Date post: | 19-Jun-2015 |
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Endocrine Glands
Endocrine Glands• Hypothalamus• Pituitary
– Anterior lobe– Posterior lobe
• Thyroid gland• Parathyroid
glands• Adrenal Glands
– Cortex– Medulla
• Islets of Langerhans
• Gonads– Ovaries– Testes
• Pineal gland• Thymus• others
Hormonal Communication
Hypothalamus
• Part of brain– Regulates ANS,
emotions, feeding/satiety, thirst, body temperature, etc.
– Hormones related to these functions
• “Releasing hormones”
• Axonal transport to posterior lobe
Anterior Pituitary
• “Releasing” hormones regulate AP aka adeno hypo physis “glands” “under” “growth”
• All proteins– TSH (thryoid stimulating
hormone/thyrotropin)
– ACTH (adrenocorticotropic hormone)
– FSH (gonadotropin)– LH (gonadotropin)
• Tropins/tropic hormones
– GH (growth hormone)– Prolactin-releasing H
Hypothalamic Pituitary Axis Animation : IP Web
Anterior Pituitary
Anterior P. Homeostatic Imbalances
Growth hormone (GH or hGH)– Promotes mitosis, cell division– Elongation of long bones, etc.– Healing of wounds Lack of hGH
retards growth – Hypersecretion in youth produces
giantism– Hyposecretion in childhood
produces pituitary dwarfism– Hypersecretion in adult produces
acromegaly
Posterior Pituitary
• Axonal transport to Posterior Pituitary akaneuro hypo physis
“nerve” “under” “growth”
• Hypothalamic cell bodies synthesize – oxytocin – ADH
Pituitary—Posterior lobe• Oxytocin
– Stimulates smooth muscle contraction of uterus & mammary glands.
• Antidiuretic H.– Stimulates water
reabsorption in collecting ducts.
– Stimulates vasoconstriction (vasopressin)
– Lack diabetes insipidus
Posterior Pituitary Homeostatic Imbalances
ADH– Hyposecretion produces
diabetes insipidus “tasteless”– Excessive thirst and urination
• central or neurogenic DI • gestagenic or gestational
DI • nephrogenic DI • dipsogenic DI
Diabetes Insipidus Foundation, Inc.
Thyroid Gland• Location in neck
– Inferior to larynx– Anterior & lateral to
trachea
• Composed of follicles– Follicle cells produce
thyroglobulin• Thyroxin (T4)• Triiodothyronine (T3)
– Both “thyroid hormone”, body’s major metabolic hormone
• Parafollicular/ C cells• Calcitonin
– Decreases blood Ca2+ by depositing it in bones
Homeostatic imbalances• Hypothyroidism results
– Myxedema (in adults)
– Goiter—low levels of iodine
– Cretinism (in children)
• Hyperthyroidism results– Graves disease
Parathyroid Glands
• Four small glands embedded in posterior of thyroid– Parathyroid hormone
(PTH)– Stimulates osteoclasts
to free Ca2+ from bone– Stimulates Ca2+ uptake
from intestine & kindey
Hormonal Regulation of Calcium
Parathyroid Homeostatic Imbalances
• Severe hyperparathyroidism causes massive bone destruction
• If blood Ca2+ fall too low, neurons become overactive, resulting in tetany
Feedback Loop• Negative feedback in
calcium homeostasis. A rise in blood Ca2+ causes release of calcitonin from the thyroid gland, promoting Ca2+ deposition in bone and reducing reabsorption in kidneys.
• A drop in blood Ca2+ causes the parathyroid gland to produce parathyroid hormone (PTH), stimulating the release of Ca2+ from bone.
• PTH also promotes reabsorption of Ca2+ in kidneys and uptake of Ca2+ in intestines.
Adrenal Glands
One on top of each kidney
• Cortex– Corticosteroid– glandular
• Medulla– Catecholamines– neurohormonal
• Epinephrine• Norepinephrine
Adrenal Cortex• Cortex
– Activity stimulated by ACTH– Controls prolonged responses
by secreting corticosteroids. – Mineralcorticoids
• Aldosterone regulate salt and water balance
– Glucocorticoids• Cortisol regulate glucose
metabolism and the immune system.– Gonadocorticoids
• Androgens• Estrogens
Adrenal Cortex Imbalances• Hypersecretion leads
to Cushing’s disease– ACTH-releasing
tumors or side effects of corticoid drugs.
