Unit 9- Endocrine System/thermoregulation

Question 1

What 2 kinds of glands are there?

Answer 1

Exocrine and endocrine

Question 2

What do exocrine glands do, with an example?

Answer 2

Secret solutions outside the body through ducts, eg sweat glands

Question 3

What are endocrine glands? And what do they secrete

Answer 3

Glands without ducts so secrete he I also into the tissue fluid and then blood
- endocrine glands secret hormones

Question 4

How do hormones move around the body?

Answer 4

In the blood stream

Question 5

How do hormones affect organs

Answer 5

• target organs have specific receptor molecules in their cells which hormones bind to
• forms a hormone receptor complex
• this affects the cells function in some way

Question 6

Why do hormones not affect all cells?

Answer 6

Hormones will only bind to cells with the specific receptor complementary to it and ignore the cells without

Question 7

How does adrenaline lead to the break down of glycogen?

Answer 7

• adrenaline hormone binds to receptor on cell membrane
• forming a hormone receptor complex
• this activates another protein in the cell membrane, adenylyl cyclase
• adenylyl cyclase catalyses the production of cyclic AMP (cAMP) from ATP
• activating a cascade of enzymes which breaks down glycogen into glucose

Question 8

What is the secondary messenger when adrenaline binds to a cell to initiate the cascade reaction which breaks down glycogen into glucose?

Answer 8

Cyclic AMP

Question 9

How does release of oestrogen into the blood stimulate lining of the uterus

Answer 9

• oestrogen is a lipid soluble steroid
• it diffuses through the cell membrane
• oestrogen binds to a receptor protein in the cytoplasm, forming a hormone receptor complex
• the complex can now pass into the nucleus through nuclear membrane
• when the complex binds to DNA it stimulates transcription of the genes

Question 10

What is another name for a molecule that stimulates transcription?

Answer 10

Transcription factor

Question 11

Why is no secondary messenger needed for oestrogen?

Answer 11

Oestrogen is lipid soluble so can pass through the cell membrane

Question 12

What type of hormones are there?

Answer 12

• lipid based steroids

- proteins

Question 13

Give an example of a lipid based steroid and it’s function

Answer 13

• oestrogen

- to act as a transcription factor producing proteins that thicken the uterus lining

Question 14

Give an example of a protein hormone and what it does

Answer 14

Adrenaline

- binds to cell membrane causing a cascade reaction that breaks down glycogen into glucose

Question 15

Difference between endocrine and nervous system

Answer 15

Endocrine:
Transmitted in blood
Target can be any cell
Slow acting
Long lived response
Effects specific cells
Nervous system:
Transmitted by neurones
Targets muscles or glands
Fast acting
Short lived response
Effect localised by neurone anatomy

Question 16

Why is negative feedback more common in control systems than positive feedback?

Answer 16

• negative feedback prevents change and maintains a dynamic equilibrium
• positive feedback mollified conditions increasing instability
• most body systems require a dynamic equilibrium so negative feedback is more common

Question 17

Give 2 examples of positive feedback

Answer 17

• blood clotting cascade, when a few platelets stimulate many more platelets
• childbirth, when the foetus stretches the cervix, the hypothalamus detects the stretch and makes the uterus contract more stretching the cervix more

Question 18

Why is negative feedback important for enzymes?

Answer 18

Most enzymes are sensitive to conditions

The negative feedback system maintains a dynamic equilibrium keeping pH, temperature and water potential constant

Question 19

Give the a basic over view of negative feedback?

Answer 19

A change is detected and the effectors are stimulated responding to oppose the change

Question 20

What is an ectotherm? Give an example

Answer 20

An organism that relies on heat from the external environment
Any cold blooded reptile

Question 21

What is an endothermic, give an example

Answer 21

Organisms that are able to produce body heat to maintain core body temperature through metabolic processes
Eg any mammal or birds

Question 22

How does the core body and peripheral body temperature vary in endotherms?

Answer 22

Core body temp remains constant

Peripheral can fluctuate

Question 23

What controls thermoregulation in the body?

Answer 23

Hypothalamus

Question 24

Where does the hypothalamus receive impulses from to maintain body temperature?

Answer 24

Thermoreceptors in skin monitor peripheral temperature

Thermoreceptors in hypothalamus measure blood temperature (core temp)

Question 25

What responses can the hypothalamus initiate if body temp is too low or high?

Answer 25

- vasoconstriction/dilation - sweating - contract pili muscles to erect hairs - contract skeletal muscles (shivering) - secrete adrenaline/thyroxine to increase metabolic reactions

Question 26

Explain how vasodilation effects body temp

Answer 26

- vasodilation increases blood flow to the skin - so heat can radiate more quickly - dilation of sphincter muscles results in more blood flow to skin surface, additional heat loss

Question 27

Describe the step by step process of how you respond to rise core body temp

Answer 27

- Thermoreceptors in skin or hypothalamus detect low body temp - sensory neurones send impulse to hypothalamus - heat gain centre in hypothalamus sends impulses via autonomic nervous system - erector muscles, skeletal muscles and sphincter muscles contract, glands secrete adrenalin

Question 28

What 2 thermoregulatory systems exist in the hypothalamus?

Answer 28

- heat gain centre | - heat loss centre

Question 29

What does the heat loss system do?

Answer 29

- responds to high body temperature - sends impulses via autonomic nervous system - sweat glands secrete sweat, vascular muscles dilate, adrenal glands are inhibited causing lethargy reducing metabolism

Question 30

Features of ectotherms:

Answer 30

- get heat from external sources - body temp fluctuates - low energy demand due to low basal metabolism - behavioural temperature control - cold blooded

Question 31

Features of endotherms

Answer 31

- body temp from metabolism - core body temp is constant - high energy demand due to high metabolic rate - can cope with extreme conditions - behavioural and physiological temperature control - mammals

Question 32

Why do we shiver when we have a fever?

Answer 32

- chemicals are secreted by white blood cells that reset the thermoregulatory centres to 2 degrees above normal - patients shiver to gain heat, which kills bacteria

Question 33

How do mammals conserve food when hibernating?

Answer 33

- release hormones which lower the metabolic rate, resetting body temp at around 5 degrees

Question 34

Why do lizards only need to feed once a week on average?

Answer 34

- such a low metabolic rate energy is conserved for much longer than in endotherms