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A Level Bio Edexcel > Unit 9- Endocrine System/thermoregulation > Flashcards

Unit 9- Endocrine System/thermoregulation Flashcards

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1
Q

What 2 kinds of glands are there?

A

Exocrine and endocrine

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2
Q

What do exocrine glands do, with an example?

A

Secret solutions outside the body through ducts, eg sweat glands

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3
Q

What are endocrine glands? And what do they secrete

A

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

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4
Q

How do hormones move around the body?

A

In the blood stream

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5
Q

How do hormones affect organs

A
  • 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
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6
Q

Why do hormones not affect all cells?

A

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

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7
Q

How does adrenaline lead to the break down of glycogen?

A
  • 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
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8
Q

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

A

Cyclic AMP

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9
Q

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

A
  • 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
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10
Q

What is another name for a molecule that stimulates transcription?

A

Transcription factor

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11
Q

Why is no secondary messenger needed for oestrogen?

A

Oestrogen is lipid soluble so can pass through the cell membrane

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12
Q

What type of hormones are there?

A
  • lipid based steroids

- proteins

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13
Q

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

A
  • oestrogen

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

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14
Q

Give an example of a protein hormone and what it does

A

Adrenaline

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

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15
Q

Difference between endocrine and nervous system

A 
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
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16
Q

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

A
  • 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
17
Q

Give 2 examples of positive feedback

A
  • 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
18
Q

Why is negative feedback important for enzymes?

A

Most enzymes are sensitive to conditions

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

19
Q

Give the a basic over view of negative feedback?

A

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

20
Q

What is an ectotherm? Give an example

A

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

21
Q

What is an endothermic, give an example

A

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

22
Q

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

A

Core body temp remains constant

Peripheral can fluctuate

23
Q

What controls thermoregulation in the body?

A

Hypothalamus

24
Q

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

A

Thermoreceptors in skin monitor peripheral temperature

Thermoreceptors in hypothalamus measure blood temperature (core temp)

25
Q

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

A
  • vasoconstriction/dilation
  • sweating
  • contract pili muscles to erect hairs
  • contract skeletal muscles (shivering)
  • secrete adrenaline/thyroxine to increase metabolic reactions
26
Q

Explain how vasodilation effects body temp

A
  • 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
27
Q

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

A
  • 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
28
Q

What 2 thermoregulatory systems exist in the hypothalamus?

A
  • heat gain centre

- heat loss centre

29
Q

What does the heat loss system do?

A
  • 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
30
Q

Features of ectotherms:

A
  • get heat from external sources
  • body temp fluctuates
  • low energy demand due to low basal metabolism
  • behavioural temperature control
  • cold blooded
31
Q

Features of endotherms

A
  • 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
32
Q

Why do we shiver when we have a fever?

A
  • 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
33
Q

How do mammals conserve food when hibernating?

A
  • release hormones which lower the metabolic rate, resetting body temp at around 5 degrees
34
Q

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

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

A Level Bio Edexcel (51 decks)

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