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OCR A level Biology > 5.1.5 - Plant & Animal Responses > Flashcards

5.1.5 - Plant & Animal Responses Flashcards

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1
Q

Nastic responses

A

Plant responses in which the direction of the plant response is independent of the stimulus

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2
Q

Herbivory

A

Consumption of plants

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3
Q

Abiotic

A

Physical

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4
Q

Tropisms

A

Directional growth responses in plants

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5
Q

Phototropisms

A

Influenced by light e.g. plants grow towards light to photosynthesise due to auxin moving unilaterally

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6
Q

Geotropism

A

Influenced by gravity
Plants recieve unilateral gravitational stimulus (downwards)
Shoots are -vely geotropic and roots are +vely geotropic

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7
Q

Thigmotropism

A

Influenced by touch

Shoots of climbing plants e.g. ivy winding around other plants or solid structures for support

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8
Q

Chemotropism

A

Influenced by chemicals

Pollen tubes grow down the style of a plant towards the ovary where fertilisation takes place

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9
Q

Plant hormones

A 
Cytokinins
Abscisic acid (ABA)
Auxins
Giberellins 
Ethene
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10
Q

Effects of cytokinins

A

Promote cell divison
Delay leaf senescence - increases shelf life
Overcome apical dominance - lateral growth
Promote cell expansion

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11
Q

ABA

A

Inhibit seed germination and growth
Stimulate cold protective responses
Cause stomatal closure when the plant is stressed by low water availability

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12
Q

Effect of auxins

A

Promote cell elongation in roots - low conc
Promote shoot growth/ demote root growth - high conc
Inhibit growth of side shoots
Inhibit leaf abscission
Selective weedkiller
Promote cell division in cambium

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13
Q

Effect of gibberellins

A

Promote seed germination - break bud dormancy (works against ABA)
Promote growth of stems - elongation of internodes
Develop seedless fruit and fruit setting
Acts synergistically w/ auxin

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14
Q

Effect of ethene

A

Promote fruit ripening - starch to sugar and breaks down chlorophyll and cell wall
Stimulates cells in abscission zone to expand and breaks cell wall causing leaf to fall off
Opp to auxin

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15
Q

How do plants avoid herbivores

A

Tannins - phenolic compounds; toxic to herbivores and microorganisms
Alkaloids - make plants taste bitter
Mimosa leaves fold up in response to touch - scares insects

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16
Q

Abscission in deciduous plants

A

Decreases production of auxin
More sensitive to ethene
Gene expression of enzymes in abcission zone
Cellulase breaks down cell walls in separation layer of abscission zone
Vascular bundles sealed off, fatty materials for neat, waterproof scar

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17
Q

Mechanism of seed germination

A

Seed absorbs H2O and activates embryo
Begins to produce gibberellins
Gene expression –> produces amylases and proteases to break down starch food stores
Glucose is used as a respiratory substrate and in protein synthesis

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18
Q

Mechanism of stomatal closure

A 
Levels of soil water falls
Roots produce ABA
Transported and binds to guard cells 
Increases pH, charged particles move out 
Increases wp, water moves out 
Loss of turgor closes stoma
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19
Q

Proof of gibberellins causing seed germination

A

Mutant varieties that lack gibberellin do not germinate but w/ external gibberellin they do
When gibberellin inhibitors are addeed to normal seeds they dont grow

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20
Q

Apical Dominance Effect

A

Auxin produced at the apex, inhibits growth of lateral buds

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21
Q

Experimental evidence for apical dominance

A

Removal of apical buds allows lateral bud to grow
Auxin/synthetic auxin placed on cut tip continues to inhibit the growth of side shoots

Plant 30 plants of same type, age, genotype and weight in same soil
Remove tip of 10 and apply auxin paste
Remove tip of another 10 and add paste w/out auxin
Leave last 10 as control
Sig. increase of no. of side shoots grown in first 10

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22
Q

Recent research on apical dominance

A

Auxin stimulates production of ABA (inhibits growth)
When apex is removed as is the source of auxin, ABA levels decrease
Most cytokinins go to tip so when tip is removed cytokinins spread evenly around plant promoting growth

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23
Q

Where does growth occur in plants

A

Apical meristems

Lateral bud meristems

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24
Q

Mechanism of cell elongation by auxin

A 
Tip produces auxins, diffuses down 
Promotes active transport of H+ into cell walls
Lowers pH, optimum pH for expansins
Breaks H bonds within cellulose
Reduces rigidity and H2O enters
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25
Q

