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ENDOCRINE
SYSTEM
TWO GREAT CONTROLLING
SYSTEMS
Nervous System . . . . . . . . .
. . . . . . . Endocrine System
1) NERVOUS SYSTEM
• Regulates activity via action potential
impulses ~ AP’s
• Impulses carried by specific sensory or
motor neurons
• Uses “synaptic communication” to
carry message
• Targets specific cells ~ for specific
response
• Response is immediate & usually short
lasting
2) ENDOCRINE SYSTEM
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Controls cell activity by secreting hormones ~
EXCITE
Hormones = “Chemical Messengers”
Secreted into blood & transported throughout
body
Generalized Widespread Response ~ Adrenalin or
GH
Targeted specific cells: TSH or FSH
Diverse or very specific effects: Insulin ~ specific
Adrenalin ~ diverse
Response on target cells is delayed ~ due to
circulation
Delayed, prolonged or continuous response
ENDOCRINE SYSTEM ~
Controlling Spectrum
MAJOR processes controlled by hormone
release
Reproduction
Testosterone
Estrogen
Follicle Stimulating Hormone
Leutenizing Hormone
Oxytocin ~ “Post Pit”
Growth & Development
Growth Hormone & Thyroid Hormone
Body Defense Mechanisms
Corticosteroids ~ Cortisone ~ Antiinflammatory
Anti-Stress
Corticosteroids ~ Gluconeogenesis
Electrolyte, Water & Nutrient Balance
Aldosterone ~ Na+ retention ~ water
retention
Anti-Diuretic Hormone ~ ADH
Cell Metabolism & Energy Regulation
Insulin & Thyroid Hormone
Digestive Processes
TWO GLANDULAR SYSTEMS OF
BODY
1. EXOCRINE GLANDS
~ Merocrine . . . Apocrine . . . Holocrine ~
< PUREST ------------------------------ MESSY >
Secreted onto body surfaces ~ via ducts
Secretions are non-hormonal
Secreted & ACT LOCALLY in a target area only
DO NOT secrete into blood or lymphatics
Can be large in size or extensive in numbers ~ millions
Examples of Exocrine Glands
Mucous Glands
Sudoriferous Glands
Sebaceous or Oil Glands
Salivary Glands
Mammary Glands
Liver
Enteric Glands
Reproductive Glands
Secrete
Mucous
Sweat
Sebum
Saliva
Milk
Bile
Digestion
Several
Pancreas ~ Both Exocrine & Endocrine
2. ENDOCRINE GLANDS
“Ductless Glands” ~ produce hormones ~ NO DUCTS
Secrete hormones most directly into blood
Surrounded by many capillaries ~ allows secretion into
blood
Hormones travel through body ~ act on specific target
organs
Can have a generalized effect or specific target effect
Effects can be short, prolonged or continuous lasting
Small Glands ~ very localized, & few in numbers ~ 12
groups
ENDOCRINE GLANDS
Pituitary Gland
Pineal Gland
Thyroid Gland
Parathyroid Gland
Thymus Gland
Adrenal Gland
Heart
Small Intestines
Kidney
Pancreas
Gonads (ovaries & testes )
Hypothalamus
Other Specialized Cells can produce hormones
Adipose Tissue . . . .Tumors or cancer cells
CHEMISTRY OF HORMONES
Hormones ~ “chemical messengers” ~ “First
Messengers”
Control other parts of body from where
secreted
“Endocrine Communication” ~ NOT NEURAL
MOST Secreted into blood & circulatory
system
Regulate functions of other cells somewhere
else
Major Hormone Classifications
1.Amino Acid Hormones ~ MOST
COMMON
Most hormones are globular proteins or
peptides
2. Lipid Hormones
Steroid Hormones ~ from cholesterol
Gonadal hormones ~ estrogen, testosterone
Adrenalcorticoids hormones ~ corticosteroids
Eicosanoids (eye cos an oids)
Increase inflammation & cause swelling
NON-CIRCULATING hormones ~ act locally only
Released from most cell membranes & have a
highly localized response
Prostaglandins ~ most common
MECHANISM OF HORMONE
ACTION
Hormones effect target cells ~ alter cell activity
Increase or decrease types & rates of cellular
processes
Up-Regulation ~ increased sensitivity to
hormone effects
