Who is Claude Bernard and what were his contributions to his field?
He was a doctor of physiology and stated that the endocrine system regulated the internal workings of the animal primarily working on the function of the pancreas.
What are the principal characteristics of the endocrine system?
- Hormones are released directly into the bloodstream
- the maintenance of the internal environment of the body
- regulation of growth and development of organism
List the endocrine glands
hypothalamus, pituitary, thyroid, parathyroid, adrenal, thymus, and pancreas
- other glands and/or organs can have endocrine function,
i.e.,
heart, kidney, etc. - also the ovaries and testes
The functions of the hypothalamus
links the nervous and endocrine systems and controls the pituitary gland
The functions of the pituitary gland
controls other endocrine glands and regulates growth, blood pressure, and water balance
The functions of the thyroid gland
control the release of energy from food molecules inside cells
The functions of the parathyroid glands
they regulate the amount of calcium in the blood
The functions of the adrenal glands
They release several hormones like adrenaline which triggers the body to respond in emergency situations as well as hormones that affect salt, water balance in kidneys and blood sugar.
The functions of the thymus glands
help the immune system to develop during childhood
The functions of the pancreas
produces insulin and glucagon, which helps to control glucose levels in the blood
The functions of ovaries and testes
Ovaries
release sex hormones, involved with changes in female body (estrogen) and triggering egg development (estrogen and progestrone)
Testes
releases testosterone, which controls changes in male body and regulating sperm production
What are hormones?
they are chemical substances which our body creates to act as messengers to coordinate bodily functions.
Most are proteins that consist of amino acid chains
What functions to hormones control and how do they travel?
- control the activity of entire organs
- growth and development
- reproduction and sex characteristics
- usuage and storage of energy
- involved in controlling the levels of fluid, salt and sugar in the blood
Hormones travel via the bloodstream to target cells which will have a receptor for that specific hormone.
Endocrine regulation
the control of physiological processes via hormones released into the bloodstream
How does a cell become a target for a specific hormone?
By having a specific receptor for that hormone
Major hormones and systems
(Top-Down organization of endocrine system)
The hypothalamus produces releasing factors that stimulate the production of hormones in the anterior pituitary gland which will act on a peripheral endocrine gland that will release another hormone.
Cell bodies in the hypothalamus synthesize the posterior pituitary gland hormones which will be released via synapses.
What two general classes of hormones are there?
Water-soluble and lipid-soluble
The differences between water-soluble and lipid-soluble hormones
Water-soluble hormones are made in endocrine cells and are packaged into secretory granules. They can travel to target w/o being bound to blood proteins with a receptor on the cell surface of target.
Lipid-soluble hormones also made in endocrine cells but not packaged. They passively diffuse out of cell and become complexed w/ blood protein (globulins). Their receptor resides in the nucleus or on cytoplasm of target.
What are the four chemical classes of hormones, their solubility and receptor?
Amine (epinephrine), water-soluble, receptor on cell surface
Amine (thyroid hormone). lipid-soluble, intracellular receptor
Peptide/protein, water-soluble, cell surface receptor
Steroids, lipid-soluble, intracellular receptor
How does hormone chemistry affect function?
It determines solubility, receptor type and transport in the blood.
What are prohormones vs. prehormones?
Prohormones are an inactive precursor modified into an active hormone, while Prehormones are converted to active form in target cells.
What are the differences between synergistic, permissive, and antagonistic hormone effects?
Synergistic: combined effect is greater than individual
Permissive: one hormone allows another to act fully
Antagonistic: hormones oppose each other
What is priming?
Increased sensitivity of a target cell after repeated hormone exposure
What is desensitization/downregulation?
Loss of responsiveness due to prolonged high hormone levels
Which hormones use nuclear receptors?
steroid and thyroid hormones
How do nuclear receptors change cell function?
They bind DNA and regulate gene transcription through dimerization, co-activators/ co-repressors.
Which hormones use secondary messenger receptors?
peptide and catecholamine hormones or hydrophilic hormones
What is the second messenger system?
The first messenger will bind to the receptor on the cell membrane which will activate an intracellular protein which will make a second messenger and so on until it reaches the target and creates a cellular response.
This often occurs by the sequential activation of protein kinases
The second messenger systems include:
- Adenylate cyclase, catalyzes the conversion of ATP to cyclic AMP
- Guanylate cyclase, catalyzes the conversion of GMP to cyclic GMP
- Calcium and calmodulin, phospholipase C (catalyzes phosphoinositide turnover producing inositol and diacyl glycerol
How are half receptors and dimers related?
Some receptors exist as inactive half receptors that when ligand binds come to together to form a dimer. This process is known as dimerization.
What is a tyrosine kinase receptor and an example?
a receptor w/ intrinsic kinase activity for example an insulin receptor
What glands are in the HP axis and where are they located?
- Hypothalamus (in brain, above pituitary)
- Pituitary gland (at the base of the brain)
- Adrenal glands (sit on top of kidneys)
What hormones does anterior pituitary gland release and their functions?
- ACTH (Adrenocorticotrophic Hormone): secretes glucocorticoid
- TSH (Thyroid-stimulating hormone): stimulates the release of T3 and T4
- GH (Growth hormone)
- FSH (Follicle stimulating hormone): (female- stimulates follicle growth and estrogen production/ male- stimulates sperm production in testes)
- LH (Luteinizing hormone): female- triggers ovulation and stimulates progesterone production/ Male- stimulates testosterone production
- Prolactin: stimulates milk production
What are trophic hormones?
They are hormones that stimulate other endocrine glands to grow and release their own hormones
What hormones of the posterior pituitary gland are released as well as function and where are they synthesized?
- ADH (Antidiuretic hormone): conserves water
- Oxytocin: smooth muscle contraction
They are synthesized in the hypothalamus
What is the main releasing controller of pituitary secretions?
The hypothalamus which acts as the control center
What is neuroendocrine reflex?
a reflex where a nervous system stimulus triggers the release of hormones from hypothalamus/ posterior pituitary.
What does 'master gland' refer to?
the anterior pituitary gland controlling multiple endocrine glands
What hormones does the hypothalamus produce?
- TRH (thyrotropin releasing hormone): stimulates TSH and prolactin
- GnRH (Gonadotropin): stimulates FSH and LH
- CRH (Corticotropin): stimulates ACTH
- GHRH (growth hormone): stimulates growth hormone
- GHIH (growth hormone inhibiting hormone/somatostatin
- PIH (prolactin inhibiting hormone): inhibits GH and TSH
- PRH (prolactin releasing hormone): inhibits prolactin