Hormonal communication

What is the endocrine system made up of?

Endocrine glands.

What is an endocrine gland?

A group of cells which are specialised to secrete chemicals - hormones - directly into the bloodstream.

What do examples of endocrine glands include?

The pancreas and adrenal glands.

What does the pituitary gland at the base of the brain make?

Several hormones, which in turn control the release of other hornomes.

What does the close proximity of the pituitary gland to the hypothalamus ensure?

That the nervous and hormonal responses of the body are closely linked and coordinated.

What do exocrine glands, such as those in the digestive system secrete?

Chemicals through ducts into organs, or to the surface of the body.

Why are hormones often referred to as chemical messengers?

Because they carry information from one point to another. They can be steroids, proteins, glycoproteins, polypeptides, amines or tyrosine derivatives.

Where are hormones secreted?

Directly into the blood when a gland is stimulated. This can occur as a result of a change in concentration of a particular substance, such as blood glucose concentration.

Once secreted, where are hormones transported,a and what do they do?

In the blood plasma all over the body. The hormones diffuse out of the blood and bind to specific receptors for that hormone, found on the membranes or the cytoplasm of the cells in target organs - target cells.

What does the type of hormone determine?

The way it causes its effect on a target cell.

What are steroid hormones?

Hormones that are lipid-soluble: they pass through the lipid component of the cell membrane and bind to steroid hormone receptors to form a hormone-receptor complex.

Where may the receptors for steroid hormones be present?

In the cytoplasm or the nucleus depending on the hormone.

What does the hormone-receptor complex formed act as?

A transcription factor which in turn facilitates or inhibits the transcription of a specific gene.

What is an example of a steroid hormone?

Oestrogen.

What are non-steroid hormones?

Hormones that are hydrophilic, and so cannot pass directly through the cell membrane.

Where do non-steroid hormones bind to receptors?

On the cell surface of the target cell. This triggers a cascade reaction mediated by second messengers.

What is an example of a non-steroid hormone?

Adrenaline.

Why is it that hormonal communication is slower and less specific than neuronal communication?

Hormones are not released directly onto their target cells.

Why do hormones have a longer lasting and widespread effect?

Because they are not broken down as quickly as neurotransmitters.

What are the adrenal glands?

Two small glands located on top of each kidney.

What are the adrenal glands made up of?

Two distinct parts surrounded by a capsule:

• The adrenal cortex.

• The adrenal medulla.

What is the adrenal cortex?

The outer region of the glands, producing hormones vital to life like cortisone and aldosterone.

What is the adrenal medulla?

The inner region of the glands, producing non-essential hormones like adrenaline.

What is the production of hormones by the adrenal cortex controlled by?

Hormones released from the pituitary gland in the brain.

What are the three main types of hormones produced by the adrenal cortex:

• Glucocorticoids.

• Mineralocorticoids.

• Androgens.

What are glucocorticoids?

These include cortisol and corticosterone. The release of these hormones is controlled by the hypothalamus.

What is the role of cortisol?

It helps regulate metabolism by controlling how the body converts fats, proteins and carbohydrates to energy.

What is the role of corticosterone?

It works with cortisol to regulate immune responses and suppress inflammatory reactions.

What is the role of mineralocorticoids?

The main one is aldosterone.

What is the role of aldosterone?

It helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and bodily fluids.

What are androgens?

These are small amounts of male and female sex hormones, but not as important as oestrogen and testosterone secreted by the testes and ovaries.

When are the hormones of the adrenal medulla released?

When the sympathetic nervous system is stimulated. This happens when the body is stressed.

What are the hormones secreted by the adrenal medulla?

• Adrenaline.

• Noradrenaline.

What does adrenaline do?

It increases the heart rate, sending blood quickly to the muscles and brain. It also rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver.

What does noradrenaline do?

It works with adrenaline in response to stress, producing effects such as increased heart rate, widening of pupils and widening of air passages in the lungs.