endocrine system 1 Flashcards
Understand the functional difference between the nervous and endocrine systems Understand the mechanisms by which hormones operate Describe the structure of the five major hormone classes and provide an example of each Describe a generalised negative feedback loop
endocrine vs nervous
endocrine - long term homeostasis across a RANGE of tissues and organs
nervous - responds to short-term stimuli at specific receptors that induce responses at specific effectors
endocrine glands relase what?
hormones directly into the bloodstream or tissues of the body
what do exocrine glands release
release chemical substances through ducts to outside the body or onto another surface within the body i.e. digestive enzymes
what are paracrine hormones
work locally
what are autocrine hormones
self regulate and work on the cells that secrete them
how is endocrine activity regulatedq
by negative feeback loops
- A stimulus causes an increase in the production of a hormone
- Hormones bind to receptors in target cells which causes a response
- The response causes a chemical change near the endocrine organ
- This change acts as a second stimulus and stops hormone production
how are calcium levels regulated humorally
by parathyroid hormone (PTH) and calcitonin released by the thyroid
work antagonistically to each othr
what are the two main group types of horomones?
lipid soluble and insoluble
lipid insoluble horomones
rely on secondary messaging
- Amino acid derivatives
- Peptide/protein hormones
- Including glycoproteins
lipid soluble hormones
bind mainly directly with intracellular receptors
Steroids
Eicosanoids
what are amino acid derived horomnes manufactured from
tyrosine and tryptophan
charecteristics of a.a hormones
smallest class of hormones
end with suffix “-ine”
examples of a.a derived hormones
adrenaline - adrenal glands
thyroxine - thyroid
melatonin - pinel glands
how are peptide horomones synthesised
preprohormones
The hormone precursors then undergo several rounds of post-translational modification in the ER
- Removal of N-terminus
- Glycosylation (LH, FSH, hCG)
charecterisitics of peptide hormones
Preprohormones contain additional amino acids that facilitate folding
Peptide hormones are lipid-insoluble and rely on secondary messaging
examples of peptide hormons
adh
ooxytocin
how are steroid hormones formed
from cholesterol in the gonads and adrenal glands
- Corticosteroids form in the adrenal glands
- Sex steroids form in the gonads
charecteristics of steroid hormones
lipid-soluble and bind with intracellular receptors to form hormone-receptor complexes
- Often these are transcription factors
ex of steroid hormones
cortisol
teststerone
how are eicosanoid hormones formed
are a class of lipid hormones
They are made from polyunsaturated fatty acids with 20 carbon backbones
charecteristics of eicosanoid hormones
secreted by all tissues
short half-life - operate locally
biological activity is mediated by secondary messenger G protein-coupled receptors
ex of eicosaoid hormones
prostaglandins
