Week 2

Question 1

Name and describe the major endocrine glands?

Answer 1

Hypothalamus
Pineal
Pituitary
Thyroid
Parathyroids
Thymus
Arenals
Pancreatic Islets
Ovaries
Testes

Question 2

What is the function of the endocrine system?

Answer 2

Regualtion of body function
Body control system
Maintian homeostasis
Support cell growth
Coordinate development
Coordinate reproduction
Facilitate responses to external stimuli

Question 3

What do we need to know for each hormone?

Answer 3

Its cell of origin
Its chemical nature
Biosynthesis
Circulates free or bound form
Its principal physiological actions
- At the whole body level
- Tissue level
- Cellular level
- Molecular Level
How its secretion is regualted
Consequences of inadequate or excess secretion 
- Hypo
- Hyper

Question 4

What are hormones?

Answer 4

Chemical messengers released by endocrine glands or by specialised neurons or by organs into the blood
They are made in glands or cells
Transported in blood
Act on distant target tissue receptors
Initiate physiological responses

Question 5

What is metabolic degradation?

Answer 5

Hormone degradation = wont stay in the body forever after it competes its action it will be depredated

Question 6

How can hormones travel in blood?

Answer 6

Travels in the blood either simply dissolved in plasma (free form) or bound to plasma proteins

Question 7

How can liver disease indirectly affect hormone availability and function?

Answer 7

Plasma proteins (used by some horomes to travel in blood) are synthesised mainly in the liver; liver disease may result in abnormalities in binding protein levels and may indirectly affect hormone availabliilty and function.

Question 8

What effects the circulating level of a hormone?

Answer 8

It is determined by its rate of secretion and its circulating half-life

Question 9

What types of hormones are found in a bound form in the blood?

Answer 9

LIPOPHILIC

Question 10

What binding protein fo T3 and T4 use?

Answer 10

T4 and T3 binding to thyroxine-binding globulin (TBG), albumin, and thyroxine-binding prealbumin (TBPA)

Question 11

What binding protein does cortisol use in the blood?

Answer 11

Corstisol-binding globulin

Question 12

What binding protein does androgen and estrogen use in the blood?

Answer 12

sex hormone-binding globulin (SHBG) (also called testosterone-binding globulin, TeBG

Question 13

What binding protein does Growth Hormone use in the blood?

Answer 13

GH-binding protein (GHBP), a circulating fragment of the GH receptor extracellulr domain

Question 14

What are the pro’s of binding to plasma proteins to travel in blood?

Answer 14

These interactions provide a hormonal reservoir, prevent rapid degredation unbound hormones, restrict hormone acess to certain sites
Less susceptible to enzymatic inactivation
Bound hormones remain in blood for longer time; few hours (Steroids) to weeks (thyroid hormones)

Question 15

Whar are the three possible ways for a hormone to trigger an intracellular response on a target cell?

Answer 15

Alters channel permeability
Acts through second messenger system to alter activity of pre-existing proteins (act on enzymes to help make proteins or act on proteins themselves)
Activated special genes to cause formation of new proteins (when receptor is on nucleus)

Question 16

What intracellular changes can hormones cause?

Answer 16

Changes inplasma memrbane permeability or electrical state
Synthesis of proteins, such as enzymes (changes concentration of enzymes)
Activation or inactivation of enzymes
Stimulation of mitosis
Promotion of secretory activity

Question 17

What happens to a hormone after it has done its job?

Answer 17

Rapidly degregaded by target cells or removed from the blood by the kidneys or liver and excreted

Question 18

Where can receptor be located in a target cell?

Answer 18

Can be located on cell membrane or cytoplasm or in the nucleus

Question 19

What occurs in up regulation and how is it triggered?

Answer 19

An increase in number of target cell receptors
May occur in response to a chronic low concentration of the hormone
May occur by increasing the synthesis of new receptors, decreasing receptor degradation or activating receptors

Question 20

What occurs in down regulation and how is it triggered?

Answer 20

A decrease in the total number of target-cell receptors for a given hormone
May occue in response to chronic high extracellular concentration of teh hormone
Decrease in the number of receptors by inactivation, decreased production, destruction, temporary sequestration or receptors inside

Question 21

What does saturation refer to?

Answer 21

The degree to which receptors are ocupied by messengers
If all are ocupied, the respecotrs are fully saturated
If half are occupied, the saturation is 50 percent
Fixed number fo receptors are available - hence become saturated at some point.

Question 22

What is a competition mesenger and how is it used in drug therapy?

Answer 22

Structurally similar substances compete with each other for a receptor
Play a large part int he treatment of endocrine disease.
Pharmaceutical binds to teh receptor instead fo teh hormone stoppign something from happening

Question 23

What is an agonist?

Answer 23

A messenger that binds to a receptor and triggers the cell’s response
Often refers to a drug that mimics a normal hormones action

Question 24

What is an antagonist?

Answer 24

A molcule that competed for a receptor with a hormone normally present in the body
The antagonist binds to the hormone receptor but does not trigger the cell’s response
One hormone reduced the effectiveness of the second hormone
E.G. progesterone inhibits the responsiveness of estrogen in the uterus.

Question 25

What is permissiveness and an exmaple in the body?

Answer 25

Facilitation of one hormone action by another hormone
A hormone ‘A’ must be present for the full strength of hormone ‘B’s effect
A hormone may induce an increase in the number of receptor for a second hormone
E.G. Thyroid hormones increases the number fo receptors for epinephrine in epinephrine target cells

Question 26

What is synergism and an example in the body?

