ENDOCRINE SYSTEM Endocrine system vs Nervous system Endocrine

ENDOCRINE SYSTEM

Endocrine system vs Nervous system Endocrine Nervous Communicates via Hormones Communicates via Nervous impulses It is transported along nerves Rapid rate of distribution throughout the body Has a short term effect on the body Muscle or gland receives message Effects are localised It is transported along the blood. Slow rate of distribution throughout the body Has a long lasting effect on the body Target organ receives message Effects are widespread Nervous system sends impulses direct to the effectors e. g. Muscle to contract Endocrine system passes hormones into the blood where they travel through the body, and eventually produce their effect on the organ.

Pituitary (Master) Gland �Produces the following: � 1. Growth hormones which control growth and a deficiency of it produces a dwarf and excess of the hormone produces a giant. � 2. Hormones stimulating thyroid to make thyroxine and adrenals to make adrenalin. � 3. Antidiuretic hormones (ADH) controlling the amount of water in the urine to keep the blood concentration constant. � 4. Hormones stimulating the gonads: a) production of eggs and sperms and b) ovaries and testes to produce their own sex hormones.

Thyroid Gland �Produces Tyroxine which controls metabolic rate. �Deficiency of this hormone in children leads to a Cretin (mentally retarded dwarf) �Deficiency in adults produces Myxoedema (fat, slow metabolism, puffy face)

Sex Glands �Ovaries produce the female sex hormone Oestrogen and Progesterone at puberty. This leads to the development of female secondary sexual characteristics and take part in the menstrual cycle: � 1. Oestrogen causes repair of the uterus wall and swelling and heaviness of the breast. � 2. Progesterone causes uterus wall to become thick and full of blood. �Testes produce the male sex hormone Testosterone at puberty. It causes development of the male secondary sexual characteristics.

Adrenal Glands �It produces the hormone Adrenalin which prepares the body for the ‘flight’ or ‘fight’ response to a dangerous or emotional situation. Adrenaline has there effects on the human body: � 1. Increase in breathing and heart rate � 2. Change of glycogen to glucose in the blood � 3. widening of the blood vessels to muscles to bring more food and oxygen for physical exertion. � 4. narrowing of the blood vessels to the gut. �NB- stress also causes a release of adrenaline which in the long term can lead to plaque formation in arteries and high blood pressure.

Pancreas �This gland produces insulin which performs the following roles in the body: � 1. Makes cells take up glucose for their normal use for energy release. � 2. It causes glucose to change to glycogen for storage, thus reducing blood sugar levels. Lack of insulin causes diabetes (build up of glucose in the blood and excretion in the urine). The person urinates often and is thirsty. As glucose is not taken up by cells, the person lacks energy and is tired and weak. Daily injections of insulin is needed.

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