Chapter 18 - The Endocrine System Flashcards
Compare Nervous and Endocrine System?
Nervous and Endocrine Systems act together to coordinate all systems of the body
Nervous System:
Release Neurotransmitters that bind to receptors on Target Cells (specific)
Endocrine System:
Release Hormones (to excite), most circulate in blood and bind to receptors on Target Cells (specific)
What is Endocrine Secretions in General?
Endocrine secrete Hormones released by:
1- Endocytosis (in)
2- Exocytosis (out)
Hormones then go into Blood the Target Cells
ex:
Mitochondria - Metabolic rate
Lysosome - Secretion
Myosin Fibers - Contraction rate
Centriole - Mitotic rate
Cell Membrane - Polarity and permeability
What is the Molecule of Nervous vs Endocrine Systems?
Nervous:
Neurotransmitters released locally in response to nerve impulses
Endocrine:
Hormones delivered to tissues throughout body by blood
What is the Site of Action of Nervous vs Endocrine Systems?
Nervous:
Close to site of release, at synapse
Binds to receptors in postsynaptic membrane
Fast response
Highly specific
Endocrine:
Far from site of release (usually)
Binds to receptors on or in Target Cells
Delayed response
Better for slow responses
What is the Types of Target Cells of Nervous vs Endocrine Systems?
Nervous:
Muscle cells
Gland cells
Other neurons
Endocrine:
Cells throughout body
Many more than nervous
What is the Time to Onset of Action of Nervous vs Endocrine Systems?
Nervous:
Typically milliseconds
Very fast
Endocrine:
Seconds to hours or days
Very efficient but longer
What is the Duration of Action of Nervous vs Endocrine Systems?
Nervous:
Brief
Right away
Endocrine:
Longer
What is Exocrine Glands?
Exocrine Glands:
Secrete products into ducts
None are Hormones
Include:
1- Sudoriferous (Sweat) Glands
2- Sebaceous (Oil) Glands
3- Mucous Glands
4- Digestive Glands
5- Others throughout body
What is Endocrine Glands?
Endocrine Glands:
Secrete Hormones
Do not have ducts
They secrete Hormones directly into Interstitial Fluid that surrounds them
Hormones diffuse into Bloodstream through Capillaries and are carried to Target Cells throughout body
Include:
1- Pituitary Gland
2- Thyroid Gland
3- Parathyroid Gland
4- Adrenal Gland
5- Pineal Gland
What is Secreting Cells?
Secreting Cells:
Certain organs and tissues that are not part of the Endocrine System also secrete Hormones through their Secreting Cells
Secreting Cells can be found in:
1- Hypothalamus
2- Thymus
3- Pancreas
4- Ovaries
5- Testes
6- Kidneys
7- Stomach
8- Liver
9- Small Intestine
10- Skin
11- Heart
12- Adipose Tissue
13- Placenta
What is Target Cells?
Hormones traveling throughout body will only affect Target Cells that possess specific Protein Receptors for the Hormone
Receptors are continually being synthesized and broken down
Very divers
Very specific
On surface of Target Cells
(shape - specificity)
What is Down-Regulation?
Receptors may be Down-Regulated in presence of high concentration of Hormone
What is Up-Regulation?
Receptors may be Up-Regulated in presence of low concentration of Hormone
What is the Basic Pathway of Hormones?
Endocrine Cell release Hormones
Hormones go into Blood
Hormones travel in body
Hormones diffuse out of Blood Capillaries
Hormones bind to Receptors on Target Cells
What is Paracrine Hormones (Local Hormones)?
Paracrine Hormones affect neighboring Target Cells
What is Autocrine Hormones?
Autocrine Hormones affect the same cell that secreted them
What is Hormones’ Solubility Types?
Hormones are either:
1- Lipid-soluble
or
2- Water-Soluble
What is Lipid-Soluble Hormones?
Lipid-Soluble Hormones:
Circulate in blood bound to Transport Protein
Nonpolar
ex:
Steroid Hormones
Thyroid Hormones
Nitric Oxide
What is Water-Soluble Hormones?
Water-Soluble Hormones:
Circulate freely in Plasma
Polar
ex:
Amine Hormones
Peptide and Protein Hormones
Eicosanoid Hormones
What is Steroid Hormones?
Lipid-Soluble
(Fatty, non-polar)
1- Adrenal Cortex:
Aldosterone
Cortisol
Androgens
2- Kidneys:
Calcitriol (Active form of Vitamin D)
3- Testes:
Testosterone
4- Ovaries:
Estrogens
Progesterone
What is Thyroid Hormones?
