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Alevel Biology > 5.5 > Flashcards

5.5 Flashcards

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1
Q

What does biotic mean

A

Living

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2
Q

What does abiotic mean

A

Non livint

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3
Q

What does plants responding to stimulus help them to do

A

Survive long enough to reproduce

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4
Q

What is an example of plants responding to external stimuli

A

In high temps plants deposit thick layers of wax on leaves and in windy conditions more lignified vascular tissue

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5
Q

What are 3 chemicals plants have to deter herbivores

A

Tannins, alkaloids, pheromones

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6
Q

What are tannins

A

Toxic to microorganisms and larger herbivores, in leaves in upper epidermis and makes leaves taste bad, in roots they prevent infiltration by pathogenic microorganisms

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7
Q

What are alkaloids

A

Derived from amino acids, in plants, feeding deterant to animals by tasting butter and found in growing tips and flowers and peripheral cell layers of stems and roots

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8
Q

What are pheromones

A

Chemicals released by individual and can effect behaviour/physiology of another

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9
Q

What is tropism

A

Directional growth responses of plant

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10
Q

What is phototropism

A

Shoots grow towards light (positively phototropic) enables them to photosynthesis and stay turgid

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11
Q

What is geotropism

A

Roots grow to pull of gravity, anchors them in soil to take up water to support plant as raw materials for photosynthesis and to cool plant, also nitrate in water for synthesis of amino acids

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12
Q

What is chemotropism

A

On flower, pollen tubes grow does style, attracted by chemicals to ovary where fertilisation occurs

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13
Q

What is thigmotropism

A

Shoots of climbing plants like ivy wind round other plants or solid structures for support

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14
Q

What is a positive tropic response

A

Plant responds towards stimulus

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15
Q

What is a negative tropic response

A

Plant responds away from stimulus

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16
Q

What is a nastic response

A

Non-directional response to external stimuli

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17
Q

WhT are plant hormones

A

Chemical messengers that can be transported away from site of manufacture to act in other parts (cells or tissue) of plant

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18
Q

What produces plant hormones

A

cells in a variety of tissues

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19
Q

What do plant hormones do when they reach target cells

A

Bind to receptors on plasma membrane, only bind with complementary receptors on certain cells, specific binding ensures hormones act on correct tissue, some hormones have different effects on different tissues, some amplify effects others cancel effects

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20
Q

What do hormones influence

A

Cell division, cell elongation, cell differentiation

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21
Q

What is the effect of plant hormone cytokinins

A

Promote cell division, delay leaf senescence, overcome apical dominance, promote cell expansion

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22
Q

What is the effect of plant hormone abscisic acid

A

Inhibits seed germination, causes stomatal closure when plant stressed by low water availability

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23
Q

What is the effect of plant hormone auxins

A

Promotes cell elongation, inhibits side shoot growth, inhibits leaf abscission (leaf fall)

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24
Q

What is the effect of plant hormone gibberellins

A

Promotes seed germination and growth of stems

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25
Q

What is the effect of plant hormone ethene

A

Promotes fruit ripening

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26
Q

What 3 ways to hormones travel round plant

A

Active transport, diffusion, mass flow in phloem sap/xylem vessel

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27
Q

WhT are auxins

A

Plant hormones for regulating plant growth

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28
Q

What happens if you break shoot tip (apex) of plant

A

Plant starts to grow side branches from lateral buds that before we’re dormant, auxin from apical bud prevents lateral buds from growing when removed auxin level in shoot drops and buds grow

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29
Q

How did scientists test their hypothesis about auxin and regulating growth

A

Applied auxin paste to cut end of shoots and lateral buds didn’t grow

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30
Q

What is a limitation of scientists test about auxin and regulating growth

A

Their manipulation of plant could have unexpected effect, on exposure to oxygen, cells on cut end could have produced hormone that promoted lateral bud growth, so scientists applied ring of auxin transport inhibitor below apex of shoot and lateral buds grew

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31
Q

What did scientists conclude from their experiment with auxin and growth of lateral buds

A

Scientists said normal auxin levels in lateral buds inhibit growth but low levels of auxin promotes growth

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32
Q

What are the 2 variables in auxin and growth regulation

A

Auxin levels and growth inhibition may have no effect on each other but effect a 3rd variable, different scientists said auxin levels in lateral buds of beans increased when shoot cut off

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33
Q

What 2 other hormones do scientists now thing aid auxin in growth regulation

A

Abscisic acid and cytokinins

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34
Q

What is abscisic acid role in growth regulation

A

Inhibits bud growth, high auxin in shoot keeps abscisic acid levels high in bud when tip removed, abscisic acid levels drop and bud grows

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35
Q

What is cytokinins role in growth regulation

A

Promotes bud growth, directly applying cytokinins to bud can override apical dominance effect, high levels of auxin make shoot apex a sink of cytokinins produced in roots, when apex removed cytokinins spread evenly around plant

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36
Q

What is a example of giberillins in stem elongation and germination

A

Disease causes rice to grow very tall, component involved in giberellins and giberellic acid

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37
Q

How did scientists check giberellins effect on plants

A

When applied to dwarf plants giberellic acid made them grow taller suggests it is responsible for plant stem growth

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38
Q

What is limitation of experiment with giberellins

A

Needs to work with concentration of giberellins naturally found in plants and in parts of plant that they reach, to do this they compared giberellin in tall pea plants vs dwarf pea plants which otherwise are genetically identical, found plants with more giberellins were talker