Confirming auxin as the hormone that causes growth

A

Impregnated agar blocks w/ diff conc. of auxin
Placed them on cut shoot tips
Same effects as in reg. shoots
Curvature is directly proportional to conc of auxin used

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26
Q

Research supporting geotropism in shoots

A

Plants are grown on a slowly rotating drum (clinostat) so gravitational stimulus is applied evenly
Plants grow straight in both light and dark

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27
Q

Research supporting geotropism in roots

A

Seeds are placed in petri dishes w/ moist cotton wool that are rotated 90 degrees as seedlings grow
Cover lid w/ oil - ensure no light is coming in
All petri dishes should be in same environment
Geotropic response in the roots can be seen every 2 hours

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28
Q

Investigating role of gibberellin in stem elongation

A

Plant 40 plants
Water 20 plants normally
Water other 20 w/ diluted solution of gibberellins
Let all 40 grow for 28 days, measuring height every 7
Calculate rate at which plants grew

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29
Q

IAA

A

Natural form of auxin responsible for +ve phototropism so plant bends towards light to phostosynthesise and grow taller and grows roots to reach water and nutrients
Light stimulus detected by tip of plant

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30
Q

Central nervous system

A

Brain and spinal cord
Mostly relay neurones in brain
Mostly non-myelinated in brain and myelinated in spinal cord

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31
Q

Role of peripheral nervous system

A

Ensure rapid comm between the sensory receptors, CNS and effectors

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32
Q

Divisions of PNS

A

Sensory nerous systems

Motor nervous system

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33
Q

Sensory nervous system

A

Neurons conduct action potentials from the sensory receptor into the CNS

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34
Q

Divisions of motor nervous system

A

Autonomic

Somatic

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35
Q

Somatic nervous system

A

Motor neurones that conduct action potentials to effectors that are under voluntary control e.g. skeletal muscles
Mostly myelinated neurones
One single motor neuone connecting CNS to effector

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36
Q

Autonomic nervous system

A

Motor neurones that conduct action potentials to effectors that arent under voluntary control e.g. cardiac muscles
Mostly unmyelinated neurones
At least two motor neurones involved - connected at ganglia

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37
Q

Divisions of autonomic nervous system

A

Sympathetic

Parasympathetic

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38
Q

Ganglia in sympathetic system

A

Outside CNS, near spinal cord

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39
Q

Ganglia in parasympathetic system

A

Closer to effector tissue

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40
Q

Neurones in sympathetic system

A

Short pre-ganglionic neurones

Long post-ganglionic neurones

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41
Q

Neurones in parasympathetic system

A

Long pre-ganglionic neurones

Short post-ganglionic neurones

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42
Q

Neurotransmitter in sympathetic system

A

Noradrenaline

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43
Q

Neurotransmitter in parasympathetic system

A

Acetylcholine

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44
Q

Four sections of the brain

A

Cerebrum
Cerebellum
Medulla Oblongata
Hypothalamus and pituitary complex

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45
Q

Cerebrum

A

Largest part of human brain
Two hemispheres connected by corpus callosum
Involved in control of speech and higher thought processes e.g. planning a task

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46
Q

Cerebral cortex

A

Highly folded
Outer part of cerebrum
Involved in higher thought e.g. overriding reflexes, conscious thought, intelligence and reasoning

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47
Q

What is the cerebral cortex divided into

A

Sensory areas - recieve impulses from sensory neurones
Motor areas - send impulses out to effectors
Association areas - link info and coordinate approriate respnse

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48
Q

Cerebellum

A

Controls muscular movement and balance
Connected to cerebrum by pons
Coordination of posture

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49
Q

Medulla oblongata

A

Controls involuntary processes e.g. heart rate and breathing rate
Has specialised centres that recieve info from internal receptors and adjust breathing and heart rate accordingly

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50
Q

Hypothalamus and pituitary complex

A

Organises homeostatic responses and controls various physiological processes
Info is recieved from hypothalamus and hormones are released via the pituitary gland (controls endocrine system)

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51
Q

Reflex reactions

A

Responds to changes in the environment but not involving the brain
Sensory –> relay –> motor
Brain may be informed but doesn’t coordinate
Survival; fast, involuntary and not learned (innate)

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52
Q

Cranial reflex

A

Nervous pathway passes through the brain

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53
Q

What makes something an reflex arc

A

Receptor and effector in same place

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54
Q

Blinking reflex

A

Cranial reflex
Corneal - object toucing eyes
Optical - Light hitting back of eye (retina)

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55
Q

Patnway for corneal blinking reflex

A

Receptor
Sensory neurone on cornea
Sensory centre on pons
Non-myelinated relay neuron passes action potential to motor neurone
Motor neurone passes out of brain to facial muscles