Lipid-Soluble
(Gassy)
1- Thyroid Gland (Follicular Cells):
T3 (Triiodothyronine)
T4 (Thyroxine)
2- Endothelial Cells lining Blood Vessels:
Nitric Oxide (NO)
What is Amines?
Water-Soluble
(Amino group N, ex: NH2)
1- Adrenal Medulla:
Epinephrine
Norepinephrine (Catecholamines)
2- Pineal Gland:
Melatonin (sleep)
3- Mast Cells in connective tissues:
Histamine (allergies)
4- Platelets in blood:
Serotonin
What is Peptides and Proteins Hormones?
Water-Soluble
1- Hypothalamus:
All Hypothalamic Releasing and Inhibiting Hormones
2- Posterior Pituitary Gland:
Oxytocin
Antidiuretic Hormones (ADH)
3- Anterior Pituitary Gland:
Growth Hormone (GH)
Thyroid-Stimulating Hormone (TSH)
Adrenocorticotropic Hormone (ACTH)
Follicle-Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
Prolactin (PRL)
Melanocyte-Stimulating Hormone (MSH)
4- Pancreas:
Insulin
Glucagon
Somatostatin
Pancreatic Polypeptide
5- Parathyroid Glands:
Parathyroid Hormone (PTH)
6- Thyroid Gland (Parafollicular Cells):
Calcitonin
7- Stomach and Small Intestine (Enteroendocrine Cells):
Gastrin
Secretin
Cholecystokinin (CCK)
Glucose-Dependent Insulinotropic Peptide (GIP)
8- Kidneys:
Erythropoietin
9- Adipose Tissue:
Leptin
What is Eicosanoids?
Water-Soluble
1- All cells except RBC:
Prostaglandins
Leukotrienes
(Released everywhere except RBC)
How does Hormone Activity work?
Endocrine producing cells increase when they produce hormones
Affect Target Cell and Target organelle
Lipid-Soluble Hormone easily diffuse into membrane
Intracellular receptor
Receptor-hormone complex
nucleus
DNA
Affect gene to make DNA Transcription
mRNA
New proteins in cytosol
Alter cell activity
What is Mechanisms of Hormone Action?
Responses to the same hormone may vary depending on the hormone itself and the Target cell
Response may be:
1- Synthesis of new molecules
2- Changing permeability of the cell membrane
3- Stimulating transport of a substance into or out of the cell (ex: Insulin)
4- Altering rate of metabolic actions
5- Causing contractions of Smooth or Cardiac muscles
What is Mechanism of Lipid-Soluble Hormones Action?
1- Hormone bound to transport Protein in blood
2- Free hormone diffuses into cell
3- Binds to Intracellular Receptor
4- Activated Receptor-Hormone Complex alters gene expression
5- Newly formed mRNA directs synthesis of specific proteins on ribosomes
6- New proteins alter cells’ activity
What is Mechanism of Water-Soluble Hormones Action?
1- Free hormone travels in blood
2- Hormone binds to Receptor on surface of cell
3- Binding of hormone (First Messenger) to its receptor activates G Protein which activate Adenylyl Cyclase
4- Activated Adenylyl Cyclase converts ATP to cAMP (Second Messenger)
5- cAMP serves as Second Messenger to activate Protein Kinases
6- Activated Protein Kinases phosphorylate cellular proteins
7- Millions of Phosphorylated Proteins cause reactions that produce physiological responses
8- Phosphodiesterase inactivates cAMP
How does Target Cell Respond to Hormone?
Target Cell responds to hormone based on:
1- The hormone’s concentration in the blood
2- The number of hormone receptors on the Target Cell
3- Influences exerted by other hormones
4- Some hormones work more effectively when a second hormone is present to assist them (Synergistic Effect)
5- Some hormones oppose the action of other (Antagonistic Effect)
What is Control of Hormone Secretion?
Hormones are secreted in short bursts when needed
Secretion is regulated by:
1- Signals from the Nervous System
2- Chemical changes in the blood
3- Other Hormones
Most Hormone regulation is via Negative Feedback Loop
A few Hormone regulation via Positive Feedback Loop
ex:
1- Glucocorticoid level in blood decreases
2- Neurosecretory Cells in Hypothalamus increase Corticotropin-Releasing Hormone (CRH) and decrease Cortisol
3- Corticotrophs in Anterior Pituitary increase Adrenocorticotropic Hormone (ACTH)
4- Cells of Zona Fasciculata in Adrenal Cortex secrete Glucocorticoids
5- Increased level of Glucocorticoid in blood
What is Hypothalamus and Pituitary Gland?
