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Chapter 16Endocrine System
Lecture 14
Marieb’s HumanAnatomy and
Physiology
Marieb Hoehn
2
Lecture Overview
• The Adrenal Glands
• The Pancreas
• Other Endocrine Tissues
• Stress and its effects
• Life-span changes
3
Location/Blood Supply of the Adrenal
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
4
Adrenal Glands
Adrenal cortex and medulla are functionally distinct
Figure from: Hole’s Human A&P, 12th edition, 2010
5
Hormones of the Adrenal MedullaEpinephrine (80%) and Norepinephrine (20%)
• derived from amino acid tyrosine• hormones of ‘fight or flight’ are called catecholamines
• release controlled by sympathetic nervous system (neural control of hormone release)• hormone releasing cells are considered equivalent to postganglionic sympathetic neurons
• increases heart rate and blood pressure• dilates respiratory airways• promotes glycogenolysis and gluconeogenesis• activates reticular formation• increases metabolic rates
6
Adrenal Cortex and its Hormones
• Yellowish appearance of cortex is due to stored lipids, especially cholesterol and various fatty acids
• Produces more than 25 steroid hormones
• Hormones of the Adrenal Cortex are…– Called adrenocortical steroids, or corticosteroids
– Carried in blood by transcortins
– Essential to life
– Affect cellular metabolism by determining the nature and concentration of cellular enzymes
– Not stored in cell
7
Adrenocortical Steroids - Aldosterone
• increases blood volume and pressure by promoting conservation of sodium ions and water (distal tubules of kidney)
• Activated by 1) the renin-angiotensin system and by 2) changing concentrations of of Na+ and K+
• Zona glomerulosaAldosterone is a mineralocorticoid
Figure from: Hole’s Human A&P, 12th edition, 2010
8
Adrenocortical Steroids - GlucocorticoidsCortisol (hydrocortisone) – a glucocorticoid
• protein synthesis, protein catabolism • increases fatty acid release (glucose-sparing effect)• stimulates gluconeogenesis• controlled by CRH from hypothalamus and ACTH from anterior pituitary
Produced in the Zona Fasciculata
Blood levels peak shortly after arising in morning
Glucocorticoids have anti-inflammatory and anti-immune effects Figure from: Hole’s Human A&P, 12th edition,
2010
9
Anti-Inflammatory Effects of Steroids
Eicosanoids are important paracrine factors that mediate many processes in the body, including:
- Inflammation- blood vessel constriction - blood clotting- smooth muscle contraction and relaxation
Figure from: Hole’s Human A&P, 12th edition, 2010
10
Adrenocortical Steroids - Androgens
Adrenal androgens (gonadocorticoids)• supplement sex hormones from the gonads (release stimulated slightly by ACTH; inhibitory stimulus unknown). Mostly dehydroepiandrosterone (DHEA)
• may be converted to estrogen in the blood (♀)
• When secreted in normal amounts, neither adrenal androgens or estrogens affect sexual characteristics (may affect sex drive in ♀)
• Produced in the Zona Reticularis
• Tumors of this region can lead to androgenital syndrome (masculinization)
11
Endocrine Pancreas
Figures from: Hole’s Human A&P, 12th edition, 2010
12
Cells of the Pancreatic Islets
• Alpha cells - Glucagon
• Beta cells – Insulin, amylin
• Delta cells– Somatostatin (growth hormone-inhibiting hormone,
GH-IH)• Suppresses release of insulin and glucagon
• Slows rates of food absorption
• F cells– Pancreatic polypeptide (inhibits GB contractions –
exact physiological role is uncertain)
13
Insulin
Insulin decreases blood glucose levels by allowing cells to take up glucose from the blood
