Endocrine system 2 Flashcards
What are the primary endocrine organs?
- Hypothalamus
- Pituitary glands
- Pineal glands
- Thyroid glands
- Parathyroid
- Adrenal cortex & medulla
- Endocrine pancreas
- Ovaries (f), placenta (f), testes (m)
Describe the position of the hypothalamus & the pituitary?
- Pituitary is attached to the hypothalamus, small P shaped organ
- In the lower area of the brain
Where do the anterior and posterior pituitary glands develop?
Anterior –> embryological developemnt: up-growth from roof of mouth
Posterior –> down-growth of the brain
How do the hypothalamus and the anterior pituitary connect?
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
Where are the capillary beds around the pituitary?
Two capillary beds, one in anterior pituitary & one in the pituitary stalk
What is nicknamed the “master switchboard”?
Hypothalmus
What is nicknamed the “master gland”?
Anterior pituitary
What is the endocrine axis?
Interactions between the hypothalamus, the pituitary and peripheral endocinre glands, with feedback regulation of hormone secretion
Refer to the axis diagram
Re-watch the video for tropic hormones of hypothalamus & anterior pituitary as it’s a long process
You noted this on your to-do list, it’s slides 10-15
Also include HPA axis as this needs to be finished
What is the process of the posterior pituitary releasing a hormone?
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
What is the role of the posterior pituitary?
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
What are the 2 main hormones released from the posterior pituitary?
- Arginine vasopressin, AVP (or ADH)
- Oxytocin
What is the 2 areas that AVP (ADH) target?
- Blood vessels
- Kidney
What action does AVP (ADH) have on the blood vessels?
Vasoconstriction –> via V1 receptors (at higher AVP)
What action does AVP (ADH) have on the kidney?
(distal convoluted tubules & collecting ducts)
To increase permeability and, hence, re-absorption of water, via V2 receptors
(renal notes will help w this)
Do both males and females produce oxytocin?
Yes - however it is better understood in females
When is oxytocin released?
Its release is stimulated by suckling, and by cervical stimulation (partuition - the process of giving birth)
What is the actions of oxytocin?
- Stimulate “milk let-down”, expression of breast milk
- Uterine smooth muscle - contraction
- Maternal behaviour / sexual behaviour / social bonding?
Where is oxytocin produced and released from?
Produced –> hypothalamus
Released –> posterior pituitary
(same for ADH - but is stored in pituitary before release)
Where is the pineal gland found?
A pine nut sized gland in the centre of the brain
What does the penial glad produce?
Melatonin
Derived from tryptophan
When is melatonin secreted?
It is secreted at night “hormone of darkness”
(period of darkness/inactivity)
What is the role of melatonin?
- Promotion of sleep
- Seasonal fluctuations of melatonin (associated w longer daylight hours) are important triggers for seasonal breeding, migration & hibernation
What cycle is melatonin involved in?
In the control of the body’s circadian rhythm in synchrony with the light-dark cycle
What can melatonin be used to treat?
Insomnia & jet-lag
Where is the thyroid hormone located?
In your throat –> the size of a small plum cut in two halves
What are the hormones that they thyroid produces?
Thyroxine (T4) & tri-iodothyronine
T in T4 & T3 = tyrosine
Number = no. iodines attached
How are T3 and T4 made?
A process called iodination - iodine atoms are added to tyrosine residues to form either;
mono-iodotyrosine (MIT) or di-iodotyrosine (DIT)
What two molecules combine to from T4?
Two X di-iodotyrosine
DIT + DIT = T4
(process called coupling forms this)
What two molecules combine to from T3?
A di-iodotyrosine and a mono-iodotyrosine
DIT + MIT = T3
(process called coupling forms this)
What is the enzyme used to catalyse the production of T3 & T4?
Thyroid peroxidase (TPO)
What is the structure of MIT?
Tyrosine, iodinated at 3’ of ring = MIT
What is the structure of DIT?
Tyrosine, iodinated at 3’ and 5’ of ring = DIT
What happens to T4 in the periphery?
Most T4 is converted to T3 in the periphary
Most actions of thyroid hormones are by T3 (most biologically active)
What does DIT + MIT =?
Reverse tri-iodothyronine, rT3
What is the actions of the thyroid hormones (T3 and T4)?
- Increase metabolism in the body (all cells)
- Generalised increase in functional activity of almost all tissues - important for normal development & maturation of CNS
What is the actions of the thyroid hormones (T3 and T4)?
- Increase metabolism in the body (all cells)
- Generalised increase in functional activity of almost all tissues - important for normal development & maturation of CNS
What is the action of thyroid hormone (calcitonin)?
Involved in calcium homeostasis (with PTH, vit D3)
Dec plasma Ca2+
How doe T3 and T4 inc metabolism in the body?
- Inc basal metabolic rate (BMR)
- Inc metabolism of CHOs, proteins & fats