Answer 26

Occur when the actions of several hormones are complementary and their combined effect is greater than teh sum of their separate effects
- Synergistic action fo FSH and testosterone, both of whicha re required for maintaining the normal raate of spermatogenesis
Synergism results from each hormone’s influence on the number or affinity of receptors fro the toehr hormone
Growth Hormone -> growth
INsulin -> Growth
GH + Insulin -> GROWTH^^^

Question 27

What are the 3 different classifications of hormones?

Answer 27

Proteins and polypeptide hormones
Steroid Hormones
Derivatives of Amino Acid Tyrosine

Question 28

What are Eicosnaoids and their function in the body?

Answer 28

Eicosanoids - derived from arachidonic acid, a 20-carbon fatty acid
Paracrine factors that coordincate cellular activities and affet enzymatic processes (such as blood clotting) in extracellular fluids
Some eicosanoids (such as leukotrienes) have seconary roles as hormones
A second group of eicosanoids - prostaglandis - involved primarily in coordinating local cellular activities

Question 29

What are the main characteristics of peptide and protein hormones? (e.g. solubility, transportation in blood, storage, uses, mechanism of action etc)

Answer 29

Range from small peptides (of only three peptides) to large proteinsa nd glycoproteins (protein with a carboxylic acid attached)
Highly water soluble (hydrophilib) and have low lipid solubility (lipophobic)
Transported in blood in free form (by dissolcing in plasma)
Stored in secretory granules until needed
Hormoes secreted by pituitary, pancreas, GI tract, hypothalamus, kidneys, thyroid cells, parathyroid, liver and heart are of this type
Mechanism of action:
- Bind to receptors on the surface of cell
- Most often by formation of second messengers inside the target cells

Question 30

How are protein hormones synthesised?

Answer 30

Synthesised on the rough end of the endoplasmic reticulum of the different endocrine cells (similar to other proteins)
Preprohormones (inactive) are synthesised by ribosomes on rough ER and cleaved to from prohormones (INACTIVE)
Prohormones is cleaved to final hormones (Active) and packaged into secretory vesicles (Golgi Apparatus)
Enzymes in teh vessicles cleave the prohormones to produce smaller, biologically active hormones.

Question 31

What are the properties of amine hormones?

Answer 31

All formed from tyrosine
2 types
- Thyroid hormones and Catechnolamines (adrenaline and noadrenaline)
Stores until they are secreted
Catecholamines have cell membrane receptors like typical peptide hormones and 50% travel in bound form in blood (UNBOUND 50% BOUND, LIPOPHOBIC, HYDROPHILIC)
Thyroid hormones behave more like steroid hormones with intracellular receptors (BOUND, LIPOPHILIC, HYDROPHOBIC)
- These hormones first bing directly with receptor proteins in teh nucelus

Question 32

What are the main characteristics of a steroid hormone?

Answer 32

Secreted by adrenal cortex, gonads and placenta
Cholesterol is the commone precursor - synthesis occurss in mitochondria and ER
Lipid soluble hormone - can diffuse into cell (LIPOPHILIC)
Each of the conversions from cholesterol to a specific steroid hormone requires the assistance of a number of enzymes that are limited to certain steroidogenic organs
- Key enzyme necessary for the production of cortisl is found onliy in the adrenal cortex
Not stored after their formation
Travel in bound (binding to plasma proteins) - they have long half life than protein hormones

Question 33

How does steroid biosynthesis occur?

Answer 33

The initial step in steriogenesis is the conversion of cholesterol to pregenolone
Cholesterol to pregenonlon by the action of the cytochome P450 side-chain cleavage enzyme (cholesterol desmolase)
THe different sections of teh adrenal cortex have specific enzymatic features - result in preferential syntehsis of glucocorticoids, mineralocorticoids, or androgens, depending on the region
All steroid hormones are not the end products of the pathway
INSERT IMAGE

Question 34

What is the mechanism of action of protein hormones?

Answer 34

Receptors for these hormones are found on the cell membrane of target cells.
Hormones (first messengers) bind with receptors to form receptor hormone complex
Receptor hormone complex results in the formation of second messengers inside the target cell to bring about cell response.

Question 35

What is a G-protein-linked hormone receptor and how does it work?

Answer 35

Many hormones activate receptors by coupling with groups of cell membrane proteins - g proteins
Activated G proteins induced intracellular signals that either open or close ion channels, or change the activity of an enzyme in the cytoplasm of the cell (to form second messengers)
The two main enzymes that interact with G proteins are adneylate cyclase and phospholipase C

Question 36

What is the role of calcium as a second messenger?

Answer 36

The calcium ion (CA2+) functions as a second messenger in a great variety of cellular responses to stimuli
Hormone increases (in some cases decreases) cytoplasmic calcium level either by opening calcium channels on cell membrane or their release from endoplasmic reticulum,
Calcium combines with another intracellular protein - calmodulin (has 4 calcium sites)
On binding calcium, the calmodulin changes shape, which allows it to activate or inhibit a large variety of enzymes and other proteins
Calcium combines with calcium-binding intermediary proteins other than calmodulin - these proteins then act in a manner analogous to calmodulin

Question 37

What is the role of Diacyl Glycerol and Ionsitol Triphosphate (IP3)?

Answer 37

Hormone receptor complex activates teh enzyme phophlipase C
Phospholipase C catayzes breakdown of phophatidyl ionsitol bisphsophate (PIP2) to diacyl glycerol (DAG) and inositol triphosphate (1P3) [two second messengers]
DAG activated portein kinase C which in turn brings bout changed in enzymatic activity of cell
IP3 brings about release of calcium from the endoplasmic reticulum
Oxytocin, TRH, GHRH, ADH use Phosphilipase C second messenger systems