Endocrine System

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Endocrine System
2014
Anatomy K and L
Mrs. Shott
Homeostasis is preserved through
intercellular communication
• Nervous system and Endocrine system work together to maintain
homeostasis
• HOW DO THEY COMMUNICATE?
• Chemical messengers called HORMONES – relay info between cells
• Hormones act on target cells or tissues that respond to the presence of the hormone
10-1 – Comparison of Nervous and Endocrine
• Nervous System – FAST
• Endocrine – Slow, and ongoing action
-Both systems rely on chemicals that bind to specific receptors
on target cells
- Both systems SHARE various chemical messengers
-Both systems regulated mainly by negative feedback
-Both systems coordinate and regulate activities of other cells
and tissues, organs and systems to maintain homeostasis
Endocrine vs Exocrine
• Endocrine cells – glandular secretory cells that release their
secretions into the extracelluar fluid
• Exocrine cells – release their secretions into epithelial surfaces
3 Classes of Hormones
1. Amino Acid derivatives – structurally similar to amino acids (the
building blocks of proteins)
• Examples:
• Epinephrine, Norepinephrine, Thyroid hormones and Melatonin
3 Classes of Hormones
2. Peptide hormones – chains of amino acids
Examples: Antidiuretic hormone (ADH), Oxytocin, Growth hormone (GH),
Prolactin (PRL)
3 Classes of Hormones
3. Lipid Derivatives – there are 2 classes of lipid based hormones:
steroid hormones and eiocosanoids
Steroid hormones – lipids that are structurally similar to
cholesterol; released by the reproductive organs and adrenal
glands; not water soluble, bound to specific transport proteins in
blood
Eiocosanoids – fatty acid based compounds derived from
arachidonic acid; includes prostaglandins
Peptides
Insulin
Glucagon
Growth hormone
Vasopressin (ADH,
Antidiuretic
hormone)
Prolactin
Erythropoietin
Atrial natriuretic
peptide (ANP)
Amines
T4 (thyroxine)
Norepinephrine
T3
(triiodothyronine)
Epinephrine
Melatonin
Steroids
Estradiol
Aldosterone
Cortisol
Testosterone
Glucocorticoids –
cortisol,
corticosterone,
cortisone
Calcitriol
Progesterone
Estrogens
Control of Endocrine Activity
• Hormonal secretion is controlled by negative feedback mechanisms
• Levels of hormone secretion can be affected by:
• Levels of certain substances in the blood
• Hormonal stimuli – changing levels in circulating hormones
• Neural stimuli – resulting from the arrival of neurotransmitter at a neuroglandular
junction
Hypothalamus – provides highest level of endocrine control
It links the nervous and endocrine systems
Hypothalamus  Pituitary glandTarget cell or tissue
1. It acts as an endocrine organ by releasing hormones into the
bloodstream at the posterior lobe of the pituitary gland
2. It secretes regulatory hormones that control the activities of
endocrine cells in the anterior lobe of the pituitary gland
3. It exerts direct neural control over the endocrine cells of the
adrenal medulla
Pituitary Gland
• Divided into 2 portions –
• Anterior lobe – produces 7 hormones and is composed of glandular tissue
• Posterior lobe – produces 2 hormones and is composed of neural tissue
(axons of hypothalamic neurons that manufacture hormones)
Figure 10-6 The Hypophyseal Portal System and the Blood Supply to the Pituitary Gland.
Hypothalamic nuclei
producing ADH
and oxytocin
Hypothalamic neurons
producing regulatory
hormones
HYPOTHALAMUS
Optic
chiasm
Capillary
beds
ANTERIOR LOBE OF
PITUITARY GLAND
Mamillary body
Hypophyseal artery
Infundibulum
Portal veins
Hypophyseal artery
POSTERIOR LOBE OF
PITUITARY GLAND
Endocrine cells
Hypophyseal veins
© 2013 Pearson Education, Inc.