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39
Q

How can you show giberellins directly effect stem elongation

A

Researchers must know how giberellins are formed, they worked out the Le gene responsible for converting giberellic acid to GA, researchers then chose pea plant with mutation what blocks giberellin production, these were only 1cm tall, when researchers grafted homozygous plant (can’t convert giberellic acid to GA1) and it grew taller

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40
Q

What do shoots with no giberellic acid have instead

A

Enzyme to convert giberellic acid to GA and can use unused giberellic acid from normal plants, as shoot grew tall it confirmed giberellins cause stem elongation by loosening cell wall and cell division by stimulating production of proteins that control cell cycle

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41
Q

How do giberellins promote seed germination

A

When seed absorbs water, embryo releases giberellins which travels to aleurone layer in endosperm region of seed

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42
Q

What does giberellin enable production of

A

Amalyse which breaks down starch to glucose, providing substrate for respiration for embryo so it grows, glucose also used for protein synthesis

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43
Q

What does plant cell wall limit

A

Cells ability to divide and expand

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44
Q

Where does growth occur in plants

A

Only in places with immature cells that can still divide (meristems)

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45
Q

What are the 3 meristems in plants and 4th found in some plants

A

Apical meristems, lateral bud meristems, lateral meristems and 4th intercalary meristems

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46
Q

What is apical meristem

A

At tips of roots and shoots and responsible for roots and shoots getting longer

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47
Q

What is lateral bud meristems

A

Found in buds and give rise to size shoots

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48
Q

AhT is lateral meristems

A

Form cylinder near outside of roots and shoots and responsible for widening roots and shoots

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49
Q

What is intercalary meristems

A

Located between nodes when leaves and buds branch off stem, growth between nodes responsible for shoots getting longer

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50
Q

When investigating phototropic responses what is the difference between control plant and experimental plant

A

Control plant illuminated from all side, experimental plant only illuminated from one side

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51
Q

What are the results of phototropic response experiment

A

After several days shoot bends to light as shady side has elongated more than illuminated side

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52
Q

When investigating geotropic responses what is control and what is experimental plant

A

Control plant spun very slowly by machine so gravity effect applied evenly to all sides, experimental plant plant isn’t spun so gravity only applied to one side

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53
Q

What we’re results from geotropic response experiment

A

Experimental plant, root bends down as upper side of root has elongated more than lower side, control, roots and shoots grow horizontally

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54
Q

What has series of experiments shown is responsible for phototropic responses

A

Chemical messenger

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55
Q

What did Darwin work confirm in phototropic responses

A

Shoot tip responsible for phototropic responses

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56
Q

What did Boysen-Jensens work confirm

A

Water and/or solutes need to move backwards from shoot tip for phototropism to occur

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57
Q

How did Boysen-Jensons experiments show water/solutes need to move back from shoot tip for phototropism to occur

A

When permeable gelatine block inserted behind shoot tip, shoot still showed positive phototropism, when impermeable mica block inserted, no phototropic response

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58
Q

How did Darwin experiments show phototropism

A

Control bend to light, if tip removed it stayed straight, stayed straight if tip had opaque cap, bend to light of tip had transparent cap, bend to light of base had opaque shield

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59
Q

How was phototropic effect artificially stimulated to show chemical messenger existed

A

Shoot tip placed on agar block, chemical later identified as auxin, diffuses from shoot tip to agar

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60
Q

What was done to confirm role of auxin as chemical messenger

A

Agar blocks impregnated with different concentrations of auxin and gives same results, using series of blocks with different auxin concentrations created by cereal dilution gives shoot curvature in proportion to amount of auxin

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61
Q

Where is auxin produced and where does it travel to

A

Produced at apex of shoot and travels to cell in zone of elongation making shoot grow

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62
Q

What happens to shoot with auxin when light even on all sides vs when light shines on one side

A

Auxin promotes even shoot growth but when light on one side it causes auxin to be transported to shaded side causing cells to elongated quicker so shoot bends to light

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63
Q

What is the extent to which a cell elongated proportional to

A

Concentration of auxin

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64
Q

What does auxin do

A

Increase stretchiness of cell wall by promoting active transport of hydrogen ions by ATPase on plasma membrane into cell wall, resulting low pH gives optimum conditions for wall loosening enzyme expansins to work

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65
Q

How do expansins work and increased hydrogen ions

A

Break bonds in cellulose and increased hydrogen ions disrupt hydrogen bonds so wall less rigid so can expand as cell takes in water

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66
Q

What 2 enzymes have been identified in redistribution of auxin due to light

A

Phototropin 1 and 2, their activity promoted by blue light

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67
Q

How does phototropin cause redistribution of auxin due to activity being promoted by blue light

A

Blue light main component of white light that causes phototropic response, so lots of phototropin 1 on light side but less on shaded side, gradient causes redistribution of auxin through their effect on PIN proteins

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68
Q

What are PIN proteins and where are they found

A

Transmembrane proteins found dorsally, ventrally or laterally on plasma membrane of cells and control efflux of auxin from each cell sending auxin in different directions in shoot depending on location on plasma membrane

