Homeostasis- thermoregulation and the liver

Question 1

what is homeostasis?

Answer 1

the regulation of internal conditions to maintain optimum conditions to function

Question 2

what is negative feedback?

Answer 2

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.

Question 3

what is positive feedback?

Answer 3

a change in the internal environment is detected by sensory receptors and effectors are stimulated to reinforce that change and increase the response.

Question 4

how is blood clotting an example of positive feedback?

Answer 4

platelets stick to damaged region and release factors for more platelets.

Question 5

how is a positive feedback present during childbirth?

Answer 5

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.

Question 6

what is thermoregulation?

Answer 6

maintenance of a constant core body temperature to maintain optimum enzyme activity.

Question 7

what physical processes change body temp due to surroundings?

Answer 7

-exothermic chemical reactions
-latent heat of evaporation
-radiation (transmission of electromagnetic waves)
-convection
-conduction (heating from collision of molecules)

Question 8

what are ectotherm animals?

Answer 8

animals which are dependent on their surroundings to warm their bodies e.g invertebrates, fish, amphibians and reptiles

Question 9

why do many ectotherms living in water not need to thermoregulate?

Answer 9

because of the high heat capacity of water however animals that live on land do as temperatures change from seasons

Question 10

what are endotherm animals?

Answer 10

animals which rely on metabolic processes to warm up e.g mammals and birds

Question 11

what behavioural responses may be taken place by an ectotherm? (to heat up)

Answer 11

-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

Question 12

what behavioural responses may be taken place by an ectotherm? (to cool down)

Answer 12

-seeking for shade
-press bodies to cool areas
-orientate bodies so minimum surface area exposed to sun
-minimise movements

Question 13

what are some physiological adaptations for ectotherms to keep warm?

Answer 13

-dark colours absorb more radiation
-alter heart rate to increase/ decrease metabolic rate
-eat less food

Question 14

How do endotherms detect temperature changes?

Answer 14

-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

Question 15

how do endotherms regulate their internal temperature?

Answer 15

-use internal exothermic metabolic activities to keep them warms
-energy requiring physiological responses to cool down

Question 16

in what ways do endotherms cool down?

Answer 16

-vasodilation
-increased sweating
-reducing insulating effect of hair or feathers

Question 17

How does vasodilation help cool down endotherms?

Answer 17

-arterioles near surface of skin dilate as arteriovenous shunt vessels constrict
-increased radiation, heat loss

Question 18

How does increased sweating help cool down endotherms?

Answer 18

-sweat secreted from sweat gland across skin
-sweat evaporates causing heat loss
-licking skin causes evaporation

Question 19

How does reducing the insulating effect of hair or feathers help cool down endotherms?

Answer 19

when body temperature increases, the erector pili muscles in the skin relax as a result hair and feathers lie flat to the skin

Question 20

what anatomical adaptations do endotherms have to help cool down?

Answer 20

large surface area to volume ration (e.g ears) to maximise cooling

Question 21

how do endotherms warm up?

Answer 21

vasoconstriction, decreased sweating, raising body hairs or feathers and shivering

Question 22

how does vasoconstriction help endotherms warm up?

Answer 22

-arterioles near the skin surface constrict
-arteriovenous shunt vessels dilate so little blood flow to skin surface
-little radiation takes place

Question 23

how does decreased sweating help endotherms warm up?

Answer 23

prevents cooling from evaporation

Question 24

how does raising body hairs or feathers help warm up endotherms?

Answer 24

-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

Question 25

how does shivering help endotherms warm up?

Answer 25

-rapid, involuntary contracting and relaxing of large voluntary muscles in the body -metabolic heat from exothermic reaction warm up body and raise core temperature

Question 26

What anatomical adaptations do endotherms have to help warm up?

Answer 26

-minimise surface area to volume ration (e.g small ears) -thick layer of insulating fat under skin (blubber) -hibernation

Question 27

how does hibernation work?

Answer 27

-build up fat stores -build well insulated shelter -lower metabolic rate

Question 28

what are the two control centres in controlling thermoregulation in endotherms?

Answer 28

-heat loss centre -heat gain centre -sophisticated feedback system

Question 29

Describe heat loss centre?

Answer 29

-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

Question 30

Describe heat gain centre?

Answer 30

-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

Question 31

what are the main metabolic waste products in mammals?

Answer 31

-carbon dioxide (from respiration) -bile pigments -nitrogenous waste products (urea)

Question 32

how are bile pigments formed?

Answer 32

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.

Question 33

How are nitrogenous waste products (urea ) formed?

Answer 33

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.

Question 34

What veins surround the liver?

Answer 34

-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

Question 35

What are liver cells also called?

Answer 35

hepatocytes

Question 36

Describe the structure of a hepatocyte?

Answer 36

-large nuclei -lots of mitochondria

Question 37

Describe the structure of the liver?

Answer 37

-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

Question 38

what are the main functions of the liver?

Answer 38

-carbohydrate metabolism -deamination of excess amino acids -detoxification

Question 39

how is the liver involved in carbohydrate metabolism?

Answer 39

-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

Question 40

How does the liver play a vital role in protein metabolism?

Answer 40

-hepatocytes synthesis plasma proteins -hepatocytes carry out transamination -hepatocytes carry out deamination

Question 41

what is transamination?

Answer 41

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.

Question 42

What is deamination?

Answer 42

removal of amine group from a molecule as the body cannot store excess amino acids.

Question 43

How does deamination occur?

Answer 43

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.

Question 44

what is the ornithine cycle?

Answer 44

the cycle when ammonia produced from deamination is converted to urea is a set of enzyme controlled reactions

Question 45

How do hepatocytes break down hydrogen peroxide(toxic)?

Answer 45

hepatocytes contain enzyme catalase which splits hydrogen peroxide into oxygen and water

Question 46

How do hepatocytes break down ethanol (toxic)?

Answer 46

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