Down-Regulation ~ less sensitive to
hormone effects
Activity is very specific on a specific target cell
EG: Epinephrine causes blood vessel walls
to contract
It will also cause an increase in heart rate
HORMONE EFFECTS ON
TARGET CELLS
1. Change plasma membrane permeability
2. Change electrical charge of plasma membranes
3. Stimulate secretory activity of cells
4. Stimulate mitosis & cell division
5. Stimulate Enzyme Activation or Deactivation ~ MOST
COMMON
Forms NEW proteins within cells
Amino Acid Hormones ~ cAMP Second Messenger
6. Stimulate Gene Activation ~ COMMON
Lipid/Steroid Hormones ~ Form New Proteins
EXAMPLES ~ MECHANISMS OF
HORMONE ACTION
AMINO-ACID HORMONES (“PEPTIDES”) ~ MOST COMMON
Utilizes a Second Messenger System
Hormone ~ is the first messenger
Hormone CANNOT penetrate cell membrane ~ to big
Binds to “hormone receptor” site on target cell
Receptor binding ---> activates a “G-protein” --->
which activates an effector enzyme
Effector Enzyme = Adenylate cyclase
Adenylate cyclase generates Second Messenger ~ cAMP
cAMP activates protein kinase - - -> form NEW PROTEINS
inside cell
MANY reactions follow & cause specific cell activities
LIPID ~ STEROID HORMONES “from CHOLESTEROL”
Utilizes: Gene Activation ~ NO 2nd messenger
system
Smaller & lipid soluble ~ can penetrate cell
membrane
Once inside target cells ~ gene activation occurs
DNA is “transcribed” to messenger RNA ~ mRNA
mRNA ~ stimulates production of NEW proteins
HORMONE TARGET CELL
ACTIVATION & SPECIFICITY
Major hormones circulate in blood to all
tissue
Specific hormones effect only specific
tissue cells
Hormone Receptors ~ located on or in cells
Target Cells have specific hormone receptors on cell
membranes or inside target tissue that bind
hormones
Receptor Binding is required for activity
SOME receptors are found only on/in SPECIFIC
CELLS
Example: ACTH stimulates only the adrenal cortex
SOME receptors are found on/in MOST BODY CELLS
Example: Thyroxine stimulates most cells
Insulin affects all cells of body
Target Cell Activation Requirements
Adequate Hormone Blood Levels
Specific Receptor Binding Sites
Adequate Number of Receptors on or within cells
Specific Bonding Affinity between Hormone &
Receptor
Any +/- Changes in any of the above results in:
Endocrine Dysfunction  Up Regulation OR
 Down Regulation
ENDOCRINE DYSFUNCTION
Up-Regulation ~ Sensitization ~ Stimulation
Occurs when target cells form MORE receptors in
response to hormone presence
Down-Regulation ~ Desensitization ~ Inhibition
Occurs when prolonged exposure to high hormone
levels causes LOSS of receptors
Desensitizes target cells resulting in lower activity
Hormones also STIMULATE or INHIBIT other hormones
EG: Estrogen stimulates Progesterone release
Progesterone antagonizes Estrogen action
DURATION OF HORMONAL
ACTIVITY ~ “Half-Life”
Dependent on circulating blood levels of
Hormone
1) Rate of Release into the blood
2) Speed of Inactivation & Removal from the
body
Methods of Inactivation ~ Removal from body
1) Degradation by enzymes in target cells
2) Removed from blood via Kidney and Liver
3) Excreted in Urine or Feces
HALF-LIFE
Time required to reduce blood concentrations by 50%
Ranges from seconds to minutes to hours or longer
What is the Half-Life? . . . .If blood concentration is 20
units &
. . . . . 15 units remain after 7 minutes
. . . . . 10 units remain after 14 minutes = HALF-LIFE
. . . . . 5 units remain after 21 minutes
Endocrine Reflexes ~ CONTROL
HORMONE RELEASE
Blood levels are precisely controlled for optimal effects
1) POSITIVE FEEDBACK MECHANISM
As hormone is released, target organ stimulates
the release of more hormone . . . more . . . more . . .