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69
Q

What is activity of PIN proteins controlled by

A

Pinoids

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70
Q

What does one theory say about phototropins and pinoids

A

Phototropins affect pinoid activity which effects pin activity

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71
Q

What does recent evidence suggest about phototropins and pinoids

A

Phototropins may only effect pinoid activity and pin activity in pulse induced phototropism (short bursts of light) with another independent mechanism able to operate on continuous light

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72
Q

How is auxin involved in geotropic responses and how was it discovered

A

Auxin accumulates on lower side of roots lying flat where it inhibits cell elongation, upper side continues to grow and roots bend downwards, auxin promotes cell elongation on lower side making root lying flat bend upwards

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73
Q

Why does auxin cause different geotropic responses root and shoot

A

Root and shoot cells in elongation zone exhibit different responses to same concentration of auxin

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74
Q

What does the concentration of auxin that stimulates shoot growth so to root growth

A

Inhibits it

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75
Q

What are artificial auxins used for

A

To stop leave and fruit drop and promote flowering in commercial flower production, but high concentration of auxin can promote fruit drop

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76
Q

When is it useful for auxin to promote fruit drop

A

If too many small fruit that are be difficult to sell, auxin causes plant to grow fewer larger fruits

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77
Q

What is a commercial use for auxin in taking cuttings

A

Dipping end of cuttings in rooting powder before planting encourages root growth , rooting powder has auxin and so does talcum powder

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78
Q

What is a commercial use for auxin in seedless fruit

A

Treating unpollinated flower with auxin can promote seedless fruit growth, applying auxin promotes ovule growth causing production of auxins by tissues in developing fruit helping to complete development

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79
Q

What is a commercial use for auxin in herbicides

A

Auxins used as herbicides to kill weeds as they’re man made, plants find them more difficult to breakdown and can act within plant for longer promoting shoot growth so stem can’t support itself, buckles and dies

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80
Q

What do cytokinins do in commercial uses

A

Delay leaf senescence and used to stop yellowing of lettuce leaves after picking, used in tissue culture to mass produce plants

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81
Q

How is cytokinins used in mass production of plants

A

They promote bud and shoot growth form small pieces of tissue from parent plant, producing short shoot with many side branches that can be split to lots of small plants each grown separately

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82
Q

How are gibberellins used in artificial fruit production

A

Delay senescence in citrus fruits extending time fruit can be left unpicked and last shipping, if acting with cytokinins they can elongate apples to improve their shape, grape stalks elongate so less compact and grapes grow bigger

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83
Q

How are gibberellins used in brewing

A

When barley seed germinates aleurone layer of seed produces amylase that breaks starch to maltose and adding gibberellins speeds up process and then malt can be produced by drying and grinding seeds

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84
Q

How are gibberellins used in sugar production

A

Spraying sugar cane with gibberellins stimulates growth between nodes so stem elongates which is useful as cane sugar stores sugar in cells of internodes making more sugar available from each plant

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85
Q

How are gibberellins used in plant breeding

A

Nbl

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86
Q

What is the aim of plant breeding

A

To produce plant with desired characteristics by breeding plants over many generations

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87
Q

How are gibberellins used in plant breeding (increase production)

A

Speed up process by enduring seed formation in young trees

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88
Q

What are commercial uses for stopping gibberellins

A

Keeps flowers short and stocky and ensures internodes of crop plants stay short preventing lodging (occurs when wet stems bend over as weight of water collects on ripening seed head making crop hard to harvest

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89
Q

What is ethene and what does it mean if it’s commercial use

A

It’s a gas so can’t be directly sprayed but scientists developed a form of it which can be sprayed, is easily absorbed and slowly releases ethene inside plant

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90
Q

What are commercial uses of ethene

A

Speeding up Fruit ripening, promote fruit drop in cotton, cherry and walnut, promote female sex expressions in cucumbers, reducing self pollination and increasing yield, promotes lateral growth in some plants, yielding compact flowering stems

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91
Q

What is restricting ethene effect useful for

A

Storing fruit at low temp with little oxygen and high CO2 stops ethene synthesis and fruit ripening so fruit stored for longer (banana shipped from Caribbean) and also it can increase shelf life of cut flowers

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92
Q

Why do organisms require communication system

A

To response to external and internal environment to survive and need communication system to respond

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93
Q

What do all communication systems need to enable

A

Detection of change in environment, cell signalling between body parts, coordination of range of effectors to carry out responses to sensory input, enable suitable response

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94
Q

What may a rapid and well coordinated response involve

A

Coordinated muscle action, control of balance and posture, temp regulation and coordination with endocrine system (role of nervous system)

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95
Q

What are the 2 main categories the nervous system is divided into

A

Peripheral nervous system and central nervous system

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96
Q

What is the peripheral nervous system divided into

A

Sensory system and motor system

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97
Q

What is central nervous system divided into

A

Brain and spinal cord

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98
Q

What is the motor system subdivided into

A

Somatic nervous system and autonomic nervous system

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99
Q

What do most of the brains pathways rely on

A

Neurones which have multiple connections enabling complex neural pathways

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100
Q

What are most cells in the central nervous system (brain) and what are they called

A

Non-myelinated cells and tissue looks grey in colour (grey matter)

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101
Q

What is grey matter part of in spinal cord

A

Non-myelinated relay neurones

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102
Q

As well as grey matter what does spinal cord also contain large amount of

A

Myelinated neurones making outer region of white matter

103
Q

What is myelinated neurones role in spinal cord

A

Carry action potentials up and down spinal cord for rapid communication of longer distances

