ and K+ in your blood. it exchanges 1 for the other in the kidneys. If you get rid of Na+ you keep more K+ and visa versa.
They are secreted from cells in the Zona Glomerulosa in the Adrenal Cortex.
Describe the Pancreas
It is located in the abdomen posterior and inferior to the stomach. The body of the pancreas is anterior to the aorta and inferior vena cava. The tail of the pancreas extends to the left.
It is primarily an exocrine gland. 98-99% of the pancreas has nothing to do with hormones, it makes digestive enzymes, however it has endocrine cells (1% Pancreatic Islets, Alpha and Beta cells) embedded within non-endocrine tissues.
It secretes 2 PEPTIDE hormones, Insulin and Glucagon. Which are antagonistic to each other in regulating blood glucose.
Describe the Pancreatic Islets
Comprise ~1% of the cells in the pancreas. They consist of 2 cells, Alpha cells produce Glucagon and Beta cells which produce Insulin.
What do Alpha Cells of the Pancreatic Islets do?
They produce GLUCAGON. They are stimulated by low blood sugar and they cause an increase in blood sugar by increasing Glycogen storage breakdown. This is an increase in Gluconeogenesis which turns broken down amino acids into glucose.
What do Beta Cells of the Pancreatic Islets do?
They produce INSULIN. They are stimulated by an increase in blood sugar, insulin is released and a decrease in blood sugar occurs due to increased GLYCOGEN (sugar storage in liver/skeletal muscle) synthesis.
Describe Diabetes Mellitus:
It has two forms:
Insulin Dependant (TYPE 1): Beta cells are destroyed by the bodies immune system and you can't produce enough insulin. This is an autoimmune disease.
Non-Insulin Dependant (TYPE 2): Beta cells still produce insulin but the insulin is defective and cant act on target cells OR target cells are defective and can't recognize the insulin. This second scenario is the most common where the target cells have downregulated their receptor sites so far that they ignore the insulin.
Describe Alpha and Beta cells as it relates to HYPERGLYCEMIA:
In Hyperglycemia the Beta cells are not producing enough insulin and/or Alpha cells are producing too much glucagon.
Describe Alpha and Beta cells as it relates to HYPOGLYCEMIA:
In Hypoglycemia the Beta cells are producing too much insulin and/or the Alpha cells are not producing enough glucagon.
Where are the SEX STEROIDS produced?
In the Gonads, the Testes and Ovaries and to a lesser extent in the Adreneal Glands.
Describe the Testes as an Endocrine Gland.
The INTERSTITAL Cells of the testes produce Androgens, mostly testosterone. The INTERSTITIAL Cells are stimulated by LUTEINIZING HORMONE secreted by the Anterior Pituitary gland.
Causes the development of male sexual characteristics and their maintenance.
What are INTERSTITIAL CELLS? Where are they found? What do they produce? What needs to happen for them to produce this?
They are the cells that produce Androgen hormones, primarily testosterone. They are found in the Testes in males. They need the ANTERIOR PITUITARY GLAND to secrete LUTEINIZING hormone to stimulate the secretion of Androgens.
Describe the Ovaries as an Endocrine Gland.
As an egg develops it is surrounded by FOLLICULAR CELLS which produce estrogens, primarily ESTRODIAL. These cells are stimulated by FOLLICLE STIMULATING HORMONE from the ANTERIOR PITUITARY GLAND. This causes the development of female sexual characteristics and prepares the uterus for pregnancy and the breasts/mammary glands for lactation.
AFTER ovulation the FOLLICULE changes to the CORPUS LUTEIUM. The corpus lutetium produces PROGESTERONE. The Corpus Luteium is stimulated by LUTEINIZING HORMONE secreted from the ANTERIOR PITUITARY GLAND. This maintains the thick lining of the uterus needed for pregnancy.
What hormones do the Kidneys produce?
Renin (Blood Pressure)
Erythropoietin (RBC development)
Calciferol (Blood Calcium)
What hormone does the Heart Produce?
Atrial Natriuretic Hormone (Blood Sodium)
What hormone does the Liver produce?
Angiotensin (Blood Pressure)
What hormone does the Thymus produce?
Thymopoietin (Lymphocyte Development)