Week 6 Endocrinology 1

Question 1

Physiological Importance

Answer 1

Controls many/most aspects of physiology, via secretion of hormones

• Endocrine and neuronal (nervous) systems are considered the 2 major control systems

• However, substantial interaction between them (emergence of ‘neuroendocrinology’ as a discipline)

• Endocrine systems also interact with e.g. the cardiovascular, digestive and immune systems

Question 2

Endocrinology in the News!

Answer 2

Hormones are related to ‘media-friendly’ topics e.g.
– Sex
– Metabolism/appetite
– Body clocks
– Behaviour
– Major diseases (diabetes, cancer etc)

• Endocrine disrupters
• Drug treatment
– HRT, oral contraceptives (inc. “male pill”)
– Anabolic steroids/athletics

Question 3

What is a Hormone?

Answer 3

The word “hormone” 1st used by Ernest Starling (1905) – Duodenal secretion(s) stimulate pancreatic activity

• Chemical messenger secreted into blood to act (usually) on distant target(s)

• Present at very low concentrations in the blood, as highly specific mechanisms of action in target tissues

• Hormones can be grouped by biochemistry and physiological function

• Dynamics of secretion and action vary greatly, depending on the hormone and its physiological role

Question 4

Endocrine and Related Signalling Mechanisms

Answer 4

First cell > releases into blood supply and then a ct on next cell

Neuro endocrine = nerve cell releasing

Autocrine = releases into extracellular space and acts on the same cell

Paracrine = acts on adjacent cell

Question 5

Hormone Biochemistry

Answer 5

3 main groups,
• Amino acid derivatives
– Tryptophan (melatonin)
– Tyrosine(others,e.g. adrenaline)

• Peptides
– TRH (3aa)
– Growthhormone(200aa)
• Steroids

Question 6

Hormonal Regulation of Physiology

Answer 6

Hormones regulate most aspects of physiology and are often placed in 4 groups,
– reproduction (e.g. follicle stimulating hormone, sex steroids)
– energy balance (e.g. insulin, thyroid hormones, leptin, orexin, ghrelin)
– growth & development (e.g. growth hormone, thyroid hormones, sex steroids)
– homeostasis(e.g.vasopressin,aldosterone)

• Other roles include, – biological rhythms

• Variable time course of hormone action – seconds/minutes(e.g.adrenaline)
– hours/days (e.g. steroids, thyroid hormones)

Question 7

Anatomy of the Endocrine System

Answer 7

Endocrine glands/organs
– ductless glands that secrete hormones into the blood

– (NB exocrine gland: secretes onto an epithelial surface, such as of the gut lumen, usually via a duct)

• Pancreas acts as both an endocrine and an exocrine gland
– located throughout the body
– often contain multiple cell types, which have different function (e.g. the pituitary gland)

Question 8

Major Endocrine Organs

Answer 8

Hypothalamus = link with pituitary gland, together are the major control centre

Thyroid gland

Parathyroid glands

Adrenal glands

Pancreas = endocrine and exocrine

Ovaries and testes

Question 9

Other Important Endocrine Organs

Answer 9

Pineal gland
– secretes melatonin
– important for biological rhythms
• Adipose tissue (fat) & Gastrointestinal tract
– secrete many hormones involved in energy balance & metabolism
• Placenta
– secretes hormones involved in foetal and maternal development

Question 10

Heterogeneity’ of Endocrine Organs

Answer 10

Heterogeneity: amount of variation within a subject (opposite of homogeneity: uniformity of a subject)

Different cell types are subject to different control mechanisms (inputs) and secrete different hormones that have different physiological roles