more
EG: Oxytocin ~ Childbirth
2) NEGATIVE FEEDBACK MECHANISM ~ MOST
COMMON
As blood hormone levels rise, target organs inhibit
further hormone release ~ on . . . off . . . on . . . off
EG: thermostat in a house
EG: High blood sugar ---> insulin release --->
---> glucose uptake into cells ---> lower blood sugar
TYPES OF ENDOCRINE GLAND
RELEASE STIMULI
Endocrine Gland Reflexes
Stimulate glands to produce & release
hormones
1) Humoral Stimuli ~ ions &
chemicals
2) Neural Stimuli ~ nerve impulses
3) Hormonal Stimuli ~ other
hormones
HUMORAL STIMULI
Hormones secreted in direct response to changing
blood levels of certain IONS & CHEMICALS
Examples:
Low blood Ca+ ---> parathyroid gland to secrete
parathyroid hormone (PTH) ---> higher blood Ca+ --->
reduced secretion of PTH
High blood sugar ---> pancreas to secrete insulin --->
lowering of blood sugar
NEURAL STIMULI
Nerve IMPULSES (AP’s) stimulate
hormone release
EG: Stress ---> Sympathetic NS
activation ---> adrenal medulla
secretes catecholamines
Adrenalin ~ norepinephrine &
epinephrine
HORMONAL “TROPIC” STIMULI
~ COMMON
Occurs when an endocrine gland releases hormones
that stimulate OTHER endocrine glands to release
hormones
Hypothalamus ~ Highest level of endocrine control
Integrates activities of endocrine & nervous system
Produces Hormones that regulates Pituitary Gland
Pituitary produces other hormones that regulate
OTHER glands
Hypothalamic-Pituitary -Target Endocrine Gland
Feedback Loop
SEVERAL Hypothalamus
“Regulating” Hormones
Thyrotropic Releasing Hormone (TRH)
Stimulates release of TSH from Ant. Pituitary
TSH stimulatesThyroid Hormone from Thyroid
Corticotropin Releasing Hormone (CRH)
Stimulates release of ACTH from Ant. Pituitary
Stimulates Adrenal Hormones from Adrenals
Gonadotropin Releasing Hormone (GnRH)
Stimulates release of FSH & LH from Ant. Pit.
Stimulates Testosterone, Estrogen & Progesterone
from Gonad
12 MAJOR ENDOCRINE
ORGANS
12 MAJOR ENDOCRINE
ORGANS
PITUITARY GLAND
Also called the “Hypophysis” ~ “Master Gland of
Body”
Protected by sella turcica of the sphenoid bone
At the base of the brain ~ not a part of nervous
system
Infundibulum ~ “stalk” ~ connects pituitary to
hypothalamus
Two lobes: Anterior Pituitary ~ “adenohypophysis”
Posterior Pituitary ~ “neurohypophysis”
Hormones of the Anterior Pituitary
HYPOTHALAMUS
Located above the brain stem ~ in diencephalon
Controls Autonomic Nervous System
1. Controls emotion ~ rage, fear, anger, pleasure
2. Body temperature regulation
3. Food intake regulation ~ appetite
4. Water balance & thirst regulation
Controls Endocrine System
Produces Hormones that “regulate” the Anterior
Pituitary
Produces two hormones released by the Posterior
Pituitary
ADH . . . . . . Oxytocin
HYPOTHALAMUS
Produces “Releasing & Inhibiting” Regulating
Hormones
Carried via “Hypophyseal Portal System”
Ant. Pit.
Vascular connection ~ hypothalamus & Ant. Pit
“Releasing” Hormones
Stimulate secretion of Anterior
Pituitary Hormones
“Inhibiting” Hormones
Inhibit release of Anterior Pituitary
Hormones
to
Produces 2 “Neuro-Hormones” for Posterior
Pituitary
Paraventricular Nucleus ----> Oxytocin
Supraoptic Nucleus ----> Anti-diuretic
Hormone ~ ADH
Carried via “Hypothalamic-Hypophyseal
Tract” by axons to posterior pituitary
Neuro-Hormones are secreted by Posterior
Pituitary
“Hypophyseal Portal System”
Vascular connection ~ hypothalamus &
anterior pituitary
“Hypothalamic-Hypophyseal Tract”
Neural connection ~ hypothalamus &
posterior pituitary
ANTERIOR PITUITARY ~ “Master
Endocrine Gland”
ANTERIOR PITUITARY ~ “Master
Endocrine Gland”
Anterior Lobe ~ “Adenohypophysis”
Controlled by the hypothalamus via regulating
hormones
Hypophyseal Portal System
Fenestrated Capillaries ~ vascular bed connections
Allows hypothalamic hormones to circulate
through the anterior pituitary
Regulating Hormones ~ regulate the secretions of
other hormones from anterior pituitary gland
Secretes 6 major hormones ~
ALL ARE PROTEINS
Instantaneous Response ~ NO storage in Anterior Pit.