Binding enhances glucose uptake
Brain, kidneys, liver, RBCs are insulin independent
Insulin release is also affected by the ANS
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
14
Glucagon
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
Raises blood glucose levels by: - stimulating breakdown of stored molecules- increasing release and formation of glucose
15
Insulin and Glucagon
Example of a humoral stimulus (glucose) for hormone secretion
Figure from: Hole’s Human A&P, 12th edition, 2010
16
Pineal Gland
Pinealocytes synthesize melatonin from serotonin
17
Melatonin
• regulates circadian rhythms - daily changes in physiological processes that follow a regular pattern
Light (eyes) → retina → hypothalamus → reticular formation
melatonin pineal sympathetic fibers spinal cord
• may control onset of puberty (melatonin levels decline at puberty)
• helps regulate female reproductive cycle
• may protect CNS against free radicals (antioxidant)
18
Other Endocrine GlandsReproductive Glands
• ovaries secrete estrogen and progesterone• testes secrete testosterone• placenta secretes estrogen, progesterone, and gonadotropins, e.g., hCG
Thymus Gland• secretes thymosins• promotes development of T-lymphocytes
Heart• secretes natriuretic peptides (ANP, BNP)
- Natri = sodium; uretic = in the urine- promote loss of water and Na+ at the kidney- secreted when atria/ventricles are stretched
- inhibit renin release- inhibit secretion of ADH and aldosterone
19
Other Endocrine Glands• Adipose Tissue
– Leptin• After eating, adipose tissue absorbs glucose and lipids• Peptide hormone, leptin, is released• Binds to receptors in hypothalamus (esp. arcuate and paraventricular
nuclei)– Alters levels of other substances in brain– Increased sympathetic activity– Decreased insulin secretion– Permissive effect on GnRH (effects on reproductive function)– Sense of satiety and suppression of appetite
• Levels are normal in most obese individuals; receptors or cellular pathways may be defective
– Resistin• Reduces insulin sensitivity throughout body (insulin antagonist)• May be one of the ‘missing links’ between obesity and diabetes
– TNF - in obese people, inhibits glut4 protein; activates stress hormones
21
Stress
Types of Stress• physical stress• psychological (emotional) stress
(Stress is any condition, physical or emotional, that threatens homeostasis)
Stress Response (General Adaptation Syndrome [GAS])
• hypothalamus triggers sympathetic impulses to various organs• epinephrine is released• cortisol is released to promote longer-term responses
Three general phases of the GAS in response to stress A R E:
• Alarm phase• Resistance phase• Exhaustion phase
22
Responses to StressExhaustion - lipid reserves
- production of glucocorticoids - electrolyte imbalance - damage to vital organs
Figure from: Hole’s Human A&P, 12th edition, 2010
23
GH Abnormalities
Growth Hormone Ups and Downs
• Gigantism - hypersecretion of GH in children • Acromegaly – hypersecretion of GH in adults• Dwarfism – hyposecretion of GH in children
Age 9 Age 16 Age 33 Age 52
Figure from: Hole’s Human A&P, 12th edition, 2010
24
Diabetes (= Overflow)• Diabetes Mellitus (DM)
– Hyposecretion or hypoactivity of insulin– Three P’s of Diabetes Mellitus (mellitum = honey)
• Polyuria (increased urination)• Polydipsia (increased thirst)• Polyphagia (increased hunger)
– Hyperglycemia, ketonuria, glycosuria
• Renal Glycosuria– excretion of glucose in the urine in detectable amounts– normal blood glucose concentrations or absence of
hyperglycemia
