The Endocrine System

By Evil Mr. Bleecker

Endocrine vs Nervous System

NERVOUSNERVOUS ENDOCRINEENDOCRINE• Uses impulses sent along axons and chemical neurotransmitters at synapses

• Uses chemical hormones released from glands into the blood

• Receptors are on post-synaptic membrane

• Receptors are on the plasma membranes of target cells or intercellular

• Signals are very fast (milliseconds)

• Signals are slower (seconds to days)

• Response is immediate but short-lived

• Response is delayed but more sustained

Characteristics of Hormones

Hormones: exert their effects some distance from where they

are produced

are active under very low (nanogram 10-9) concentrations in the blood

usually have a short half-life in the body - several seconds to 60 mins. They are degraded by enzymes in their target cells or in the kidney or liver.

Characteristics of Hormones

Hormones bring about their effects by altering cell activity. The precise response depends on the target cell type.

Typical cellular effects include: Altering membrane permeability Stimulating protein synthesis Activating enzymes Inducing cells to secrete materials Stimulating mitosis

Control of Hormone Release

Synthesis and release of most hormones are regulated by a Negative Feedback SystemNegative Feedback System. As hormone levels rise, they cause target organ effects which inhibit further hormone release.

Hormone - Target Cell Specificity

Hormones circulate to virtually all tissues but influence the activity of only certain tissue cells, known as its target cells.

The Hypothalamus Contros the Anterior Pituitary

Hypothalamus “tastes blood” for hormone levels. It sends orders to the anterior/posterior pituitary to regulate the release of hormones.

Hormonal control rather than by nerves

Hypothalamus neurons synthesize releasing and inhibiting hormones.

Hormones secreted regulate the secretions of the anterior pituitary

GLANDHORMONETARGET ORGAN

NORMAL EFFECTS OF HORMONE

EFFECTS OF HYPER- AND HYPOSECRETION

CONTROL OF RELEASE

pituitary gland

Pituitary gland is located in the diencephalon below the hypothalamus

Structurally and functionally divided into: Anterior lobe Posterior lobe

Anterior Pituitary – Master Gland

growth hormone - GH prolactin- PRL adrenocorticotropic

hormone - ACTH thyroid stimulating

hormone - TSH lutenizing hormone - LH follicle-stimulating

hormone - FSH

posterior pituitary

antidiuretic hormone – ADH

oxytocin - OT

pituitary glandgrowth hormone

Direct effects are the result of GH binding its receptor on target cells.

Target cells then believe they should take in more nutrients and grow, then divide

GROWTH HORMONE DISORDERS

Gigantism (Acromegaly) refers to a condition characterized by extreme physical size and stature due to a hyper-secretion of growth hormone during infancy, childhood or adolescence

12 year-old with mother

Remember Andre the Giant? (WWF)At the Start of his Career

By the End of his Career Topping out at 625 lbs!

Click for the action------>

GROWTH HORMONE DISORDER #2

Dwarfism results from a GH deficiency in childhood, leading to a maximum height of 4 feet typically with normal body proportions. If diagnosed before puberty, hormone replacement therapy can promote nearly normal growth.

Dwarfed brothers with researcher in India

THE THYROID GLAND

Thyroid gland is a large gland located in the neck, just below the larynx. Needs IODINE to work properly.

Thyroid follicle cells stimulated by the anterior pituitary gland hormone TSH = Thyroid-stimulating Hormone

Secretes THRYOXIN = adjusts metabolism for all body cells – ie. Burning more glucose

Goiter - Due to iodinedeficiency

Hypothyroid in Infants

Cretinism: Hypothyroid from end of 1st

trimester to 6 months after birth. Severe mental retardation

Short disproportionately sized body with a thick neck and tongue

Hypothyroid in Adults

In adults, it is called Myxedema:

Accumulation of proteins and fluid in subcutaneous tissue.

Symptoms: Decreased metabolic rate. Weight gain. Decreased ability to adapt

to cold. Lethargy (= fatigue)

Hyperthyroid in Adults

Grave’s disease

Elevated metabolic rate (rapid heartbeat, sweating, nervousness) and bulging eyeballs (expophthalmia)

HORMONES OF CALCIUM BALANCE

Calcitonin - protein Produced by thyroid

Reduces blood serum calcium levels by stimulating calcium uptake in bone

Important only in childhood when bones are quickly growing

Parathyroid Glands – Calcium II

Parathyroid Hormone (PTH) Produced by parathyroid glands

Opposite effect to Calcitonin Increases blood calcium levels by enhancing absorption of calcium in the small intestine, bone and promoting Ca2+ reabsorption in the kidney

Adrenal Gland

Paired organs that cap the kidneys. Each gland consists of an outer cortex

and inner medulla.