104
Q

What protects spinal cord and what is between each section of it

A

Protected by vertebral column, between each vertebrae peripheral nerves enter and leave spinal cord carrying action potentials to and from rest of the body

105
Q

What is the role of peripheral nervous system

A

Ensures rapid communication between sensory receptors, CNS and effectors

106
Q

What is peripheral nervous system composed of

A

Sensory and motor neurones that are usually bundled together in a connective tissue sheath to form nerves

107
Q

What are sensory fibres that enter CNS

A

Dendrons of sensory neurones

108
Q

What do dendrons of sensory neurones conduct

A

Action potentials from sensory receptors into CNS

109
Q

What is sensory neurone structure

A

Neurones have cell body in dorsal root leaving to spinal cord and short axon connecting to other neurones in CNS

110
Q

What does the motor nervous system do

A

Conducts action potentials from CNS to effectors and subdivided according to function of motor nerve

111
Q

What does somatic nervous system consist of

A

Motor neurones that conduct action potentials from CNS to effectors, that are under voluntary control like skeletal muscles, these are mostly myelinated so rapid response and always single motor neurone connecting CNS to effector

112
Q

What does the autonomic nervous system consist of

A

Motor neurones that conduct action potentials from CNS to effectors that aren’t under voluntary control, including glands, cardiac muscle and smooth muscle in blood vessel walls, airways and digestive system walls, control of many of these effectors don’t require rapid response and most non-myelinated neurones, atleast 2 neurones involved in connection between CNS and effectors, these neurones connect at small swellings called ganglia

113
Q

How does autonomic nervous system mostly operate

A

Independently of conscious control

114
Q

What is autonomic nervous system responsible for

A

Controlling majority of homeostatic mechanisms and so plays vital role in regulating internal environment of body

115
Q

What is autonomic nervous system subdivided into and what is each of its roles

A

Sympathetic nervous system (prepares body for activity), parasympathetic nervous system (conserves energy)

116
Q

What are parasympathetic and sympathetic nervous systems to each other

A

Antagonistic systems as action of 1 system opposes action of another

117
Q

At rest how to para and sympathetic nervous systems work

A

Action potentials travel along neurone at low frequency and controlled by subconscious of brain

118
Q

What is structure of sympathetic NS

A

Has many nerves leading out of CNS, each leading to different effector

119
Q

What is structure of parasympathetic NS

A

Has few nerves leading out of CNS which divide up and lead to different effectors

120
Q

What are other structural feature of sympathetic NS

A

Ganglia just outside CNS, short pre-ganglionic neurones, noradrenaline neurotransmitter, increase activity, most active in stress

121
Q

Other structural features of parasympathetic NS

A

Ganglia in effector tissue, long pre-ganglionic neurones, acetylcholine neurotransmitter, decreases activity, most active in sleep or relaxation

122
Q

What are effects of sympathetic NS

A

Increase HR and ventilation rate, dilates pupils, reduces digestive activity, orgasm

123
Q

Effects of parasympathetic NS

A

decrease HR and ventilation rate, constructs pupils, increase digestive activity, sexual arousal

124
Q

What are 4 main parts of brain

A

Cerebrum, cerebellum, hypothalamus/pituitary complex, medulla oblongata

125
Q

What is cerebrum

A

Largest part of brain and organises most of higher thought processes like unconscious thought and memory

126
Q

What is cerebellum

A

Coordinates movement and balance

127
Q

What is hypothalamus/pituitary complex

A

Organises homeostatic response and controls various psychological processes

128
Q

What is medulla oblongata

A

Coordinates many autonomic responses

129
Q

How is the cerebrum divided

A

Has 2 hemispheres connected via major tracts of neurones called corpus callosum

130
Q

What is the outermost layer of cerebrum

A

Consists of thin layer of nerve cell bodies called cerebral cortex

131
Q

How high brain functions does cerebrum control

A

Conscious thought, conscious actions, emotional responses, intelligence, reasoning, judgement, decision making, factual memory

132
Q

How is cerebral cortex subdivided

A

Subdivided into areas responsible for specific activity or body region: sensory area, association area, motor area

133
Q

What is sensory area in cerebral cortex

A

Receive action potentials indirectly from sensory receptors, size of region allocated to receive input from different receptors age related to sensitivity of areas that input received form

134
Q

What are association area in cerebral cortex

A

Compare sensory inputs with previous experience, interpret what input means and judge appropriate response

135
Q

What are motor areas in cerebral cortex

A

Send action potentials to effectors (muscles and glands), sizes of regions allocated to deal with different effectors related to complexity of movements needed in body, motor areas on left side of brain control effectors on right side of body and vice versa

136
Q

What does cerebellum contain and involved in

A

Contains over half of all neurones in brain, involved with balance and fine coordination of movement, for this must receive info from many sensory receptors and process info accurately

137
Q

What are examples of sensory receptors that supply cerebellum info

A

Retina, balance organs in inner ear, spindle fibres in muscles which give info about muscle length and joints

138
Q

Where is conscious decision to contract voluntary muscles initiated

A

Cerebral cortex but cerebral cortex doesn’t provide complex signals required to coordinate complex movements

139
Q

What does cerebellum coordinate and give examples

A

Fine control of muscular movements like maintaining body position and balance, like cycling (judging positive of objects which moving body) and coordinating contraction and relaxation of antagonistic skeletal muscles when walking

