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UACE Biology > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

What is homeostasis?

A

The relative constancy of the body’s internal environment regardless of the conditions in the external environment.

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2
Q

What is cybernetics?

A

The science of control systems, i.e., self-regulating systems that operate by means of feedback mechanisms.

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3
Q

What is a feedback system?

A

A mechanism in which an input stimulus causes an output response that ‘feeds back’ to the initial input.

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4
Q

What are the three components of a feedback system?

A
  • Detector eg hypothalamus
  • Regulator eg pituitary gland
  • Effector eg thyroid gland
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5
Q

What is negative feedback?

A

A mechanism in which the effect of deviation from the normal condition triggers a sequence of events that restores the system to its set point and afterwards the mechanism is switched off.

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6
Q

What is positive feedback?

A

A mechanism in which the effect of deviation from the normal condition intensifies the original response such that the change tends to proceed in the same direction as the initial stimulus.

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7
Q

Why are positive feedback mechanisms few in biological systems?

A

Because positive feedback mechanisms cause larger deviations from the normal set point and may lead to unstable conditions and extreme states.

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8
Q

What is the function of the liver in glucose regulation?

A

The liver maintains a steady blood glucose concentration by conversion of glucose to glycogen (if above the norm) and vice versa (if below the norm), under the influence of hormones.

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9
Q

What is gluconeogenesis?

A

The formation of glucose from non-carbohydrate sources.

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10
Q

How does adrenaline affect blood glucose levels?

A

Adrenaline causes hydrolysis of glycogen to glucose during acute stress or excitement, increasing glucose concentration in blood.

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11
Q

What causes insulin-dependent diabetes?

A

Insufficient secretion of insulin.

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12
Q

What causes insulin-independent diabetes?

A

Insensitivity of cells to insulin.

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13
Q

What are the symptoms of diabetes mellitus?

A

High blood sugar, glycosuria, frequent copious urination, abnormal thirst, visual disturbances, itching of genitals, fatigue, rapid weight loss, and drowsiness.

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14
Q

What is the function of the liver in maintaining blood glucose concentration?

A

The liver maintains a steady blood glucose concentration by conversion of glucose to glycogen (if above the norm) and vice versa (if below the norm), under the influence of hormones.

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15
Q

What are the functions of the liver?

A

The liver maintains a steady blood glucose concentration, regulates amino acids and proteins, regulates lipids, forms red blood cells and lymphocytes in foetus and breaks down worn out red blood cells in adults, synthesizes plasma proteins, produces bile, stores fat soluble vitamins and water soluble vitamins, stores minerals, stores blood, destroys hormones, and detoxifies poisonous substances.

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16
Q

What are the main reactions of the ornithine cycle?

A

The amino group of an amino acid is removed and reacts with hydrogen to form ammonia, ammonia reacts with carbondioxide to form carbamoyl phosphate, carbamoyl phosphate reacts with ornithine to form citrulline, citrulline diffuses into the cytoplasm and reacts with aspartate to form argininosuccinate, argininosuccinate splits into arginine and fumarate, arginine is hydrolysed to form urea and ornithine, and urea formed is carried by the blood stream to the kidneys for excretion in urine.

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17
Q

What is atherosclerosis?

A

The narrowing of arteries usually due to lipid build up.

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18
Q

What is endothermy?

A

The ability of animals to maintain a constant body temperature.

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19
Q

What is an endotherm?

A

An organism capable of maintaining a stable body temperature independent of the environmental temperature, by generating heat metabolically when environmental temperature is low.

20
Q

What is a homeotherm (homoiotherm)?

A

An organism capable of maintaining a stable body temperature independent of the environmental temperature.

21
Q

What is a poikilotherm?

A

An animal with a body temperature that fluctuates with that of the external environment.

22
Q

What is an ectotherm?

A

An animal whose body temperature is regulated by behaviour or by the surroundings.

23
Q

What are the advantages of endothermy?

A

Animals are able to exploit various environments regardless of the existing temperatures, enzyme-controlled reactions proceed without much interruption most of the time, and plenty of energy is availed to support body processes.

24
Q

What is the advantage of ectothermy?

A

There is low food intake since regulation of temperature is by behavioural means and from the environment.

25
Q

What are the functions of the skin?

A

The skin is the major organ involved in temperature regulation, provides protection against mechanical damage, ultra violet radiation from the sun, microorganism invasion and water loss of underlying tissues, is a sense organ, and is an excretory organ of urea, salt and excess water.

26
Q

What are the physical and physiological means of response to hot conditions?

A

Vasodilation, increased sweat production, panting, relaxation of erector pili muscles, and reduced metabolic rate.

27
Q

What are the behavioral means in man in response to hot conditions?

A

Taking cold drinks, putting on light clothing, moving to shady places, taking a bath, and being active mainly at night.

28
Q

What are the physical and physiological means of response to cold conditions?

A

Vasoconstriction, reduced sweat production, contraction of erector pili muscles, increased metabolic rate, and shivering.

29
Q

What are the behavioral means in man in response to cold conditions?

A

Taking hot drinks, putting on thick clothing, moving near fire/heat sources, turning on heat in houses.

30
Q

What is the lower critical temperature?

A

The temperature below which an animal’s metabolic rate increases to maintain body temperature.

31
Q

What is the lower lethal temperature?

A

The temperature below which an animal’s metabolic rate cannot maintain body temperature, leading to death.

32
Q

What is the high critical temperature?

A

The temperature above which an animal’s metabolic rate increases to maintain body temperature.

33
Q

What is the upper lethal temperature?

A

The temperature above which an animal’s metabolic rate cannot maintain body temperature, leading to death.

34
Q

What is the efficiency range (range of thermo neutrality)?

A

The external temperature range at which the body’s physical mechanisms are capable of maintaining temperature constant.

35
Q

What are the structural adaptations of organisms to cold habitats?

A

Thick fur/hair, thick layer of subcutaneous fat, larger body size, reduced size of extremities.

36
Q

What are the adaptations other than structural of organisms to cold environments?

A

Countercurrent heat exchange systems, hibernation, migration.

37
Q

What is hibernation?

A

Seasonal response by animals to cold temperature during which they become dormant, body temperature and metabolic rate fall.

38
Q

What are the structural adaptations of organisms to hot habitats?

A

Smaller body size, large thin extremities, thin insulation with fat.

39
Q

What are the adaptations other than structural of organisms to hot environments?

A

Aestivation, panting, thermal gaping, thermal dancing, salivation.

40
Q

What is aestivation?

A

Seasonal response by animals to drought or excessive heat during which they become dormant.

41
Q

Describe temperature control in ectotherm.

A

Basking, hiding, panting, thermal gaping, thermal dancing, salivation.

42
Q

Describe the role of the brain in temperature regulation.

A

Monitors variation in body temperature, sends impulses to effectors to maintain temperature.

43
Q

How do plants avoid overheating?

A

Transpiration, wilting, shiny cuticle, small needle-like leaves.

44
Q

How do plants avoid overcooling?

A

Producing spores or seeds, losing leaves, orientating leaves.

45
Q

Give examples of a positive feedback mechanism

A

-A 10 degree increase in temperature doubles metabolic activity, releasing more heat that raises the activity even more.
-During childbirth, oxytocin release stimulates contraction of uterus muscles, which in turn stimulates further oxytocin release until the foetus is expelled.

46
Q

Fewer nephrons are advantageous to a camel in what way?

A

Less water is filtered and lost in urine

UACE Biology (30 decks)

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