Endocrine System Flashcards
Name glands within the endocrine system
Hormones
• Operate over a long range
• Secreted into the blood by endocrine glands in response to a specific signal
• Transported in the blood to their target cells
The endocrine system provides the means to:
• interpret the electrical signals from the brain as biochemical signals
• allow the various differentiated cells of the body to work in harmony
• maintain homeostasis
What is the hypothalamus and what do its hormones do ?
• Connected to the pituitary via the pituitary stalk and regulates the two lobes by neural and hormonal pathways
• Hypothalamic hormones regulate the secretion of anterior pituitary hormones
What does the pituitary do, how long is it, where is it found and what are the two distinct parts
-The pituitary together with the hypothalamus form the primary interface between the electrical activity of the brain and the biochemical activity of other body organs.
-The pituitary is about 1 cm in diameter lying in a bone cavity at the base of the skull.
-Two distinct parts - the anterior lobe (derived from the ectoderm of the buccal cavity) and the posterior lobe (derived from neural tissue)
Anterior pituitary
Responds to signals from the hypothalamus to secrete:
• Adrenocorticotrophic hormone (ACTH)
• Thyroid stimulating hormone (TSH)
• Growth hormone
• Follicle stimulating hormone (FSH) and luteinising hormone (LH),
• Prolactin
• Melanocyte stimulating hormone
Posterior pituitary
Stores and secretes two hormones:
-Anti-diuretic hormone (vasopressin) (ADH) which regulates re-absorption of water in the kidneys and hence fluid balance
-Oxytocin - allows secretion of milk in response to suckling
• Both these hormones are synthesised in the hypothalamus
Virtually all the biochemical processes involved in homeostasis are ultimately controlled by either the……………. or the…………..
Hypothalamus or pituitary
Parathyroids
-Four glands associated with the thyroid.
-Secrete parathyroid hormone which increases serum calcium and
-calcitonin which decreases serum calcium.
Thyroid
-thyroid gland secretes calcitonin and the thyroid hormones - Triiodothyronine (T3) and its precursor thyroxine (T4). Very little is free in blood - the majority is bound to thyroxine binding protein.
-Thyroid hormones increase the metabolic rate of all body tissues and the plasma level is controlled by a feedback loop.
The pancreas
-Islets of Langerhans secrete insulin, glucagon and somatostatin
-Glucagon - secreted from a2 or A cells.
-Insulin - from B or B cells
-Somatostatin from o or D cells
Insulin and glucagon
-Operate together to maintain blood sugar in both fasting and fed states.
-Additional control in fasting provided by epinephrine, glucocorticoids and growth hormone which minimise glucose uptake and maximise conversion of amino acids to glucose ensuring a supply of glucose for those tissues that cannot use fats (e.g. brain and kidney)
Adrenal cortex produces…..
-Glucocorticoids such as cortisol which regulate fat, carbohydrate and protein metabolism and have anti-inflammatory activities
-Mineralocorticoids such as aldosterone which regulate water and electrolyte balance
-Adrenogenital corticoids (androgens and oestrogens) which affect sexual function
Adrenal medulla
-Secretes adrenaline and noradrenaline.
-Increased amounts are secreted at times of physical or emotional stress in response to sympathetic nerve stimulation
Catecholamines
-Dopamine
-Noradrenaline (norepinephrine)
-Adrenaline (epinephrine)
-Secreted by some neurones and the chromafin cells of the adrenal medulla
Effects of catecholamines
Growth hormone
-Growth Hormone Releasing Hormone (GHRH)
-Hypophyseal Portal System
-Anterior Pituitary - GH
-191 aa peptide
-Cell membrane receptor
-Pulsatile - varies the amount produced
-Majority produced during sleep - particularly one hour after proper sleep commences
What does the growth hormone do
• Increases protein production
• Increases calcium retention & mineralisation of bones
• Increases muscle mass (sarcomere hypertrophy)
• Promotes lipolysis - metabolism of fats
• Dec uptake of glucose by liver
• Promotes gluconeogenesis
• Stimulates the Immune System
• Increases deiodination of T4 to T3
