Describe hormone receptors
- only effects specific target tissues
- receptors are constantly synthesised
- if hormone level is high receptors are down regulated
- if hormone level is low receptors are upregulated
Describe mechanisms of action of hormones
- Depends on cell and hormone
- Hormones must bind to their receptors which then trigger synthesis, degradation, motility changes=, secretion and electrical impulses
- Target cells tend to have 2000-10000 receptors per hormone
Describe lipid hormones
- hormone diffuses into cell
- activated receptor hormone complex alters gene expression
- newly formed mRNA directs synthesis of specific proteins on ribosomes
- new proteins alter cell activity
Describe water soluble hormones
- binding of hormone to its receptor activates G-protein which activates adenylate cyclase
- activated adenylate cyclase converts ATP to CAMP
- CAMP serves as a second messenger to activate protein kinase
- activated protein kinases phosphorylate cellular protein
- millions of phosphorylated proteins cause reactions that produce a physiological response
- Phosphodiesterase inactivates cAMP
What is synergistic?
Working together
What is Antagonistic?
Work separately
Describe peptide hormones
Degraded by plasma enzymes = short half life
Describe lipid hormones
Bound to carrier globulins can be deactivated by passage through the liver = longer half life
Describe the hypothalamus
major link between nervous and endocrine - controls the pituitary gland which secretes multiple hormones
What 8 hormones are secreted by the hypothalamus?
Thyrotropin releasing Dopamine Growth Hormone Somatostatin Gonadotropin Corticotropin Oxytocin Vasopressin
What 11 hormones are secreted by the pituitary gland and separated into Anterior, Posterior and Intermediate?
Anterior
- Growth hormone
- Adrenocorticotropic
- Folecule stimulating
- Leutinising
- Prolactin
- thyroid stimulating
Posterior
- Oxytocin
- Vasopressin
- Oxytocin stored
- Antidiuretic
Intermediate
- Melanocyte
What 2 hormones are secreted by the thyroid?
Triiodothyronine
Thyroxine
What hormone is secreted by the pineal gland?
Melatonin
Describe somotrophs
secrete human growth hormone which stimulates tissues to release insulin like growth factors
Describe Thyrotrophs
secrete thyroid stimulating hormone to regulate the thyroid gland
Describe gonadotrophs
sex cells secrete FSH and LH cause secretion of oestrogen and progesterone in ovaries, sperm production and testosterone in testes
Describe lactotrophs
secrete prolactin
Describe Corticotrophs
secrete adrenocorticotropic hormone, stimulate adrenal cortex to produce glucocorticoids some secrete melanocyte stimulating hormone
What 5 secreting cells can be found in the anterior pituitary gland?
- Somotrophs
- Thyrotrophs
- Gonadotrophs
- Lactotrophs
- Corticotrophs
Describe the negative feedback regulation of the pituitary gland
- negative feedback hormones from target glands decreases activity of the pituitary gland
- secretory activity of thyrotrophs, gonadotrophs and corticotrophs are decreased when blood levels of their target gland hormone rise
What are the most abundant cells in the anterior pituitary?
Somatrophs
Describe diabetogenic effect of hGH
stimulates hyperglycaemia in turn stimulates the pancreas to secrete insulin constantly which can cause beta cell burnout therefore causing diabetes
Describe the posterior pituitary
- Does not synthesise hormones it stores and releases 2 hormones, oxytocin and ADH (vasopressin)
- consists of axons and axon terminals, more than 10000 hypothalamic neuro-secretory cells
- produced in hypothalamus where they are packaged into vesicles and stored in axon terminals
- nerve impulses trigger their exocytosis
Describe the thyroid gland
- inferior to the larynx composed of right and left lateral lobes on either side of trachea
- thyroid follicles make up most of the thyroid gland
- produces tetraidothyromine and triiodothyronine
- stores its hormones in large quantities
- maintain internal integrity of the tissue
