The Endocrine System Lectures 12 + 13

Question 1

What is the endocrine system?

Answer 1

Network of glands and hormones is important because it regulates metabolism, growth and reproduction
Uses chemicals for long term regulation

Question 2

What is the pituitary gland?

Answer 2

Termed as the “master gland” controls other endocrine glands

Question 3

What is the thyroid gland?

Answer 3

Regulates metabolism, energy generation and growth

Question 4

What is a parathyroid gland?

Answer 4

It’s important for calcium balance in the body

Question 5

What is adrenal glands?

Answer 5

Produce hormones like adrenaline and cortisol, essential for stress response

Question 6

What is the pancreas?

Answer 6

Key in glucose regulation, produces insulin and glucagon

Question 7

What is gonads? (Ovaries/testes)

Answer 7

Responsible for producing sex hormones and gametes

Question 8

What does the endocrine consist of?

Answer 8

Consists of number of remote glands; secrete hormones, highly vascurised
Hormones are transported in blood to distant sites.
Cells affected are called target cells, the hormones interact with specific receptors

Question 9

What are hormones?

Answer 9

Hormones are biochemical messengers produced in one part of the body, travelling to another part to exert their effect.

Question 10

How can hormones be classified?

Answer 10

They can be classified according to their chemical composition

Polypeptide hormones
largest group
e.g. anti-diuretic hormone (ADH) and oxytocin

Amine hormones
derivatives of amino acid tyrosine
e.g. adrenaline and noradrenalin

Steroid hormones
derivatives of cholesterol
e.g. testosterone and oestrogen

Question 11

Peptide hormones:

Answer 11

Oxytocin and ADH are peptide hormones that are 9 amino acids long. Both are released by the posterior pituitary gland and share a similar structure (only 2 amino acids differ).
Peptide hormones are synthesized as preprohormones, cleaved to prohormones, then to active forms.

Question 12

Amine hormones:

Answer 12

Amine hormones are derived from aromatic amino acids. L-dopa, dopamine, noradrenaline and adrenaline are all derived from tyrosine (which can be formed from dietary phenylalanine).

Question 13

Steroid hormones:

Answer 13

The steroid hormones all share a similar structure and are derived from cholesterol.
Steroid and thyroid hormones, being lipid-soluble, travel bound to specific carrier proteins, extending their half-life. Peptide hormones are usually water-soluble and circulate freely, with a shorter half-life.

The pharmacokinetics of synthetic hormones used in treatments, like insulin or steroid medications, is fundamentally influenced by these properties.

Question 14

Cell surface receptors:

Answer 14

Peptide and amine hormones are hydrophilic and bind to cell-membrane receptors activating second messenger pathways, which change the metabolic state of the target cell.

One of the second messenger pathways is activation of cAMP which in turn activates intracellular protein kinases.

Question 15

Hormones and receptors and how they are specific:

Answer 15

Hormone receptors are specific to each hormone and dictate the cellular response. They are located either on the cell surface (for peptide and amine hormones) OR within the cell (for steroid hormones).
Combine with a protein receptor on outside of membrane & activate a second messenger system; e.g. cAMP, altering the activity of pre-existing intracellular proteins, usually enzymes
The multiple steps of a second messenger system have a cascading, or multiplying effect, which greatly amplifies the original signal
Time to response is at least a few minutes, i.e. time taken to activate & release the enzyme

Question 16

Intracellular receptors:

Answer 16

Steroid hormones are hydrophobic and diffuse into the target cell, where they bind a cytoplasmic or nuclear receptor that allows them to act as transcription factors to alter the gene expression of the cell.

Question 17

The pituitary gland: the master gland in detail

Answer 17

Some neurosecretory cells in the hypothalamus secrete releasing factors into the bloodstream that cause cells in the anterior pituitary gland to release hormones.

The hypothalamic–hypophysial portal system is the conduit that connects the brain to the anterior pituitary. The portal system is made up of two capillary beds
The hypothalamus of the midbrain communicates with the pituitary gland

Some neurosecretory cells of the hypothalamus extend their axons all the way to the posterior pituitary gland, where they release their hormones into the bloodstream. The 2 hormones involved are anti-diuretic hormone (ADH) and oxytocin. .

Question 18

How does the hypothalamus control the pituitary gland?

Answer 18

The posterior pituitary is a neural extension of hypothalamus. It is called the neurohypophysis
The neurosecretory neurons produce
oxytocin
Anti-diuretic hormone (ADH)
The anterior is anatomically linked to hypothalamus via circulation. It is called the adenohypophysis
It synthesizes prolactin - stimulates milk secretion
TSH, ACTH, FSH, LH, GH - all tropic (act on other endocrine tissues) “Trophins”

Question 19

Hypothalamic hormones: Posterior pituitary gland:

Answer 19

There’s two types one being:
Go on physiology 1 endocrine system slide 25/26
NEED TO MEMORISE IT

Question 20

Hypothalamic hormones: Anterior pituitary gland:

Answer 20

Go on physiology 1 endocrine system slide 25/26
NEED TO MEMORISE IT

Question 21

How is hormones secretion controlled

Answer 21

Hormones secretion is controlled by feedback loops.

Negative feedback- rising level of a hormone will inhibit its own production
-it has a role in homeostasis; which is the ability of the body (or a cell) to maintain a condition of stability (or equilibrium) within its internal environment when exposed to external changes

Positive feedback- the rising level of a hormone will stimulate its own production

Question 22

The negative feedback results:

Answer 22

Negative feedback results in steady state conditions or homeostasis

The sensor and effector may be a single cell, an endocrine organ, or a series of endocrine organs.

(To get a good mark in the module you need to memorise one example of negative feedback) example of glucose is on slide 32 and 34**

Question 23

Control of the blood glucose:

Answer 23

For the majority of healthy individuals, normal blood glucose levels are as follows:

Up to 7.8 mmol/L (140 mg/dL) 2 hours after eating
Between 4.0 to 5.4 mmol/L (72 to 99 mg/dL) when fasting

Question 24

What are the effects of insulin?

Answer 24

Insulin causes cells of the muscles, the liver, and other organs to become permeable to the glucose. The glucose leaves the blood and enters the cells

Question 25

Control of thyroid hormone secretion:

Answer 25

Slide 36-38
Also includes example of negative feedback control

Question 26

What is hyperthyroidism and Grave’s disease?

Answer 26

Grave’s disease is a common cause of hyperthyroidism, an over production of thyroid hormone which causes enlargement of the thyroid and other symptoms such as exophthalmos, heat intolerance and anxiety

Question 27

Most common cause of hyperthyroidism:

Answer 27

Graves disease is an autoimmune disorder in which antibodies are produced that bind to the TSH receptor. Instead of causing destruction of follicle cells, these antibodies act as agonists, stimulating the receptor to cause synthesis of T3 and T4, and proliferation of follicle cells.

Question 28

Control of cortical hormone secretion:

Answer 28

Slide 41

Question 29

Positive feedback:

Answer 29

In positive feedback, the stimulus causes a response, and that response causes a further response in the same direction.

The sensor and effector may be a single cell, an endocrine organ, or a series of endocrine organs.

Read and memorise slide 45 for positive feedback control of labour

Summary questions from slide 47- 50