Hypothalamus and Pituitary Gland work together to control other Endocrine Glands
Infundibulum:
Connects Hypothalamus to Pituitary Gland
What is Pituitary Gland?
Anterior Lobe: (Adenohypophysis)
75% of the weight
Secrete 7 Hormones
Posterior Lobe: (Neurohypophysis)
Made of neural tissue
Release 2 Hormones made by Hypothalamus
What is Hypothalamus?
Secrete Releasing and Inhibiting Hormones that control the release of hormones by the Pituitary Gland
They reach the Pituitary Gland via the Hypophyseal Portal System
What is Growth Hormone (GH)?
(Also called Somatostatin)
Secreted by:
Somatotrophs
Hypothalamic Releasing Hormone (stimulates secretion):
Growth Hormone-Releasing Hormone (GHRH)
Hypothalamic Inhibiting Hormone (suppresses secretion:
Growth Hormone-Inhibiting Hormone (GHIH)
What is Thyroid-Stimulating Hormone (TSH)?
(Also called Thyrotropin)
Secreted by:
Thyrotrophs
Hypothalamic Releasing Hormone (stimulates secretion):
Thyrotropin-Releasing Hormone (TRH)
Hypothalamic Inhibiting Hormone (suppresses secretion:
Growth Hormone-Inhibiting Hormone (GHIH)
What is Follicle-Stimulating Hormone (FSH)?
Secreted by:
Gonadotrophs
Hypothalamic Releasing Hormone (stimulates secretion):
Gonadotropin-Releasing Hormone (GnRH)
Hypothalamic Inhibiting Hormone (suppresses secretion:
N/A
What is Luteinizing Hormone (LH)?
Secreted by:
Gonadotrophs
Hypothalamic Releasing Hormone (stimulates secretion):
Gonadotropin-Releasing Hormone (GnRH)
Hypothalamic Inhibiting Hormone (suppresses secretion:
N/A
What is Prolactin (PRL)?
Secreted by:
Lactotrophs
Hypothalamic Releasing Hormone (stimulates secretion):
Prolactin-Releasing Hormone (PRH) - thought to exists but unknown
Hypothalamic Inhibiting Hormone (suppresses secretion:
Prolactin-Inhibiting Hormone (PIH) - which is Dopamine
What is Adrenocorticotropic Hormone (ACTH)?
(Also called Corticotropin)
Secreted by:
Corticotrophs
Hypothalamic Releasing Hormone (stimulates secretion):
Corticotropin-Releasing Hormone (CRH)
Hypothalamic Inhibiting Hormone (suppresses secretion:
N/A
What is Melanocyte-Stimulating Hormone (MSH)?
Secreted by:
Corticotrophs
Hypothalamic Releasing Hormone (stimulates secretion):
Corticotropin-Releasing Hormone (CRH)
Hypothalamic Inhibiting Hormone (suppresses secretion:
Dopamine
What Controls Secretions of Thyrotrophs, Gonadotrophs, and Cortictrophs?
Negative feedback loops
ex:
Hypothalamus secretes CRH
CRH stimulates release of ACTH in Anterior Pituitary
ACTH stimulates release of Cortisol by Adrenal Cortex
Elevated Cortisol inhibits release of CRH by Hypothalamic Neurosecretory Cells and ACTH by Anterior Pituitary Corticotrophs
What is the Most Plentiful Anterior Pituitary Hormone?
Human Growth Hormone (hGH)
Released in bursts every few hours by Somatotrophs
Their activity is controlled by 2 Hypothalamic Hormones:
GHRH and GHIH
What affects GHRH?
1- Hypoglycemia
2- Decreased blood levels of fatty acids
3- Increased blood levels of amino acids
4- Sympathetic activity
5- Deep sleep
6- Testosterone, Estrogens, Thyroid Hormones, and Ghrelin
Results in GH
Metabolic effects on cells
Insulin-Growth Factors (IGF)
Growth of bone, muscle, and other tissues
What affects GHIH?
1- Hyperglycemia
2- Increased blood levels of fatty acids
3- Decreased blood levels of amino acids
4- Obesity
5- Aging
6- High blood levels of GH and IGFs
Results in no GH
Which Hormones does Anterior Pituitary make?
GH
TSH
FSH
LH
PRL
ACTH
MSH
What is the Target Tissues and Principal Action of GH?
1- Target:
Liver
(other tissues)
2- Actions:
Stimulates liver, muscles, cartilage, bone, and other tissues to synthesize and secrete IGF
IGF promote growth of body tissues
GH acts directly on Target Cells to enhance lipolysis and decrease Glucose uptake
What is the Target Tissues and Principal Action of TSH?