• Hyposecretion leads to Addison’s Disease– Deficits in
glucocorticoids and mineralcorticoids
Adrenal Medulla• Medulla
– The adrenal medulla mediates short–term responses by secreting catecholamine hormones.
– Cells are modified neurons (lack axons)
• Epinephrine (adrenaline)• Norepinephrine (noreadrenaline)
– enable a rapid ( fight-or-flight ) responses to stress by increasing blood glucose and blood pressure and directing blood to the heart, brain, and skeletal muscles.
Pancreas• Consists of two major
types of secretory tissues which reflects its dual function – Exocrine gland
• secretes digestive juice • localized in the acinar cells
– Endocrine gland • releases hormones• localized in the islet cells
(islets of Langerhans)
Pancreatic Islets• “About a million”
embedded in pancreas• Control centers for
blood glucose– Insulin from beta cells– Glucagon from alpha
cells
Insulin Glucagon
Islets of Langerhans• Insulin stimulates
glucose uptake, glycogenesis
• Glucagon stimulates glycogenolysis, glucose release from liver (vs gluconeogenesis)
Feedback Loop
•A rise in blood glucose causes release of insulin from beta cells the pancreas, promoting glucose uptake in cells and storage as glycogen in the liver.
•A fall in blood glucose stimulates alpha cells in the pancreas to secrete glucagon, which causes the liver to break down glycogen and release glucose.
Pancreas Homeostatic ImbalancesDiabetes “siphon” mellitus mel= “honey”
Symptoms:•Polyuria•Polydipsia•Polyphagia
Blood Level Regulation in Diabetics
Gonads• Ovaries
– Estrogens– Progesterone
• Testes– Testosterone
• Reproductive functions when we study reproductive system.
Pineal gland• Melatonin
– ? Inhibits early puberty– ? Day/night cycles
• Timing of sleep, body temperature, appetite
• Secretes melatonin during darkness– Participates in setting the
body’s clock• Melatonin is a potent
antioxidant• Melatonin is high when young
and is reduced as we age
Thymus
• Thymus gland• Thymopoietins,
thymic factor, thymosins– Influence
development of T lymphocytes
Non-Endocrine Gland Hormones
• Stomach (gastrin)• Small intestine (duodenumintesetinal
gastrin, secretin, cholecystokinin)• Heart (atrial natriuretic peptide)• Kidneys (erythropoietin, active vitamin D3)• Adipose tissue (leptid, resistin)• Skin • Placenta (human chorionic gonadotropin,
human placental lactogen, relaxin)
Functions regulated by the Endocrine System
• Growth• Healing• Water balance & Blood Pressure• Calcium Metabolism• Energy Metabolism• Stress• Regulation of other Endocrine
Organs
Growth
• Growth hormone-releasing hormone
• Human growth hormone (hGH)• Thyrotropin (TSH)• Thyroxine & triiodothyronine• Calcitonin • Somatostatin (GHIH)
Healing
• Growth hormone-releasing hormone
• Human growth hormone (hGH)• Thyrotropin (TSH)• Thyroxine & triiodothyronine• Calcitonin • Glucagon, Insulin• Erythropoietin
Water balance & Blood pressure
• ADH• Aldosterone• Angiotensin II• Atrial natriuretic H.• Epinephrine
Calcium Metabolism
• Calcitonin• Parathyroid H. (PTH)• Estrogens/androgens• Growth hormone
Energy Metabolism
• Thyroxine & triiodothyronine• Thyroid-stimulating H. (thyrotropin,
TSH)• Epinephrine & norepinephrine• Insulin• Glucagon• Adrenocorticotropic H. (ACTH) • Cortisol
Stress
• Epinephrine & norepinephrine
• T4 &T3 ??
• ACTH• Cortisol