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Gd 12 LS 2018 > Endocrine System > Flashcards

Flashcards in Endocrine System Deck (55):


  • A useful substance or fluid produced by cells and released to to the surrounding medium.
  • E.g. Sweat, enzymes and hormones


Endocrine glands

Secrete hormones into blood vessels that then transport these to target organs


Exocrine glands

Glands with ducts to carry secretions to places where they are required


The endocrine system

  • A system consisting of various endocrine glands releasing hormones
  • which act as chemical messengers targeting specific organs


Name at least 5 major glands making up the endocrine system

  • Hypothalamus
  • Pituitary
  • Thyroid
  • Thymus
  • Pancreas
  • Adrenal
  • Testes
  • Ovaries


Functions of hormones

  • Regulate secretions from endocrine or exocrine glands
  • control growth and development of the body
  • maintain homeostasis
  • regulate metabolism and energy release
  • react to stimuli in emergency situations
  • control reproduction process


When hormones act together for a common effect

Synergistic hormones


When hormones act against each other or the effect of one cancels out the effect of the other

Antagonistic hormones


Over secretion of hormones

Hyper secretion


Under secretion of hormones

Hypo secretion


The role of the hypothalamus

  • Part of the brain that links the nervous and endocrine systems
  • maintains homeostasis
  • controls other glands
  • particularly involved with pituitary gland function
  • produces ADH (secreted by pituitary)


The role of the pituitary gland (hypophysis)

  • Referred to sometimes as the master gland
  • Releases hormones that control metabolic functions and many other endocrine glands


Five hormones secreted by pituitary

  • Growth hormone GH (growth)
  • Thyroid stimulating hormone  TSH (thyroid to produce thyroxin)
  • Follicle stimulating hormone FSH (ovary or testes function)
  • Lutenising hormone  LH (ovary or testes function)
  • prolactin (mammary gland function)


Thyroid gland function

Pituitary gland releases thyroid stimulating hormone (TSH)

Thyroid stimulated to produce thyroxin:

  • controls basic metabolic rate of cells
  • increases nervous system activity
  • increases cardiac output
  • affects mental and physical growth and sexuality
  • affects alimentary system



Over-secretion of thyroxin

Graves' disease:

  • Increased metabolic rate
  • nervousness
  • weight loss
  • rapid heart rate
  • shaky, sweaty and hyperactivity
  • goitres causing bulging eyes



Under secretion of thyroxin:

cretinism in children:

  • low metabolic rate
  • retarded growth and mental development,
  • thick skin and protruding tongue
  • retarded sexual development

myxoedema in adults:

  • feel cold,
  • gain weight,
  • thick skin,
  • slow mentally and physically


Structure of the pancreas

Exocrine gland (digestive juices) Endocrine gland (islets of Lagerhans): -alpha cells secrete glucagon -beta cells secrete insulin


Role of insulin and glucagon

Antagonistic hormones - negative feedback interaction. Hypothalamus detects if blood sugar too high Insulin secretion increased and more glucose converted to glycogen Hypothalamus detects if blood sugar too low Glucagon secretion increased and more glycogen converted to glucose



-Not enough insulin produced resulting in elevated blood glucose levels -Extra glucose is excreted by the kidneys -Diabetics need to control intake of carbohydrates and may need daily insulin


Type 1 diabetes

Life long condition Pancreas does not produce enough insulin Daily use of insulin required


Type-2 diabetes

-Body cells become resistant to insulin or pancreas makes insufficient insulin -Can be triggered by obesity and lack of physical fitness -treatment varies according to the specific nature of the disease e.g. daily insulin


The function of anti-diuretic hormone (ADH)

-Regulates water content and body temperature -Osmoreceptors in hypothalamus detect if concentration of solutes in the blood high. -The hypothalamus stimulates the pituitary to release ADH -ADH increases permeability of distal convoluted tubule of the nephron -more water is reabsorbed, less water in urine -a lower concentration of solutes in the blood inhibits secretion of ADH -permeability of the distal convoluted tubules decreases -less water reabsorbed, more water in urine


Location of the adrenal glands

One above each kidney


Hormones produced by the adrenal glands

Aldosterone Adrenaline


Function of aldosterone

Aldosterone targets nephrons in kidney. Increases reabsorption of sodium (salt balance in blood) which also affects water movement by osmosis. Together with ADH it brings about water balance in the body.