140
Q

What does fine control by cerebellum often require first

A

Learning and once learnt becomes second nature and involved in unconscious control to coordinate needs of complex nervous pathways which are strengthened by practice

141
Q

What becomes programmed into cerebellum

A

Complexity of activity and neurones from cerebellum conduct action potentials to motor areas, so motor output to effectors can be finely controlled

142
Q

How are cerebrum and cerebellum connected

A

By pons

143
Q

What does hypothalamus control

A

Homeostatic mechanisms in body, it contains own sensory receptors and acts by negative feedback to maintain constant internal environment

144
Q

How does temp regulation work in hypothalamus

A

Hypothalamus detects change in body temp and receives sensory input from temp receptors in skin which will imitate responses to temp change that regulate body temp in narrow range, these responses may be mediated by nervous system or hormonal system via pituitary gland

145
Q

How is osmoregulation controlled by hypothalamus

A

Hypothalamus contains osmoreceptors that monitor water potential in blood, when water potential changes osmoregulatory centre initiates response to reverse change, response mediated by hormonal system via pituitary gland

146
Q

What does the pituitary gland and in conjunction with and what are its 2 lobes

A

Conjunction with hypothalamus and posterior lobe and anterior lobe

147
Q

What is posterior lobe of pituitary gland

A

Linked to hypothalamus by specialised neurosecretory cells, hormones like ADH manufactured in hypothalamus pass down neurosecretory cells and released into blood from pituitary gland

148
Q

What is anterior lobe of pituitary gland

A

Produces own hormones released into blood in response to releasing factors produced by hypothalamus to pituitary, hormones from anterior pituitary control many physiological processes in body like response to stress, growth, reproduction and lactation

149
Q

What does medulla oblongata control

A

Non-skeletal muscles by sending action potentials out through autonomic nervous system

150
Q

What does medulla oblongata contain

A

Centres for regulating several vital processes like cardiac centre regulates HR, vasomotor centre regulates circulation and BP, respiratory centre controls rate and depth of breathing

151
Q

How do the centres in medulla oblongata work

A

They receive sensory info and coordinate vital functions by negative feedback

152
Q

What are reflex actions

A

Responses to changes in environment that don’t involve any processing in brain to coordinate movement

153
Q

Why is nervous pathway short as possible

A

So reflex is rapid

154
Q

What 3 neurones do reflex pathways have

A

Sensory, relay, motor,

155
Q

What is the brains involvement in reflex action

A

Aware it’s happening but not involved in coordination

156
Q

What is the purpose of reflex actions

A

Survival value, reflex used to get out of danger, stop damage to body and used to maintain balance

157
Q

What do reflex actions include

A

Blinking reflex and knee jerk reflex

158
Q

What is the blinking reflex

A

Causes temporary closure of eyelids to protect eye from damage

159
Q

How does blinking reflex work

A

Passes through part of the brain, reflex is a cranial reflex but doesn’t involve thought and since receptors and effectors in same place it’s a reflex arc

160
Q

What sudden environment changes stimulate blinking reflex

A

Foreign object touching eye (corneal reflex), bright light (optical reflex), loud noise, sudden movement close to eye

161
Q

What is corneal reflex mediated by

A

Sensory neurone in cornea, when it enters pons, synapse connects sensory neurone to relay neurone which passes action potential to motor neurone, motor neurone passes back out of brain to facial muscles causing eyelid to blink

162
Q

Why is the corneal reflex quick and what does it cause

A

It is short, and usually causes both eyelids to close

163
Q

In corneal reflex where does sensory neurone pass action potential to

A

Myelinated neurones in pons which carry action potential to sensory region in cerebral cortex to inform higher centres of brain that stimulus occurred (reflex can be overridden by conscious control)

164
Q

What do high parts of the brain do in corneal reflex if it want reflex inhibited

A

Send inhibitory signals in motor centre in pons, myelinated neurones carrying signals to/from cerebral cortex transmit action potentials more rapidly than non-myelinated relay neurones in pons, so, inhibitory action potentials can stop formation of action potential in motor neurone

165
Q

What is purpose of optical reflex

A

Protects light sensitive cells from retina damage

166
Q

How does optical reflex work

A

Stimulus detected by retina and reflex mediated by optical centre in cerebral cortex

167
Q

Is optical or corneal reflex faster

A

Corneal is faster

168
Q

What is knee jerk reflex

A

Spinal reflex, nervous pathway passes spinal cord not brain

169
Q

What is knee jerk involved in

A

Reflex involved in coordination movement and balance

170
Q

How does knee jerk reflex work

A

Quadriceps contract to straighten leg and this muscle attaches to lower leg by patella tendon that connects patella to lower leg bones at front of knee, when muscle at front of knee stretch specialised stretch receptors detect increase in muscle length, and if stretch unexpected reflex action causes contraction of muscle

171
Q

What happens when we stand still in knee jerk reflex

A

Muscle in front of thigh will stretch if knee bends or body leans back, contraction of muscle straightens knee or brings body back upright, response must be rapid so body stays balanced

172
Q

How many neurones does knee jerk pathway have and what are they

A

Sensory neurone and motor neurone (2)

