Lecture 18

Question 1

Define the terms endocrinology and hormone

Answer 1

Endocrinology: the study of the biosynthesis, the storage, the chemistry, the physiological function of hormones and the cells that secrete them.
Hormone: A chemical must be produced from an organ, released into the blood and transported to a different organ

Question 2

What are the similarities and differences between the endocrine system and nervous system

Answer 2

Similarities:
- Respond to changes in diet, environmental, chemical or physical inputs
• Release signalling molecules via endocytosis. In the neuronal system that is entirely down to depolarisation. In endocrine system this is due to the presence of calcium cells.
• Neurones and endocrine cells (e.g. adrenal medulla) can be depolarized- release noradrenaline/adrenaline

Differences:
• Neuronal is quick and endocrine slow
• Neuronal is short term, endocrine is long term
- Neuronal has a single target and endocrine has globular effects

Question 3

What are the four ways that hormones can regulate production and effect

Answer 3

1. Autocrine- Hormone acts back on the cell that secreted it, or cells nearby
2. Paracrine- Hormone carried to target over short distance via intestinal fluid
3. Endocrine- Distant target via blood stream
4. Neurocrine- Hormonal signal originates in a neurone and after axonal transport to the bloodstream, is carried to distant target cells

Question 4

What are some examples of water soluble and lipid soluble hormones

Answer 4

Water soluble: (Catecholamines, Peptide/protein hormone)

Lipid soluble: Thyroid hormones/ steroids

Question 5

What are the likely target receptors for water and lipid soluble hormones?

Answer 5

Water: g-coupled receptors and tyrosine kinase
Lipid: Diffuse through cell membrane and bind to DNA

Question 6

What effects hormone activity?

Answer 6

• Rate of production
• Rate of delivery
• Rate of degradation

Question 7

What are the differences in negative and positive feedback?

Answer 7

In negative feedback, the response is in such a way as to reverse the direction of change in order to maintain homeostasis
In positive feedback the variable is changed even more in the same direction. For example during labour the production of the hormone oxytocin

Question 8

What is the parathyroid hormone?

Answer 8

The parathyroid glands are about the size of a pea
Located behind the thyroid gland
The hormone regulates levels of calcium (increasing)and phosphate (decreasing) in the blood

Question 9

How does the parathyroid hormone complete its function?

Answer 9

It acts on the bone by increasing the number of osteoclasts which break down bone matrix and release Ca2+ and phosphate into the blood
It acts on the kidneys by slowing the rate at which Ca2+ is lost from blood into urine and increases the loss of phosphate from blood in urine
It acts on the GI tract by producing Calcitrol which increases the rate of Ca2+ and phosphate absorption from food

Question 10

Which cells in the parathyroid gland secrete calcitrol?

Answer 10

Para follicular cells