Endocrine system 2

Question 1

What are the primary endocrine organs?

Answer 1

• Hypothalamus
• Pituitary glands
• Pineal glands
• Thyroid glands
• Parathyroid
• Adrenal cortex & medulla
• Endocrine pancreas
• Ovaries (f), placenta (f), testes (m)

Question 2

Describe the position of the hypothalamus & the pituitary?

Answer 2

• Pituitary is attached to the hypothalamus, small P shaped organ
• In the lower area of the brain

Question 3

Where do the anterior and posterior pituitary glands develop?

Answer 3

Anterior –> embryological developemnt: up-growth from roof of mouth

Posterior –> down-growth of the brain

Question 4

How do the hypothalamus and the anterior pituitary connect?

Answer 4

Cell bodies & the neuron repsonsible for the scretion of hypothalamic releasing factors (hormones)

Releasing facotrs pass along the portal vessles to reach capillary bed of the anterior pituitary, to control secretion of anterior pituitary hormones

Question 5

Where are the capillary beds around the pituitary?

Answer 5

Two capillary beds, one in anterior pituitary & one in the pituitary stalk

Question 6

What is nicknamed the “master switchboard”?

Answer 6

Hypothalmus

Question 7

What is nicknamed the “master gland”?

Answer 7

Anterior pituitary

Question 8

What is the endocrine axis?

Answer 8

Interactions between the hypothalamus, the pituitary and peripheral endocinre glands, with feedback regulation of hormone secretion

Refer to the axis diagram

Question 9

Re-watch the video for tropic hormones of hypothalamus & anterior pituitary as it’s a long process

Answer 9

You noted this on your to-do list, it’s slides 10-15

Also include HPA axis as this needs to be finished

Question 10

What is the process of the posterior pituitary releasing a hormone?

Answer 10

1) Hormone is made & packaged in the cell body of neuron

2) Vesicles are trasnported down the cell

3) Vesicles containing hormone are stored in posterior pituitary

4) Hormones are released into blood

Question 11

What is the role of the posterior pituitary?

Answer 11

Nueroendocrine cells synthesise vasopressin & oxytocin (in cell bodies located in hypothalamus)

Hormones are transported alogn neurons, stored in the axon termini - in the posterior pituitary

Question 12

What are the 2 main hormones released from the posterior pituitary?

Answer 12

• Arginine vasopressin, AVP (or ADH)
• Oxytocin

Question 13

What is the 2 areas that AVP (ADH) target?

Answer 13

• Blood vessels
• Kidney

Question 14

What action does AVP (ADH) have on the blood vessels?

Answer 14

Vasoconstriction –> via V1 receptors (at higher AVP)

Question 15

What action does AVP (ADH) have on the kidney?

Answer 15

(distal convoluted tubules & collecting ducts)

To increase permeability and, hence, re-absorption of water, via V2 receptors

(renal notes will help w this)

Question 16

Do both males and females produce oxytocin?

Answer 16

Yes - however it is better understood in females

Question 17

When is oxytocin released?

Answer 17

Its release is stimulated by suckling, and by cervical stimulation (partuition - the process of giving birth)

Question 18

What is the actions of oxytocin?

Answer 18

• Stimulate “milk let-down”, expression of breast milk
• Uterine smooth muscle - contraction
• Maternal behaviour / sexual behaviour / social bonding?

Question 19

Where is oxytocin produced and released from?

Answer 19

Produced –> hypothalamus

Released –> posterior pituitary

(same for ADH - but is stored in pituitary before release)

Question 20

Where is the pineal gland found?

Answer 20

A pine nut sized gland in the centre of the brain

Question 21

What does the penial glad produce?

Answer 21

Melatonin

Derived from tryptophan

Question 22

When is melatonin secreted?

Answer 22

It is secreted at night “hormone of darkness”

(period of darkness/inactivity)

Question 23

What is the role of melatonin?

Answer 23

• Promotion of sleep
• Seasonal fluctuations of melatonin (associated w longer daylight hours) are important triggers for seasonal breeding, migration & hibernation

Question 24

What cycle is melatonin involved in?

Answer 24

In the control of the body’s circadian rhythm in synchrony with the light-dark cycle

Question 25

What can melatonin be used to treat?

Answer 25

Insomnia & jet-lag

Question 26

Where is the thyroid hormone located?

Answer 26

In your throat –> the size of a small plum cut in two halves

Question 27

What are the hormones that they thyroid produces?

Answer 27

Thyroxine (T4) & tri-iodothyronine

T in T4 & T3 = tyrosine
Number = no. iodines attached

Question 28

How are T3 and T4 made?

Answer 28

A process called iodination - iodine atoms are added to tyrosine residues to form either;

mono-iodotyrosine (MIT) or di-iodotyrosine (DIT)

Question 29

What two molecules combine to from T4?

Answer 29

Two X di-iodotyrosine

DIT + DIT = T4

(process called coupling forms this)

Question 30

What two molecules combine to from T3?

Answer 30

A di-iodotyrosine and a mono-iodotyrosine

DIT + MIT = T3

(process called coupling forms this)

Question 31

What is the enzyme used to catalyse the production of T3 & T4?

Answer 31

Thyroid peroxidase (TPO)

Question 32

What is the structure of MIT?

Answer 32

Tyrosine, iodinated at 3’ of ring = MIT

Question 33

What is the structure of DIT?

Answer 33

Tyrosine, iodinated at 3’ and 5’ of ring = DIT

Question 34

What happens to T4 in the periphery?

Answer 34

Most T4 is converted to T3 in the periphary

Most actions of thyroid hormones are by T3 (most biologically active)

Question 35

What does DIT + MIT =?

Answer 35

Reverse tri-iodothyronine, rT3

Question 36

What is the actions of the thyroid hormones (T3 and T4)?

Answer 36

• Increase metabolism in the body (all cells)
• Generalised increase in functional activity of almost all tissues - important for normal development & maturation of CNS

Question 36

What is the actions of the thyroid hormones (T3 and T4)?

Answer 36

• Increase metabolism in the body (all cells)
• Generalised increase in functional activity of almost all tissues - important for normal development & maturation of CNS

Question 37

What is the action of thyroid hormone (calcitonin)?

Answer 37

Involved in calcium homeostasis (with PTH, vit D3)

Dec plasma Ca2+

Question 38

How doe T3 and T4 inc metabolism in the body?

Answer 38

• Inc basal metabolic rate (BMR)
• Inc metabolism of CHOs, proteins & fats