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56
Q

If the corneal blinking reflex is to be overridden

A

Sensory neurone on cornea
Myelinated relay neurones inform brain
Allows reflex to be overriden (inhibitory neurone) - faster so reflex can be overriden before it happens

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57
Q

Knee-jerk reflex

A

Spinal reflex
Unexpected stretching of quadraceps –> detected by muscle spindles –> causes a reflex reaction (no relay neurone) –> quadraceps contract

58
Q

Spinal reflex

A

Involves the spinal chord rather than the brain

59
Q

Muscle spindles

A

Stretch receptors that detect increase in muscle length

60
Q

Class of hormones

A

Steroid - produced in reproductive organs and adrenal cortex
Peptide - insulin, ADH, adrenaline

61
Q

Hypothalamic - anterior axis

A

Hypothalamus releases hormones (releasing factors)
Pass down a portal vessel to anterior pituitary gland
Anterior pituitary gland releases tropic hormones e.g. for thyroid and adrenal

62
Q

Tropic hormones

A

These stimulate other endocrine glands

63
Q

Mechanism of steroid hormones

A

Steroid hormone combines w/ steriod receptor in cytoplasm
Hormone-receptor complex enters nucleus
Complex binds to receptor sites on DNA, activating mRNA transcription
mRNA leaves nucleus
Ribosome translates mRNA into new protein in cytoplasm

64
Q

Mechanism of peptide hormones

A

Adrenaline in the blood binds to membrane bound receptor
Stimulates G-protein to activate Adenyl cyclase
Converts ATP to cAMP
cAMP acts as second messenger by moving into the cell cytoplasm and causing an effect

65
Q

Thyroxin

A

Increases metabolic rate in most cells

66
Q

How is thryoxin released

A

Hypothalamus releases TRH
Travels to anterior pituitary gland and releases TSH
Travels to thyroid through portal vessel and releases thyroxine

67
Q

TRH

A

Thyrotropin releasing hormone

68
Q

TSH

A

Thyroid stimulating hormone

69
Q

How are glucocorticoids (cortisol) released

A

Hypothalamus releases CRH
Travels to anterior pituitary gland and releases ACTH
Travels to adrenal cortex through portal vessel and releases cortisol

70
Q

Cortisol

A

Released as a response to chronic stress

Stimlates breakdoen of glycogen

71
Q

Coordination of flight or fight

A

Sensory input
Action potential travels to sensory centres (cerebrum)
Signals passed to association areas
If a threat is recognised, cerebrum stimulates hypothalamus
Hypothalamus stimulates symapthetic nervous system and stimulates release of hormones from anterior pituitary gland

72
Q

How is the fight or flight response formed

A

Hypothalamus activates sympathetic nervous system
Impulses activate glands and smooth muscle
Activated adrenal medulla
Secretion of adrenaline into the bloodstream
Hypothalamus also secretes releasing factors e.g. CRH and TRH

73
Q

CRH

A

Corticotropic releasing hormone

74
Q

ACTH

A

Adrenocorticotropic hormone

75
Q

Physiological changes in fight or flight response

A

Pupils dilate - more light enters eyes, retina becomes more sensitive
Heart rate and bp increase
Ventilation depth and rate increases
Less digestion
Blood glucose increases
Metabolic rate increase - faster coversion of glucose to ATP
Endorphins released in brain
Erector pili muscles in the skin contract

76
Q

Why do erector pili muscles stand up in fight or flight response

A

Hairs/ fur stands up - signs of aggression

77
Q

Why are endorphins released in the fight or flight response

A

Wounds inflicted don’t prevent activity

78
Q

Why must plants be able to respond to their environment

A

Cope w/ changing conditions

Avoid antibiotic stress

79
Q

How does auxin cause cell elongation (2 marks)

A

Loosens rigid cellulose framework

Osmotic uptake of water allows cell elongation

80
Q

Why do cut plants w/ agar blocks w/ auxin placed on the rhs bend to the lhs

A

Auxin produced at tip
Diffuses laterally to rhs
Cells on rhs exhibit greater elongation
Bending to the left

81
Q

How does auxin act as a selective weedkiller

A

Rapid cell elongation so plant grows too quickly
No extra lignified tissue
Stem collapses or loss of extra water from leaves

82
Q

What happens when the apex is removed from a plant

A

Once apex is removed, auxin production stops
Apical dominance is stopped
Lateral growth is not inhibited and lateral buds develop

83
Q

Types of muscle

A

Skeletal (voluntary)
Cardiac
Involuntary (smooth)

