L14. Endocrine System

Question 1

Endocrine glands

Answer 1

• secrete products into ducts which empty into body cavities or body surface
• eg. sweat, oil, mucous, digestive, salivary, mammary

Question 2

Endocrine glands

Answer 2

• secrete products (hormones) directly into bloodstream ie. no ducts
• eg. hypothalamus, pituitary, thymus, pancreas, thyroid, parathyroid, adrenal, pineal, etc

Question 3

Control systems- ways to get the message across

Answer 3

NERVOUS SYSTEM
- detect neural pathways
- very fast response
- electrochemical
HORMONAL SYSTEM
- no detected pathway
- chemicals released into blood stream 
- effects are widespread and sustained 
- response is relatively slow

Question 4

Three classes of hormones

Answer 4

• Steroid hormones
• Peptide hormones
• Monoamines

Question 5

Steroid hormones

Answer 5

• derived from cholesterol (lipids/ fats)
• secreted by gonads, adrenal cortex, etc
• hydrophobic (cannot travel freely in blood- bound to carrier)
• crosses directly through the plasma membrane and bind to receptors in the cell/ nucleus

Question 6

Peptide hormones

Answer 6

• derived from amino acid (proteins/ polypeptides)
• secreted by hypothalamus, anterior and posterior pituitary, etc
• hydrophilic (travel freely in blood)
• binds to receptors on the cell surface> second messenger activated

Question 7

Monoamines

Answer 7

• derived from amino acids retaining an amino group

Question 8

Transport proteins

Answer 8

• transport proteins are albumins and globulins- made by liver
• only unbound hormones are allowed to exit the capillaries and reach targeted cells

Question 9

Properties of bound hormones

Answer 9

Bound hormones remain inactive and circulate in the blood

• protected against being broken down by enzymes
• prevents excretion by kidneys
• acts as a long-lasting blood reservoir

Question 10

Hormone receptors are located:

Answer 10

• on the cell surface (plasma membrane)

- intracellular (the membrane of mitochondria, nucleus and other organelles)

Question 11

Saturation

Answer 11

• when all the receptors on the target cell are already bound to a hormone molecule, adding more hormone will not increase the effect

Question 12

How do hormones work?

Answer 12

Hormones bind to receptors and:

• initiates synthesis of new molecules
• alter membrane permeability
• alter the rate of metabolism
• each target cell responds to a hormone differently

Question 13

Action of lipid soluble hormones

Answer 13

Hydrophobic lipid-soluble hormones (STEROIDS) have no problems diffusing through the plasma membrane into the cytoplasm

• binds to receptors inside the cell
• activate receptors (turn certain genes on/ off)
• new mRNA is formed > synthesis of new proteins
• new protein alters cellular activity (metabolism)

Question 14

Action of water soluble hormones

Answer 14

Hydrophilic water-soluble hormones (PEPTIDES) are unable to enter the cell

• hormone binds to cell surface receptor (1st messenger)
• once bound, a second messenger protein (cAMP) is generated inside the cell
• 2nd messenger causes the disired response through a series of cascading events (ie. speed up/ slow down physiological response)
• cAMP is then quickly broken down by enzymes
• cell response stops unless more hormones are available