T1 L1: Intro to the endocrine system Flashcards
How were hormones discovered?
The effects of castration were observed. Castrated chicken wouldn’t develop secondary characteristics. If the testicles were transplanted into the abdomen then the secondary characteristics would still develop indicating that the testes were releasing something needed for development
Which gland is important for control of metabolic rate and calcium homeostasis?
The thyroid and Parathyroid
What is Myxedema?
A condition caused by severe hypothyroidism
Symptoms: Thickening of skin, fatigue, weight gain, depression, dry skin, and brittle hair
What is Cretinism?
A condition characterized by physical deformity and learning difficulties that is caused by congenital thyroid deficiency
What is the endocrine function of the pancreas?
Secrete insulin and glucagon into the blood to control blood glucose concentration and glucose utilisation
What is the exocrine function of the pancreas?
Secretes digestive enzymes directly into the GI tract
Where is the pancreas located in terms of the stomach?
Behind the stomach
What is the medulla of the adrenal glands responsible for?
The stress response
What is the cortex of the adrenal glands responsible for?
Stress, sodium, and glucose homeostasis
How much does the Pituitary gland weigh?
0.5g
What is the Pituitary gland responsible for?
It secretes hormones responsible for:
- growth
- blood pressure
- energy management
- All functions of the sex organs
- Thyroid gland activity
- Childbirth
- Pain relief
- Temperature regulation
What are the testes and ovaries responsible for?
The development of secondary characteristics
What are the 2 divisions of hormones?
Peptide hormones Steroid hormones (+Thyroid hormones)
What are the characteristics of peptide hormones?
- Chain of amino acids that’s highly water soluble
- Susceptible to protease attack so can’t be ingested
- Unable to cross the cell membrane
- Act on cell-membrane receptors
- Rapid onset of action
- Short half-life and duration of action
What are the characteristics of steroid and thyroid hormones?
- Highly lipid soluble
- Poorly water soluble so have to be carried by proteins in the blood
- Only unbound hormones is biologically active
- Able to cross the cell membrane
- Act on intracellular receptors
- Orally active
- Long half-life and duration of action
- Slow onset
How is Thyroxine (T4) administered?
Orally as a tablet
How do G-protein couples receptors work?
A hormone binds to the 7 transmembrane helices receptor, activating a G-protein to cause synthesis of a second messenger (cAMP or Inositol Triphosphate)
The second messengers phosphorylate intracellular, regulatory proteins to influence cellular activity
How do Tyrosine kinase receptors work?
It’s a membrane-bound protein.
Often 2 receptors need to be present for hormone activation because it’s a dimerised receptor. One hormone binds to each receptor, the receptor will then act as an enzyme to phosphorylate Tyrosine
Which type of receptor do Insulin and Prolactin use?
Tyrosine Kinase Receptors
How do steroid hormone receptors work?
The hormone crosses the cell membrane and binds to the receptor in the cytoplasm. The hormone-receptor complex travels to the nucleus where it binds to the hormone-response element of DNA to influence gene transcription
What does the pituitary gland secrete that controls the secretion of other glands?
Stimulating (Trophic) hormones
What is Pseudohypoparathyroidism?
PHP is a genetic disorder in which the body fails to respond to parathyroid hormone
Describe the process through which the pituitary gland stimulates the production of T3 and T4
The hypothalamus will release Thyrotrophin releasing hormone (TRH) which stimulates the anterior pituitary gland to produce Thyroid stimulating hormone (TSH) which stimulates the thyroid to secrete T3 and T4
What does the hypothalamus release to stimulate the posterior pituitary gland?
Releasing hormones
What effect does taking T4 supplements have on the negative feedback loop?
The thyroid will stop producing it because the negative feedback loop will be signalling that the body already has enough
What is Leptin and what does it do?
A hormone released by cells in adipose tissue. It acts of the hypothalamus to inhibit appetite
How can defects in Leptin be linked to obesity?
When the Leptin pathway doesn’t work properly, appetite isn’t inhibited so the person will over eat and gain weight
