Endocrinology lesson notes from ov1113 introductory biological sciences highlighted with pictures and diagrams
city university of london introduction to optometry course
Endocrinology
Control and integrate many processes
1. Reproduction
2. Growth and development
Endocrine secrete hormones into systemic
circulation
Hormones transported in blood to a tissue where
they have specific action
Compare with exocrine glands - meibomian,
lacrimal, sweat
Hormone is a chemical substance that is
secreted by a specialised endocrine cell directly into the blood to exert an effect on distant
target cells, target cells can be local but local target cells are called paracrines or autocrines
Hormones made of?
Hormones are amino acid based; polypeptides
- cannot diffuse through plasma membrane
- Water soluble
- Most common eg, TRH, TSH, GnRH, FSH, LH, insulin, glucagon
Modified amino acids
- small and cannot diffuse through plasma membranes
- Water soluble
- Eg, thyroxine
Steroids
- synthesised from cholesterol
- Small, fat soluble, can diffuse through plasma membrane
- Eg, cortisol, oestrogen, testosterone (ie gonadal and adrenocortical)
Hormone release stimulates (3 types)
, Humoral stimulus- occurs when there’s a low conc of Ca2+ in capillary blood so parathyroid
glands secrete parathyroid hormone (PTH) to increase Ca2+ conc.
Neural stimulus- action potentials in preganglionic sympathetic fibres (CNS) travel to adrenal
medulla. So the adrenal medulla secretes epinephrine and norepinephrine.
Hormonal stimulus- hormone released from hypothalamus trigger anterior pituitary gland to
stimulate other endocrine glands to secrete hormones eg, thyroid gland, adrenal cortex
Negative feedback
Secretes melatonin- peaks at night
Causes drowsiness and lowers body
temperature
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