Endocrine system

Chapter 45

Endocrine system Regulation & communication Blood system Glands (ductless) Hormones (chemicals) Target tissues

Bloodvessel Response

(a) Endocrine signaling

Nervous system Regulation & communication Nerves Axon Neurotransmitters Synapse

Both systems (overlap) Neurohormone Released by the nervous system Into blood stream (ADH)

Norepinephrine Chemical involved in both Nervous system (cleft) Endocrine system (adrenal gland)

Both systems Neural control of endocrine system Hypothalamus Regulates hormonal secretion of the

anterior pituitary Glands derived from nervous tissue Adrenal medulla, posterior pituitary

& pineal gland

Local regulators Paracrine Messages between neighboring cells 1. Cytokines

Regulate immune system 2. Growth factors

Regulate cell growth 3. NO

Vasodilation (local blood vessels)

Local regulators 4. Prostaglandins 20-carbon fatty acid Derived from lipids in plasma

membrane Found in many organs Released into interstitial fluid

Local regulators 4. Prostaglandins A. Immune system

inflammation B. Reproductive system

Labor Semen

C. Digestive system Inhibit gastric secretions Increase gut motility

Local regulators D. Respiratory system

Some cause dilation Some cause constriction

E. Circulatory system Platelets

F. Urinary system Renal vasodilation Increased excretion

Hormone types 1. Polypeptide

Short, <100 aa, insulin, ADH 2. Glycoprotein

>100 aa, carbohydrate attached, FSH, LH 3. Amines

Tyrosine & tryptophan Adrenal medulla (NE, Epinephrine) Thyroid (T3 & T4

Pineal (Melatonin)

Hormone types 4. Steroids

Lipids from cholesterol Testosterone Estradiol, progesterone Aldosterone, cortisol

Mechanism of regulation 1. Enter the cell Lipophilic Lipid soluble 2. Do not enter the cell Lipophobic Water soluble

Mechanism of regulation 1. Lipophilic (Steroids, thyroxine) Not water soluble Plasma attached to protein carriers Target cell-release carrier Cross plasma membrane Bind receptor protein (+/- nucleus) Hormone receptor binds DNA Protein synthesis

Mechanism of regulation

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Mechanism of regulation 2. Lipophobic or too large Bind receptors on target cell

membrane A. Triggers second-messenger system cAMP IP3/Ca+2

B. Causes change in an ion channel

Mechanism of regulation

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Mechanism of regulation

Mechanism of regulation

Mechanism of regulation

Thyroid Neck 2 lobes/isthmus T4 (tetraiodothyronine) thyroxine T3 (triiodothyronine) Regulates metabolism in the body Calcitonin Stimulates Ca2+ uptake into bones Decreases serum Ca+2

Thyroid

Parathyroid glands Neck 4 small glands on top of thyroid PTH (parathyroid hormone) Increase in blood calcium levels Stimulates osteoclasts Break down calcium phosphate crystals Stimulates kidneys to reabsorb Ca2+

Activates Vitamin D

Parathyroid glands

Pancreas Abdomen behind stomach Islets of Langerhans Insulin ( cells) Decreases blood glucose levels Stores in glycogen (liver/muscle) & fat

(adipose cells) Glucagon ( cells) Increases glucose blood levels

Pancreas

Ovaries Abdomen Estrogen Secondary female characteristics Menstruation Progesterone Prepares/maintains pregnancy

Testes Inguinal region Testosterone Maintain male characteristics

Ovaries and Testes

Steroids

Adrenal glands Small glands on top of kidneys 1. Adrenal cortex Outer layer 2. Adrenal medulla Inner layer

Adrenal glands Adrenal cortex A. Corticosteriods Cortisol (glucocorticoid) Increases serum levels of glucose Gluconeogenesis Converts aa to glucose Exercise or fasting

Adrenal glands B. Mineralcorticoids Aldosterone Stimulates kidneys to reabsorb Na+1

Stimulates kidneys to eliminate K+1

C. Gonadocorticoids Androgens Sex characteristics

Adrenal glands Adrenal medulla Catacholamines Epinephrine/norepinephrine Increased heart rate, BP, glucose

blood levels, Dilation of bronchioles Decreased blood flow to skin and gut

Adrenal glands

Pituitary gland (hypophysis) In the brain Hangs by a stalk from hypothalamus 1.Anterior Adenohypophysis Developed from epithelial tissue 2. Posterior Neurohypophysis Developed from the neural tissue Nerve axons from hypothalamus end here

