Endocrine System Flashcards
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)
Secretions
- A useful substance or fluid produced by cells and released to to the surrounding medium.
- E.g. Sweat, enzymes and hormones
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
Hyperthyroidism
Over-secretion of thyroxin
Graves’ disease:
- Increased metabolic rate
- nervousness
- weight loss
- rapid heart rate
- shaky, sweaty and hyperactivity
- goitres causing bulging eyes
Hypothyroidism
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
Diabetes
-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
Testosterone
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
hypophysis/pituitary
The part of the brain that secretes releasing factors to control the hormone secretions of the hypophysis/pituitary gland
Hypothalamus
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
Dwarfism
Growth disorder in children caused by an over-secretion/hypersecretion of growth hormone
Gigantism
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.