Adrenal Cortex

Adrenal cortex Stimulated hormonally (ACTH = Adrenal

CorticoTropic Hormone)

Secretes corticosteroids1. Glucocorticoids – raises blood

glucose, increases protein breakdown. Another is cortisone = anti-inflammatory

2. Aldosterone (Mineralcorticosteroid) – sodium reabsorption in kidneys

3. Sex Hormones – stimulates sex organs, development of reproductive organs

Negative Feedback Loop

Low blood sodium sensed by kidneys enzyme Angiotensin secreted which turns on secretion of aldosterone by kidney

Increased H20 absorbed to raise pressure

GLUCOCORTICOIDS At high concentrations, cortisol has pronounced anti-

inflammatory and anti-immune effects including:

Depressing cartilage and bone formation

Inhibiting inflammation

GLUCOCORTICOIDS in Excess

Cushing’s disease = glucorticoid excess

Symptoms include hyperglycemia (high blood sugar), loss of muscle and bone protein, moon face, and a redistribution of fat to the abdomen and posterior neck (causing a “buffalo hump”)

Excess of aldosterone causes excessive Na reabsorption, flooding tissues with water = edema

GLUCOCORTICOIDS – Insufficiencies

Addison’s disease is the major hypo-secretory disorder of the adrenal cortex, usually involving of both glucocorticoids and mineralcorticoids. Victims lose weight, demonstrate hypoglycemia and reduced levels of sodium, and show an increase in skin pigmentation (bronzing)

JFK had Addison’s, which he kept from public knowledge

Synthesizes and secretesEpinepherine and some NorEpinepherine

Sympathetic Nervous System hormones made here!!!

Fight or Flight!!!

Adrenal Medulla

ANTIDIURETIC HORMONE Antidiuretic Hormone (ADH; vasopressin) The main

regulator of body’s water (osmotic)balance

ADH increases the reabsorption rate of water in kidney

Secretion is regulated in the hypothalamus by osmoreceptors, which sense water concentration

Pancreas

Islets of Langerhans secrete insulin into the bloodstream

Insulin tells cells to absorb sugar and store it

Huge storage in liver as GLYCOGEN and in muscles!!!

Homeostatis & Regulating Blood Sugar Levels

Negative feedback loops If blood sugar rises, insulin is secreted to bring

it down If blood sugar lowers, glucagon is secreted to

place sugar into the blood

INSULIN

Diabetes mellitus results from hypo-secretion of insulin or hypo-activity of insulin. When insulin is absent or deficient, blood sugar levels remain high after a meal because glucose is unable to enter most tissue cells.

DIABETES

Type I diabetes mellitis (insulin-dependent) afflicts 750, 000 Americans.

Autoimmune disease (the insulin secreting beta cells of the Islets of Langerhans are attacked by immune cells)

Insulin is not produced or secreted, requiring regular insulin

injections.

DIABETES

Type II diabetes mellitis (non-insulin-dependent) afflicts 7.5 million Americans

Insulin resistance - Insulin is usually produced but the receptors do not respond. Loss of receptors possible – can have all the insulin there, but can’t absorb it.

DIABETES & HEREDITY Heredity plays a role - an estimated 30% of

Americans carry a gene that predisposes them to Type II diabetes.

Lifestyle play a role - Type II diabetics are almost always obese and sedentary. Adipose tissue produces a hormone-like chemical that may prevent uptake of insulin

PINEAL GLAND

Secretes melatonin: Production stimulated by

the hypothalamus Sets daily = circadian

rhythms. Melatonin secretion

increases with darkness and peaks in middle of night.

MELATONIN

Melatonin secretion has been linked to seasonal affective disorder (SAD) in people living in northern latitudes like Alaska. Melatonin is elevated in the winter months, and it may lead to depression, long bouts of sleeping, and eating binges. Sun lamps with a full spectrum of light are helpful therapy for some people.

The Midnight Sun

Thymus Gland & Hormones of the Immune System

Secretes thymosins that aid in the maturity of lymphocytes inside the lobules of the thymus.

Hormones of Digestion & Sex

Digestion - gut hormones – ex Gastrin & fullness

Sex hormones . . . . 1. Testes

produce androgens (testosterone) Puberty - secondary sexual characteristics such as

Pubic hair, Muscular strength, Deepening of voice2. Ovaries

produce estrogens and progesterone. Puberty - secondary sexual characteristics such as

Pubic hair, Breast development, Widening of hips, onset of menstrual cycle

Effects of Anabolic Steroids

1995 1997 2002 2005

Severe Acne

Gynecomastia

Accelerated Balding

Homeostasis – the Balance

Hypothalamus produces ADH and thus regulates blood osmolarity (osmotic balance)

Endocrine system controls secretion of epinephrine and norepinephrine and thus controls fight or flight responses.

Controls blood calcium levels. Muscle contraction.

Insulin encourages uptake of glucose by cells and storage of glucose as glycogen in the liver and muscles.