L34: Endocrine system Flashcards
What is the function of the endocrine system?
It regulates homeostasis by secreting hormones that influence metabolism, growth, and organ function
How do endocrine glands differ from exocrine glands?
Endocrine glands are ductless and release hormones directly into the bloodstream, while exocrine glands use ducts to transport secretions.
Where is the hypothalamus located?
At the base of the brain, just above the pituitary gland.
What are the main functions of the hypothalamus?
It regulates body temperature, thirst, hunger, sleep, blood pressure, and hormone secretion.
Where is the pituitary gland located?
It sits in the sella turcica (a cavity in the sphenoid bone) and is connected to the hypothalamus by the infundibular stalk.
What are the two parts of the pituitary gland?
Anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis).
What is the embryological origin of the anterior pituitary?
It develops from pharyngeal tissue.
Name six hormones secreted by the anterior pituitary.
- ACTH (Adrenocorticotropic hormone) – Stimulates the adrenal cortex.
- TSH (Thyroid-stimulating hormone) – Stimulates the thyroid.
- LH (Luteinising hormone) – Regulates ovulation and testosterone production.
- FSH (Follicle-stimulating hormone) – Stimulates egg and sperm production.
- PRL (Prolactin) – Stimulates milk production.
- GH (Growth hormone) – Stimulates cell growth and metabolism.
What is the embryological origin of the posterior pituitary?
It develops from neural tissue.
What hormones are stored and released by the posterior pituitary?
Oxytocin – Stimulates uterine contractions and milk ejection.
Antidiuretic hormone (ADH) – Regulates water retention in the kidneys.
How are these hormones transported to the posterior pituitary?
Via the hypothalamohypophyseal tract (nerve axons).
What system connects the hypothalamus to the anterior pituitary?
The hypothalamohypophyseal portal system.
How does negative feedback work in hormone regulation?
High hormone levels signal the hypothalamus to reduce hormone production, preventing excess secretion.
Where is the thyroid gland located?
In the anterior neck, in front of the trachea, spanning C5 to T1.
What are the two main thyroid hormones and their functions?
- Thyroxine (T4) – Regulates metabolism.
- Triiodothyronine (T3) – Active form, increases basal metabolic rate.
What hormone lowers blood calcium levels, and how?
Calcitonin – It promotes calcium storage in bones.
How many parathyroid glands are there, and where are they located?
Four glands (two superior, two inferior) on the posterior surface of the thyroid.
What hormone does the parathyroid gland secrete, and what is its function?
Parathyroid hormone (PTH) – Increases blood calcium levels by stimulating bone resorption and enhancing kidney and intestinal calcium absorption.
Where are the adrenal glands located?
On the superior-medial aspect of the kidneys, at T11/T12 level.
Name the three layers of the adrenal cortex and the hormones they produce.
- Zona glomerulosa → Aldosterone (regulates water & salt balance).
- Zona fasciculata → Cortisol (regulates glucose metabolism, reduces inflammation).
- Zona reticularis → Androgens (precursors for sex hormones).
What does the adrenal medulla produce, and what is its function?
Adrenaline & noradrenaline → Initiate the sympathetic (fight-or-flight) response.
What are the two functions of the pancreas?
- Exocrine function → Secretes digestive enzymes into the duodenum.
- Endocrine function → Releases hormones into the bloodstream.
What are the four cell types in the Islets of Langerhans and their hormones?
- Alpha cells → Glucagon (raises blood glucose).
- Beta cells → Insulin (lowers blood glucose).
- Delta cells → Somatostatin (inhibits insulin & glucagon).
- PP cells → Pancreatic polypeptide (regulates pancreatic enzyme secretion).
Where are the ovaries and testes located?
Ovaries → Pelvic cavity.
Testes → Scrotum (outside the body cavity).
What hormones do the ovaries and testes secrete?
Ovaries → Oestrogen & progesterone (regulate the menstrual cycle & pregnancy).
Testes → Testosterone (develops male secondary sexual characteristics).
How does the hypothalamus communicate with the anterior and posterior pituitary?
Anterior pituitary → Hypothalamohypophyseal portal system.
Posterior pituitary → Hypothalamohypophyseal tract (nerve axons).
What are hormones?
Chemical messengers secreted by endocrine glands that regulate bodily functions.
What is the difference between endocrine and nervous system signalling?
Endocrine system → Uses hormones, slower but longer-lasting effects.
Nervous system → Uses electrical impulses, faster but short-lived responses.
What are the three major types of hormones?
- Peptide hormones – Made of amino acids (e.g., insulin, ADH).
- Steroid hormones – Derived from cholesterol (e.g., cortisol, oestrogen).
- Amino acid-derived hormones – Modified amino acids (e.g., adrenaline, thyroxine).
How do hormones travel in the body?
Through the bloodstream, binding to target cells via specific receptors.
What are releasing hormones from the hypothalamus?
Hormones that stimulate the anterior pituitary to release specific hormones, e.g.:
TRH (Thyrotropin-releasing hormone) → Stimulates TSH release.
CRH (Corticotropin-releasing hormone) → Stimulates ACTH release.
GnRH (Gonadotropin-releasing hormone) → Stimulates FSH & LH release.
What are inhibiting hormones from the hypothalamus?
Hormones that prevent the anterior pituitary from releasing specific hormones, e.g.:
Somatostatin → Inhibits GH & TSH release.
Dopamine (Prolactin-inhibiting hormone, PIH) → Inhibits prolactin release.
How is the anterior pituitary different from the posterior pituitary?
Anterior pituitary → Produces its own hormones, regulated by the hypothalamus.
Posterior pituitary → Stores & releases hypothalamic hormones (ADH & oxytocin).
What is the function of Melanocyte-Stimulating Hormone (MSH)?
Controls melanin production in the skin and may influence appetite & sexual function.
What mineral is required for thyroid hormone production?
Iodine – Found in iodised salt and seafood.
What condition results from iodine deficiency?
Goitre – An enlarged thyroid due to insufficient T3 & T4 production.
What is the difference between hyperthyroidism and hypothyroidism?
Hyperthyroidism → Excess thyroid hormones → Weight loss, rapid heartbeat, heat intolerance.
Hypothyroidism → Insufficient thyroid hormones → Weight gain, fatigue, cold intolerance.
What is the antagonist hormone to calcitonin?
Parathyroid Hormone (PTH) – Raises blood calcium by increasing bone breakdown.
What are the three zones of the adrenal cortex and their primary hormones?
- Zona Glomerulosa → Aldosterone (Water & sodium retention).
- Zona Fasciculata → Cortisol (Glucose metabolism, stress response).
- Zona Reticularis → Androgens (Sex hormone precursors).
What is Cushing’s syndrome?
Excess cortisol production → Causes weight gain, moon face, muscle weakness, high blood sugar.
What is Addison’s disease?
Adrenal insufficiency → Causes low cortisol & aldosterone levels, fatigue, low blood pressure.
How does aldosterone regulate blood pressure?
It increases sodium retention, which increases water retention, raising blood pressure.
What is the role of prolactin?
It stimulates milk production in breastfeeding women.
Which hormone is responsible for contractions during childbirth?
Oxytocin