Tropic Hormones: Hormonal Stimuli
Regulate the secretory action of OTHER endocrine
glands to release other hormones
TSH
Thyroid Stimulating Hormone
ACTH
Adrenal Corticotropic Hormone
FSH
Follicle Stimulating Hormone
LH
Leutenizing Hormone
Non-tropic Hormones: Effects NONENDOCRINE glands
GH
Growth Hormone
PRL
Prolactin
ANTERIOR PITUITARY - “TROPIC”
HORMONES
THYROID STIMULATING HORMONE ~
TSH
TRH ~ Thyrotropin Releasing Hormone Hypothalamus Stimulates release of TSH
from Anterior Pituitary
TSH (tropic) ~ stimulates Thyroid Gland to
secrete Thyroid Hormone
Negative Feedback “Shut Off” Mechanism
Rising blood levels of TH “shuts off” the
Hypothalamus & Anterior Pituitary to block
further TSH release
Factors releasing TRH from Hypothalamus
1. Increased Energy Demands
2. Need to raise metabolic rate
3. Need to produce & release heat
EG: Pregnancy
Cold temperatures
Exercise
Fever
ADRENOCORTICOTROPIC HORMONE ~ ACTH
CRH ~ Corticotropin Releasing Hormone Hypothalamus Stimulates release of
ACTH from Anterior Pituitary
ACTH tropic action: stimulates the adrenal
cortex to release several other hormones:
1) Gluco-corticoids ~ corticosteroids ~ mostly
2) Gonado-corticoids ~ androgens ~ small amount
3) Mineralo-cortacoids ~ aldosterone
Negative Feedback “Shut Off”
Mechanism
Rising blood levels of “corticoids” cause Anterior
Pituitary & Hypothalamus to block further CRH
release
Factors stimulating CRH release:
fever
hypoglycemia
stress
dehydration
shock
blood loss
low blood pressure
GONADOTROPINS
FSH ~ Follicle Stimulating Hormone
LH ~ Leuteinizing Hormone
GnRH ~ gonadotropin releasing hormone
from Hypothalamus Stimulates release
of FSH or LH from Anterior Pituitary
FSH and LH ~ action is tropic
Stimulate gonad activity ~ ovaries & testes ~ at puberty
FSH ~ stimulates sperm & egg production
LH ~ cause ovarian follicle maturation &
ovulation
~ causes release of Gonadal Hormones
Estrogen ~ Female ~ controls menstrual
cycle
Progesterone ~ Female ~ maintains
pregnancy
Testosterone ~ Male Testicular Hormone
Negative Feedback “Shut-Off”
Mechanism
Rising blood levels of gonad hormones
causes the Hypothalamus to block
GnRH release, & inhibits FSH & LH
release from Anterior Pituitary
ANTERIOR PITUITARY - “NONTROPIC” HORMONES
GROWTH HORMONE ~ GH ~ “Somatotropin”
“Anabolic Hormone” ~ stimulates most body cells
to increase in size and divide
GH targets bones & skeletal muscles
Stimulates epiphyseal plate & long bone growth
Increases skeletal muscle mass
“Insulin-growth factor” ~ Somatomedins ~ enhance GH
Protein produced in liver & muscle stimulate growth
GH Actions
1) Stimulates protein synthesis ~ anabolic ~
muscles
2) Stimulates cartilage & bone development
3) Stimulates fats for energy ~ increases
glucose
4) Converts glucose to glycogen stores for
future
5) Causes a “diabetogenic” effect
Causes glycogen breakdown & release of
glucose into blood causing ↑ blood sugar
GROWTH HORMONE ~ GH ~
“Somatotropin”
Secretion of GH ~ NOT a feedback mechanism
GHRH – GH Releasing Hormone
Hypothalamic hormone - stimulates
release of GH
GHIH – GH Inhibiting Hormone –
Somatostatin
Hypothalamic hormone - inhibits release
of GH
PROLACTIN ~ PRL
PRL has direct action on non-endocrine
mammary cells; Stimulates milk production
by breast (not release)
PRL is controlled by Hypothalamus
PRH ~ Prolactin “Releasing” Hormone =
seratonin; Causes prolactin release from
Ant. Pituitary
PIH ~ Prolactin “Inhibiting” Hormone =
dopamine; Prevents prolactin secretion
from Ant. Pituitary
PRL Levels fluctuates in females with ESTROGEN
Low Estrogen stimulates PIH ---> LESS Prolactin
High Estrogen levels stimulates PRH ---> MORE PRL
Menstruation ~ HIGH Estrogen ---> PRH ---> MORE PRL
Breast swelling & tenderness ~ temporary
Generally NO milk production
Pregnancy ~ cause HIGH levels of PRH near term
Infant Suckling ~ stimulates PRH ---> MORE PRL
PRL Hyper-Secretion ~ occurs in nursing mothers
PRL Hypo-Secretion – only occurs in heavy nursers
POSTERIOR PITUITARY
Neurohypophysis ~ Posterior Lobe + Infundibulum
Neural Portion (axons) is an extension of the
Hypothalamus; Stores two “neurohormones”
produced in the hypothalamus
1) Oxytocin ~ effects uterus & mammaries