Anterior Lobe of Pituitary Gland
1. TSH – Thyroid stimulating hormone = triggers the release of thyroid
hormones
2. ACTH – Adrenocorticotropic hormone = stimulates the release of
glucocorticoids by the adrenal glands
3. FSH – Follicle stimulating hormone = stimulated estrogen secretion
and egg development in females and sperm production in males
4. LH – Luteinizing hormone = causes ovulation and progestin
production in females and androgen (testosterone) production in
males
Anterior Lobe of Pituitary Gland
5. PRL – Prolactin = stimulates the development of the mammary
glands and the production of milk
6. GH – Growth hormone = stimulates cell growth and replication by
triggering the release of somatomedins (a family of growthpromoting proteins produced by the liver, skeletal muscle, bone and
other tissues) from liver cells
7. MSH – Melanocyte stimulating hormone – may be secreted during
fetal development, early childhood, pregnancy, or certain diseases.
Stimulates melanocytes to produce melanin
Posterior Lobe of Pituitary Gland
1. ADH – Antidiuretic hormone = decreases the amount of water lost
at the kidneys (secreted primarily by the supraoptic neurons)
2. OXT – Oxytocin = in females oxytocin stimulates smooth muscle
cells in the uterus and contractile cells in the mammary glands. In
males it stimulates the contractions of the smooth muscles in the
sperm duct and prostate gland. (secreted primarily by the
paraventricular neurons)
Figure 16.5 The hypothalamus controls release of hormones from the pituitary gland in two different ways. (1 of 2)
Posterior Pituitary:
Paraventricular nucleus
Hypothalamus
Posterior lobe
of pituitary
Optic
chiasma
Infundibulum
(connecting stalk)
Hypothalamichypophyseal
tract
Supraoptic
nucleus
Inferior
hypophyseal
artery
Axon terminals
2
Oxytocin and ADH are transported down
the axons of the hypothalamic- hypophyseal
tract to the posterior pituitary.
3 Oxytocin and ADH are stored in axon
terminals in the posterior pituitary.
Posterior lobe
of pituitary
Oxytocin
ADH
© 2013 Pearson Education, Inc.
1 Hypothalamic neurons synthesize
oxytocin or antidiuretic hormone
(ADH).
4
When hypothalamic neurons fire, action
potentials arriving at the axon terminals
cause oxytocin or ADH to be released into
the blood.
Figure 16.5 The hypothalamus controls release of hormones from the pituitary gland in two different ways. (2 of 2)
Anterior Pituitary:
Hypothalamus
Anterior lobe
of pituitary
Superior
hypophyseal
artery
2
Hypothalamic hormones travel through
portal veins to the anterior pituitary where
they stimulate or inhibit
release of hormones made in the anterior
pituitary.
3 In response to releasing hormones,
the anterior pituitary secretes hormones
into the secondary capillary plexus. This
in turn empties into the general
circulation.
GH, TSH, ACTH,
FSH, LH, PRL
Anterior lobe
of pituitary
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Hypothalamic
neurons synthesize
GHRH, GHIH, TRH,
CRH, GnRH, PIH.
1 When appropriately stimulated, hypothalamic
neurons secrete releasing or inhibiting
hormones into the primary capillary plexus.
Hypophyseal
portal system
• Primary capillary
plexus
• Hypophyseal
portal veins
• Secondary
capillary plexus
A portal system
is two capillary
plexuses (beds)
connected by
veins.
• Ok – Endocrinology – is a whole BRANCH of medicine,
so at this point we have to pick and choose what to
cover… otherwise we’d spend the rest of the year on this
unit!
• The next few slides aren’t in your book, they’re from a
different Anatomy text, you don’t have to KNOW
everything here, the “jist” of it is the chain of command…
take pics if you wish!
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Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (2 of 4)
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Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (3 of 4)
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Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (4 of 4)
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Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (1 of 4)
© 2013 Pearson Education, Inc.
Figure 16.8 Regulation of thyroid hormone secretion.
Hypothalamus
TRH
Anterior pituitary
TSH
Thyroid gland
Thyroid
hormones
Target cells
© 2013 Pearson Education, Inc.
Stimulates
Inhibits
Figure 16.9 The thyroid gland.
Hyoid bone
Thyroid cartilage
Common carotid
artery
Inferior thyroid
artery
Trachea
Epiglottis
Colloid-filled
follicles
Follicular cells
Superior thyroid
artery
Isthmus of
thyroid gland
Left subclavian
artery
Left lateral
lobe of thyroid
gland
Aorta
Parafollicular cells
Gross anatomy of the thyroid gland, anterior view
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Photomicrograph of thyroid gland
follicles (145x)
Table 16.2 Major Effects of Thyroid Hormone (T4 and T3) in the Body (1 of 2)
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Table 16.2 Major Effects of Thyroid Hormone (T4 and T3) in the Body (2 of 2)
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Figure 16.11 Thyroid disorders.
