The endocrine system Flashcards
Semester 1 year 1
What does the endocrine system regulate?
-development
-growth
-reproduction
-parturition (giving birth)
-lactation
-metabolism
-blood pressure
-conc. of ions in blood
-behaviour
What are hormones?
Signalling molecules/mediators secreted from endocrine cells into the blood
Where are endocrine cells found?
-in endocrine tissues or glands
-close proximity to capillary beds
What do endocrine cells enable?
Enable cell signalling across long distances to distant target tissues
Is endocrine signalling slow or fast, and specific or non-specific?
-slow due to long distance
-specific to receptors but not specific to particular tissues/organs
What can hormones be?
-protein e.g insulin
-amino acid derived e.g adrenaline
-steroid e.g estradiol
What does hormone type influence?
Its cell membrane permeability
For peptide hormones, what are they synthesised from, how are they released, what are their receptors and what is their response time?
synthesis-from amino acids
release-secretory granules + exocytosis
receptors-cell membrane surface receptors
response time-seconds to minutes
For amino acid derived hormones, what are they synthesised from, how are they released, what are their receptors and what is their response time?
synthesis-derivatives of tyrosine. Requires specific enzymes
release-vesicles via exocytosis (except thyroid hormone)
receptors-cell membrane surface receptors (except thyroid hormone)
response time-seconds to minutes (except thyroid hormone)
For steroid hormones, what are they synthesised from, how are they released, what are their receptors and what is their response time?
synthesis-metabolites of cholesterol. Requires specific enzymes
release-lipid soluble
receptors-diffuse into cells + bind to intracellular/nuclear receptors
response time-hours to days
What are the classic 7 endocrine glands?
- pituitary - anterior + posterior
- thyroid
- parathyroids (4 of them)
- adrenals - cortex + medulla (on top of kidneys)
- ovaries
- testes
- endocrine pancreas
What are some endocrine tissues?
-hypothalamus
-kidneys
-gastrointestinal tract
-heart
-liver
-adipose tissue
-endocrine factors + neuropeptides (can be called hormones but don’t properly fit)
Where is the adenohypophysis?
-Anterior lobe of the pituitary (towards the front)
-develops from an upward projection of the pharynx
What does the adenohypophysis do?
-troph cells are stimulated by hormones and are carried in the hypophyseal portal system from hypothalamic neurons
-different hormones stimulate different troph cells
What is a nuclei in a nervous system?
Group of cell bodies that perform the same function
What is a hypophyseal portal system?
Blood travels through different areas to different organs before returning to the heart
Where is the neurohypophysis?
-posterior lobe of pituitary (towards back)
-develops from a downward projection of the brain (neural tissue)
What does the neurohypophysis do?
Releases hormones from the large diameter neurons directly into systemic circulation
What are the major pituitary hormones?
-oxytocin: important for parturition + lactation
-ADH: important for fluid balance
-growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), gonadotropic hormones (FSH + LH): tropic hormones
What hormones does the thyroid gland secrete?
T3 and T4 amino acid derived hormones
What is the synthesis and release of hormones from the thyroid gland dependent upon?
-hypothalamic-pituitary hormones
-iodine: essential trace element
How are hormones secreted from the thyroid gland transported?
Across cell membranes using facilitated diffusion
What do hormones released from the thyroid gland bind to and regulate?
Bind to nuclear receptors to regulate transcription. Also regulates metabolism and development + growth
What does the parathyroid gland release, what does it regulate and what does it target?
Releases parathyroid hormone (PTH) - peptide
Regulates: plasma calcium + plasma phosphate
Targets: bones, intestine, kidneys
How does PTH regulate plasma calcium by negative feedback?
- increased plasma Ca2+ by Chief cells
- decreased PTH released
- decreased kidney tubule reabsorption
- decreased bone Ca2+ resorption (taking Ca2+ out of bones)
- decreased intestinal Ca2+ absorption
- results in lowering plasma Ca2+
What is the structure of the adrenal gland?
-adrenal cortex (outer layers)
-adrenal medulla (middle part)
What does the adrenal cortex do?
-releases steroid hormones
-split into 3 layers (2 main ones):
-zona glomerulosa released mineralocorticoid
-zona fasciculata releases glucocorticoid which influences glucose levels
What does the adrenal medulla do?
-chromaffin cells (which have neuronal properties) release adrenaline via exocytosis
-releases catecholamines –> adrenaline, noradrenaline
What are the cells in the endocrine pancreas?
Islets of Langerhans:
- beta cells release insulin
-alpha cells release glucagon
both are released into portal blood to influence the liver
How does the pancreas decrease blood glucose?
Negative feedback loop:
1. increased blood glucose detected by beta cells of Islets of Langerhans
2. secrete insulin
3. if secreted to liver, decrease in glucose synthesis
4. if secreted to muscle, increase in glucose storage
5. decrease blood glucose
What hormones are produced in the ovaries?
Cells within the developing follicles of the ovary produce the steroid hormones oestrogen + progesterone
-can switch from using negative feedback loops to positive feedback loops
What hormones are produced in the testes?
-Leydig cells in testes produce the steroid hormone testosterone
-testosterone is found in males + females –> one step process from testosterone to oestrogen
-stimulates protein synthesis
-can lead to development and growth