2) Antidiuretic Hormone ~ ADH ~ retains water
Neurohormones released into capillary beds of
posterior pituitary in response to neural
stimulation ~ Humoral
OXYTOCIN ~ “Post pit”
PRODUCED in hypothalamus ~ Paraventricular Nuclei
Uterus & Cervic Stretching during childbirth
stimulates
Released from Posterior Pituitary ~ Positive
Feedback
Effects: 1) Stimulates uterus muscle contraction
2) Stimulates mammaries to release & “letdown”
3) Stimulates sexual arousal & orgasm
4) Promotes nurturing & cuddling ~ “nesting”
Highest Concentrations ~ during childbirth & nursing
Synthetic Drug ~ induces labor & stimulates milk “letdown”
ANTIDIURETIC HORMONE ~ ADH
What is “Diuresis”??? = Excess Urine
production
ADH = “Anti-Urine Hormone” = AGAINST DIURESIS
“Vasopressin” ~ causes vasoconstriction & elevates Blood
Pressure
PRODUCED in hypothalamus ~ Supra Otic Nuclei
Stimulated by need to retain fluids
Dehydration ~ Excess sweating ~ no fluid intake
Hemorrhage ~ Blood Loss
Low blood pressure & Shock
Released from Posterior Pituitary into blood
Effects:
1) Targets Kidneys ----> Water Retention
2) Prevents urine formation ----> water
retention; Reabsorbs water back into blood
in kidneys
3) Increases blood pressure ~ due to
vasoconstriction & retained fluid volume in
blood
Controlled by Negative feedback “Shut-Off”
Mechanism
Inhibited by High Blood Volume . . . High
Blood Pressure. . . Fluid Retention . . . OverHydration
ADH INHIBITORS ~ BLOCK ADH ~ “Diuretics”
Stimulate urine production & fluid loss
Results in copious urine production & output
Flushes water from body ~ Dehydration
Morning after dry mouth & intense thirst ~
drinking
Decreases Blood Fluid Volume ----> lowers
BP
Examples of ADH Inhibitors ~ ALL act as DIURETICS
Drinking excessive fluid & Alcoholic beverages
Diuretic Drugs ~ Diet Pills ~ Dexetrene
Hypertension Drugs ~ to lower blood pressure
THYROID GLAND
Largest “pure” endocrine ONLY gland in
body ~ “Butterfly”
On the trachea ... Anterior throat area … below the
larynx
Two lateral lobes connected by a median
isthmus
Blood Supply ~ via thyroid artery off common
carotid artery
Extremely vascular ~ Surgery very difficult
Internal Thyroid Tissue Histology
1. Follicular Cells - spherical cells ~ surround lumen;
Produce thyroglobulin ~ glycoprotein
2. Lumen of follicle ~ stores colloid
Colloid = thyroglobulin + attached iodine
“Iodinated Thyroglobulin”
Precursor for Thyroid Hormone ~ T3 or T4
3. Parafollicular Cells ~ around & between the follicle
Endocrine cells that produce calcitonin
Calcitonin ~ lowers blood calcium levels
Thyroid Gland is Unique . . .
Only endocrine gland that stores
hormones in large quantities ~ in
colloid THYROID HORMONE ~ TH
“Body’s major “metabolic hormone”
Thyroid Hormone is two Iodine
containing hormones
T4
Thyroxine ~ STORED FORM ~ NOT ACTIVE
90% of TH ~ secreted by follicle cells
T3
Triiodothyronine ~ NOT stored ~ “ACTIVE”
Formed at target tissues by conversion of
T4 (STORED)
>>>
T3 (“Active)
Thyroid Hormone affects most cells except:
Brain ... Spleen ... Testes ... Uterus ... Thyroid
Effects of Thyroid Hormone
1. Stimulates carbohydrate, lipid & protein metabolism
Glucose & fat catabolism ~ energy produced
Protein & cholesterol synthesis ~ growth
2. Increases basal metabolic rate & O2 consumption
Calorigenic Effect ~ burn calories ~ body heat
Promotes normal oxygen use by cells
3. Regulates tissue growth, development, & function
Thyroid Hormone Release ~ “Negative Feedback”
1. Falling blood levels of thyroxin (T4) ---->
Hypothalamus to release thyrotropic
releasing hormone (TRH)
2. TRH ----> anterior pituitary to release thyroid
stimulating hormone (TSH) into blood
3. TSH ----> Thyroid to release thyroxin (T4 &
T3) into blood
4. Thyroxin (T4 & T3) is carried to target organ
receptors
T3 is formed at the target tissue by conversion of T4
5. T3 or T4 actively exert effects on the target
tissue
6. Rising blood levels of T3/T4 “shuts off”
hypothalamus --> inhibits release of TRH
(hypothalamus) & TSH (Ant. Pit)
Factors Triggering TSH release from anterior pituitary:
Any conditions increasing body energy requirements
Pregnancy ~ requires energy for fetus
