Physiology: Endocrine Control Systems I

Question 1

What body functions are regulated by endocrine control systems?

Answer 1

Metabolism

Growth

Development

Water and electrolyte balance

Reproduction

Behaviour

Question 2

What non-endocrine tissue produce hormones?

Answer 2

Kidneys (EPO)

Cardiac Cells (ANP)

Skeletal muscle (myokines)

Adipose tissue (leptin)

Question 3

What are the mechanisms of hormone release?

Answer 3

Humoral: Respond to changing levels of ions or nutrients in the blood.

Neural: Stimulation by nerves

Hormonal: Stimulation received from other hormones

Question 4

What are the components of an endocrine axis?

Answer 4

Detection of homeostatic imbalance

Ligand-receptor actvates secretory apparatus

Release of hormone from cell

Hormone in extracellular fluid - blood transport

Target organ recognition of hormone - receptor

End organ response to hormone

Detector sense return to homeostasis - negative feedback

Hormone is cleared

Synthesis of hormone reserves

Question 5

Why shouldn’t glucocorticoids be used for too long?

Answer 5

When activated for too long the body downregulates glucocorticoid receptors.

Question 6

Why does hepatitis cause increase activity of adrenaline and other catecholamines?

Answer 6

It prevents them from being metabolised due to damage to the liver.

Question 7

What are the 3 types of hormones?

Answer 7

Hydrophilic - Protein/peptide hormones

Really small variable - Tyrosine-derived hormones

Hydrophobic - Steroid hormones

Question 8

Name some tyrosine derived hormones:

Answer 8

Epinephrine

NorE

Dopamine

Triiodothyronine

Thyroxin

Question 9

Name some peptide hormones:

Answer 9

Oxytocin

Vasopressin

Angiotensin

Melanocyte-stimulating hormone

Somatostatin

Thyrotropin-releasing hormone

Gonadotropic-releasing hormone

Question 10

How are peptide hormones released?

Answer 10

Via exocytosis after being stored in secretory granules or vesicles

Question 11

How are protein/peptide hormones in action and inactivation?

Answer 11

Act rapidly and are short lived because they are destroyed within minutes.

Inactivation is the result of receptor mediated endocytosis or sequestration by kidney and then excretion.

Question 12

Which hormones are important for raising cAMP?

Answer 12

Protein hormones that activate the adenylyl cyclase-cAMP second messenger system.

Question 13

What enzymes do Enzyme-linked receptors usually activate and what class of hormone activates these receptors?

Answer 13

JAK-STAT, activated by protein hormones usually.

Question 14

How do steroid hormones activate their receptors?

Answer 14

They bind intracellular receptors, they are also transported via the blood using transport proteins.

Some receptors are cytosolic and others are nuclear

Question 15

How are steroid hormones inactivated?

Answer 15

Cytochrome P450 oxidase

Conjugated

Excretion in bile

Question 16

How are steroid hormones produced?

Answer 16

They are made from lipids that are moved around between smooth ER and the mitochondria. They are made from building up cholesterol from LDL.

Question 17

Where are steroid hormones most often broken down?

Answer 17

In the liver.

Question 18

What are the features of steroid-secreting cells?

Answer 18

They have abundant smooth ER

Steroids directly diffuse across plasma membrane

Abundant lipid droplets which are used for steroid production

Question 19

Are tyrosine derived hormones water or lipid soluble?

Answer 19

They are both:

Some are water soluble such as catecholamines and dopamine

Others are lipid soluble such as thyroxin

Question 20

How are tyrosine derived hormones deactivated?

Answer 20

Via enzymatic degradation (COMT, MAO)

Question 21

Where do thyroid hormones bind to their receptors?

Answer 21

They bind to nuclear receptors

Question 22

What determines sensitivity of cells to stimulation?

Answer 22

Number of receptors

Affinity of receptors

Downstream signalling molecules

The capacity to respond is determined primarily by the number of functional cells.

Question 23

What is overload desensitization?

Answer 23

Prolonged exposure to stimulus decreases cells response to the level of exposure.

Allows receptors to respond to changes in concentration of a signal rather than absolute concentration.

Question 24

What is the master controller of most endocrine systems?

Answer 24

The hypothalamus - pituitary -x axis

Question 25

How is the hypothalamus able to control the anterior pituitary?

Answer 25

From the hypothalamic-hypophyseal tract for posterior pituitary

Anterior pituitary has a rich blood supply from the hypothalamic-hypophyseal portal vessels which control anterior pituitary hormone production.

Question 26

What does the anterior pituitary produce?

Answer 26

Lots of tropic hormones; i.e hormones that travel to another gland to cause it to produce hormones.

eg. FSH, LH, somatotropics (GH), Corticotropics (eg ACTH), prolactin

Question 27

What does the posterior pituitary produce?

Answer 27

Hormones synthesized in the hypothalamus which travel down axons to posterior pituitary.

Main hormones are:

Oxytocin which acts on breast and uterus. Important for lactation and uterine contraction.

ADH: Involved in ADH reabsorption in kidney.

Question 28

Where is ADH originally produced?

Answer 28

Supraoptic and paraventricular nuclei

Question 29

What does the hypothalamus do?

Answer 29

It controls the anterior pituitary releasing hormones which travel to pituitary.