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Definitions in endocrinology
ENDOCRINE GLAND
a group of cells which secret “messenger” molecules directly into the bloodstream
HORMONE
The bioactive “messenger” molecule secreted by an endocrine gland into the blood, which is not simply a metabolic by product or energy substrate
ENDOCRINE
relates to hormone’s action on target cells at a distance from source
PARACRINE
relates to hormone’s action on nearby target cells e.g. within immediate area around source
AUTOCRINE
relates to hormone having an effect on its own immediate source
Endocrine system vs nervous system (3 differences)
Classes of hormones?
Proteins/polypeptide hormones - receptors are on cell surface. do not cross the cell membrance
Steroid hormone ( act as primary messengers)
„Since they are lipid soluble pass easily through cell membrane
„They act as the primary messenger
„Act at nuclear level
„Effects transcription and translation and synthesis of new proteins
Amines (tyrosine derivatives; epinephrine, NE, thyroid hormones)
Derived from the single anino acid -tyrosine
mechanism of action similar to
steroids or
ploypeptide hormones
Miscellaneous
Mechanism of hormone action
As a primary messenger
- Steroids and thyroid hormones cross cell membranes eliminates need for the second messenger
- Directly bines to the nucleus or protein in cytoplasm
Through second messenger
- C AMP
- Peptide hormones and catechoaminees
Mechanism of action of hormones? (3 ways)
A general hormone elicits response
Alteration of iron channel permeability
Via 2nd Messenger
peptide hormones (eg ADH)
Activation of specific genes at nuclear level steroid hormones - cortisol
Classical endocrine glands (6)
pituitary gland
Thyroid gland
Parathyroid gland
Pancreas
Adrenal glands
Gonads
Organs with endocrine functions
Brain - BNP
Heart - ANP
Liver - somatomedin
GI tract - Gastrin, GLP / GIP
Kidneys - Erythropoietin
Adipose tissue
Placenta - HCG
Endocrine effects
