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A Level Biology > Homeostasis, Hormones & Excretion > Flashcards

Homeostasis, Hormones & Excretion Flashcards

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1
Q

What is homeostasis

A

Maintaining a constant internal environment despite changes in external and internal factors

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2
Q

What is negative feedback

A

The mechanism that reverses a change, bringing the system back to the optimum

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3
Q

What is positive feedback

A

The mechanism that increases a change, taking the system further away from the optimum
- change is detected and exaggerated

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4
Q

What conditions do cells need to maintain

A
  • temperature
  • pH
  • aqueous environment that keeps the substances and products in solution
  • freedom from toxins and excess inhibitors
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5
Q

What is cell signaling

A

The way in which cells communicate with each other

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6
Q

Why are multicellular organisms more efficient than single celled organisms

A

Cells are differentiated
- specialized to Freeform a particular function

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7
Q

What does a good communication system do

A
  • cover the whole body
  • enable cells to communicate with each other
  • enable specific communication
  • enable rapid communication
  • enable both short and long term responses
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8
Q

What are the two major systems of communication

A
  • neuronal system
  • hormonal system (endocrine)
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9
Q

What is the neuronal system

A

An interconnected network of neurons that signal to each other across synapse junctions
- enable rapid response to stimuli

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10
Q

What is the endocrine/hormonal system

A

System that uses the blood to transport its signals
- secrete the hormone directly into the blood
- travels through the body
- only recognized by specific target cells
- enables longer term responses

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11
Q

What are aspects that are maintained by homeostasis

A
  • body temperature
  • blood glucose concentration
  • blood salt concentration
  • water potential of the blood
  • blood pressure
  • carbon dioxide concentration
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12
Q

Example of the response pathway

A
  • stimuli
  • receptor
  • communication pathway (cell signaling)
  • effector
  • response
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13
Q

What sensory receptors

A

Cells/sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials

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14
Q

What processes must occur for negative feedback

A
  • change to the internal environment must be detected
  • the change must be signaled to the other cells
  • must be an effective response that reverses the change in conditions
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15
Q

What happens to chemical reactions when temperature rises

A
  • occur more quickly
  • more kinetic energy
  • collide more often
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16
Q

What is an ectotherm

A

An organism that relies on external sources of heat to maintain body temperature

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17
Q

What are endotherms

A

Organisms that use heat from metabolic reactions to maintain body temperature

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18
Q

What might ectotherms do if they are too cold

A
  • move into a sunny area
  • lie on a warm surface
  • expose a larger surface area to the sun
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19
Q

What might ectotherms do if they are too warm

A
  • move out of the sun
  • move underground
  • reduce the body surface exposed to the sun
20
Q

Advantages of being an ectotherm

A
  • less of their food is used in respiration
  • more of the energy and nutrients gained from food can be converted to growth
  • need to find less food
  • can survive for long periods without food
21
Q

Disadvantages of being an ectotherm

A
  • less active in cooler temperatures
  • risk of predation
  • cannot take advantage of available food when cold
22
Q

Ways skin has adapted to cool down

A
  • sweat glands produce sweat
  • sweat evaporated to increase heat loss
  • hairs lie flat
  • vasodilation
23
Q

ways skin has adapted to heat up

A
  • little to no sweat produced
  • insulating layer of air is trapped above the skin
  • hair erector muscle contracts to pull hair upright
  • vasoconstriction
24
Q

What is vasodilation

A

Blood cells open up allowing more blood to flow through capillaries
- more heat lost through radiation

25
Q

What is vasoconstriction

A

Blood vessels constrict allowing less blood to flow through capillaries
- less heat lost by radiation

26
Q

How do skeletal muscles react when too hot

A

Fewer contraction
- less heat is released

27
Q

How do skeletal muscles react when too cold

A

Spontaneous muscle contractions
- shivering

28
Q

Advantages of being endothermic

A
  • maintain a fairly constant body temperature whatever the temperature externally
  • remain active even when external temperatures are low
  • take advantage of pray that may be available/ escape predators
  • inhabit colder parts of the planet
29
Q

Disadvantages of being endothermic

A
  • use a significant part of their energy intake to maintain body temperature in the cold
  • need more food
  • use a lower proportion of energy from food for growth
  • may overheat in hot weather
30
Q

Where are temperature receptors in the brain (thermoregulatory center)

A

Hypothalamus

31
Q

What does the hypothalamus do if the core temperature is too low

A
  • changes in the skin to reduce heat loss
  • release of heat through extra muscular contractions
  • increased metabolism in order to release more heat from exergonic reactions
32
Q

What does the thermoregulatory center do

A
  • monitors blood temperature
  • detects changes in the core body temp
33
Q

What are the different thermoregulatory centers within the hypothalamus

A
  • heat loss center activation
  • heat gain center activation
  • sensory or motor neurons
34
Q

What is excretion

A

The removal of metabolic waste from the body

35
Q

What is metabolic waste

A

A substance that is produced in excess by the metabolic processes in the cells
- may become toxic

36
Q

Examples of metabolic waste

A
  • carbon dioxide from respiration
  • nitrogen containing compounds: urea
  • other compounds: bile pigments
37
Q

What are the excretory organs in the body

A
  • lungs
  • liver
  • skin
  • kidneys
38
Q

What do hydrogen ions do to RBC

A

Affect the pH of the cytoplasm

39
Q

What do hydrogen ions do to haemoglobin

A

Reduces its affinity to oxygen
- affecting oxygen transport

40
Q

Chemicals that reduce oxygen transport

A
  • haemoglobinic acid
  • carbaminohaemoglobin
41
Q

Order of urine out of the kidney

A
  • kidney
  • ureter
  • bladder
  • urethra
42
Q

Where are extra amino acids taken

A

Liver

43
Q

What is deamination

A

Removal of amino group from amino acids

44
Q

What are the metabolic functions of the liver

A
  • control blood glucose, amino acids and lipid levels
  • synthesize bile, plasma proteins and cholesterol
  • synthesize RBC in the fetus
  • store vitamin A,D and B12, iron and glycogen
  • detoxification of alcohol and drugs
  • breakdown of hormones
  • destruction of RBC
45
Q

Order of what amino acids are converted into

A
  • amino acid
  • ammonia
  • urea

A Level Biology (13 decks)

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