Learn: Endocrine System

What is a Hormone?

A chemical which is released into the blood

Describe how Hormones Work to Inflict a Change on a Target Cell?

- Hormone is secreted into the blood via a gland

- Hormones bind to receptors in the target cell

- Binding to the receptors causes specific changes to the cell

What is a Target Cell?

A cell which has a receptor specific to an affecting hormone

Where are Receptors in a Target Cell Located?

On or within the plasma membrane

What is Down Regulation?

Decrease in # of receptors to make the cell less responsive to a hormone

What is Up Regulation?

Increase in # of receptors to make the cell more responsive to a hormone

What is the Functions of the Endocrine System?

To maintain homeostasis

How does the Endocrine System Maintain Homeostasis?

- Store/utilise energy

- Regulates growth and reproduction

- Controls responses to external stimuli

Describe Some Ways a Hormone Effects a Target Cell

- Changes permeability of the cell membrane

- Synthesis of Molecules

- Enzyme activation/deactivation

- Secretory Activity Regulation

- Stimulates mitosis

What is an Exocrine Gland?

- Secretes using ducts

- Secretes into cavities, lumen or organs or onto body surface

What is an Endocrine Gland?

- Secretes into interstitial fluid then into capillaries

- No ducts

- Some of the most vascular tissue in the body

Describe the Step-By-Step Process of How Endocrine Glands Secrete

Secreting Cell -> Interstitial Fluid -> Capillaries -> Blood -> Target Cell

What are the 10 Major Glands of the Body?

1. Anterior Pituitary Gland

2. Posterior Pituitary Gland

3. Thyroid Gland

4. Parathyroid Gland

5. Adrenal Cortex

6. Adrenal Medulla

7. Ovaries

8. Testes

9. Pineal Gland

10. Pancreas

What are the Three Types of Hormone Release?

- Neural

- Humoral

- Hormonal

What is a Neural Hormonal Release?

Stimulate by the nervous system

What is a Humoral Hormone Release?

Stimulated by a chemical change in blood

What is a Hormonal Hormone Release?

Stimulated by the presence or absence of other hormones

What are the Two Types of Chemical Classification?

- Lipid-soluble

- Water-soluble

Describe the Characteristics of a Lipid-Soluble Hormone

- Derived from cholesterol

- Transported via transport proteins in the blood

- Can pass through the phospholipid-bilayer

Describe the Characteristics of a Water-Soluble Hormone

- Derived from amino-acids and peptides

- Dissolve into the blood plasma

- Bind to receptors ON the cell membrane

Describe the Process of How Lipid-Soluble Hormones Effect the Target Cell

1. Diffuse through membrane

2. Bind to receptors in cytosol or nucleus

3. Binding alters gene expression

4. New mRNA is formed directing synthesis of a new protein

5. New protein alters cell activity

Describe the Process of How Water-Soluble Hormones Effect the Target Cell

1. Binding with surface receptors activate g-protein

2. G protein activates adenylate cyclase

3. Adenylate cyclase converts ATP to cAMP

4. cAMP activates cellular protein kinases

5. Protein kinases phosphorylate other proteins causing a response

What is the Main Exception to the Chemical Classifications

- Thyroid hormones T3, T4

- Classifies as water soluble even though it is derived from tyrosine (amino acid)

- Can pass through phospholipid bilayer

What is a Protein Kinase?

An enzyme which causes the phosphorylation of other proteins

What is the Hypophyseal Portal System?

Collection of capillaries which connect the hypothalamus to Anterior Pituitary Gland

What is the Hypothalamohypophyseal tract?

Nerves which connect the posterior pituitary gland to the hypothalamus

What are the Main 6 Hormones Released From the Anterior Pituitary Gland

- Human Growth Hormone

- Thyroid Stimulating Hormone

- Follicle Stimulating Hormone

- Luteinizing Hormone

- Prolactin

- Adrenocorticotropic Hormone

Describe the Characteristics of Human Growth Hormone

Released: Anterior Pituitary Gland

Effect: Promotes production and secretion of insulin-like growth factors which stimulate tissue growth

Regulation: Growth hormone releasing hormone, Growth hormone-inhibiting hormone (hormonal)

Describe the Characteristics of Thyroid Stimulating Hormone

Released: Anterior Pituitary Gland

Effect: Stimulates cells of thyroid to produce triiodothyronine (T3) and thyroxine (T4)

Regulation: Thyroid-releasing hormone (hormonal)

Describe the Characteristics of Follicle Stimulating Hormone

Released: Anterior Pituitary Gland

Effect: Stimulates maturation of ovarian follicles & sperm production in males

Regulation: Gonadotrophin-releasing hormone (hormonal)

Describe the Characteristics of Luteinizing Hormone

Released: Anterior Pituitary Gland

Effect: Ovulation in Females, testosterone production in males

Regulation: Gonadotrophin-releasing hormone (hormonal)

Describe the Characteristics of Prolactin

Released: Anterior Pituitary Gland

Effect: Stimulates milk production by mammary glands'

Regulation: Prolactin-releasing hormone in response to baby sucking breast (hormonal)

Describe the Characteristics of Adrenocorticotropic Hormone

Released: Anterior Pituitary Gland

Effect: Production/ release of cortisol, androgens and aldosterone

Regulation: Corticotropin-releasing hormone

What are the Two Main Hormones of the Posterior Pituitary Gland?

