HOMEOSTASIS Flashcards
(17 cards)
What is homeostasis?
- Maintaining a constant internal environment despite changes to the external environment
e.g. maintain co2 concentration, temperature conditions
Why is homeostasis important?
-Enzymes won’t function properly
-Energy and resource allocation
-Controlling the movement of molecules
How is homeostasis achieved?
What is a positive feedback system?
- A change in the internal environment of a body is detected by sensory receptors and effectors reinforce to this change and increase the response
- E.g. Oxytocin stimulates the uterus to contract, pushing the baby head harder against the cervix producing more oxytocin, continues until baby is born
What is a negative feedback system?
- Effectors work to reverse the change and restore conditions to their basic level
- Work to reverse the initial stimulus
E.g. Control of blood sugar levels by insulin and glucagon
Examples of behavioural responses in ectotherms
- They can increase their body temperature through conduction by pressing their bodies against the hot ground
E.g. Galapagos iguanas will contract their muscles increasing cellular metabolism to increase body temperature - May bask in the sun, ortinetate their bodies so maximum SA is exposed to sun
E.g. butterflies spread their wings and orientate towards sun - To cool down, they may seek shade, hiding in cracks in rocks
- Press their bodies against cold rocks or emerge in available water or mud
Examples of physiological responses in ectotherms
- Dark colours absorb more radiation than light colours
- Less food then endothermic as they use less energy regulating temperatures
- Lizards living in cold climates are dark coloured
What does the term excretion mean
- The removal of waste products of metabolism in the body
What are the responses in endotherms? (Peripheral Temperature Receptors)
- The peripheral temperature receptors detect a change in the surface temperature
- The temperature receptors in the hypothalamus act as a thermostat of the body controlling the responses that maintain the core temperature
What are the two control centres?
- The heat loss centre
- The heat gain centre
What is the heat loss centre?
- Activated when the temp of the blood flowing through the hypothalamus increases
- Sends impulses through motor neurones to effectors in skin and muscles triggering responses to lower temp
E.g. Sweating, hair lowered as hair erector muscles relax, decrease metabolic rate.
What is the heat gain centre?
- Activated when temp of the blood flowing through the hypothalamus decreases.
- Sends impulses through the nervous systems to effectors in the skin and muscles, triggering responses to raise the core temp
E.g. Shivering, Increased metabolic rate, hair raised by contraction of hair erector muscles, vasoconstriction
What is the name and functionof the two important blood vessels
- Hepatic artery and portal vein
- Portal vein carry nutrients from the stomach, spleen and intewstines
- Continually bring blood and oxygen to the liver cells
What is the function of liver?
- Carbohydrate metabolism
- Deamination of excess amino acids
-Detoxification
What is the name of the blood vessel which leaves the liver
- The hepatic vein
What is the structure of the liver?
- Hepatocytes have a large nuclei, prominent Golgi apparatus, lots of mitochondria (they are metabolically active cells)
-Blood fro the hepatic artery and hepatic portal vein is mixed in spaces called sinusoids = this increases the oxygen content of the blood - Sinusoids contain Kupffer cells which act as macrophages, ingesting foreign particles
-Hepatocytes secrete bile into spaces called canliculi and drains into bile ductules which take it. to the gall bladder
What are the two steps of excess amino acids
1) deamination = AA’s cannot be stored, excess AA’s are delaminated
2)ornithine cycle = highly toxic and soluble ammonia can damage the brain if it accumulates. Ammonia can be converted to urea and transported to kidney for excretion in urine
3)Ammonia + Carbon dioxide -> Urea and water
order = ornithinene, citruline, argenine
