Living Control Mechanisms

Question 1

What is homeostasis?

Answer 1

Maintenance of a constant internal environment

Question 2

Examples of homeostasis in the body

Answer 2

Potassium levels
Temperature
Hydrogen ion
Glucose
Blood oxygen

Question 3

What are the stages of the homeostasis model?

Answer 3

Set Point
Control Centre
Effectors
Regulated variable
Sensor
Control centre etc

Question 4

Why is communication important in homeostasis?

Answer 4

Cells must communicate with each other to achieve homeostasis

There needs to be a co-ordinated response

Question 5

What are the two different communication systems in homeostasis?

Answer 5

Endocrine - hormones
Nervous - electrical

Question 6

What is a receptor?

Answer 6

The thing that receives the signal

Question 7

What is autocrine signalling?

Answer 7

Cells talking to themselves

Form of cell signalling in which a cell secretes a hormone or chemical messenger that binds to autocrine receptors on that same all

Question 8

What is paracrine signalling?

Answer 8

Cells talking to neighbouring cells a short distance away

Type of cellular communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells

Question 9

How is the signal in paracrine signalling transport?

Answer 9

•Signal diffuses across gap between cells

•Inactivated locally, so doesn’t enter the blood stream

Question 10

Give examples of paracrine signalling

Answer 10

Interleukins
•Signalling in the immune system
•Mainly between white blood cells

Platelet derived growth factor (PDGF)
•Released from platelets
•Regulates cell growth

Question 11

What is endocrine signalling?

Answer 11

Cells talking to other cells elsewhere in the body

Hormones are secreted by specialised endocrine cells and carried through the circulation to act on target cells at distant body sites

Question 12

Give examples of endocrine organs/glands?

Answer 12

• Hypothalamus
• Pituitary
•Thyroid
• Adrenals
• Pancreas
• Ovaries
• Testes

Question 13

What is a hormone?

Answer 13

Molecule that acts as a chemical messenger

Question 14

What are amino acid hormones?

Answer 14

Synthesised from tyrosine
Example; adrenaline

Question 15

What are hormones classified according to?

Answer 15

Classified according to structure;
●Amino-acid derivatives
●Peptide
●Steroid

Question 16

What are peptide hormones?

Answer 16

●Made of amino acids
●Vary in size from few amino acids to small proteins
●Some have carbohydrate side chains (glycoproteins)
●Hydrophillic (like water)

Question 17

What do peptide and amino acid hormones have in common?

Answer 17

Produce a quick reaction in the body

Question 18

What type of hormone is TSH?

Answer 18

Peptide hormones

Question 19

What are steroid hormones?

Answer 19

●All made from cholesterol
●Different enzymes modify molecule to produce a variety of hormones
●Can’t dissolve in water
●Can dissolve in lipids

Question 20

How do steroid hormones work?

Answer 20

Steroid hormones produce a slow response

Question 21

Give an example of a steroid hormone

Answer 21

Testosterone

Question 22

What is a positive feedback loop?

Answer 22

Signal is amplified

When the product of a reaction leads to an increase in that reaction

Question 23

What is a negative feedback loop?

Answer 23

Allows the body to regulate itself

The process starts when there is an increase in output from a body system, which results
In higher levels of certain proteins or hormones

Question 24

Give an example of a negative feedback loop

Answer 24

Pituitary-thyroid loop

Question 25

What is the set point?

Answer 25

What we are aiming for