THE ENDOCRINE SYSTEM

Question 1

What is the role of Homeostasis?

Answer 1

To maintain internal conditions for optimum enzyme action and cell function

Question 2

List the physiological factors controlled by homeostasis

Answer 2

• core body temperature
• metabollic waste (e.g. CO2 & O2)
• blood Ph
• glucose concentration
• water potential of blood
• concentration of CO2 & O2 in the blood

Question 3

What are the 2 coordination systems in mammals that transfer information to different parts of the body for maintaining optimal conditions?

Answer 3

• NERVOUS SYSTEM
• ENDOCRINE SYSTEM

Question 4

What does the Nervous Systems consist of?

Answer 4

• The Central Nervous System (brain+ spinal cord)
• The Peripheral Nervous System (all of the body’s nerves)

Question 5

How do the Nervous Systems communicate to coordinate a response?

Answer 5

Electrical nerve impulses - signals that pass along neurones

Question 6

What are a bundle of neurones?

Answer 6

Nerves

Question 7

What do Neurones do?

Answer 7

coordinate the activities of:

• sensory receptors e.g those in the eyes
• decision making centres in the CNS
• effectors (muscles or glands)

Question 8

What is a hormone?

Answer 8

A chemical substance produced by an endocrine gland that transmits information from one part of an organism to another to bring about a change eg. altering the activity of one or more target organs

Question 9

Name the endocrine glands

Answer 9

Pituitary - ‘master gland’ at base of brain
Thyroid - produces thyroxine
Pancreas - produces insulin
Testes - produce testosterone
Ovaries - produce oestrogen
Adrenal glands - produce adrenaline

Question 10

Why do the endocrine glands need a good blood supply?

Answer 10

For the hormones to enter the bloodstream immediately to travel to the target organ to trigger a response

Question 11

What is needed for hormones to produce a response?

Answer 11

Receptors on the cell surface membrane or inside cells.
They have to be complementary to the hormone to cause an effect

Question 12

What are the key factors that need to be controlled by homeostasis and why?

Answer 12

• Temperature
• pH

a stable core temperature and blood pH are vital for enzyme activity

Question 13

What would happen to enzyme activity if there was a decrease in body temperature?

Answer 13

1. molecules move slower = less frequent collisions
2. less frequent enzyme - substrate complexes
3. enzyme and substrate collide with less energy —> decreasing likelihood of bonds forming

Question 14

What would happen to enzyme activity if there was an increase in body temperature?

Answer 14

1. molecules would move faster = more frequent collisions
2. more enzyme - substrate complexes
3. they collide with higher energy meaning it’s more likely for bonds to form.

Question 15

What would happen to enzyme activity if the body’s temperature got too high?

Answer 15

1. a very high increase in body temp would cause enzymes to denature
2. this causes bonds to break
3. changing the tertiary structure of the enzyme
4. changing its shape permanent damaging the active site
5. no more lock & key

Question 16

What would happen to enzyme activity if there was a change in pH levels?

Answer 16

1. enzymes denature at extremes of pH
2. Hydrogen & ionic bonds hold the tertiary structure together
3. Solutions with an excess of H+ ions (acidic) or an excess of OH- ions (alkaline) causes these bonds to break
4. Altering the shape of the active site
5. No more lock & key