The Endocrine System

Question 1

What is the endocrine system?

Answer 1

-Theendocrine systemis a collection of glands that produce ~30 hormones
-Regulate metabolism, growth and development, tissue function, reproduction, sleep and mood, among other things
-Works along side nervous system

Question 2

What are the classes of hormones?

Answer 2

Amino acid derivatives
Peptide hormones
Lipid derivatives

Question 3

How are hormones distributed?

Answer 3

Hormones enter bloodstream and circulate freely or are bound to carrier proteins
Feely circulating hormone is active for only a short period of time

Question 4

How are hormones inactivated?

Answer 4

-Binding to receptor on target cell
-Absorbed and degraded by liver or kidneys
-Degraded by enzymes in the blood

Question 5

What is the mechanism of action?

Answer 5

Binding of hormones to their target receptor modifies cellular activities
Cell receptors have a specific ligand
Each cell type has receptors for different hormones
Two broad types of hormone receptors
Plasma membrane receptors
Intracellular receptors

Question 6

How do plasma membrane receptors work?

Answer 6

Adrenaline, noradrenaline, dopamine and peptide hormones bind to plasma membrane receptors
Second messengers are used
cAMP, Ca ions
Hormone binds to membrane receptor on the extracellular side of the membrane
Activates a G protein
Causes intracellular release of thousands of second messengers
Two different types of plasma membrane receptors dependent on second messenger used

Question 7

G proteins and cAMP

Answer 7

Hormone binds to receptor on the membrane
G protein is activated and it then activates adenylate cyclase
Adenylate cyclase converts ATP into cAMP
cAMP functions as a second messenger by activating kinases
Kinases cause the phosphorylation and activation of other proteins

Question 8

Name 6 endocrine organs

Answer 8

Pituitary gland
Thyroid gland
Parathyroid gland
Adrenal gland
Pineal gland
Pancreas

Question 9

What is the pituitary gland

Answer 9

Major endocrine gland
Small, oval, pea-sized gland inferior to the hypothalamus
Anterior and posterior lobes – differ in function
All hormones use cAMP as second messenger
Release of hormones from pituitary is controlled by the hypothalamus

Question 10

What hormones are of the anterior lobe?

Answer 10

-Thyroid-stimulating hormone (TSH)
Triggers release of thyroid hormones from thyroid gland

-Adrenocorticotropic hormone (ACTH)
Controls release of steroid hormones from adrenal cortex

-Gonadotrophins
Follicle-stimulating hormone (FSH)
Luteinising hormone (LH)

-Prolactin (PRL)
-Growth hormone (GH)
-Melanocyte-stimulating hormone (MSH)
-

Question 11

Hormones of the posterior lobe

Answer 11

-Antidiuretic hormone (ADH)
Acts on kidneys to retain water and decrease urination

-Oxytocin
Stimulates contraction of uterine wall
Stimulates release of milk
Contraction of sperm duct and prostate

Question 12

What does the thyroid gland produce?

Answer 12

The thyroid hormones

Question 13

What are the effects of thyroid hormones?

Answer 13

-Elevate rates of O2 and energy consumption
-Increase HR and force of contraction
-Maintain normal sensitivity of respiratory centres to changes in O2 and CO2 conc.
-Stimulates RBC formation
-Stimulates activity on other endocrine tissues

Question 14

What is calcitonin?

Answer 14

-Also produced by thyroid gland
-Regulates Ca conc. in the body
-Decreases Ca conc. in blood
-Inhibits osteoclasts – slows rate of release of Ca ions from bone
-Stimulates Ca excretion from kidneys

Question 15

What is the function of the parathyroid gland?

Answer 15

2 pairs of parathyroid glands embedded in the thyroid gland
Parathyroid hormone – regulates Ca conc.
Mobilises Ca from bone by affecting osteoblast and osteoclast activity
Enhances Ca resorption by kidney
Stimulates secretion of calcitriol by the kidneys
Increases Ca conc. in blood

Question 16

What is the production of the adrenal cortex?

Answer 16

Production of corticosteroids
Aldosterone – stimulates conservation of Na ions and elimination of K ions
Targets kidneys, sweat glands, salivary glands
Cortisol and corticosterone – increase rates of glucose and glycogen synthesis by the liver, anti-inflammatory effects
Androgen – male sex hormone

Question 17

What is the function of the adrenal medulla?

Answer 17

Adrenaline
Noradrenaline
In skeletal muscle, A and NA trigger mobilisation of glycogen reserves and accelerate glucose breakdown
In adipose tissues, fats are broken down into fatty acids
In the liver, breaks down glycogen
In the heart, causes an increase in rate and force of muscle contraction

Question 18

What is the function of the pineal gland?

Answer 18

-Production of melatonin
-Suggested functions include:

-Inhibiting reproductive functions
-Protects against damage by free radicals
-Influences circadian rhythms

Question 19

Pancreas- what does the alpha cells produce?

Answer 19

glucagon

Question 20

Pancreas- what do the beta cells produce?

Answer 20

insulin

Question 21

Pancreas- what do the delta cells produce?

Answer 21

growth hormone-inhibiting hormone

Question 22

Pancreas- what do the F cells produce?

Answer 22

produce pancreatic polypeptide

Question 23

What happens to hormone levels throughout ageing?

Answer 23

-Few changes in hormone levels with age
-Exception reproductive hormones
-Some endocrine tissues become less responsive with age
(In elderly, levels of insulin released after a meal are reduced)