chapter 14 p1

Question 1

the nervous system detects

Answer 1

and responds to changes in the internal and external environment.

Question 2

The body has a second system

Answer 2

the endocrine system, which works alongside the neuronal system to react to changes.
The endocrine system uses hormones to send information about changes in the environment around the body to bring about a designated response.

Question 3

The endocrine system

Answer 3

The endocrine system is made up of endocrine glands.
An endocrine gland is a group of cells which are specialised to secrete chemicals - these chemicals are known as hormones, and are secreted directly into the bloodstream.
By contrast, exocrine glands, such as those in the digestive system, secrete chemicals through ducts into organs, or to the surface of the body.

Question 4

Examples of endocrine glands include

Answer 4

the pancreas and adrenal glands.
The pituitary gland at the base of the brain makes several hormones, which in turn control the release of other hormones.
The close proximity of the pituitary gland to the hypothalamus ensures that the nervous and hormonal responses of the body are closely linked and coordinated.

Question 5

diagram of endocrine glands

Answer 5

Question 6

Hormones:

Answer 6

• chemical messengers-they carry information from one part of the body to another.
• They can be steroids, proteins, glycoproteins, polypeptides, amines, or tyrosine derivatives.
• Although they are chemically different, they share many characteristics.
• Hormones are 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.
• It can also occur as the result of another hormone or a nerve impulse.

Question 7

Once hormones are secreted:

Answer 7

the hormones are transported 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 in the cytoplasm of cells in the target organs.
These are known as target cells.
Once bound to their receptors the hormones stimulate the target cells to produce a response

Question 8

The type of hormone determines the way it causes its effect on a target cell. For example:

Answer 8

Steroid hormones
Non-steroid hormones

Question 9

Steroid hormones

Answer 9

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.
The receptors may be present in the cytoplasm or the nucleus depending on the hormone.
The hormone-receptor complex formed acts as a transcription factor which in turn facilitates or inhibits the transcription of a specific gene.
Oestrogen is an example of a hormone which works in this way.

Question 10

Non-steroid hormones

Answer 10

are hydrophilic so cannot pass directly through the cell membrane.
Instead they bind to specific receptors on the cell surface membrane of the target cell.
This triggers a cascade reaction mediated by chemicals called second messengers.
Adrenaline is an example of a hormone which works in this way.

Question 11

diagram of steroid hormones

Answer 11

Question 12

Hormonal versus neuronal communication:

Answer 12

As hormones are not released directly onto their target cells, this results in a slower and less specific form of communication than neuronal communication.
However, as hormones are not broken down as quickly as neurotransmitters, it can result in a much longer lasting and widespread effect.
For example, the hormones insulin and glucagon are responsible for controlling blood glucose concentration.
A number of organs are involved in this response.

Question 13

features of hormonal system

Answer 13

• communication is by chemicals called hormones
• transmission is by the blood system
• transmission is usually relatively slow
• hormones travel to all parts of the body, but only target organs respond
• response is widespread
• response is slow
• response is often long-lasting
• effect may be permanent and irreversible

Question 14

features of nervous system

Answer 14

• Communication is by nerve impulses
• transmission is by neurones
• transmission is very rapid
• nerve impulses travel to specific parts of the body
• response is localised
• response is rapid
• response is short-lived
• effect is temporary and reversible

Question 15

Adrenal glands:

Answer 15

The adrenal glands are two small glands that measure approximately 3cm in height and 5cm in length.
They are located on top of each kidney and are made up of two distinct parts surrounded by a capsule:
* The adrenal cortex
* The adrenal medulla

Question 16

• The adrenal cortex

Answer 16

the outer region of the glands.
This produces hormones that are vital to life, such as cortisol and aldosterone.

Question 17

• The adrenal medulla

Answer 17

the inner region of the glands.
This produces non-essential hormones, such as adrenaline which helps the body react to stress.

Question 18

diagram of Adrenal glands

Answer 18

Question 19

Adrenal cortex:

Answer 19

The production of hormones by the adrenal cortex is itself controlled by hormones released from the pituitary gland in the brain.
There are three main types of hormones produced by the adrenal cortex

three main types of hormones produced by the adrenal cortex:
Glucocorticoids
Mineralocorticoids
Androgens

Question 20

Glucocorticoids

Answer 20

These include cortisol which helps regulate metabolism by controlling how the body converts fats, proteins, and carbohydrates to energy.
It also helps regulate blood pressure and cardiovascular function in response to stress.

Another glucocorticoid hormone released is corticosterone.
This works with cortisol to regulate immune response and suppress inflammatory reactions.
The release of these hormones is controlled by the hypothalamus.

Question 21

Mineralocorticoids

Answer 21

The main one produced is aldosterone which helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and body fluids.
Its release is mediated by signals triggered by the kidney.

Question 22

Androgens

Answer 22

Small amounts of male and female sex hormones are released - their impact is relatively small compared with the larger amounts of hormones, such as ostrogen and testosterone, released by the ovaries or testes after puberty, but they are still important, especially in women after the menopause.

Question 23

Adrenal medulla:

Answer 23

The hormones of the adrenal medulla are released when the sympathetic nervous system is stimulated.
This occurs when the body is stressed.
The hormones secreted by the adrenal medulla are:
Adrenaline
noradrenaline

Question 24

Adrenaline

Answer 24

This 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.

Question 25

Noradrenaline

Answer 25

This hormone works with adrenaline in response to stress, producing effects such as increased heart rate, widening of pupils, widening of air passages in the lungs, and the narrowing of blood vessels in non-essential organs (resulting in higher blood pressure).