BMS1058 - Endocrinology Flashcards
What is the difference between endocrine, neruoendocrine, autocrine and paracrine signalling?
What are the 3 main groups of hormones?
Amino acid derivatives - e.g. tryptophan (melatonin), tyrosine etc
Peptides - e.g. TRH, Growth hormone
Steroids
What do hormones affect?
Reproduction
Energy balance
Growth and development
Homeostasis
Biological rhythms
What do endrocrine glands do? Describe them.
Secrete hormones into blood
Ductless. Located throughout body. Often contain multiple cell type.
e.g. hypothalamus, pituitary gland, thyroid gland, adrenal glands, pancreas, ovaries etc
What does Pineal gland secrete?
What about adipose tissue and GI tract? Placenta?
Pineal gland - secretes melatonin
Adipose tissue - secretes many energy balance and metabolism related hormones
Placenta - secretes fetal and maternal development hormones
What is heterogeneity?
The amount of variation within a subject
How does secretion of peptide and steroid hormones compare?
Steroid hormones:
- lipophilic
- diffuse across membranes and bind to receptors inside the cells
Peptide hormones:
- bind to cell surface receptors
How are steroid hormones transported in the blood?
Bound to plasma proteins
What do many proteins/protein hormones require to be fully functional?
Further processing / modification
What are preprohormones?
Inactive precursor from single gene. Cleaved to form active components.
(peptide hormones)
What is dimerisation?
When subunits from different genes combine to form an active product.
What are the two categories of receptors?
Memebrane-bound receptors
and
Intracellular receptors
What are the 3 basic domains of membrane-bound receptors?
What hormones are they involved with?
Extracellular - binds hormone
Transmembrane
Intracellular - to affect change in the cell
Involved with hydrophilic peptide and amine hormones.
The reponses that membrane-bound receptors induce are generally _______. What are some examples?
Rapid
e.g. change in membrane permeability (adrenaline) / change in enzyme activity (insulin)
What hormones are intraellular receptors involved with? What do they stimulate? How fast/slow is this response?
Steroids and thyroid hormones
Stimulate gene expression -> delayed and prolonged response
Which of the following hormones is subject to post-translational modification?
(a) TSH
(b) testosterone
(c) progesterone
TSH (thyroid stimulating hormone) - peptide hormone
What is the role of the Pituitary gland? How many cell types does it have? What regulates these cells?
It is an important gateway between central and peripheral endocrine organs.
Has 5 major endocrine cell types, regulated by the hypothalamus via inhibitory and/or releasing factors.
What does the Pituitary portal system do?
Transfers releasing and inhibitory hormones form hypothalamus to anterior pituitary (via capillaries and veins).
[Hypothalamus regulation of the anterior pituitary]
How does the hypothalamus regulate the Posterior pituitary gland?
Hormones produced in nerve cells in hypothalamus and travel down nerve strain into posterior pituitary.
Compare neg and pos feeback loops
Negative:
- Imposes “brake” on system
- Important for homeostasis
- Common
Positive:
- Amplifies original signal
- Rare but useful in certain circumstances when a large response is required
- Requires cut-off mechanism
Give an example of a negative feeback loop with hormones
Give an example of a positive feedback loop with hormones
Oestrogen usually inhibits LH
secretion. But, oestrogen surge occurs around day 12 of cycle.
High oestrogen drives change
from -ve to +ve feedback.
+ve feedback causes LH surge, which induces ovulation.
After ovulation, drop in oestrogen conc causes resumption of -ve feedback and thus LH/FSH secretion falls.
What difference would you expect to see in the cellular morphology of endocrine cells that secrete (a) peptide vs (b) steroid hormones?
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