If the sodium level is too high in the blood...

Less aldosterone secreted Less sodium ions reabsorbed by blood More sodium ions excreted Sodium levels decrease


Over secretion of aldosterone results in...

Too much salt in the blood Water retained resulting in odema (swelling) in the tissues


Function of adrenaline

Prepares the body to cope with emergency or stress Also known as fight or flight hormone: -increases breathing rate -speeds conversion of glycogen into glucose -accelerates heart rate and blood pressure -increases blood flow to muscles and brain by dilation of vessels -reduces blood flow to digestive system and skin by constriction of vessels -increased metabolism in brain and muscles -increased muscle tone and sweating -stimulates release of cortisone -pupils dilate


Hormone produced by testes



Hormones produced by ovaries

Oestrogen (from Graafian follicle) Progesterone (from corpus luteum)


Function of testosterone

-Development of male secondary characteristics -develops and maintains reproductive organs -sperm production -increased red blood cells at puberty -increased height


Function of oestrogen

-Develops and maintains female secondary sexual characteristics -develops and maintains reproductive organs -at puberty increases physical growth


Effect of hypo (under) secretion of testosterone

Sterility Addison's disease


Effect of hyper (over) secretion of testosterone

Increased masculinity, rate of growth and metabolism Called virilisation


Effect of hypo (under) secretion of oestorogen and progesterone

Addison's disease


Effect of hyper (over) secretion of oestrogen and progesterone

Irregular ovulation Softening of bones Unusual uterus development


Positive feedback mechanisms in the endocrine system

Mechanisms that cause continued or increased secretion.


Negative feedback mechanisms in the endocrine system

Mechanisms that make adjustments to bring the body back within an acceptable range. When too high, the gland secreting it reduces secretion and when too low, it increases secretion.


Negative feedback of thyroxin levels

-when thyroxin level too low -pituitary is stimulated to secrete more TSH -more TSH causes thyroid gland to secrete more thyroxin -thyroxin levels raised -when thyroxin level too high -pituitary is inhibited from secreting TSH -less TSH causes thyroid gland to secrete less thyroxin -thyroxin levels decreased.


Hypo- (under) and hyper- (over) secretion of growth hormone (GH)

Hypo: dwarfism Hyper: giganitism in children, acromegaly in adults


Hypo- (under) and hyper- (over) secretion of thyroid stimulating hormone (TSH)

Hypo: cretinism in children, myxoedema in adults Hyper: Grave's disease


Hypo- (under) and hyper- (over) secretion of prolactin

Hypo: no milk secretion Hyper: excess milk secretion


Hypo- (under) and hyper- (over) secretion of adreno-cortico tropic hormone (ACTH)

Hypo: under-secretion of adrenalin and aldosterone Hyper: over-secretion of adrenaline and aldosterone


Hypo- (under) and hyper- (over) secretion of anti-diuretic hormone (ADH)

Hypo: diabetes insipidus Hyper: excessive water retention


Usual cause of goitre and cretinism

Lack of iodine in the diet Thyroid gland needs iodine to make thyroxin If there is not enough iodine the thyroid grows larger (goitre) and during pregnancy the foetus may not develop properly


chemical coordination

The type of control and coordination brought about by hormones in the blood


endocrine glands

ductless glands that release their secretions directly into the bloodstream, which transports them to the target organs


exocrine glands

glands that release their secretions via ducts to a body cavity or to the exterior


Master gland at the base of the brain, attached by a short stalk to the hypothalamus



The part of the brain that secretes releasing factors to control the hormone secretions of the hypophysis/pituitary gland



The hormone, and where it is secreted from, that stimulates the thyroid to secrete the hormone thyroxin

TSH/thyroid-stimulating hormone secreted by the hypophysis/pituitary gland


The hormone, and where it is secreted from, that promotes the growth of the skeleton and muscles by stimulating the synthesis of proteins

STH/growth hormone secreted by the hypophysis/pituitary gland


Growth disorder in children caused by an under-secretion/hyposecretion of growth hormone



Growth disorder in children caused by an over-secretion/hypersecretion of growth hormone



Growth disorder in adults caused by an over-secretion/hypersecretion of growth hormone and the symptoms

Acromegaly Enlarged bones of the face (especially jawbone), hands and feet.