Pituitary gland

Anterior pituitary gland All hormones stimulate growth in

target organs Tropins A. GH (growth hormone) Somatotropin Stimulates muscle growth (bone)

Anterior pituitary gland B. ACTH Adrenocorticotropic hormone Corticotropin Stimulates adrenal cortex (cortisol) C. TSH Thyroid-stimulating hormone Thyrotropin Stimulates thryroid to produce thyroxine

Anterior pituitary gland D. LH Luteinizing hormone Stimulates ovulation & lining of

uterus Stimulates testes to produce

testosterone

Anterior pituitary gland E. FSH Follicle stimulating hormone Stimulates the egg development Development of sperm F. Prolactin Stimulates mammary glands to

produce milk

LH, FSH

Anterior pituitary gland G. MSH Melanocyte-stimulating hormone Causes darkening of skin in some

fish, amphibians & reptiles

Posterior pituitary gland A. ADH Antidiuretic hormone (vasopressin) Stimulates water retention in the

kidneys B. Oxytocin Milk ejection from mammary glands Stimulates uterine contractions in

labor

Pituitary gland

Pineal gland Small mass of tissue located near

center of brain Synthesizes & secretes melatonin

(modified aa) Regulates functions related to day

and night Seasons

Hypothalamus

Spinal cord

Posteriorpituitary

Cerebellum

Pinealgland

Anteriorpituitary

Hypothalamus

Pituitarygland

Hypothalamus

Thalamus

Cerebrum

Hypothalamus control Posterior pituitary (direct) Stimulation in hypothalamus Causes release of hormone from

axon in pp ADH released increased blood

osmolality Oxytocin released due to baby

suckling

Hypothalamus

Posteriorpituitary

Anteriorpituitary

Neurosecretorycells of thehypothalamus

Hypothalamus

Axon

HORMONE OxytocinADH

Kidney tubulesTARGET Mammary glands,uterine muscles

Hypothalamus control Controls release of AP hormones Neurons in Hypothalamus secrete

releasing or inhibiting hormones Anterior Pituitary (negative

feedback)

Hypothalamus

thyroid

Cold

Pathway

Stimulus

Hypothalamus secretesthyrotropin-releasinghormone (TRH )

Example

Sensoryneuron

Neurosecretorycell

Bloodvessel

+

Anterior pituitary secretesthyroid-stimulatinghormone (TSHor thyrotropin )

thyroid

Cold

Pathway

Stimulus

Hypothalamus secretesthyrotropin-releasinghormone (TRH )

Neg

ativ

e fe

edb

ack

Example

Sensoryneuron

Neurosecretorycell

Bloodvessel

Anterior pituitary secretes thyroid-stimulatinghormone (TSHor thyrotropin )

Targetcells

Response

Body tissues

Increased cellularmetabolism

–

Thyroid gland secretes thyroid hormone (T3 and T4 )

–

Anterior pituitary

Hypothalamicreleasing andinhibitinghormones

Neurosecretory cellsof the hypothalamus

HORMONE

TARGET

Posterior pituitary

Portal vessels

Endocrine cells ofthe anterior pituitary

Pituitary hormones

Tropic effects only:FSHLHTSHACTH

Nontropic effects only:ProlactinMSH

Nontropic and tropic effects:GH

Testes orovaries

Thyroid

FSH and LH TSH

Adrenalcortex

Mammaryglands

ACTH Prolactin MSH GH

Melanocytes Liver, bones,other tissues

Problems Thyroid Graves disease Over production of thyroxine Cretinism To little thyroxine in children Leads to delayed skeletal and

mental growth

Hyperthyroidism

Negative feedback

Problems Diabetes mellitus Decreased insulin Decreased response to insulin Increased blood sugar

Diabetes

Problems Growth hormone (anterior

pituitary) Gigantism too much hormone Pituitary dwarfism to little hormone Acromegaly to much hormone

after growth plates are fused

Acromegaly

Problems Addison’s disease Insufficiency in ACTH Increased pigmentation of skin Imbalance of electrolytes