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Parathyroid hormones
• Parathyroid glands – 2 pairs embedded in the posterior
surfaces of the thyroid gland
• Chief cells – secrete parathyroid hormone
• PTH causes increased calcium concentrations in body fluids (the
opposite of Calcitonin – secreted by C cells in the thyroid – causes
decreased calcium concentrations in body fluids)
Figure 16.12 The parathyroid glands.
Pharynx
(posterior
aspect)
Capillary
Thyroid
gland
Parathyroid
glands
Esophagus
Trachea
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Parathyroid
cells
(secrete
parathyroid
hormone)
Oxyphil
cells
The Adrenal Glands
• Adrenal glands – 2 parts
– Adrenal cortex – 3 zones that produce different corticosteroids,
the outer zone produces mineralcorticoids, the middle zone
produces glucorticoids and the inner zone produces androgens.
– Adrenal medulla – produces 2 hormones, epinephrine (E, or
adrenaline) and norepinephrine (NE, or noradrenaline)
Adrenal Cortex
• Three layers of cortex produce the different
corticosteroids
– Zona glomerulosa—mineralocorticoids
– Zona fasciculata—glucocorticoids
– Zona reticularis—gonadocorticoids
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Figure 16.14 Microscopic structure of the adrenal gland.
Hormones
secreted
Capsule
Zona
glomerulosa
Aldosterone
Adrenal gland
• Medulla
• Cortex
Cortex
Zona
fasciculata
Cortisol
and
androgens
Kidney
Medulla
Zona
reticularis
Adrenal
medulla
Drawing of the histology of the
adrenal cortex and a portion of
the adrenal medulla
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Epinephrine
and
norepinephrine
Photomicrograph (115x)
Mineralocorticoids
• Regulate electrolytes (primarily Na+ and K+) in ECF
– Importance of Na+: affects ECF volume, blood volume, blood
pressure, levels of other ions
– Importance of K+: sets RMP of cells
• Aldosterone most potent mineralocorticoid
– Stimulates Na+ reabsorption and water retention by kidneys;
elimination of K+
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Glucocorticoids
• Keep blood glucose levels relatively constant
• Maintain blood pressure by increasing action of
vasoconstrictors
• Cortisol (hydrocortisone)
– Only one in significant amounts in humans
• Cortisone
• Corticosterone
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Glucocorticoids: Cortisol
• Released in response to ACTH, patterns of eating and activity,
and stress
• Prime metabolic effect is gluconeogenesis—formation of glucose
from fats and proteins
– Promotes rises in blood glucose, fatty acids, and amino acids
• "Saves" glucose for brain
• Enhances vasoconstriction  rise in blood pressure to quickly
distribute nutrients to cells
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Androgens
• Androgens – the adrenal cortex in both sexes produces
small quantities of androgens – the sex hormones
produced in large quantities by the testes in males
• Converted to estrogens in the bloodstream
• The importance of adrenal production in both sexes is
unclear
Adrenal Medulla
• Medullary chromaffin cells synthesize epinephrine
(80%) and norepinephrine (20%)
• Effects
– Vasoconstriction
– Increased heart rate
– Increased blood glucose levels
– Blood diverted to brain, heart, and skeletal muscle
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Adrenal Medulla
• Responses brief
• Epinephrine stimulates metabolic activities, bronchial
dilation, and blood flow to skeletal muscles and heart
(involved in fight or flight response)
• Norepinephrine influences peripheral vasoconstriction and
blood pressure
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Pineal Gland
• Secretes melatonin
• 3 functions:
– Inhibition of reproductive function (timing of sexual maturation)
– Antioxidant activity – protect CNS neurons from free radicals
– Establishment of day-night cycles of activity – Circadian
rhythms
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Pancreas
• Triangular gland partially behind stomach
• Has both exocrine and endocrine cells
– Acinar cells (exocrine) produce enzyme-rich juice for digestion
– Pancreatic islets (islets of Langerhans) contain endocrine
cells
• Alpha () cells produce glucagon (hyperglycemic hormone)
• Beta () cells produce insulin (hypoglycemic hormone)
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Figure 16.18 Photomicrograph of differentially stained pancreatic tissue.
