Endocrinology Flashcards
(47 cards)
What is positive feedback?
The response to change is to enhance change
In what three ways can a hormone negative feedback loop go wrong?
- Too much hormone secreted
- Too little hormone secreted
- Change in sensitivity of the target cells
List all the main endocrine glands
Hypothalamus Pituitary gland Parathyroid and thyroid glands adrenal glands Pancreas Ovaries and testes
Where is the hypothalamus?
Below the thalamus, just above the brainstem. It forms the ventral part of the diencephalon. bThis is the central core of the cerebrum and has connections to both right and left hemispheres.
Where is the pituitary gland?
It is a midline structure in the pituitary fossa of the sphenoid bone.
What connects the hypothalamus to the pituitary gland
Infundibulum
What it the pituitary gland anatomically and functionally divided into?
The anterior and posterior pituitary gland
What hormones are released by the posterior pituitary gland?
Oxytocin
ADH
How do hormones get from the hypothalamus to the posterior pituitary?
- Axons of hypothalamic neurones pass down the infundibulum into the posterior pituitary. These hypothalamic neurones manufacture 2 hormones (ADH and oxytocin)
- These hormones are then transported to the posterior pituitary within the axoplasm by axoplasmic transport.
What is an axoplasm?
The cytoplasm of axons
What hormones does the anterior pituitary gland release?
GH Prolactin TSH (thryroid stimulating hormone) ACTH (adrenocorticotrophic hormone) LH FSH
How do the hypothalamus and anterior pituitary gland work?
Hypothalamic neurones secrete either releasing hormones or inhibitory hormones to stimulate or prevent the release of its hormones into the bloodstream.
What do the hypothalamic neurones secreted their hormones into?
A portal system of veins “The hypophyseal portal system” This drains venous blood from the hypothalamus to the anterior pituitary capillary beds.
How does the anterior pituitary get its hormones into the blood stream?
A second set pof veins drains the venous blood to the hypophyseal veins and then eventually to the SVC. (and then around the body)
What is the definition of a portal system?
A capillary bed that lies between 2 sets of veins.
What does the thyroid gland need to manufacture its hormones?
Iodine
What are the two thyroid hormones?
Triiodothyronine (T3)
Thyroxine (T4)
What do thyroid hormones do?
Regulate the metabolism and stimulate growth. T3 is essential for life
What is an enlarged thyroid gland called? What can cause this?
Goitre
Dietary lack of iodine
What is the thyroid gland attached to?
The larynx
Where are the parathyroid glands?
On the posterior surface of the thyroid gland’s lobes
What do parathyroid glands do?
They manufacture and secrete parathyroid hormone (PTH) which controls the amount of calcium in the blood and bones?
How are the parathyroid glands controlled?
Not by the pituitary but they monitor the blood calcium levels directly and respond to this.
What is the blood supply to the thyroid gland?
The superior thyroid artery which is a branch off the external common carotid, and the inferior thyroid artery which is a branch of the subclavian artery
