Hormone Synthesis And Action

Question 1

Definition of endocrine system

Answer 1

A system of ductless glands and cells that secrete hormones
Regulates - metabolism, homeostasis and reproduction

Question 2

List of endocrine glands

Answer 2

Pineal glands
Hypothalamus
Pituitary
Thyroid
Parathyroid
Thymus
Pancreas
Adrenal
Kidney
GIT
Ovaries/ testis

Question 3

What are Endocrine Glands

Answer 3

Release secretions (hormones) into blood directly from cells - ductless glands

Question 4

What are exocrine glands?

Answer 4

(Not part of endocrine system) release their secretions outside the body and may be ducted e.g. gut secretions, sweat glands

Question 5

What are mixed glands?

Answer 5

Pancreas produces digestive juice + insulin, glucagon and somatostatin

Question 6

What is a hormone?

Answer 6

Hormone is a substance secreted directly into the blood by specialised cells
Hormones are present in only minute concentrations in the blood and bind to specific receptors on target cells

Question 7

What are the 2 major regulatory systems of the body

Answer 7

Nervous
Endocrine

Question 8

Comparisons between nervous and endocrine systems

Answer 8

Few NT vs many hormones
Generally rapid vs generally slow
Generally short lived vs generally long lasting
Localised vs widespread

Question 9

Three mechanisms of chemical signalling

Answer 9

Intracrine
Autocrine
Paracrine

Question 10

What is intracrine signalling

Answer 10

Generated by a chemical acting within the same cell

Question 11

What is autocrine signalling

Answer 11

Chemical or hormone secreted
And binds to autocrine receptors on the same cell

Question 12

What is paracrine signalling

Answer 12

Chemical communication between neighbouring cells

Question 13

What is the “classical” endocrine and neuroendocrine signalling mechanism

Answer 13

A chemical released by a specialised group of cells int circulation and acting on a distant target tissue

Question 14

What is feedback control of hormonal release

Answer 14

Process by which body senses change and responds to it

Question 15

What is negative feedback

Answer 15

Process by which body senses change and activates mechanism to reduce it
The final product of an endocrine cascade acts to inhibit the release of hormones higher up the cascade

Question 16

What is positive feedback

Answer 16

Process by which body senses change and activates mechanism to amplify it

Question 17

3 main groups of hormones?

Answer 17

Peptide hormones
Steroid hormones
Amine hormones

Question 18

What is the most common hormone

Answer 18

Peptide hormone

Question 19

Features of peptide hormones

Answer 19

Made of amino acids
Hydrophilic
Preformed and stored in membrane bound vesicles ready for release by exocytosis

Question 20

How are peptide hormone synthesised?

Answer 20

Produced on RER as large precursor molecule - “preprohormone”
Matures into prohormone via cleavage of N terminal signal sequences
Bioactive hormone prod as result of enzymatic processing

Question 21

What are the subunits of pituitary glycoprotein hormones

Answer 21

Alpha subunit - genetic subunit for all hormones
Beta subunit - specific to each hormone

Released from anterior PG

Question 22

Some hormones secreted from anterior pituitary gland

Answer 22

Thyroid stimulating hormone TSH
Luteinising hormone LH
Follicle stimulating hormone FSH
Growth hormone GH
ACTH
Prolactin

Question 23

Precursor of steroid hormones

Answer 23

Cholesterol

Question 24

What is the rate limiting step in the production of steroid hormones

Answer 24

Pregnenolone
CYP11A

Question 25

Examples of steroid hormones

Answer 25

Adrenal cortex (glucocorticoid and mineral corticoids) and sex hormones (testosterone/ oestrogen)

Question 26

Features of steroid hormones?

Answer 26

Hydrophobic Not stored - synthesised as required, then diffuse out of cell

Question 27

How are steroid hormones synthesised

Answer 27

Hydrolysis of esters and release of cholesterol Cholesterol to pregnenolone in mitochondria (steroid hormones cannot be stored so stored as precursor) Processing of pregnenolone in SER

Question 28

How is the movement of cholesterol to mitochondrion regulated

Answer 28

Regulated by steroid acute regulatory protein (StAR) ACTH regulates StAR activity and processing of cholesterol

Question 29

The secretions of different zonas in the adrenal cortex

Answer 29

Zona glomerulosa - aldosterone Zona fasciculata - cortisol Zona reticularis - adrenal androgens

Question 30

How are enzymes involved in the synthesis of specific hormones

Answer 30

Specific tissue contains cells expressing enzymes leading to specific hormone synthesis

Question 31

What does increase in secretion reflect?

Answer 31

Reflects accelerated rates of synthesis

Question 32

How are steroid hormones eliminated

Answer 32

By inactivating metabolic transformations and excretion in urine or bile

Question 33

Features of thyroid hormones

Answer 33

Amine hormones Small Non polar Hydrophobic Soluble in plasma membranes

Question 34

Transportation of steroid & thyroid

Answer 34

Binding increases: - solubility - half life Reservoir in blood Specific binding proteins TBG and CBG Or non specific binding proteins Albumin - loose binding

Question 35

Receptors of protein hormones

Answer 35

Cell surface receptors Activate second messenger cascade and change cellular function

Question 36

What are the receptors of steroid hormones

Answer 36

Intracellular receptors Cytoplasm or nuclear Hormone-receptor complex binds to HRE

Question 37

Types of endocrine disorders

Answer 37

Hormones in excess Hormone deficiency

Question 38

Causes and treatment of excess primary disorders

Answer 38

Hormones in excess: Often caused by tumours/ exogenous intake of hormone Treatment - surgical removal of gland

Question 39

Causes and treatment of insufficiency

Answer 39

Hormones in deficiency: Primary - primary organ inadequate Secondary - tropic hormone deficient/ autoimmune destruction Treatment - replacement therapy Orally absorbed, long half life Injection - otherwise degraded in GIT

Question 40

What is the outcome of deficiency or excess of growth hormone

Answer 40

Deficiency: Dwarfism Excess: Gigantism

Question 41

What is the outcome of deficiency or excess of ADH

Answer 41

Deficiency diabetes insipidus Excess hypervalemia

Question 42

What is the outcome of deficiency or excess of insulin

Answer 42

Diabetes mellitus Coma

Question 43

Examples of peptide hormones

Answer 43

GH CRH corticotropins