173
Q

How are high parts of brain involved in knee jerk action

A

It’s informed of reflex but as no relay neurone the reflex can’t be inhibited

174
Q

What does inhibition of knee jerk reflex need

A

Rapid myelinated neurones passing inhibitory action potentials to synapse before motor neurone stimulated, in absence of relay neurone, motor neurone stimulated directly by sensory neurone and insufficient delay to enable inhibition

175
Q

How does knee jerk reflex work when walking and running

A

Knee must bend and will stimulate muscle spindles but complex patterns of nervous impulses coming from cerebellum can inhibit reflex contractions, as action potentials sent to hamstring stimulating it to contract, inhibitory action potentials sent to synapse in reflex arc to prevent reflex contractions of opposing muscles

176
Q

What do mammals complex sensory mechanisms do

A

Monitor changes in internal and external environment which provide input to brain which assimilates inputs and coordinates response for survival

177
Q

What may input include info about to the brain

A

Blood glucose from islets of langerhans, info from stretch receptors in stomach or pain receptors in joints and skin

178
Q

Are response to internal/external environment short or long term

A

Both, short like homeostatic mechanisms or long like reproduction behaviour

179
Q

How many the brain coordinate responses through output to effectors

A

Action potentials in somatic NS, action potentials in para/sympathetic parts of autonomic NS, causing release of hormones via hypothalamus and pituitary gland

180
Q

What is fight or flight response

A

Detecting threat to survival stimulated this response and leads to physiological changes so mammal prepares for activity

181
Q

What are physiological changes with fight or flight

A

Pupils dilate, HR/BP rises, vasoconstriction, blood glucose increases, metabolic rate increase, erect pili muscle in skin contact, ventilation rate increases, endorphins released in brain

182
Q

What is purpose of dilated pupils in fight or flight

A

More light enters eye making retina more sensitive

183
Q

What is purpose of increased HR/BP in fight or flight

A

Increased blood flow to deliver more oxygen and glucose and remove CO2 and toxins

184
Q

What is purpose of increased HR and BP in fight or flight

A

More blood flow to deliver oxygen and glucose and removal of CO2 and toxins

185
Q

What is purpose of vasoconstriction in fight or flight

A

Diverts blood flow from skin and digestive system to muscles

186
Q

What is purpose of increased blood glucose in fight or flight

A

Supplies energy for muscular contractions

187
Q

What is purpose of increased metabolic rate in fight or flight

A

Converts glucose to ATP

188
Q

What is purpose of erect pili muscles on skin contract in fight or flight

A

Makes hair stand up

189
Q

What is purpose of increased ventilation rate in fight or flight

A

Increases gaseous exchange so more oxygen in blood for aerobic respiration

190
Q

What is purpose of endorphins released in brain in fight or flight

A

Wound inflicted on mammal don’t prevent activity

191
Q

How is fight or flight coordinated

A

Receptors that detect external threat (eyes, ears, nose), internal receptors may also detect threat (pain or sudden increase/decrease in blood pressure) and cerebrum uses this to coordinate response

192
Q

What is the 4 steps to coordination of fight or flight

A

1.input feeds into sensory centres in cerebrum 2.cerebrum passes signal to associated centres 3.if threat recognised cerebrum stimulates hypothalamus 4.hypothalamus increases activity in sympathetic NS and stimulates release of hormones from anterior pituitary gland

193
Q

What does autonomic nervous system control

A

Physiological mechanisms

194
Q

What does increasing stimulation of sympathetic nervous system increase

A

Effector activity but nervous communication used for rapid responses not prolonged response

195
Q

If fight or flight from danger needs a prolong response how does it work

A

Endocrine system, sympathetic nervous system stimulates adrenal medulla so adrenaline released and has wide range of effects on cells

196
Q

What is adrenaline

A

A first messenger, it’s an amino acid derivative so can’t enter target cells and must cause effect inside cell without entering it

197
Q

What is the 3 steps of adrenaline mechanism of action

A

1.adrenaline binds to adrenaline receptors on plasma membrane, receptor associated with G protein on inner surface of plasma membrane which is stimulated to activate enzyme adenyl cyclase 2.adenyl cyclase converts ATP to cyclic AMP which is 2nd messenger inside cell 3.cAMP causes effect inside cell by activating enzyme action precise effect depends on cell adrenaline bound to

198
Q

What does the hypothalamus secrete into blood and what happens next

A

Secretes releasing factors which pass down portal vessel to pituitary gland and stimulate release of tropic hormones from anterior pituitary gland (stimulates activity in many endocrine glands)

199
Q

What is corticoteopin

A

Releasing hormone from hypothalamus which causes release of adrenocorticotropic hormone (ACTH) which passes around blood system and stimulates adrenal cortex to release hormones like cortisol causing more glucose to be released from glycogen stores or fat and protein stires

200
Q

What does thyrotropin releasing hormone cause

A

Causes release of thyroid stimulating hormone which stimulates thyroid gland to release more thyroid hormone (thyroxin) which acts on almost all body cells, increasing metabolic rate and making cells more sensitive to adrenaline

201
Q

What important roles does the heart pumping blood round circulatory system have

A

Transport of oxygen and glucose, fatty acids and amino acids to tissue, removal of waste like CO2 to prevent toxic accumulation, transport of urea from liver to kidneys, distribute heat round body or to skin to be radiated away

202
Q

What do requirements of cell and tissue vary on

A

Levels of activity, when physically active muscles need more oxygen and glucose to respire more releasing energy for contraction