Prolonged Cold ~ requires body heat
Extensive Exercise ~ requires energy & O2
Factors Inhibiting TSH release:
Somatostatin ~ growth hormone inhibitor ~ less energy
Rising levels of glucocorticoids ~ high blood sugar
High blood iodine concentration ~ Stimulates excess TH
----> shuts off Hypothalamus
THYROID GLAND HORMONES
CALCITONIN
Produced by parafollicular cells of Thyroid
Protein hormone ~ lowers blood Ca++
Direct antagonist to parathyroid hormone
Mode of Action:
1) Targets skeletal tissue & bone
2) Inhibits osteoclast activity & bone resorption
3. Inhibits release of ionic calcium from bone
4. Stimulates calcium uptake into bone
Stimulates osteoblast activity in bone
Calcitonin Secretion Stimuli:
Cycles up & down with parathryroid
hormone
Excessive blood levels of calcium ----->
“calcitonin” release ~ to lower blood
calcium
Part of “negative feedback” system with
“parathyroid hormone” from
parathyroid gland
PARATHYROID GLAND
Very tiny ~ on posterior side of thyroid
gland . . . two pairs, one on each side ~
numbers can vary
Function is antagonistic to thyroid gland
Thyroid ~ calcitonin lowers blood Ca++
Parathyroid ~ parathyroid
hormone raises
blood Ca++
Histology of Parathyroid Tissue
1. Chief Cells – round
and dark stained
Produce “Parathyroid
Hormone” ~ PTH
2. Oxyphil Cells –
function unknown
3. Capillaries extensive network
Parathyroid Hormone ~ PTH ~
“Parathormone”
Most important hormone controlling blood calcium
levels
PTH Secretion & Release Stimuli
Low blood calcium levels (hypo-calcemia) ---->
Stimulate Parathyroid Hormone release
High blood calcium levels (hyper-calcemia) ---->
inhibits Parathyroid Hormone release
Main Effect of PTH ~ increases blood calcium ion
levels
Direct antagonist to calcitonin (lowers blood Ca++ )
Parathyroid Hormone ~ PTH
Blood Calcium Balance ~ needed for many body
functions:
Nerve impulse transmission
Muscle contraction
Blood clotting
Bone development & maintenance
Mode of Action ~ Parathyroid Hormone
1. Skeletal Tissue ~ stimulates bone cells (osteoclasts)
to release calcium from bone into blood
2. Kidney ~ enhances reabsorption of calcium into
blood
3. Kidney ~ activates Vitamin D -----> increases
intestinal absorption of Ca++
ADRENAL GLAND ~ the “Stress
Gland”
Paired ~ pyramid
shaped ~ On top of
each kidney
“suprarenal glands” ~
above the kidney
Each adrenal gland ~ two distinct glands
in one
Adrenal Medulla – smaller interior part
Adrenal Cortex – larger portion
surrounds medulla
Each produces different types of
hormones
BOTH are stimulated in response to
stressful situations
Adrenal Cortex
Adrenal Cortex
Adrenal Cortex
Zona glomerulosa
Hormones
Mineralocorticoids
(Aldosterone)
Zona fasciculata
Gluco-corticoids
Cortico-steroids
(Cortisone, Cortisol)
Zona reticularis
Gonado-corticoids
Function
Mineral & water balance
Na+ retention
Gluconeogenesis
Energy Metabolism
Anti-inflammatory
Immune Supression
Sex Hormones
(Androgen)
Adrenal Medulla
Adrenal Medulla
Hormones
Hormones
Catecholamines
Adrenalin
Epinephrine
Nor-Epinephrine
Function
Increases BP
Increases HR
Dilates Bronchioles
Decrease Peristalsis
ADRENAL CORTEX
MINERALOCORTICOIDS ~ Aldosterone
Aldosterone ~ 95% of mineralo-corticoids
Produced in Zona Glomerulosa
Regulate Na+ concentration in body fluids &
blood
Retains Na+ ~ most vital ion causing fluid
retention
Sodium retention causes fluid retention ~
EDEMA
Retains water & fluid ~ same effect
as ADH
Aldosterone Effects
Reduces Na+ excretion from body
Retains Na+ from urine in kidney tubules
Retains Na+ from perspiration & saliva
Water follows sodium > > > fluid retention
Aldosterone Secretion Stimuli
Anything Requiring Fluid Retention
Decreased Na+ blood levels
Decreased blood volume
Shock
Decreased blood pressure Dehydration
Blood Loss
Aldosterone Release Mechanisms
Renin-Angiotensin-Aldosterone Mechanism ~ MAJOR
1.
Low blood pressure or lost blood volume is
sensed by juxtaglomerular apparatus in kidney
2.
Kidney releases Renin into blood
3.
Renin ----> Angiotensin I in blood
Angiotensin I ----> Angiotensin II in blood
4.
Angiotensin II stimulates adrenal cortex to release
Aldosterone which ----> Na+ retention in the kidney
5.
