Hormonal Communication Revision Notes
Endocrine Communication
Endocrine Glands
-group of specialised cells that release hormones directly into the blood stream (through capillaries in the gland)
-they are ductless glands
-e.g. adrenal, ovaries, testis, thyroid
Hormones
-chemical messengers (carry information from one part of the body to another)
-often proteins made from amino acids (also be glycoproteins, steroids, amines)
-2 types of hormones
Steroid Hormones (act on DNA directly)
Protein Hormones (bind to receptors on target cells)
Function of Hormones
Steroid Hormones
e.g. oestrogen and testosterone
-pass through plasma membrane as they are soluble
-bind to specific receptors with a complementary shape in the cytoplasm or nucleus
-forms a hormone-receptor complex
-hormone-receptor complex acts as a transcription factor which facilitates or inhibits the transcription of a gene
Protein Hormones
e.g. insulin and glucagon
-does not pass through plasma membrane as they are insoluble
-binds to specific receptors with a complementary shape on the plasma membrane
-G protein is activated in the cell when hormone is bound to receptor
-G protein activates effector molecules (converting inactive enzymes to active enzymes)
-G protein mainly activates adenyl cyclase which converted ATP to cAMP
-cAMP may act directly on proteins or cause a series of enzyme catalysed reactions
Hormonal System vs Neuronal System
Hormonal System Nervous System
Communication is by hormones Communication is by nerve impulses
Transmission is via the blood system Transmission is via neurones
Transmission is slow Transmission is rapid
Travel to all parts of the body (only target organs respond) Travel to all parts of the body
Response is widespread, slow and long-lasting Response is localised, rapid and short-lived
Effect may be permanent and irreversible Effect is temporary and reversible
Adrenal Glands
-2 small glands located above the kidney
-each gland is divided into 2 sections: adrenal cortex and adrenal medulla
-both parts have a good blood supply in which they secrete the hormones into
Adrenal Cortex
-outer capsule surrounding 3 layers of
Zona Glomerulosa – outermost layer that secretes mineral corticoids
(aldosterone helps control blood pressure by maintaining K+ and Na+ concentrations in the blood)
Zona Fasciculata – middle layer that secretes glucocorticoids
(cortisol helps regulate metabolism)
(corticosterone helps regulate the immune response and supresses inflammatory reactions)
Zona Reticularis – innermost layer that secretes androgens
(small amounts of male and female sex hormones are released which control gamete formation)
Adrenal Medulla
-found at the centre of the adrenal gland
-2 hormones are released from medulla when the body is stressed (sympathetic nervous system stimulated)
Adrenaline - increases heart rate, increases blood glucose levels, pupils dilate
Noradrenaline – increases heart rate, widens pupils and airways, narrows blood vessels in non-essential organs (works with adrenaline)
Endocrine Communication
Endocrine Glands
-group of specialised cells that release hormones directly into the blood stream (through capillaries in the gland)
-they are ductless glands
-e.g. adrenal, ovaries, testis, thyroid
Hormones
-chemical messengers (carry information from one part of the body to another)
-often proteins made from amino acids (also be glycoproteins, steroids, amines)
-2 types of hormones
Steroid Hormones (act on DNA directly)
Protein Hormones (bind to receptors on target cells)
Function of Hormones
Steroid Hormones
e.g. oestrogen and testosterone
-pass through plasma membrane as they are soluble
-bind to specific receptors with a complementary shape in the cytoplasm or nucleus
-forms a hormone-receptor complex
-hormone-receptor complex acts as a transcription factor which facilitates or inhibits the transcription of a gene
Protein Hormones
e.g. insulin and glucagon
-does not pass through plasma membrane as they are insoluble
-binds to specific receptors with a complementary shape on the plasma membrane
-G protein is activated in the cell when hormone is bound to receptor
-G protein activates effector molecules (converting inactive enzymes to active enzymes)
-G protein mainly activates adenyl cyclase which converted ATP to cAMP
-cAMP may act directly on proteins or cause a series of enzyme catalysed reactions
Hormonal System vs Neuronal System
Hormonal System Nervous System
Communication is by hormones Communication is by nerve impulses
Transmission is via the blood system Transmission is via neurones
Transmission is slow Transmission is rapid
Travel to all parts of the body (only target organs respond) Travel to all parts of the body
Response is widespread, slow and long-lasting Response is localised, rapid and short-lived
Effect may be permanent and irreversible Effect is temporary and reversible
Adrenal Glands
-2 small glands located above the kidney
-each gland is divided into 2 sections: adrenal cortex and adrenal medulla
-both parts have a good blood supply in which they secrete the hormones into
Adrenal Cortex
-outer capsule surrounding 3 layers of
Zona Glomerulosa – outermost layer that secretes mineral corticoids
(aldosterone helps control blood pressure by maintaining K+ and Na+ concentrations in the blood)
Zona Fasciculata – middle layer that secretes glucocorticoids
(cortisol helps regulate metabolism)
(corticosterone helps regulate the immune response and supresses inflammatory reactions)
Zona Reticularis – innermost layer that secretes androgens
(small amounts of male and female sex hormones are released which control gamete formation)
Adrenal Medulla
-found at the centre of the adrenal gland
-2 hormones are released from medulla when the body is stressed (sympathetic nervous system stimulated)
Adrenaline - increases heart rate, increases blood glucose levels, pupils dilate
Noradrenaline – increases heart rate, widens pupils and airways, narrows blood vessels in non-essential organs (works with adrenaline)