1- Target:
Thyroid Gland
2- Action:
Stimulates synthesis and secretion of Thyroid Hormones by Thyroid Gland
What is the Target Tissues and Principal Action of FSH?
1- Target:
Ovary
Testes
2- Action:
Females:
Initiates development of Oocytes
Induce Ovarian secretion of Estrogens
Males:
Stimulates Testes to produce sperm
What is the Target Tissues and Principal Action of LH?
1- Target:
Ovary
Testes
2- Action:
Females:
Stimulates secretion of Estrogens and Progesterone
Stimulate ovulation and formation of Corpus Luteum
Males:
Stimulates Testes to produce Testosterone
What is the Target Tissues and Principal Action of PRL?
1- Target:
Mammary Glands
2- Action:
Together with other hormones promotes milk production by Mammary Glands
What is the Target Tissues and Principal Action of ACTH?
1- Target:
Adrenal Cortex
2- Action:
Stimulates secretion of Glucocorticoids (mainly Cortisol) by Adrenal Cortex
What is the Target Tissues and Principal Action of MSH?
1- Target:
Brain
2- Action:
Exact role in humans unknown
May influence brain activity
When present in excess can cause darkening of skin
What is Posterior Pituitary Gland Hormones?
Posterior Pituitary Gland does not synthesize any hormones
It stores and releases from axon terminals 2 hormones produced by Neurosecretory Cells of Hypothalamus:
1- Oxytocin (OT)
2- Antidiuretic Hormone (ADH)
Axons from the Neurosecretory Cells form the Hypothalamohypophyseal Tract
What is Oxytocin (OT)?
OT release in response to stretch placed on Cervix during childbirth
OT affects:
Mother’s Uterus - enhances contractions
Mother’s Breasts - Stimulates milk ejection by the Mammary Glands in response to suckling
What is Antidiuretic Hormone (ADH)?
Amount of ADH secreted varies with blood osmotic pressure:
ADH decreases urine output as part of a negative feedback loop where Osmoreceptors in the Hypothalamus monitor blood osmotic pressure
An increase in blood volume causes decrease in ADH secretion
A decrease in blood volume causes increase in ADH secretion
What is Control of Secretion and Principal Action of OT?
1- Control:
Neurosecretory Cells of Hypothalamus secrete OT in response to Uterine distention and stimulation of nipples
2- Action:
Stimulates contraction of smooth muscle cells of Uterus during childbirth
Stimulates contraction of Myoepithelial Cells in Mammary Glands to cause milk ejection
What is Control of Secretion and Principal Action of ADH?
1- Control:
Neurosecretory Cells of Hypothalamus secreted ADH in response to elevated blood osmotic pressure, dehydration, loss of blood volume, pain, or stress
Inhibitors of ADH secretion include low blood osmotic pressure, high blood volume, and alcohol
2- Action:
Conserves body water by decreasing urine volume
Decrease water loss through perspiration
Raises BP by contracting arterioles
What is Thyroid Gland?
Butterfly-shaped gland
Located inferior to Larynx and anterior to Trachea
Has Right and Left Lateral Lobes
Isthmus connects both lobes
Some glands also have pyramidal lobe projecting from Isthmus
What is Follicular Glands of Thyroid?
Follicular Cells are stimulated by TSH to produce Thyroid Hormones:
1- Thyroxine (Tetraiodothyronine T4)
2- Triiodothyronine (T3)
What is Parafollicular Cells of Thyroid?
Parafollicular Cells produce the Hormone Calcitonin to regulate calcium homeostasis
How are T3 and T4 Synthesized?
T3 and T4 are synthesized and secreted in an 8-step process:
1- Iodide trapping (from blood plasma to cell)
2- Synthesis of Thyroglobulin in cell (TGB to colloid in follicle)
3- Oxidation of Iodide (becomes Iodine in Colloid)
4- Iodination of Tyrosine (with Thyroglobulin TGB in Colloid)
5- Coupling of T1 and T2
6- Pinocytosis and digestion of Colloid
7- Secretion of Thyroid Hormones
8- Transport in blood
What do Thyroid Hormones do?
Thyroid Hormones:
1- Increase Basal Metabolic Rate (BMR)
2- Help maintain normal body temperature
3- Stimulate protein synthesis
4- Increase the use of Glucose and fatty acids for ATP production
5- Upregulate Beta Receptors that attach to Catecholamines
6- Work with hGH and Insulin to accelerate body growth
What is Feedback Loop for TRH and TSH?