• Diabetes Insipidus (insipidus = tasteless)– Hyposecretion or hypoactivity of ADH– Polyuria– Polydipsia
26
Hormone Summary Table I – Pituitary HormonesTissue
Name Origin Destination Action on Target Tissue Control of Release1
FOLLICLE STIMULATING
HORMONE (FSH)
anterior pituitary
males: seminiferous tubules of testes;females: ovarian
follicle
males: sperm productionfemales: follicle/ovum maturation
Gonadotropin Releasing Hormone (GnRH)
LUETINIZING HORMONE (LH)
anterior pituitary
In males: interstitial cells in testes;
in females: mature ovarian follicle
males: testosterone secretionfemales: ovulation
Gonadotropin Releasing Hormone (GnRH)
THYROID STIMULATING
HORMONE (TSH)
anterior pituitary
thyroid secrete hormonesThyrotropin Releasing
Hormone (TRH)
GROWTH HORMONE (GH)
anterior pituitary
bone, muscle, fat growth of tissuesGrowth Hormone Rleasing
Hormone (GHRH)
ADRENOCORTICO-TROPIC HORMONE
(ACTH)
anterior pituitary
adrenal cortex secrete adrenal hormonesCorticotropin Releasing
Hormone (CRH)
PROLACTIN (PRL)anterior pituitary
mammary glands produce milkProlactin Releasing Hormone
(PRH)
ANTI-DIURETIC HORMONE (ADH)(VASOPRESSIN)
posterior pituitary
Collecting ducts of kidneys
reabsorption of water; increases blood pressure
increase in osmolarity of plasma or a decrease in blood
volume
OXYTOCIN (OT)posterior pituitary
uterine smooth muscle; breast
contraction during labor; milk letdownStretching of uterus; infant
suckling
Se(x)
T
G
A
P
27
Hormone Summary Table IITissue
Name Origin Destination Action on Target Tissue Control of Release
TRIIODOTHYRONINE (T3) & THYROXINE
(T4)
Thyroid (follicular cells)
all cells increases rate of metabolism (BMR)Thyroid Stimulating Hormone
(TSH)
CALCITONIN Thyroid (C cells)Intestine, bone,
kidney
Decreases plasma [Ca2+]( intestinal absorp of Ca; action of
osteoclasts; excretion of Ca by kidney plasma [Ca2+]
PARATHYROID HORMONE (PTH)
ParathyroidsIntestine, bone,
kidney
Increases plasma [Ca2+]( intestinal absorp of Ca; action of
osteoclasts; excretion of Ca by kidney plasma [Ca2+]
EPINEPHRINE/NOREPINEPHRINE
(Catecholamines)Adrenal Medulla
cardiac muscle, arteriole and
bronchiole smooth muscle,
diaphragm, etc
increases heart rate and blood pressure...(fight or flight)
Sympathetic Nervous System
ALDOSTERONE(Mineralocorticoids)
Adrenal CortexKidneys; sweat glands; salivary glands; pancreas
reabsorption of water and Na (increases blood pressure) and excretion of K
(mineralocorticoid)
Angiotensin II plasma [Na+] plasma [K+]
CORTISOL(Glucocorticoids)
Adrenal Cortex all cellsDiabetogenic; anti-inflammatory
(glucocorticoid)ACTH
INSULINβ-cells of
Pancreatic Isletsall cells, liver and skeletal muscle
pushes glucose into cells from blood, glycogen formation (decreases blood glucose)
plasma [glucose]SNS
GLUCAGONα-cells of
pancreatic Isletsliver and skeletal
musclebreakdown of glycogen (increase in blood
glucose) plasma [glucose]
TESTOSTERONE Testessecondary sex
organsdevelopment and maintenance LH
ESTROGEN Ovariessecondary sex
organsdevelopment at puberty and maintenance
throughout lifeLH
NATRIURETIC PEPTIDES
atria and ventricles of heart
adrenal cortex, kidneys
increased excretion of sodium and water from kidneys, blood volume, blood pressure
Stretching of atria and ventricles
28
Review
• Reaction to stress occurs in three stages– Short term
• Alarm or “fight or flight”• Reactions similar to sympathetic stimulation• Mediated by hormones of the adrenal medulla
– Long term• Resistance • Long-term raising of blood glucose• Mediated by hormones of the adrenal cortex
– Exhaustion• Failure of compensatory mechanisms