Unit 9- Endocrine System/thermoregulation Flashcards
What 2 kinds of glands are there?
Exocrine and endocrine
What do exocrine glands do, with an example?
Secret solutions outside the body through ducts, eg sweat glands
What are endocrine glands? And what do they secrete
Glands without ducts so secrete he I also into the tissue fluid and then blood
- endocrine glands secret hormones
How do hormones move around the body?
In the blood stream
How do hormones affect organs
- 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
Why do hormones not affect all cells?
Hormones will only bind to cells with the specific receptor complementary to it and ignore the cells without
How does adrenaline lead to the break down of glycogen?
- 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
What is the secondary messenger when adrenaline binds to a cell to initiate the cascade reaction which breaks down glycogen into glucose?
Cyclic AMP
How does release of oestrogen into the blood stimulate lining of the uterus
- 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
What is another name for a molecule that stimulates transcription?
Transcription factor
Why is no secondary messenger needed for oestrogen?
Oestrogen is lipid soluble so can pass through the cell membrane
What type of hormones are there?
- lipid based steroids
- proteins
Give an example of a lipid based steroid and it’s function
- oestrogen
- to act as a transcription factor producing proteins that thicken the uterus lining
Give an example of a protein hormone and what it does
Adrenaline
- binds to cell membrane causing a cascade reaction that breaks down glycogen into glucose
Difference between endocrine and nervous system
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
Why is negative feedback more common in control systems than positive feedback?
- 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
Give 2 examples of positive feedback
- 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
Why is negative feedback important for enzymes?
Most enzymes are sensitive to conditions
The negative feedback system maintains a dynamic equilibrium keeping pH, temperature and water potential constant
Give the a basic over view of negative feedback?
A change is detected and the effectors are stimulated responding to oppose the change
What is an ectotherm? Give an example
An organism that relies on heat from the external environment
Any cold blooded reptile
What is an endothermic, give an example
Organisms that are able to produce body heat to maintain core body temperature through metabolic processes
Eg any mammal or birds
How does the core body and peripheral body temperature vary in endotherms?
Core body temp remains constant
Peripheral can fluctuate
What controls thermoregulation in the body?
Hypothalamus
Where does the hypothalamus receive impulses from to maintain body temperature?
Thermoreceptors in skin monitor peripheral temperature
Thermoreceptors in hypothalamus measure blood temperature (core temp)
What responses can the hypothalamus initiate if body temp is too low or high?
- vasoconstriction/dilation
- sweating
- contract pili muscles to erect hairs
- contract skeletal muscles (shivering)
- secrete adrenaline/thyroxine to increase metabolic reactions
Explain how vasodilation effects body temp
- 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
Describe the step by step process of how you respond to rise core body temp
- 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
What 2 thermoregulatory systems exist in the hypothalamus?
- heat gain centre
- heat loss centre
What does the heat loss system do?
- 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
Features of ectotherms:
- get heat from external sources
- body temp fluctuates
- low energy demand due to low basal metabolism
- behavioural temperature control
- cold blooded
Features of endotherms
- 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
Why do we shiver when we have a fever?
- 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
How do mammals conserve food when hibernating?
- release hormones which lower the metabolic rate, resetting body temp at around 5 degrees
Why do lizards only need to feed once a week on average?
- such a low metabolic rate energy is conserved for much longer than in endotherms
