Endocrine System

Ligands

Signaling molecules

Hormones are released directly into the:

Circulatory system

What are the two categories of hormone structures?

Amino acid or steroid

What is the primary concern of the endocrine system?

Internal control

Functions of the endocrine system:

1. Coordinates body activities

2. Maintain homeostasis

3. Controls growth and development

4. Regulates metabolic process

What system does the endocrine system work with?

Autonomic nervous system

Does the nervous system control the release of some hormones?

Yes

Can hormones stimulate or inhibit nerve impulses (AP)?

Yes

How does the effect of the endocrine system compare to that of the nervous system?

Slower to take effect but longer lasting

What is the most common type of hormone?

Amino acid based

Protein and peptide hormones are:

Amino acid based and water soluable

Amino acid based hormones need what to penetrate the cells plasma membrane?

G protein linked receptor

What enzyme is activated by the G protein?

Adenylate cyclase

What does adenylate cyclase convert?

ATP to cyclic AMP

What is the second messenger?

Cyclic AMP

What does cyclic AMP activate?

Protein kinases inside the cell

What responses do kinases initiate from the target cell?

1. Catalyze phosphorylation reactions

2. Alter the permeability of the cell membrane

3. Activate enzymes

4. Promote protein synthesis

5. Stimulate the release of hormones

6. Stimulate mitosis

Small, simple molecules derived from single amino acid; water soluable

Amines

Epinephrine, norepinephrine, serotonin, histamine and melatonin are:

Examples of amines

T3 and T4 are:

Amines but fat soluble

What forms if too little iodine is available?

Goiter

What forms T3 and T4?

Tyrosine and iodine (either 3 or 4 iodine attached)

What is the name of fat soluble hormone?

Steroids

What are steroids derived from?

Cholesterol

Where are steroids produced?

Adrenal gland cortex, ovaries and testes

How do steroids enter a cell?

Diffusion through cell membrane

Where do steroid bind inside of the cell?

DNA segment inside the nucleus

What do steroid influence?

Activates or inactivates specific genes

Transcription

Protein synthesis

Thyroid hormones do not:

Attach to cytoplasmic receptors

Eicosanoids

Hormone-like and local acting ligands

What are eicosanoids derived from?

Fatty acid tails of the cell membrane that are released due to chemical or mechanical stimulation

What cells are able to produce eicosanoids?

Every cell except RBC (no nucleus)

Where do eicosanoids bind?

G protein linked receptors

Inhibit or stimulate the synthesis of second messangers (cyclic AMP)

How quickly are eicosanoids inactivated?

Rapidly; less than a minute

Eicosanoids influence:

Action of smooth muscle and inflammatory response

What medicines will inhibit eicosanoids?

Aspirin and Tylenol (prostaglandins)

What are 3 eicosanoids?

prostaglandins, thromboxanes, leukotrienes

Prostaglandins

Promote pain, inflammation and stimulates smooth muscle contraction

Thromboxane

Powerful vasoconstrictor that causes platelets to cluster and release secretions

Leukotrienes

Constrict respiratory passageways in asthma

What is the activation of a target cell dependent on?

1. Blood levels of hormone

2. Number of receptors on target cell

3. Affinity (binding strength) between cell and hormone

What are the 3 hormone interactions?

Permissiveness

Synergism

Antagonism

Permissiveness

Presence of one hormone is required for another hormone to exert its full effects (stimulate formation of receptors for the second hormone)

Synergism

Combined effect of more than one hormone on the same target cell is greater than the sum of each hormone acting independently

Antagonism

Two hormones have the opposite effect on a target cell

Three different control mechanisms of the endocrine system:

Humoral, hormonal, neural

Neural control

Nerve fibers stimulate the hypothalamus to release hormones at posterior pituitary, adrenal medulla or pineal gland

Humoral control

Chemical (nutrient or ion) in blood interacts indirectly with endocrine tissue stimulating or inhibiting the release of a hormone. Does not need to involve the hypothalamus.

Hormonal control

Involves hypothalamus secreting hormones to the anterior pituitary gland. Hypothalamus either releases RH or IH of the 6 hormones.

Endocrine vs exocrine glands

Endocrine glands release chemical substances directly into the bloodstream or tissues of the body.The chemical substances released by the endocrine glands are known as hormones. Exocrine glands release chemical substances through ducts to outside the body or onto another surface within the body.

What kind of epithelial tissues make up most glands?

Simple cuboidal

What kind of connective tissue supports glands?

Reticular

What are the major endocrine glands?

The hypothalamus, pituitary (anterior & posterior), pineal, thymus, thyroid, parathyroid, adrenal glands (cortex & medulla), pancreas, testes, and ovaries

What are other structures that secrete hormones?

Heart, stomach, kidneys

Paracrine

signals diffuse to and affect nearby cells

Autocrine

term for hormones that act on same cells that secrete them

up-regulation

target cells form more receptors in response to low hormone levels

down-regulation

target cells lose receptors in response to high hormone levels (drug tolerance)

Examples of permissive hormones

Thyroxine will up-regulate receptors for adrenaline at the heart

Example of synergism hormones

Glucagon and epi both tell the liver to break down glycogen

Example of antagonism

Insulin will decrease the blood glucose and glucagon will increase blood glucose

What 3 glands are controlled neurally?

Posterior pituitary

Pineal

Adrenal medulla

How does the hypothalamus communicate with the anterior pituitary gland?

6 hormones through the hypophyseal portal system

Andenohypophysis

anterior pituitary gland

How does the hypothalamus communicate with the posterior pituitary gland?

Releasing RH or IH through the axons and then neural hormones are released at the terminal buttons in the posterior pituitary gland

Neurohypophysis

posterior pituitary gland

What kind of tissue is the posterior pituitary gland made of?

Neural tissue

What kind of tissue is the anterior pituitary gland made of?

Glandular tissue

Hypophyseal portal system

a blood vessel system that directly connects the hypothalamus with the anterior pituitary

What are the 6 hormones released by the anterior pituitary?

1. TSH

2. Prolactin

3. FSH

4. LH (lutenizing hormone)

5. Adrenocorticotropic (ACTH)

6. GH

What are the 2 hormones released by the posterior pituitary?

1. Oxytocin

2. ADH (antidiuretic hormone)

Tropic hormones

hormones that stimulate other glands to release their hormones

non-tropic hormones

hormones that directly stimulate target cells to induce effects

How are fat soluble hormones transported in the blood?

With a plasma protein to make them water soluble

Compare half-life between water and fat soluble hormones

Longer for fat soluble, shorter for water soluble

Which organs help to filter and eliminate hormones from the body?

Kidney (urine) and liver (bile into small intestine = feces)

negative feedback loop

A feedback loop in which a system responds to a change by returning to its original state, or by decreasing the rate at which the change is occurring. Stabilizing.

Positive feedback loop

a feedback loop in which change in a system is amplified. Disruptive.

What are the two basic structures of endocrine glands?

Cords and follicles

Glands made of cord structure:

1. Adrenal cortex

2. Pancreas

3. Anterior pituitary

Glands made of follicles:

1. Ovary

2. Thyroid

Glands made of neural tissue:

1. Hypothalamus

2. Pineal gland

3. Adrenal medulla

4. Posterior pituitary

Where are oxytocin and ADH stored?

axon terminals in the posterior pituitary

Where are oxytocin and ADH produced?

hypothalamus