A detailed, thorough and organised summary of the Endocrine System chapter of the IEB Mind Action Series Life Sciences textbook. Class notes and diagrams are included throughout the summary.
These notes helped me achieved my 86% final Bio exam mark in matric.
The endocrine system allows animals to respond to external changes and
control internal bodily conditions
Chemical co-ordination: a prolonged process of communicating
information throughout the body through the use of hormones.
- The endocrine system works with the nervous system
Hormone: an organic chemical substance (usually a protein, but
sometimes a steroid) that’s secreted by an endocrine gland and carried in
the bloodstream to its target organ/s where it regulates metabolic
reactions
- Hormones don’t last long because they are broken down by
enzymes
Target organ/tissue: specific cells that have receptor sites that respond to
the corresponding hormone
- Can be a single gland/organ or scattered throughout the body
Endocrine gland: a vascular, ductless gland that secretes hormones which
are carried in the bloodstream to their target organs
- Vascular: richly supplied with blood vessels
DIFFERENCE BETWEEN ENDO AND EXOCRINE GLANDS:
- Exocrine: secretions of the gland are carried in the ducts to where
they are needed (salivary glands/liver/pancreas)
- Endocrine: don’t have ducts + secretions are carried in the
bloodstream to their target organs
, ENDOCRINE GLANDS IN THE BODY
1. THE HYPOTHALAMUS
- Secretes ADH: anti-diuretic hormone
- A part of brain, above the pituitary gland
THE ROLE OF ADH:
Osmoreceptors in blood vessels of the hypothalamus detect an increase in
osmolarity (low water levels) in the blood. Hypothalamus responds and
releases ADH
ADH helps conserve water if the body is dehydrated
- Cause more water to be reabsorbed back into the blood from the
collecting ducts of the kidney
- Therefore less water is lost in urine
2. THE PITUITARY GLAND
- Acts as a chemical co-ordinator of most
endocrine glands often called master gland
- Attached to hypothalamus at the base of brain
HORMONES SECRETED BY THE PITUITARY
(TAGFLIP)
1. TSH: Thyroid stimulating hormone
a. Stimulates the thyroid gland to secrete thyroxin
2. FSH: Follicle stimulating hormone
a. Females: FSH stimulates oogenesis in the ovary (the formation
of eggs)
b. Males: FSH stimulates spermatogenesis in testes (sperm
formation)
3. LH: luteinizing hormone
a. Stimulates ovulation (release of eggs) from ovary
b. Stimulates formation of the corpus luteum
4. Prolactin
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