Endocrine system Flashcards
What is the difference between endocrine, paracrine, and autocrine signalling?
Endocrine: travels via blood stream to distant targets
Paracrine: local hormones, nearby target cell
Autocrine: local hormone, targets itself
Neuroendocrine - neural cells that release chemical signals into the bloodstream
What are releasing hormones? Give an example
From hypothalamus to act on pituitary
GnRH
What are stimulating (or trophic) hormones? Give an example
From pituitary to act on another endocrine gland
TSH (thyroid stimulating hormone)
What are non-trophic hormones? Give an example
From an endocrine gland to target cells
eg Thyroid releases T3 and T4
What are amino hormones? Give an example
Derived from tyrosine
eg catecholamines adrenalin and noradrenalin from adrenal medulla
eg T3 and T4 from thyroid
What are peptide/protein hormones? Give an example
come from genes-> rough ER-> golgi -> vesicles
May undergo one or more post-translational
modifications including cleavage, glycosylation, disulfide bridging
eg Insulin, hGH
exocytosis is Ca dependent, vesicles are hydrophillic
What are steroid hormones? Give an example
Derived from cholesterol->pregnenolone
eg Glucocorticoids, Mineralocorticoids, Androgens, Estrogens and Progestins
What are some examples of second messengers?
- cAMP or cGMP
– phopholipids diacylglycerol and inositol
triphosphate (DAG and IP3)
– calcium
What are three changes that second messengers induce?
- Alter phosphorylation (activity) of proteins
– Alter permeability of membranes
– Indirectly influence gene expression
Whats the difference between steroid/thyroid hormones and amino/peptide hormones?
Amino/peptide work through second messengers (extracellular receptors)
Steroid/thyroid work through intracellular receptors and act as transcription factors
Desricbe negative feedback loops?
Eg T3/T4 signal hypothalamus to stop TSH which stops thyroid from releasing T3/T4
most common
low T3/T4/ low metabolic rate stimulates hypothalamus to release TRH which stimulates ant pituitary to release TSH which stimulates thyroid follicular cells to release T3/T4 into blood stream
T3 levels increase which INHIBITS release of TRH and TSH
Describe positive feedback loops
Used to amplify a signal
E.g. Oxytocin (made in hypothalamus and released by posterior pituitary)
How are T3 and T4 synthesised, stored, and secreted?
- Synthesised by follicular cells by iodination of thyrosine
- Stored in follicular colloids on the surface of thyroglobin
- Secreted by follicular cells (reuptake before release)
What are the actions of thyroid hormones?
- Metabolic effects eg calorigenisis
- Physiological effects eg RBC production, appetite
- Reproductive effects eg fertility, onset of puberty
- Developmental effects eg normal brain development
- Cellular effects
What happens when thyroid function is impaired?
Hypothyroidism: bc disease of the thyroid (1st) or from lack of stimulation by TSH (2nd)
Hyperthyroidism: bc over activity of gland eg Graves disesase (autoimmune)
Hypothyroidism: coarse skin, weight gain
Hyperthyroidism: Clinical symptoms of grave disease: sweating, tremor, muscle weakness and loss of muscle mass, upper lid retraction, impaired eye movement, patchy depigmentation of the skin, clubbing of the fingers, goitre etc
What hormones does the posterior pituitary gland secrete?
Oxytocin and vasopressin (vasopressin = anti-diuretic
hormone (ADH))
Where are osmoreceptors found?
Found in Hypothalamus
They send signals to the neuroendocrine cell in the hypothalamus that make vasopressin when plasma osmolality exceeds the threshold -> increase vasopressin secretion
SUPERRR sensitive
Where are baroreceptors found and whats their function?
In the circulatory system
Activated by Decreased blood volume/pressure
Turn on vasopressin secretory cells
Not that sensitive
What are the effects of ADH on the body?
- Kidneys retain more water
- Sweat glands stop
- Arterioles constrict (inc BP)
What stimulates ADH release?
- Hi osmolality
- Low blood volume
- Low blood pressure
- Angiotensin
- Nicotine
- Nausea
What inhibits ADH release?
- Low osmolality
- Hi blood volume
- Hi blood pressure
- Atrial natriuretic peptide
- EtOH
What is Diabetes insipidus?
Inability to secrete or to respond to ADH
Whats the difference between neurogenic and nephrogenic?
Neurogenic – hyposecretion of ADH due to damage of posterior pituitary
Nephrogenic – kidneys do not respond to ADH (pee a LOT, dehydration, thirst)
What cells does oxytocin stimulate?
- Smooth muscle cells in uterus: contract during birth
- Myoepithelial cells in mamary glands: milk ejection
