Introduction to hormones and endocrine system Flashcards
Hormones control and regulate…
Reproduction Growth and development Body temperature Water levels Metabolism Body defences
Homeostasis
Maintenance of a relatively stable internal environment against constantly changing circumstances.
When hormones go wrong
Diabetes Cancer Acromegaly (Gigantism) Hyperthyroidism (Grave's disease) Cushings syndrome
Hormone
A chemical/protein synthesised by specific tissues and secreted into the bloodstream, whereby it is carried to non-adjacent sites in the body and exerts its actions.
How is the endocrine system organised?
Only target cells with receptors for a given hormone can alter their activities in response to the hormone.
The traditional endocrine system
Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pancreas Ovaries Testes
Hypothalamus
Several hormones to regulate pituitary function
Pituitary gland
Several hormones to regulate endocrine tissue function
Thyroid gland
Thyroid hormone
Parathyroid glands
Parathyroid hormones
Adrenal glands
Cortisol, aldosterone, catecholamines
Pancreas
Insulin, glucagon
Ovaries
Oestrogen, progesterone
Testes
Testosterone
Endocrine
‘Internal secretion’
Steroid hormones
Synthesised from cholesterol Lipophilic and hydrophobic Intracellular receptors Nucleus mediated effects Slow action Lipid soluble hormone, therefore intracellular receptors
Example of Steroid hormones
Cortisol
Oestrogen
Testosterone
Progesterone
Non-steroid hormones
Polypeptides Modified amino acids Lipophilic and hydrophilic Cell surface receptors Membrane mediated effects Rapid action Water soluble hormone, therefore cell surface receptors
Example of Non-steroid hormones
Insulin
Tyrosine (EG Catecholamines and dopamine)
Tryptophan (EG 5-HT and melatonin)
Main hormone classes
Cholesterol (Steroid)
Tyrosine (Non-steroid)
Tryptophan (Non-steroid)
Protein/polypeptide (Non-steroid)
Cholesterol (Steroid)
Adrenal cortex (cortisol and aldosterone) Ovaries and placenta (Oestrogen and progesterone) Testes (Testosterone)
Tyrosine (Non-steroid)
Catecholamine (Adrenaline and Noradrenaline)
Thyroid hormones (Triiodothyronine and Thyroxine)
Dopamine
Tryptophan (Non-steroid)
Pineal gland (melatonin) GI tract, platelets and CNA (5-HT - Serotonin)
Protein/polypeptide (Non-steroid)
Hypothalamus (TRH, GnRH and GHRH)
Pituitary gland (TSH, FSH, LH, GH, ACTH, ADH and Oxytocin)
Pancrease/GI tract (Insulin and Glucagon)
Regulation of physiological functions
Metabolism - Cortisol
Water levels and blood volume - Antidiuretic hormone
Glucose levels - Insulin and Glucagon
Types of feedback control
- Metabolism regulates by HPA axis (pg 98)
- Blood volume regulation by antidiuretic hormone (pg 99)
- Regulation of blood glucose by insulin and glucagon (pg 99)
Factors controlling hormone levels
Neuronal control
Tropic control
Substrate control
Feedback control
Neuronal control
The hormone is released directly in response to neuronal stimulation.
Example of Neuronal control
ADH is secreted in response to stimulation of nuclei in the hypothalamus detecting osmotic pressure
Tropic control
The hormone is released in response to stimulation from another hormone.
Cascade
Example of Tropic control
Cortisol secreted in response to ACTH which is secreted tp CRH
Substrate control
The hormone is directly influenced by circulating blood levels of the substrate that the hormone itself controls
Example of Substrate control
Insulin is secreted in response to increased levels of circulating glucose.
Feedback control
Exceeding a certain level of hormone inhibits further hormone release (most hormones)1
Pharmacological approaches to the treatment of endocrine disorders
pCAP
