Lecture 2- Endocrine System

Question 1

Carrier Proteins for Lipid Soluble Hormones(2)

Answer 1

1. General Carrier Proteins

2. Specific Carrier Proteins

Question 2

General Carrier Proteins

Answer 2

1. Albumin-Steroids, Some thyroid Hormones

2. Transthyretin- thyroid hormones, some steroids

Question 3

Specific Carrier Proteins

Answer 3

1. Cortisol binding globulin(CBG)–>cortisol and aldosterone
2. Thyroxine Binding globulin(TBG)–> thyroid hormone
3. Sex steroid binding globulin (TEGB)–> Testosterone and estradiol

Question 4

Control of Hormone Secretion

Answer 4

• Regulated by: signals from nervous system, chemical changes of molecules, other hormones
• Hormone regulation (negative or positive feedback)

Question 5

Control of Hormone Secretion- Negative Feedback

Answer 5

• Most endocrine glands under negative feedback

- cells can sense the magnitude of the biological effect and DECREASE the response

Question 6

Control of Hormone Secretion- Positive Feedback

Answer 6

• Increased production and release of Oxytocin, enhance milk production and release, enhance contractions during childbirth
• Contraction–> head of baby activates receptors to CNS–>hypothalamus–> produce for Oxytocin

Question 7

Hormone Activity

Answer 7

• Hormones affect only specific target tissue (depends on receptors)
• Response depends on both hormones and target cells
• Target cells respond differently to the same hormone
• Hormonal effects vary

Question 8

Hormone Activity: Receptor

Answer 8

• Lock and Key mechanism

- Hormone locks onto a specific receptor

Question 9

Regulation of Hormone Effects

Answer 9

Downstream Effect determines by:

• # of receptors
• Amount of hormone secreted

Question 10

Regulation of Hormone receptors (2)

Answer 10

1. Down-regulation

2. Up-Regulation

Question 11

Down-Regulation

Answer 11

• Increase in hormone leads to DECREASE in number of receptors
• Target cell is LESS sensitive, decreases response

Question 12

Up-Regulation

Answer 12

• decrease in hormone leads to INCREASE in number of receptors
• Target cell is sensitive, better chance for hormone to find receptor

Question 13

Where do Water-soluble hormones bind?

Answer 13

-to receptors on the PLASMA membrane

Question 14

Where do lipid-soluble hormones bind?

Answer 14

• To receptors inside target cells

- Cytoplasmic or nuclear

Question 15

Surface Receptors for water- soluble hormones (3)

Answer 15

1. Single transmembrane protein
2. Membrane bound protein
3. 7 transmembrane protein (GPCR)

Question 16

Components of a GPCR

Answer 16

• Produces responses through the action of a G-Protein
• Effector protein is activated by a G protein
• Effector produces a 2nd Messanger

Question 17

G Proteins

Answer 17

• Can be stimulatory(S) or inhibitory (I)
• consist of alpha, beta, and gamma subunits
• Alpha can be Gs, Gi, Gq, and Gt
• They contain GTPase activity that hydrolyzes GTP
• can be active and inactive

Question 18

Inactive state of G proteins

Answer 18

• G protein is bound to a receptor that is not activated by a hormone
• alpha/beta/gamma subunits form a complex
• GDP is bound to the alpha subunit

Question 19

Active State of G proteins

Answer 19

• Ligand binding stimulates the exchange of GDP for GTP on the ALPHA subunit
• Alpha subunit dissociates from beta/gamma subunits
• Starts/ends in the Inactive state

Question 20

Effect Systems and their second messenger (3)

Answer 20

1. Adenylate cyclase—>cAMP
2. Phospholipase—-> Inositol phosphate
3. Ion channels–> ions

Question 21

Adenylate Cyclase and cAMP system

Answer 21

-Water-soluble hormone binds to the receptor and activates a G protein (Gs)

Question 22

Signal Amplification

Answer 22

-ADVantage= low concentration of hormone can produce large effect downstream

Question 23

Interaction of cAMP signaling

Answer 23

• Inactivation occurs by the action of the enzyme phosphodiesterase
• cAMP is inactivated to AMP

Question 24

Activation and inhibition of adenylate cyclase (AC)

Answer 24

• Gs will activate AC and increase cAMP
• Gi will inhibit AC and decrease cAMP
• EX- adrenergic receptors