203
Q

How does the circulatory system control heart activity

A

Raising/lowering heart rate, altering force of contractions, altering stroke volume (volume of blood pumped per beat)

204
Q

How is the heart muscle myogenic

A

Can initiate it’s own contractions

205
Q

WhT has high myogenic rate, atrial or ventricular muscle

A

Atrial muscle

206
Q

How does heart coordinate contractions

A

Hearts pacemaker (SAN) initiates wave of excitation that overrides myogenic action of cardiac muscle, SAN initiates action potential which travels over atrial walls through AVN and down purkyne fibres to ventricle walls causing contraction

207
Q

What in blood causes heart rate to increase

A

Adrenaline

208
Q

At rest what controls heart rate

A

SAN, but frequency of excitation waves are altered by output from cardiovascular centre in medulla oblongata

209
Q

What do nerves from cardiovascular centre in medulla oblongata supply

A

SAN, these nerves are part of autonomic NS, nerves don’t initiate contraction but affect contraction frequency

210
Q

How do nerves in cardiovascular centre in medulla oblongata control frequency of contractions

A

Action potentials sent down sympathetic nerve cause release of noradrenaline at SAN, increasing HR, action potentials sent down vagus nerve release acetylcholine, reducing HR

211
Q

How do environmental factors impact HR

A

Input from sensory receptors fed to cardiovascular centre in medulla oblongata, interaction of inputs coordinated by cardiovascular centre to ensure output to SAN appropriate

212
Q

What do sensory input to cardiovascular centre include

A

Stretch receptors in muscles, chemoreceptors in carotid arteries, concentration of CO2 in blood, stretch receptors in walls of carotid sinus monitor BP

213
Q

How is stretch receptors in muscle input to cardiovascular centre

A

Detect limb movement, send impulses to cardiovascular centre informing it extra oxygen may be needed causing increased heart rate

214
Q

How is chemoreceptors in carotid arteries input to cardiovascular centre

A

Aorta and brain monitor blood pH, when we exercise muscles produce more CO2, some reacts with water in blood plasma producing carbonic acid reducing blood pH affecting oxygen transport, change detected by chemoreceptors which send action potentials to cardiovascular centre increasing HR

215
Q

How is concentration of CO2 in blood input to cardiovascular centre

A

When stop exercising CO2 concentration in blood drops reducing activity of accelerator pathway so HR falls

216
Q

How is stretch receptors in walls of carotid sinus input to cardiovascular centre

A

They monitor BP, carotid sinus is small swelling in carotid artery increasing BP, in exercise if pressure to high change detected and stretch receptors send action potentials to cardiovascular centre reducing HR

217
Q

What happens when mechanism for controlling heart rate fails

A

Artificial pacemaker must be fitted, pacemaker delivers electrical impulses to heart muscle and placed under skin and fat on chest, it’s either connected to SAN or directly to ventricular wall

218
Q

How are muscles composed

A

Cells arranged to form fibres which can contract become shorter producing a force

219
Q

How are muscle contractions achieved

A

By interactions between protein filaments actin and myosin in muscle cells

220
Q

How do muscles elongate

A

With antagonistic pair, so muscles usually arranged in opposite pairs, 1 contracts as other elongates (antagonist may be elastic recoil or hydrostatic pressure in a chamber)

221
Q

What are 3 types of muscle

A

Involuntary smooth muscle and cardiac muscle and voluntary skeletal muscle

222
Q

What is involuntary smooth muscle structure

A

Individual cells tapered at both ends (spindle shape), each cell has nucleus and bundles of actin and myosin,

223
Q

WhT are 2 layers of smooth muscle

A

Circular layer runs round intestines and contraction causes segmentation, longitudinal layer runs along intestines causing wave like contractions

224
Q

What is muscle contraction of smooth muscle like and where is it found

A

Slow and regular, doesn’t tire quickly and controlled by autonomic NS, found in walls of tubular structures and longitudinal and circular layers oppose each other

225
Q

What is structure of cardiac muscle

A

Individual cells form long fibres which branch forming cross bridges between fibres to help ensure electrical stimulation spreads evenly over walls of chambers

226
Q

How does cardiac muscle structure help contractions

A

Structure means contraction is squeezing action, cells joined by intercalated discs (specialised cell surface membranes fused to produce gap junctions allowing free diffusion of ions between cells, action potentials pass easily and quickly along and between cardiac muscle fibres

227
Q

How does cardiac muscle contact

A

Contracts and relaxes continuously through life and doesn’t fatigue easily and contracts powerfully

228
Q

How are purkyne fibres modified for cardiac muscle contractions

A

Carry electrical impulses to coordinate contraction of chamber walls, heart muscle is myogenic but contraction rate controlled by SAN

229
Q

How does cardiac muscle look under microscope

A

Striated

230
Q

What is voluntary skeletal muscle

A

Found at joints and contraction causes movement of skeleton by bending and straightening joint

231
Q

Structure of skeletal muscle

A

Arranged in antagonistic pairs, each fibre is multinucleate and surrounded by membrane called sarcolemma, muscle cell cytoplasm called sarcoplasm and cells have many mitochondria and extensive sarcoplasmic reticulum

232
Q

How are skeletal muscle fibres arranged

A

Into many myofibrils which are contractile elements, myofibrils divided into subunits called sarcomeres which have protein filaments myosin and actin arranged into patterns giving striated appearance

