Endocrine Basics

Question 1

Endocrinology

Answer 1

• Greek words: Endon (within), krino (to separate/distinguish) and logia (study)
• Etymology= endocrine

Question 2

Endocrine system

Answer 2

Regulates all other systems of the body, ensuring homeostasis

Question 3

Hormone History

Answer 3

• Hormon or horman= that which sets in motion
• Term first introduced in 1902, Bayliss and Starling introduced this term after the discovery of secretin

Question 4

History of endocrinology

Answer 4

Dates back to 200BC in China where human urine was supposedly used for purifying hormones

Question 5

Basic Hormonal Pathway

Answer 5

Hormone producing cells release hormones into vascular system for transport throughout the body. These hormones are picked up by specific target cells with specific receptors
-Hormones need
receptors to be
considered a hormone

Question 6

Endocrine organ vascularization

Answer 6

Highly vascularized; needed for the transport of hormones

Question 7

Methods of Hormone Delivery

Answer 7

• Endocrine
• Neuroendocrine
• Paracrine
• Neurocrine
• Autocrine
• Lumonal

Question 8

Endocrine

Answer 8

Releases hormone into vascular system

Question 9

Neuroendocrine

Answer 9

Neuron is source cell, released from axon terminals into the vascular system

Question 10

Paracrine

Answer 10

Secreted out locally to nearby adjacent cells

Question 11

Neurocrine

Answer 11

Neuron source cell releases neurotransmitters into cleft which move across and act on target cells

Question 12

Autocrine

Answer 12

Source cell and the target cell are the same. Hormone going to same cell

Question 13

Lumonal

Answer 13

• Hormone delivered into the lumen of the gut
• Not widely used: peptides in gut will often degrade and inactivate hormones

Question 14

Glands of Endocrine System

Answer 14

• Hypothalamus
• Pituitary gland
• Parathyroid glands
• Thymus- Produces thymosin; immune system focus so not really covered in this module
• Adrenal glands
• Pineal gland
• Thyroid
• Pancreas
• Ovary (not covered in this module)
• Testis (not covered in this module)

Question 15

Tissues of Endocrine

Answer 15

Arises from one of all three germ layers (ectoderm, mesoderm, endoderm)

• Surface ectoderm
  ex. Adenohypophysis
• Neuroectoderm
  ex. Adrenal medulla (neural crest cells)
  ex. Neurohypophysis (neural tube)
• Mesoderm
  ex. Adrenal cortex
• Epithelial endoderm
  ex. Pancreas
  ex. Epithelial lining of gastrointestinal tract

Question 16

Steroid hormones

Answer 16

• Arise from cholesterol
• Specific enzymes are needed for synthesis

Ex. secretion of hormones

Question 17

Secretion of hormones

Answer 17

1. mRNA on ribosomes of ER bind amino acids into a peptide chain called a preprohormone. The chain is directed into the ER lumen by a signal sequence of amino acids
2. Enzymes in the ER chop off the signal sequence, creating an inactive prohormone
3. The prohormone passes from the ER through the golgi apparatus
4. Secretory vesicles containing enzymes and prohormone bud off the golgi. The enzymes chop the prohormone into one or more active peptides plus additional peptide fragments
5. The secretory vesicle releases contents by exocytosis into the extracellular space
6. The hormone moves into the circulation for transport to its target

Question 18

Multifunctionality of hormones

Answer 18

Each hormone has many different functions because there are many different pathways that they can play a role in

Question 19

Receptors

Answer 19

• All hormones act as receptors
• Activation of a receptor by a hormone leads to a number of molecular events within the cell. These molecular events are called Signal transduction pathways
• 2 types: cell membrane receptor and nuclear receptors

Question 20

Cell membrane receptors

Answer 20

mostly peptide hormones, act via second messengers or transcription factors

Question 21

Nuclear receptors

Answer 21

steroids and thyroid hormones; via transcription factors, slow but sustained effects

Question 22

Signal transduction pathways

Answer 22

The molecular events within the cell that occur after the activation of a receptor by a hormone

Question 23

Receptors binding to specific hormones

Answer 23

Hormones are ligands to receptors therefore each hormone has a one or a small number of receptors that it can actually bind to

Question 24

Ligand binding specificity

Answer 24

The ability of receptors to distinguish ligands

Eg. Estrodiol interacts with estrogen receptors, not other receptors

Eg. Norepinephrine and epinephrine bind to distinct adrenoreceptors

Question 25

What is the potential use of ligand binding specificity in medicine?

Answer 25

Want to use drugs that target the problem without targeting other areas and causing other effects.

Question 26

Agonists

Answer 26

• Hormone analogs that bind to receptors and mimic hormones, sometimes with more potency
• Still considered a ligand

Question 27

Antagonists

Answer 27

• Binds to the receptor to prevent its activation by the hormone.
• No activation occurs by antagonists and then it also prevents anything else from binding and causing activation
• Still consider a ligand