Major Endocrine Glands and Classification of Hormones

Question 1

What is a hormone?

Answer 1

Any substance elaborated by one cell to regulate another cell

Question 2

What is the biological response to hormones generally a result of?

Answer 2

An amplification or a signal transduction cascade

Question 3

At what concentration can many hormones evoke cellular and tissue effects?

Answer 3

Very low concentrations

Question 4

What provides the highest level of endocrine control?

Answer 4

The hypothalamus

Question 5

How does the hypothalamus integrate activities of nervous and endocrine systems?

Answer 5

Secretion of regulatory hormones
Synthesises hormones
Direct neural control function

Question 6

Where do the regulatory hormones released by the hypothalamus control?

Answer 6

The activities of the anterior pituitary

Question 7

Where do the hormones synthesised by the hypothalamus get transported to?

Answer 7

The posterior pituitary via the infundibulum

Question 8

What is the diurnal control of hormone levels?

Answer 8

External cues (light/dark) evoke fluctuations in hormone secretions

Question 9

What actions do hormones have?

Answer 9

Complementary and antagonistic

Question 10

How are hormones grouped?

Answer 10

Based on their structure = steroids, amine-derived or peptides and proteins

Question 11

What are steroids?

Answer 11

Lipids derived from cholesterol

Question 12

What controls the amount of steroid hormone?

Answer 12

Synthesis rate = once synthesised steroids are secreted, they are not stored

Question 13

What properties do hormones have?

Answer 13

Hydrophobic = transporter in blood plasma, unbound steroids are biologically active

Question 14

What are some examples of steroid hormones?

Answer 14

Cortisol = secreted by adrenal cortex and plays a role in mediating stress responses
Testosterone and Oestradiol = secreted from gonads and placenta and are responsible for sexual characteristics

Question 15

What are the two steps that occur when steroids cross the plasma membrane?

Answer 15

Activated hormone/receptor complex forms within the cell

Complex binds to DNA and activates specific genes = gene activation leads to production of key proteins

Question 16

What are some examples of amine hormones?

Answer 16

Catecholamines = hydrophilic and transporter unbound in blood plasma
Thyroid = bound to carrier proteins

Question 17

What are amine hormones derived from?

Answer 17

Derived from amino acids = secreted by thyroid and adrenal medulla

Question 18

Where are amines like adrenaline stored?

Answer 18

As vesicles in the cytoplasm until needed

Question 19

How do amine hormones act?

Answer 19

Bind to membrane bound receptors to evoke cellular responses

Question 20

What are peptide and protein hormones?

Answer 20

Peptide = short chains of amino acids (<50)
Protein = larger molecules

Question 21

What are some features of peptide and protein hormones?

Answer 21

Hydrophilic, transported unbound in blood plasma

Question 22

Where are peptide and protein hormones secrets from?

Answer 22

Pituitary, parathyroid, heart, stomach, liver, kidneys

Question 23

What are peptide and protein hormones synthesised as?

Answer 23

Synthesised as precursor molecules and stored in secretory vesicles

Question 24

How can different end peptide and protein hormones be made?

Answer 24

By cleaving a common precursor with a different enzyme

Question 25

How are steroid and thyroid hormones transported?

Answer 25

Insoluble in plasma = transported in blood via carrier proteins

Question 26

What are the effects of hormones binding to carrier proteins?

Answer 26

Facilitation of hormone transport
Increased half life of hormone
A reservoir for the hormone

Question 27

What is cortisol-binding globulin (CBG)?

Answer 27

Specific carrier protein that binds cortisol in a selective manner (also some aldosterone)

Question 28

What is thyroxine-binding globulin (TBG)?

Answer 28

Specific carrier protein that binds thyroxine (T4) selectively (also some tri-iodothyronin (T3))

Question 29

What is sex steroid-binding globulin (SSBG)?

Answer 29

Specific carrier protein that binds mainly testosterone and osetradiol