Thyrotropin-Releasing Hormone (TRH) from Hypothalamus and Thyroid-Stimulating Hormone (TSH) from Anterior Pituitary Gland stimulate synthesis and release of Thyroid Hormones in a 5-step process:
1- Low blood levels of T3 and T4 or low metabolic rate stimulates release of TRH in Hypothalamus
2- TRH carried by Portal Veins to Anterior Pituitary stimulates release of TSH by Thyrotrophs in Anterior Pituitary
3- TSH released into blood stimulates Thyroid Follicular Cells
4- T3 and T4 released into blood by Follicular Cells
5- Elevated T3 inhibits release of TRH and TSH
(Negative Feedback Loop)
What is the Control of Secretion and Principal Action of T3 and T4?
Follicular Cells of Thyroid
1- Control:
Secretion is increased by TRH which stimulates release of TSH in response to low Thyroid Hormone levels, low metabolic rate, cold, pregnancy, and high altitudes
TRH and TSH secretions are inhibited in response to high Thyroid Hormone levels
High Iodine level suppresses T3 and T4
2- Action:
Increase BMR
Stimulate synthesis of proteins
Increase use of glucose and fatty acids for ATP production
Increase Lipolysis
Enhance Cholesterol excretion
Accelerate body growth
Contribute to development of nervous system
What is the Control of Secretion and Principal Action of Calcitonin (CT)?
Parafollicular Cells of Thyroid
1- Control:
High blood Ca2+ levels stimulate secretion
Low blood Ca2+ levels inhibit secretion
2- Action:
Lowers blood levels of Ca2+ and HPO42+ by inhibiting bone resorption by osteoclasts and by accelerating uptake of calcium and phosphates into bone extracellular matrix
What is Parathyroid Glands?
Located on posterior aspect of each lobe of the Thyroid Gland
2 Parathyroid Glands: (on each side)
One inferior and one Superior
What are the 2 Types of Cells of Parathyroid Gland?
1- Chief Cells: (Principal Cells)
Produce Parathyroid Hormone (PTH, Parathormone)
2- Oxyphil Cells:
Function not known in normal Parathyroid Glands
Secrete excess PTH in cases of Parathyroid Cancer
How does CT help with PTH and Calcitriol?
Calcitonin (CT) produced by Thyroid Gland works in conjunction with PTH and Calcitriol to regulate calcium homeostasis
1- High level of Ca2+ in blood stimulates Thyroid Gland Parafollicular Cells to release more CT
2- CT inhibits osteoclasts, decreasing Ca2+ level
3- Low level of Ca2+ in blood stimulates Parathyroid Gland Chief Cells to release more PTH
4- PTH promotes release of Ca2+ from bone extracellular matrix into blood and slows loss of Ca2+ in urine, increasing Ca2+ level
5- (Back to loop) + PTH also stimulates kidneys to release Calcitriol
6- Calcitriol stimulates increased absorption of Ca2+ from foods, which increase blood Ca2+ level
What is Control of Secretion and Principal Action of PTH?
Chief Cells in Parathyroid Gland
1- Control:
Low blood Ca2+ levels stimulate secretion
High blood Ca2+ levels inhibit secretion
2- Action:
Increases blood Ca2+ and Mg2+ levels
Decreases blood HPO42- levels
Increase bone resorption by osteoclasts
Increase Ca2+ reabsorption and HPO42- excretion by kidneys
Promotes formation of Calcitriol (Active for of Vitamin D), which increases rate of dietary Ca2+ and Mg2+ absorption
What is Adrenal Glands?
Adrenal Glands: (Suprarenal Glands)
Located on top of each kidney
Covered by connective tissue capsule
Glands are divided into 2 regions:
1- Outer Cortex
2- Inner Medulla
What is Adrenal Cortex?
Adrenal Cortex divided histologically into 3 regions (from outside to inside):
1- Zona Glomerulosa
2- Zona Fasciculata
3- Zona Reticularis
What is Zona Glomerulosa?
Zona Glomerulosa secretes:
Mineralocorticoids:
Mainly Aldosterone
Used to regulate mineral homeostasis
What is Zona Fasciculata?
Zona Fasciculata secretes:
Glucocorticoids:
Mainly Cortisol
Affect glucose homeostasis
What is Zona Reticularis?
Zona Reticularis secretes:
Weak Androgens:
Hormones with masculinizing effects
What is Aldosterone?
Aldosterone:
Major Mineralocorticoid secreted by Adrenal Gland
Helps regulate Na+ and K+ homeostasis
What is Renin-Angiotensin-Aldosterone (RAA) Pathway?