Pancreatic islet
•  (Glucagonproducing)
cells
•  (Insulinproducing)
cells
Pancreatic acinar
cells (exocrine)
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Glucagon
• Major target—liver
• Causes increased blood glucose levels
• Effects
– Glycogenolysis—breakdown of glycogen to glucose
– Gluconeogenesis—synthesis of glucose from lactic acid and
noncarbohydrates
– Release of glucose to blood
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Insulin
• Effects of insulin
– Lowers blood glucose levels
– Enhances membrane transport of glucose into fat and muscle
cells
– Inhibits glycogenolysis and gluconeogenesis
– Participates in neuronal development and learning and memory
• Not needed for glucose uptake in liver, kidney or brain
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Figure 16.19 Insulin and glucagon from the pancreas regulate blood glucose levels.
Stimulates glucose
uptake by cells
Tissue cells
Insulin
Stimulates
glycogen
formationw
Pancreas
Glucose
Glycogen
Blood
glucose
falls to
normal
range.
Liver
Stimulus
Blood
glucose level
Stimulus
Blood
glucose level
Blood
glucose
rises to
normal
range.
Pancreas
Glucose
Glycogen
Liver
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Stimulates
glycogen
breakdown
Glucagon
Factors That Influence Insulin Release
•
•
•
•
Elevated blood glucose levels – primary stimulus
Rising blood levels of amino acids and fatty acids
Release of acetylcholine by parasympathetic nerve fibers
Hormones glucagon, epinephrine, growth hormone, thyroxine,
glucocorticoids
• Somatostatin; sympathetic nervous system
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Homeostatic Imbalances of Insulin
• Diabetes mellitus (DM)
– Due to hyposecretion (type 1) or hypoactivity (type 2) of insulin
– Blood glucose levels remain high  nausea  higher blood glucose
levels (fight or flight response)
– Glycosuria – glucose spilled into urine
– Fats used for cellular fuel  lipidemia; if severe  ketones (ketone
bodies) from fatty acid metabolism  ketonuria and ketoacidosis
– Untreated ketoacidosis  hyperpnea; disrupted heart activity and O2
transport; depression of nervous system  coma and death possible
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Diabetes Mellitus: Signs
• Three cardinal signs of DM
– Polyuria—huge urine output
• Glucose acts as osmotic diuretic
– Polydipsia—excessive thirst
• From water loss due to polyuria
– Polyphagia—excessive hunger and food consumption
• Cells cannot take up glucose; are "starving"
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Homeostatic Imbalances of Insulin
• Hyperinsulinism:
– Excessive insulin secretion
– Causes hypoglycemia
• Low blood glucose levels
• Anxiety, nervousness, disorientation, unconsciousness, even death
– Treated by sugar ingestion
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Ovaries and Placenta
• Gonads produce steroid sex hormones
– Same as those of adrenal cortex
• Ovaries produce estrogens and progesterone
– Estrogen
• Maturation of reproductive organs
• Appearance of secondary sexual characteristics
• With progesterone, causes breast development and cyclic changes in uterine mucosa
• Placenta secretes estrogens, progesterone, and human chorionic
gonadotropin (hCG)
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Testes
• Testes produce testosterone
– Initiates maturation of male reproductive organs
– Causes appearance of male secondary sexual characteristics
and sex drive
– Necessary for normal sperm production
– Maintains reproductive organs in functional state
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Other Hormone-producing Structures
• Adipose tissue
– Leptin – appetite control; stimulates increased energy
expenditure
– Resistin – insulin antagonist
– Adiponectin – enhances sensitivity to insulin
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Other Hormone-producing Structures
• Enteroendocrine cells of gastrointestinal tract
– Gastrin stimulates release of HCl
– Secretin stimulates liver and pancreas
– Cholecystokinin stimulates pancreas, gallbladder, and
hepatopancreatic sphincter
– Serotonin acts as paracrine
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Other Hormone-producing Structures
• Heart
– Atrial natriuretic peptide (ANP) decreases blood Na+
concentration, therefore blood pressure and blood volume
• Kidneys
– Erythropoietin signals production of red blood cells
– Renin initiates the renin-angiotensin-aldosterone mechanism
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Other Hormone-producing Structures
• Thymus
– Large in infants and children; shrinks as age
– Thymulin, thymopoietins, and thymosins
• May be involved in normal development of T lymphocytes in immune
response
• Classified as hormones; act as paracrines
© 2013 Pearson Education, Inc.
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