Homeostasis- thermoregulation and the liver Flashcards
what is homeostasis?
the regulation of internal conditions to maintain optimum conditions to function
what is negative feedback?
mechanism that brings about a reversal of change in conditions. It ensures the maintenance of an optimum steady state, by returning the internal environment back into its original set of conditions.
what is positive feedback?
a change in the internal environment is detected by sensory receptors and effectors are stimulated to reinforce that change and increase the response.
how is blood clotting an example of positive feedback?
platelets stick to damaged region and release factors for more platelets.
how is a positive feedback present during childbirth?
baby head pressing against cervix stimulates production of oxytocin hormone. This stimulates hormone to contact pushing the baby head against cervix harder triggering release of more oxytocin.
what is thermoregulation?
maintenance of a constant core body temperature to maintain optimum enzyme activity.
what physical processes change body temp due to surroundings?
-exothermic chemical reactions
-latent heat of evaporation
-radiation (transmission of electromagnetic waves)
-convection
-conduction (heating from collision of molecules)
what are ectotherm animals?
animals which are dependent on their surroundings to warm their bodies e.g invertebrates, fish, amphibians and reptiles
why do many ectotherms living in water not need to thermoregulate?
because of the high heat capacity of water however animals that live on land do as temperatures change from seasons
what are endotherm animals?
animals which rely on metabolic processes to warm up e.g mammals and birds
what behavioural responses may be taken place by an ectotherm? (to heat up)
-busk in the sun
-orientate their bodies for maximum surface area exposed to sun
-pressing bodies against warm ground (conduction)
-warmer due to exothermic metabolic reactions
-contracting muscles
what behavioural responses may be taken place by an ectotherm? (to cool down)
-seeking for shade
-press bodies to cool areas
-orientate bodies so minimum surface area exposed to sun
-minimise movements
what are some physiological adaptations for ectotherms to keep warm?
-dark colours absorb more radiation
-alter heart rate to increase/ decrease metabolic rate
-eat less food
How do endotherms detect temperature changes?
-peripheral temperature receptors are in the skin and detect changes
-temperature receptors in the hypothalamus detect blood temperature
-combination of two gives body great sensitivity
how do endotherms regulate their internal temperature?
-use internal exothermic metabolic activities to keep them warms
-energy requiring physiological responses to cool down
in what ways do endotherms cool down?
-vasodilation
-increased sweating
-reducing insulating effect of hair or feathers
How does vasodilation help cool down endotherms?
-arterioles near surface of skin dilate as arteriovenous shunt vessels constrict
-increased radiation, heat loss
How does increased sweating help cool down endotherms?
-sweat secreted from sweat gland across skin
-sweat evaporates causing heat loss
-licking skin causes evaporation
How does reducing the insulating effect of hair or feathers help cool down endotherms?
when body temperature increases, the erector pili muscles in the skin relax as a result hair and feathers lie flat to the skin
what anatomical adaptations do endotherms have to help cool down?
large surface area to volume ration (e.g ears) to maximise cooling
how do endotherms warm up?
vasoconstriction, decreased sweating, raising body hairs or feathers and shivering
how does vasoconstriction help endotherms warm up?
-arterioles near the skin surface constrict
-arteriovenous shunt vessels dilate so little blood flow to skin surface
-little radiation takes place
how does decreased sweating help endotherms warm up?
prevents cooling from evaporation
how does raising body hairs or feathers help warm up endotherms?
-erector pili muscles in the skin contract, pulling the hair or feathers erect
-this traps an insulating layer of air and reduces cooling through skin
-reduces heat loss
how does shivering help endotherms warm up?
-rapid, involuntary contracting and relaxing of large voluntary muscles in the body
-metabolic heat from exothermic reaction warm up body and raise core temperature
What anatomical adaptations do endotherms have to help warm up?
-minimise surface area to volume ration (e.g small ears)
-thick layer of insulating fat under skin (blubber)
-hibernation
how does hibernation work?
-build up fat stores
-build well insulated shelter
-lower metabolic rate
what are the two control centres in controlling thermoregulation in endotherms?
-heat loss centre
-heat gain centre
-sophisticated feedback system
Describe heat loss centre?
-activated when blood travelling through the hypothalamus increases
-send impulses through autonomic motor neurones to effectors in skin and muscles, triggering responses to lower core temperature
Describe heat gain centre?
-activate when blood travelling through the hypothalamus decreases
-sends impulses through the autonomic nervous system to effectors in the skin and muscles, triggering responses to raise core temperature
what are the main metabolic waste products in mammals?
-carbon dioxide (from respiration)
-bile pigments
-nitrogenous waste products (urea)
how are bile pigments formed?
breakdown of haemoglobin from old red blood cells in the liver. They are excreted in he bile from the liver into the small intestine via gall bladder and bile duct. They colour faeces.
How are nitrogenous waste products (urea ) formed?
breakdown of excess amino acids by the liver. All mammals produce urea as their nitrogenous waste. Fish produce ammonia while birds and insects produce uric acid. Urea is excreted by kidneys in urine.
What veins surround the liver?
-hepatic artery supplies oxygenated blood
-hepatic vein returns low oxygenated blood to the heart
-hepatic portal vein carries blood loaded with products of digestion from the intestines
What are liver cells also called?
hepatocytes
Describe the structure of a hepatocyte?
-large nuclei
-lots of mitochondria
Describe the structure of the liver?
-blood from hepatic artery and hepatic portal vein is mixed in spaces called sinusoids which are surrounded by hepatocytes
-mixing increases oxygen content of the blood from the hepatic portal vein, supplying the hepatocytes with enough oxygen for their needs
-sinusoids contain kupffer cells which act as resident macrophages, ingesting foreign particles
-hepatocytes secrete bile from the breakdown of blood into spaces called the canaliculi.
-Bile drains into bile ductules into gall bladder
what are the main functions of the liver?
-carbohydrate metabolism
-deamination of excess amino acids
-detoxification
how is the liver involved in carbohydrate metabolism?
-when blood glucose levels rise, insulin levels rise and stimulate hepatocytes to convert glucose to glycogen
-when blood glucose levels fall, glucagon levels rise and stimulate hepatocytes to convert glycogen into glucose
How does the liver play a vital role in protein metabolism?
-hepatocytes synthesis plasma proteins
-hepatocytes carry out transamination
-hepatocytes carry out deamination
what is transamination?
the conversion of one amino acid to another. This is important as diet dent always contain the required balance of amino acids but transamination can overcome that problem.
What is deamination?
removal of amine group from a molecule as the body cannot store excess amino acids.
How does deamination occur?
The removal of amino group rom amino acid forms ammonia which is very toxic and then urea which is very toxic in high concentrations. Urea is excreted by the kidneys. The remainder of the amino acid can be fed into cellular respiration or converted into lipids for storage.
what is the ornithine cycle?
the cycle when ammonia produced from deamination is converted to urea is a set of enzyme controlled reactions
How do hepatocytes break down hydrogen peroxide(toxic)?
hepatocytes contain enzyme catalase which splits hydrogen peroxide into oxygen and water
How do hepatocytes break down ethanol (toxic)?
hepatocytes contain enzyme alcohol dehydrogenase that breaks down ethanol to ethanal. Ethanal is then converted to ethanoate which can be used to build up fatty acids or be used in cellular respiration