Renin-Angiotensin-Aldosterone (RAA) Pathway:
Controls secretion of Aldosterone
1- Dehydration, Na+ deficiency, or hemorrhage
2- Decrease in blood volume (blood thinning)
3- Decrease in BP
4- Juxtaglomerular Cells of Kidneys
5- Increase Renin
6- Angiotensinogen (inactive)
7- Increased Angiotensin I (activated)
8- Angiotensin-Converting Enzyme (ACE) in lungs
9- Increased Angiotensin II
10- Adrenal Cortex
11- Increased Aldosterone + Increased K+ in extracellular fluid
12- In kidneys, increased Na+ and water reabsorption and increased secretion of K+ and H+ into urine
13- Increased blood volume + Vasoconstriction of arterioles
14- BP increases until returns to normal
What is Glucocorticoids?
Glucocorticoids:
Cortisol (Hydrocortisone) is the most produced
Cortisone
Corticosterone
Regulated by negative feedback loop
They help control:
1- Protein breakdown
2- Glucose formation
3- Lipolysis
4- Resistance to stress
5- Inflammation
6- Immune responses
What is Negative Feedback Loop of Glucocorticoid Secretion?
1- Decreased Glucocorticoid level in blood
2- Neurosecretory Cells in Hypothalamus increase CRH and decrease Cortisol
3- Corticotrophs in Anterior Pituitary increase ACTH
4- Cells of Zona Fasciculata in Adrenal Cortex secrete Glucocorticoids
5- Increased Glucocorticoid level in blood
What is Dehydroepiandrosterone (DHEA)?
Dehydroepiandrosterone (DHEA):
Major Androgen secreted by Adrenal Cortex
In males:
After puberty, Testosterone is secreted in much larger quantities so DHEA has virtually no effect
In females:
DHEA and other Adrenal Androgens play a major role in promoting libido (digestion, energy, etc…) and are converted to Estrogens
In menopausal women, all female Estrogens come from Adrenal Androgens
What is Adrenal Medulla?
Adrenal Medulla:
Stimulated by Sympathetic Preganglionic Neurons of ANS
What is Chromaffin Cells?
Chromaffin Cells:
In Adrenal Medulla
Secrete Epinephrine (Adrenaline)
Secrete Norepinephrine (Noradrenaline)
Both involved in Fight-or-Flight response
What is Control of Secretion and Principal Action of Mineralocorticoids?
Mainly Aldosterone
From Zona Glomerulosa Cells
1- Control:
Increased K+ level and Angiotensin II stimulate secretion
2- Action:
Increase blood levels of Na+ and water
Decrease blood level of K+
What is Control of Secretion and Principal Action of Glucocorticoids?
Mainly Cortisol
From Zona Fasciculata Cells
1- Control:
ACTH stimulate release
CRH promotes ACTH secretion in response to stress and low blood levels of Glucocorticoids
2- Action:
Protein breakdown
Glucose formation
Lipolysis
Resistance to stress
Inflammation
Immune responses
What is Control of Secretion and Principal Action of Androgens?
Mainly Dehydroepiandrosterone (DHEA)
From Zona Reticularis
1- Control:
ACTH stimulates secretion
2- Action:
Assist in early growth of axillary and pubic hair in both sexes
In females:
Contributes to libido and are source of Estrogens after Menopause
What is Control of Secretion and Principal Action of Epinephrine and Norepinephrine?
From Chromaffin Cells of Adrenal Medulla
1- Control:
Sympathetic Preganglionic Neurons release ACh, which stimulates secretion
2- Action:
Enhance effects of sympathetic division of ANS during stress
What is Pancreas?
Pancreas:
Located in the curve of the Duodenum
Both and Endocrine and Exocrine Gland
What is Acini?
Almost all of the Exocrine Cells of the Pancreas are arranged in clusters called Acini
Acini:
Produce Digestive Enzymes that are delivered to the GI Tract through Ducts
What is Pancreatic Islets (Islets of Langerhans)?
Pancreatic Islets: (Islets of Langerhans)
Clusters of Endocrine tissue scattered among Acini
Contain Secreting Cells:
1- Alpha Cells
2- Beta Cells
3- Delta Cells
4- F Cells
What is Alpha Cell?
Many cells
Located on interior edges of Acini
Secrete Glucagon
What is Beta Cells?
Most cells
Located mostly in center between Acini
Secrete Insulin
What is Delta Cells?
Some cells
Scattered in middle between Acini
Secrete Somatostatin
What is F Cells?
Some cells
Scattered on interior edges of Acini
Secrete Pancreatic Polypeptide
What is the Control of Secretion and Principal Action of Glucagon?