Na+ & water retained in the blood ---->increasing
blood volume & blood pressure ~ decreased urine
Other Aldosterone Release Mechanisms ~ MINOR
ACTH ~ adrenocorticotropic hormone
Severe stress ----> hypothalamus secretes
corticotropin releasing hormone ---->
anterior pituitary to secrete ACTH ---->
release of Aldosterone ----> Sodium
Retention Effects
Atrial Natriuretic Peptide ~ ANP ~ inhibits
aldosterone
Increased blood pressures stimulates heart
to release ANP which inhibits the reninangiotensin mechanism ----> Na+ & water
excretion & lower blood pressure
ADRENAL CORTEX HORMONES
GLUCOCORTICOIDS ~ “Cortisone”
Produced in Zona Fasciculata
Cortisol ~ hydrocortisone ~ most
significant
Cortisone ~ produced in liver from
cortisol
Glucocorticoid Effects ~ MANY
1. Reduces stress ~ prepares body for crisis
Thru gluconeogenesis & glycogenoslysis
“Diabetogenic” Effect ~ ↑ blood sugar
Converts glycogen to glucose
Converts fats to glucose
2. Stimulates protein breakdown to amino acids
3. Anti-Inflammatory ~ reduces swelling ~ “cortisone”
4. Supresses immunity ~ organ transplants
5. Stimulates appetite ~ “cortisol”
6. Used as a synthetic drug ~ allergy & inflammation
Cortisone . . . Prednisone . . . Hydrocortisone
Glucocorticoid Hormone Release stimulated by stress
Physical & Emotional trauma . . .
Hemorrhage . . . Illness
Severe stress ----> hypothalamus
secretes corticotropin releasing
hormone ----> anterior pituitary to
secrete ACTH ----> stimulates release of
Cortisol & Cortisone
GONADOCORTICOIDS ~ Sex Hormones
Produced in Zona Reticularis of Adrenal Cortex
Mainly Androgen ~ male sex hormone ~ Testosterone
Some Estrogen ~ female sex hormone
Lower concentrations than ovaries & testis
Significant levels ~ up to puberty ~ between ages of 7-13
Hyper-secretion could cause masculinization in children
Early hair ~ beard
Deeper voice
Sexual aggressiveness
ADRENAL MEDULLA
Centrally located in adrenal gland ~ Smaller
portion
Secretes CATECHOLAMINES - effects
Sympathetic NS
80% Epinephrine & 20% Norepinephrine
= Adrenaline
Release: Stress stimulates the sympathetic
nervous system ~ prepares body for crisis
Immediate Response ~ “short acting”
Sympathomimetic Effects:
Blood sugar rises
Heart beats faster
Blood pressure increases
Bronchioles dilate ~ more air
Pupils dilate ~ more light
Digestion & Peristalsis Slows
Visceral Vasodilation & Peripheral Vasoconstriction
diverts Blood to where it is needed
From skin & digestive organs to brain, heart & skeletal
muscle
MAJOR ENDOCRINE ORGANS
PANCREAS
Large, soft, triangular
- posterior to
stomach
Mixed gland:
Endocrine &
Exocrine function
Exocrine Pancreas ~ 99%
Ascinar Cells ~ epithelial cells ~ 99% of
gland
Digestive enzymes ducted into small
intestine
Amylase
~ carbohydrate
breakdown
Lipase
~ lipid breakdown
Protease
~ protein breakdown
Endocrine Pancreas ~ 1%
Islets of Langerhans~ 1% of Gland
Tiny island cluster cells among Ascinar cells
Alpha cells ~ secrete Glucagon
Beta cells ~ secrete Insulin
Both regulate blood glucose ~ effects are opposite
Glucagon ~ raises blood glucose ~ hyper-glycemic
Insulin ~ lowers blood glucose ~ hypo-glycemic
GLUCAGON
Protein produced in alpha cells ~ (islets of
langerhans)
Potent hyper-glycemic effects:  Blood Sugar
Glucagon Secretion ~ Humoral Stimuli
Stimulated by:
Falling blood sugar levels
Inhibited by:
Rising blood sugar levels
Effects of Glucagon ~ Glucagon  Blood Sugar
1. Breaks down glycogen to glucose ~
glycogenolysis
2. Stimulates Glucose Synthesis from fats &
amino acids…. “gluconeogenesis”
3. Stimulates Release of glucose from liver
into blood  blood sugar
4. Stimulates breakdown of protein to Amino
Acids…. “Catabolic Effect”
INSULIN
Small protein ~ made in beta cells ~ islets of
langerhans
Potent hypoglycemic effects
 Blood Sugar
Insulin Secretion ~ Humoral Stimuli
Stimulated by: Rising blood sugar levels
Eating a meal
Other hyperglycemic hormones
Glucagon Growth Hormone
Thyroxin
Glucocorticoids
Adrenalin
