The endocrine system Flashcards
The endocrine system is a control system with 3 main functions. What are they?
Maintenance of homeostasis
To help the body react properly to stress
Regulation of growth and development including sexual development and reproduction
How is the system organised?
Endocrine glands
Hormones
What are endocrine glands?
Tissues and organs that secrete hormones
What are hormones?
Chemical messengers released into the blood stream
Where do hormones travel?
Travel to all parts of the body, but only effective in specific target cells
What do hormones work together to control?
Feedback mechanisms
Name the endocrine organs/glands
Hypothalamus Pituitary Pineal Thymus Thyroid Parathyroid Adrenal Pancreas Gonads
How many hormones does the hypothalamus produces and how many regulate the anterior pituitary?
9
7
What are the two hormones that are released into the posterior pituitary?
Oxytocin and antidiuretic
What is also known as the master gland as it controls the majority of other endocrine glands?
Pituitary
Where is the pituitary located and what are the two lobes?
Below the hypothalamus in Sella turcica of sphenoid
Anterior Adenohypophysis
Posterior Neurohypophysis
What are the pituitary hormones?
Thyroid Melanocyte Prolactin Growth hormone Gonadotropins Adrenocorticotrophic
What does the pineal gland release?
Melatonin (at night)
When is peak secretion of melatonin?
1-5yr olds
75% lower by puberty
When is melatonin oncreaed and decreased?
Increase- SAD + PMS
Decrease- by phototherapy
Where is the thymus located?
In mediastinum superior to the heart
What does the thymus secrete?
Hormones that regulate development and later activation of T-lymphocytes
What is the largest endocrine gland?
Thyroid gland
What do follicular glands do?
Secrete thyroxine (T4) and Triiodothyronine (T3) Increase rate of metabolism
What do parafollicular cells do?
Secrete calcitonin
Decreases calcium and phosphate in blood
What does the release of the parathyroid gland do to when CA+2 levels rise?
Increase in Ca+2
Increase in bone resorption
Decrease in urinary excretion
What are the >25 steroid hormones synthesised from cholesterol?
Corticosteroids
Corticoids
What do mineralocorticoids do?
Control electrolyte balance e.g aldosterone acts on kidneys to retain Na+ and excrete K+ -> maintains blood volume and pressure
What do glucocorticoids do?
Secreted in response to ACTH
What are sex steroids?
Weak androgens and small amounts of oestrogen
Chromaffin cells secrete hormones of the adrenal medula. What are these two hormones?
Adrenaline
Noradrenaline
What do hormones of the adrenal medulla affect and when do they rise?
Affect heart rate, cardiac output, blood pressure
Rises in conditions of fear, pain and other kinds of stress
What is included in the pancreatic Islets of Langerhams?
Alpha cells Beta cells Delta cells F cells G Cells
What do alpha cells release?
Glucagon- glycogen breakdown in liver, release of glucose to blood; stimulates fat catabolism
What do beta cells release?
Insulin- synthesis of glycogen, fat and protein
What do delta cells release?
Somastatin- paracrine secretion to moderate other islet cells
What do F cells release?
Pancreatic polypeptide- Inhibits gall bladder contraction
What do G cells release?
Gastrin- stimulates acid secretion, motility and emptying of stomach
What do gonads in the ovaries produce and do?
Oestrogen and progesterone
Female reproducitve system
Menstrual cycle
Sustaining pregnancy
Preparing mammary glands for lactation
What do gonads in the testis secrete and do?
Leydig cells produce testosterone
Stimulates development of male reproductive system
Masculine physique
Sex drive
Maintains sperm production
What are the endocrine function of other organs?
Skin, heart, gut and placenta
Liver and kidneys
What is the function of skin in the endocrine system?
Keratinocytes help produce vitamin D3
What is the function of the heart in the endocrine system?
Atrial natriuretic peptide released with an increase in BP
What is the function of stomach and small intestines in the endocrine system?
Coordinate digestive motility and secretion
What is the function of the placenta in the endocrine system?
Secretes oestrogen, progesterone and others
What is the function of liver in the endocrine system?
Converts vitamin d3 to calcidiol
Secretes angiotensionogen
Secretes about 15% of erythropoietin
What is the function of kidneys in the endocrine system?
Converts calcidiol to calcitriol
Convert angiotensinogen to angiotensin
Produce 85% of erythropoietin