From Alpha Cells of Pancreatic Islets
1- Control:
Decreased blood level of Glucose, exercise, and mainly protein meals stimulate secretion of Somatostatin
Insulin inhibits secretion
2- Action:
Raises blood Glucose level by:
Glycogenosis - Accelerating breakdown of Glycogen into Glucose in liver
Gluconeogenesis - Converting other nutrients into Glucose in liver
Releasing Glucose into blood
What is the Control of Secretion and Principal Action of Insulin?
From Beta Cells of Pancreatic Islets
1- Control:
Increased blood level of Glucose, ACh (released by Parasympathetic Vagus Nerve fibers), Arginine and Leucine, Glucagon, Glucose-Dependent Insulinotropic Peptide (GIP), GH, and ACTH stimulate secretion
Somatostatin inhibits secretion
2- Action:
Lowers blood Glucose level by accelerating transport of Glucose into cells
Glycogenesis - Converting Glucose into Glycogen
Decreasing Glycogenolysis and Gluconeogenesis
Increases Lipogenesis
Stimulates protein synthesis
What is the Control of Secretion and Principal Action of Somatostatin?
From Delta Cells of Pancreatic Islets
1- Control:
Pancreatic Polypeptide inhibits secretion
2- Action:
Inhibits secretion of Insulin and Glucagon
Slows absorption of nutrients from GI Tract
What is the Control of Secretion and Principal Action of Pancreatic Polypeptide?
From F Cells of Pancreatic Islets
1- Control:
Meals containing protein, fasting, exercise, and Acute Hypoglycemia stimulate secretion
Somatostatin and elevated blood Glucose level inhibit secretion
2- Action:
Inhibits Somatostatin secretion, Gallbladder contraction, and secretion of Pancreatic Digestive Enzymes
What is Negative Feedback Loop of Insulin and Glucagon Secretion?
1- Hypoglycemia stimulates Alpha Cells to secrete Glucagon
2- Glucagon acts on liver cells to convert Glycogen into Glucose, and from Glucose from Lactic Acid and certain Amino Acids
3- Glucose released by liver cells raises blood Glucose level to normal
4- If blood Glucose continues to rise, Hyperglycemia inhibits release of Glucagon
1- Hyperglycemia stimulates Beta Cells to secrete Insulin
2- Insulin acts on various body cells to accelerate facilitated diffusion of Glucose into cells, speed conversion of Glucose into Glycogen, increase uptake of Amino Acids and increase protein synthesis, and speed synthesis of fatty acids
3- Blood Glucose level falls
4- If blood Glucose continues to fall, Hypoglycemia inhibits release of Insulin
What are Ovaries and Testes?
Gonads: Ovaries and Testes
Produce Gametes (Oocytes and Sperm)
Ovaries produce 2 Estrogens (Estradiol and Estrone), Progesterone, Relaxin, and Inhibin
Testes produce Testosterone
What is Estrogen and Progesterone Principal Action?
Together with Gonadotropic Hormones of Anterior Pituitary, regulate female reproductive cycle
Maintain pregnancy
Prepare Mammary Glands for lactation
Promote development and maintenance of female secondary sex characteristics
What is Relaxin (RLX) Principal Action?
Increases flexibility of Pubic Symphysis during pregnancy
Helps dilate Uterine Cervix during labor and delivery
What is Testosterone Principal Action?
Stimulates descent of Testes before birth
Regulates sperm production
Promotes development and maintenance of male secondary sex characteristics
What is Inhibin Principal Action?
Inhibits secretion of FSH from Anterior Pituitary
What is Pineal Gland?
Pineal Gland:
Attached to roof of the Third Ventricle of the brain
Secrets Melatonin
Melatonin:
Helps regulate body’s biological clock
What is Thymus?
Thymus:
Located behind Sternum between Lungs
Produces:
Thymosin
Thymic Humoral Factor (THF)
Thymic Factor (TF)
Thymopoietin
These hormones promote maturation of the Immune System’s T Cells
(T Cells mature in the Thymus)
What is the Source and Action of Cholecalciferol?
1- Source:
Skin
2- Action:
Plays a role in synthesis of Calcitriol, the active form of Vitamin D
What is the Source and Action of Gastrin?
1- Source:
GI Tract
2- Action:
Promotes secretion of Gastric Juices
Increase movements of Stomach
What is the Source and Action of Glucose-Dependent Insulinotropic Peptide (GIP)?
1- Source:
GI Tract
2- Action:
Stimulates release of Insulin by Pancreatic Beta Cells
What is the Source and Action of Secretin?