Inhibited by:
Lower blood sugar levels
Major Effects of Insulin ~ opposite of glucagon
1. Enhances glucose uptake & utilization by all cells
2. Stimulates glycogen storage in muscle & liver
Inhibits Glycogenolysis ~ lowers blood sugar
3. Inhibits conversion of fats & amino acids to glucose
Inhibits Gluconeogenesis ~ lowers blood sugar
4. Stimulates protein synthesis from amino acids
“Anabolic Effect”
5. Stimulates Glucose conversion to fat for storage
OTHER ENDOCRINE ORGANS
PINEAL GLAND
Tiny pine cone shaped
. . . in epithalamus
of diencephalon
Soft tissue landmark ~
pineal sand/calcium
for brain X-rays
PINEAL GLAND
Endocrine function is a mystery ~
biorythms/sleep-wake/temp
MELATONIN ~ pineal gland hormone
* Peak levels at night make us
drowsy
* Stimulation of pineal gland related
to visual light
* Influences sleep/wake cycle, body
temperature, & appetite ~ biorythms
THYMUS
• Large in infants &
children ~ provides
immunity in children
• Located deep to
sternum in upper
thorax at base of
heart
• Becomes adipose
tissue & connective
tissue with age ~
scars
THYMUS
Secretes hormones:
Thymopoitens
Thymosins
Effect: Normal development of Tlymphocytes ~ T-cells
Important in the immune response ~
infant & young
GONADS
Male Gonads ~ Testis
Female Gonads ~ Ovaries
Produce more sex hormones than the
adrenal cortex . . .
Release regulated by FSH & LH
gonadotropins from pituitary
OVARIES
• Two oval shaped . . .
Posterior abdominal
cavity
• Produce ova or
eggs for fertilization
• Produce female
ovarian hormones
OVARIES
ESTROGEN ~ release influenced by FSH
Released from follicle cells of ovaries
Causes maturation of reproductive organs
Female secondary sex characteristics ~ puberty
Menstrual cycle ~ uterus cyclic changes
PROGESTERONE ~ release influenced by LH
Released from corpus luteum ~ old follicle
Maintains pregnancy ~ secreted for months
TESTES
• Two ~ Located in
“extra-abdominal”
sac ~ scrotum
• Produce sperm
(influenced by FSH)
& male sex hormone
TESTES
Testicular Hormones ~ male hormone ~
androgens
TESTOSTERONE ~ release influenced by LH
Produced in interstitial cells of testis
Causes maturation of male reproductive
organs
Male secondary sex characteristics & sex
drive
Necessary for normal sperm production
OTHER HORMONE PRODUCING STRUCTURES
Not really endocrine glands . . . but have
other endocrine cells
HEART
Atrial wall stretched by excess fluid volume &
pressure
Releases: Atrial Natriuretic Peptide ~ ANP
Effects of ANP:
Inhibits Aldosterone release by adrenal cortex
Inhibits sodium & fluid retention
Reduces blood volume & lowers blood pressure
GASTROINTESTINAL TRACT (GIT)
ORGANS
Several Hormones Released to aid digestion
Hormone
Source
Target Organ & Effect
Gastrin
Stomach
Stomach HCL Release
Serotonin
Stomach
Stomach Contraction
Intestinal gastrin
Duodenum
Inhibits stomach HCL
Slows GI Motility
Secretin
Duodenum
Inhibits gastric secretions
Release bicarbonate from
pancrease & liver
Cholecystokinin
Duodenum
Pancreatic juices & bile
Amylase~CHO
Lipase~Fats
Protease~Proteins
KIDNEY
Erythropoietin ~ EPO
Influences bone marrow to produce more RBC’s
Renin
Stimulates Aldosterone
SKIN
Cholicalciferol
Precursor to Vitamin D3
Intestine absorb of Ca++
HORMONES INVOLVED IN
GROWTH
Involves coordination of several
endocrine organs
Important Hormones: Growth Hormone
Thyroid Hormone
Insulin
Parathyroid Hormone
Calcitrol ~ for Ca++
absorption
Reproductive Hormones
HORMONES INVOLVED IN AGING
Few functional changes with age ~ most
work until death
Major changes involve decline of
reproductive hormones
Decline in Growth Hormone
Other changes due to disease processes ~
i.e., diabetes
HORMONES INVOLVED IN STRESS
Stress Activates the General Adaptation
Syndrome
Involves: Hypothalamus . . . Adrenal
Gland . . . Organs
Alarm Phase
~ immediate fight or flight ~ adrenaline
Neural Stimulation ~ immediate ~ short acting
Catecholamines:
Epinephrine & Norepinephrine
Sympathetic Effects: ↑ BP . . . ↑ HR . . . ↓
Digestion