233
Q

How does skeletal muscle contact

A

Powerfully and quickly but fatigues easily

234
Q

What are skeletal muscle contractions stimulated by

A

Somatic nervous system, junctions between nervous system and muscle called neuromuscular junction (similar to synapse)

235
Q

What are the 5 steps to stimulation of contraction of voluntary skeletal muscle

A

1.action potential arriving at axon terminal opens calcium ion channels in membrane and calcium ions flood into axon end 2.vesicles of acetylcholine move to and fuse with end of membrane 3.acetylcholine diffuse across gap and fuse with receptors in sarcolemma 4.opens sodium ion channel allowing sodium ions to enter muscle fibre, causing depolarisation of sarcolemma 5.wave of depolarisation spreads along sarcolemma and down transverse tubules into muscle fibre

236
Q

What do motor neurones do in stimulating muscle contraction

A

Some stimulate single muscle fibres but many motor neurones divide and connected to several muscle fibres, all these muscle fibres contract together providing stronger contraction called motor unit

237
Q

What are myofibrils

A

Contractile units of skeletal muscle

238
Q

What are 2 types of protein filaments and myofibrils

A

Thin filaments lined up to make up light band held together by Z line, thick filament which make dark band, thick and thin filaments overlap but in middle of dark band no overlap (H zone), distance between 2 Z lines called sarcomere (functional unit of muscle), thick and thin filament surrounded by sarcoplasmic reticulum

239
Q

What are thin filaments myofibrils

A

Composed of actin, each filament has 2 chains of actin subunits twisted round each other, wound around a molecule of tropomyosin to which globular molecules of troponin attached

240
Q

How many polypeptides does each troponin complex have

A

3 polypeptides, 1 binds to actin, 1 to tropomyosin and 3rd binds to calcium when it’s available

241
Q

What are tropomyosin and troponin in thin filaments part of

A

Mechanism to control muscular contractions, at rest these molecules cover binding sites to which thick filaments can bind

242
Q

What is thick filament structure

A

Each thick filament has Bundle of myosin molecules, each myosin has 2 protruding heads which stick out at each end of molecule, these heads are mobile and can bind to actin when binding sites exposed

243
Q

What is sliding filament hypothesis

A

During contraction light band and H zone get shorter so Z lines move closer together and sarcomeres get shorter, during contraction thick and thin filaments side past one and other

244
Q

What is sliding action of thin and thick filaments caused by

A

Movement of myosin heads, when muscle stimulated tropomyosin moved aside, exposing binding sites on actin, myosin heads attach to actin and move causing actin to slide past myosin

245
Q

What are the 6 steps to controlling muscle contraction

A

1.when muscle stimulated action potential passes along sarcolemma and down transverse tubules into muscle fibre 2.action potential carried to sarcoplasmic reticulum which stores calcium ions and causes release of calcium ions to sarcoplasm 3.calcium ions bind to troponin altering shape pulling tropomyosin aside exposing actin binding sites 4. Myosin heads bind to actin forming cross bridges between filaments 5. Myosin heads move pulling actin filament past myosin filament 6.myosin dead’s detach from actin and can bind again further up actin filament

246
Q

What do cross bridges form between

A

Actin and myosin filaments, and once contraction occurred, calcium ions rapidly pumped back into sarcoplasmic reticulum allowing muscle to relax

247
Q

How does ATP supply energy for contractions

A

Part of myosin head acts as ATPase and hydrolyses ATP to ADP and Pi releasing energy

248
Q

4 steps to Myosin head hydrolysing ATP to ADP and Pi

A

1.myosin head attaches to actin filament forming cross bridge 2.myosin head moves causing thin filament to slide past myosin filament (power stroke) during which ADP and Pi released from myosin head 3.after power stroke new ATP molecule attaches to myosin head breaking cross bridge 4.myosin head then returns to original position as ATP hydrolysed releasing energy to make this movement occur, myosin head can now make new cross bridge further along actin filament

249
Q

Why must ATP be constantly regenerated in skeletal muscles

A

Many myosin heads involved in contractions so huge need for ATP and ATP available in muscle tissue only enough to support 1sec of contraction

250
Q

What are 3 mechanisms involved in maintaining ATP supply

A

Aerobic respiration in mitochondria, anaerobic respiration in sarcoplasm of muscle tissue, creatine phosphate in sarcoplasm

251
Q

How does aerobic respiration in mitochondria regenerate ATP In skeletal muscles

A

Muscle tissue has lots of mitochondria for aerobic respiration, Bohr effect helps release more oxygen from haemoglobin into blood but in intense activity rate of ATP production limited by delivery of oxygen to muscle tissue

252
Q

How does anaerobic respiration in sarcoplasm of muscle tissue regenerate ATP In skeletal muscles

A

It releases a little more ATP from respiratory substrates but leads to production of lactate which is toxic, only lasts few seconds before lactic acid builds up and causes fatigue

253
Q

How does creatine phosphate in sarcoplasm regenerate ATP In skeletal muscles

A

It acts as reserve store for phosphate groups, phosphate can be transferred from creatine phosphate to ADP molecules creating ATP molecules rapidly, enzyme creatine phosphatransferase involved, supply of creatine phosphate supports muscle contraction by further 2-4secs

Alevel Biology (25 decks)

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