1- Source:
GI Tract
2- Action:
Stimulates secretion of Pancreatic Juice and Bile
What is the Source and Action of CCK?
1- Source:
GI Tract
2- Action:
Stimulates secretion of Pancreatic Juice
Regulates release of Bile from Gallbladder
Causes feeling of fullness after eating
What is the Source and Action of Human Chorionic Gonadotropin (hGC)?
1- Source:
Placenta
2- Action:
Stimulates Corpus Luteum in Ovary to continue production of Estrogens and Progesterone to maintain pregnancy
What is the Source and Action of Estrogen and Progesterone from Placenta?
1- Source:
Placenta
2- Action:
Maintains pregnancy
Help prepare Mammary Glands to secret milk
What is the Source and Action of Human Chorionic Somatomammotropin (hCS)?
1- Source:
Placenta
2- Action:
Stimulates development of Mammary Glands for lactation
What is the Source and Action of Renin?
1- Source:
Kidneys
2- Action:
Part of reaction sequence that raises BP by bringing about Vasoconstriction and secretion of Aldosterone
What is the Source and Action of Erythropoietin (EPO)?
1- Source:
Kidneys
2- Action:
Increases rate of RBC formation
What is the Source and Action of Calcitriol (Active Form of Vitamin D)?
1- Source:
Kidneys
2- Action:
Aids in absorption of dietary calcium and phosphorus
What is the Source and Action of Atrial Natriuretic Peptide (ANP)?
1- Source:
Heart
2- Action:
Decreases BP
What is the Source and Action of Leptin?
1- Source:
Adipose Tissue
2- Action:
Suppresses appetite
May increase FSH and LH activity
What is Eicosanoids?
Eicosanoids:
Locally-acting hormones derived from the 20-Carbon fatty acid Arachidonic Acid
Certain hormones stimulate cell growth and division
Several newly discovered hormones called Growth Factors are involved in tissue development, growth, and repair
What is Epidermal Growth Factor (EGF)?
Produced in Submaxillary (Salivary) Glands
Stimulate proliferation of epithelial cells, Fibroblasts, Neurons, and Astrocytes
Suppress some Cancer Cells and secretion of Gastric Juice by Stomach
What is Platelet-Derived Growth Factor (PDGF)?
Produced in blood platelets
Stimulate proliferation of Neuroglia, smooth muscle fibers,, and Fibroblasts
Appear to have role in wound healing
May contribute to Atherosclerosis development
What is Fibroblast Growth Factor (FGF)?
Found in Pituitary Gland and brain
Stimulate proliferation of many cells derived from Embryonic Mesoderm (Fibroblasts, Adrenocortical Cells, smooth muscle fibers, Chondrocytes, and Endothelial Cells)
Stimulate formation of new blood vessels (Angiogenesis)
What is Nerve Growth Factor (NGF)?
Produced in Submandibular (Salivary) Glands and Hippocampus of brain
Stimulate growth of Ganglia in embryo
Maintains sympathetic nervous system
Stimulates Hypertrophy and differentiation of Neurons
What is Tumor Angiogenesis Factors (TAFs)?
Produced by normal and Tumor Cells
Stimulate growth of new capillaries, organ regeneration, and wound healing
What is Transforming Growth Factors (TGFs)?
Produced by various cells as separate molecules:
TGF-Alpha has activities similar to Epidermal Growth Factor (EGF)
TGF-Beta inhibits proliferation of many cell types
What is Eustress?
Helpful everyday stress that prepares us to meet challenges
What is Distress?
Type of harmful stress that may be damaging
1- The Fight-or-Flight Response (1st Stage of Stress Response):
Stimulates body’s resources to prepare for immediate activity
2- The Resistance Reaction (2nd Stage of Stress Response):
Lasts longer
If lasts too long, Exhaustion will result
What is Development of Endocrine System?
Glands of Endocrine System develop from all 3 Primary Germ Layers
How does Aging affect Endocrine System?
Aging brings changes in levels of most hormones:
Some hormone levels increase while some decrease
Levels of other hormones like Epinephrine and Norepinephrine remain the same
Histologically, most endocrine glands reduce in size and contain increasingly more fibrous connective tissue with age
What are some Endocrine System Disorders?
1- Pituitary Gigantism and Acromegaly:
Caused by excess secretion of GH
2- Goiter:
Caused by reduction in production of Thyroid Hormone
3- Graves Disease (with Associated Exophthalmos):
Develops due to excess Thyroid Hormone
4- Cushing’s Syndrome:
Caused by excess secretion of Glucocorticoids