1. Oxytocin

2. Antidiuretic Hormone

Describe the Characteristics of Oxytocin

Released: Posterior Pituitary Gland

Effect: Increases uterine contractions, let down response in breast feeding

Regulation: Receptors in the cervix & nipple send signals to the hypothalamus which relays them (neural)

Describe the Characteristics of Antidiuretic Hormone

Released: Posterior Pituitary Gland

Effect: Increases reabsorption of water by the nephrons in the kidney

Regulation: Increased plasma osmolality and decreased blood volume (humoral)

What Makes the Posterior Pituitary Gland Unique to the Other Major Ones?

It doesn't create its hormones itself, they are produced in the hypothalamus

What is the Main Hormone Released by the Pineal Gland?

Melatonin

Describe the Characteristics of Melatonin

Released: Pineal Gland

Effect: Induces drowsiness, peak concentration at night, thought to cause sleep

Regulation: Supressed by bright light (neural)

What are the Main Two Hormones Released by the Thyroid Gland?

- Thyroid Hormones (T3, T4)

- Calcitonin

Describe the Characteristics of the Thyroid Hormones (T3, T4)

Released: Thyroid Gland

Effect: Increased metabolic rate, cell growth and body heat production

Regulation: Thyroid-stimulating hormone (hormonal)

Describe the Characteristics of Calcitonin

Released: Thyroid Gland

Effect: Decreases blood calcium by increasing excretion, promotes storage of calcium in bone and inhibits absorption by intestines

Regulation: Blood calcium concentration (Humoral)

What is the Main Hormone Released by the Parathyroid Gland?

Parathyroid Hormone

Describe the Characteristics of Parathyroid Hormone

Released: Parathyroid Gland

Effect: Increased blood calcium by activating osteoclasts

Regulation: Blood calcium levels (humoral)

What are the Main Three Hormones Released by the Adrenal Cortex?

- Aldosterone (mineral corticoid)

- Cortisol (Glucocorticoid)

- Androgens (weak sex hormones)

Describe the Characteristics of Aldosterone

Released: Adrenal Cortex

Effect: Increased Na reabsorption and potassium excretion, thereby increasing water reabsorption

Regulation: Production of Angiotensin II in response to blood pressure (hormonal)

Describe the Characteristics of Cortisol

Released: Adrenal Cortex

Effect: Increased protein breakdown, glucose formation and depresses immune system

Regulation: Adrenocorticotropic hormone (hormonal)

Describe the Characteristics of Androgens

Released: Adrenal Cortex

Effect: In women, promotes libido and converted into oestrogens by other body tissues

Regulation: Adrenocorticotropic hormone, although not fully understood (hormonal)

What are the Two Main Hormones Released By the Adrenal Medulla?

1. Epinephrine

2. Norepinephrine

Describe the Characteristics of Epinephrine/Norepinephrine

Released: Adrenal Medulla

Effect: Fight or Flight Response

Regulation: Sympathetic nervous system (neural)

What is the Ration of Released Epinephrine to Norepinephrine?

80% - 20%

What are the Two Main Hormones Released by the Pancreas?

1. Glucagon

2. Insulin

Describe the Characteristics of Glucagon

Released: Pancreas

Effect: Increased blood glucose by stimulating the breakdown or stored liver glycogen

Regulation: Blood glucose concentration (humoral)

Describe the Characteristics of Insulin

Released: Pancreas

Effect: Decreased blood glucose by promoting the storage of glucose as glycogen

Regulation: Blood glucose concentration (humoral)

Which Types of Cells are Responsible for the Release of Glucagon and Insulin in the Pancreas?

Glucagon - Alpha Cells

Insulin - Beta Cells

What are the Two Main Hormones Released by the Ovaries?

- Oestrogen

- Progesterone

Describe the Characteristics of Oestrogen and Progesterone

Released: Ovaries

Effects: Regulate menstrual cycle and are responsible for female characteristic development

Regulation: Luteinizing hormone & follicle stimulating hormone (hormonal)

What is the Main Hormone Released by the Testes?

Testosterone

Describe the Characteristics of Testosterone

Released: Testes

Effect: Sperm production and male sexual development

Regulation: Luteinizing hormone (hormonal)