84
Q

Voluntary (skeletal muscle)

A 
Striated 
Multinucleate 
Regularly arranged —> contraction in one direction 
Attached to bone by tendon 
Tubular 
Nerves from peripheral, somatic (rapid)
85
Q

Cardiac muscle

A

Specialised striated (parallel myofibrils)
Branched fibres
Uninucleated
Cross bridges allow simultaneous contraction
Dark bands - intercalated discs
Nerves from autonomic nervous system

86
Q

Involuntary (smooth muscle)

A

Non striated
Nerves from autonomic nervous system
No reg. arrangement - diff cells can contract in diff directions
Fibres are spindle shaped and uninucleated
Used in hollow organs (peristalsis)

87
Q

Sarcolemma

A

Plasma membrane that encloses bundles of muscle fibre

88
Q

Why may the sarcolemma fold in

A

Spread impulse throughout sarcoplasm

Contract at the same time

89
Q

Sarcoplasm

A

Shared cytoplasm within muscle fibres

90
Q

How are muscle fibres formed

A

Fusion of several embryonic muscle cells - gap between adjacent cells would be a weakness
(That’s why it’s multinucleate)

91
Q

Sarcoplasmic reticulum

A

Modified version of ER

Provides strength and stored Ca^2+

92
Q

Protein filaments

A

Myosin

Actin

93
Q

Muscle organisation

A 
Muscle 
Fascicles 
Muscle fibres 
Myofibrils 
Protein filaments
94
Q

Connective tissue

A

Tendons

95
Q

Light band (I)

A

Thin actin held together by Z line

96
Q

Dark band (A)

A

Both actin and myosin
Entire length of myosin
Myosin held together by M line

97
Q

M line

A

Midpoint of myosin

Has no heads

98
Q

Z line

A

Found at the centre of each light band

99
Q

Sarcomere

A

Functional unit of muscle
From one Z line to another
Sub unit of myofibrils

100
Q

Why is muscle considered a tissue

A

Muscle fibre
Blood vessels
Nerves
Connective cells

101
Q

Characteristics of sliding filament model

A

Z lines get closer
Sarcomeres shortens
I band narrows
H zone narrows

102
Q

What does simultaneous contraction of several sarcomeres allow

A

Myofibrils and then muscle fibres to contract —-> enough to pull a bone

103
Q

Neuromuscular junction

A

Action potential arriving at axon of motor neurone opens VG Ca2+ to flood into tip
Vesicles of acetylcholine to move towards membrane & fuse
Acetylcholine diffuses across synapse and binds to receptors on sarcolemma
Na+ channels open and wave of depolarisation passes down transverse tubules
Passes to SR which releases Ca2+ into the sarcoplasm

104
Q

Cross bridge muscle contraction cycle

A

Tropomyosin is blocking myosin binding site in actin
Ca2+ binds to troponin causing a conformational change, tropomyosin moves
Myosin heads bind to actin, forming cross bridges between filaments
Myosin heads move, pulling the actin filament. ADP and Pi are released during the power strike
A new ATP molecule attaches to myosin head, breaking cross bridge
ATP hydrolyses and myosin head returns to its orig. position

105
Q

Where does SR get Ca^2+

A

Active absorption from sarcoplasm

106
Q

Supply of ATP for muscular contraction

A

Aerobic respiration - oxidative phosphorylation
Anaerobic respiration - glycolysis
Glycogen —> glucose
Creatine phosphate can combine w/ ADP to form ATP

107
Q

Where is creatine phosphate found

A

Sarcoplasm

108
Q

Supply of energy of slow twitch muscle

A

Aerobic respiration

109
Q

Supply of energy for fast twitch muscle

A

Anaerobic respiration

110
Q

Where is the cardiovascular centre

A

Medulla oblongata - this alters the excitation wave frequency

111
Q

Frequency of heart excitation

A

60-80 bpm

112
Q

What is the heart rate regulated by

A

SAN

Nerves connect cardiovascular centre to the SAN

113
Q

Nerves involved in controlling heart rate

A

Accelerans

Vagus

114
Q

Accelerans

A 
Causes release of noradrenaline at SAN 
Increases HR (sympathetic)
115
Q

Vagus nerves

A

Causes release of acetylcholine at SAN, reduces HR (parasympathetic)

116
Q

Sensory inputs that increase HR

A

Increased muscle movement (muscle stretch receptors)
Decrease in pH (chemoreceptors)
Adrenaline in blood

117
Q

Sensory inputs that decrease HR

A

Increase in bp (stretch receptors - carotid sinus)

Decrease in dissolved CO2 (chemoreceptors)

118
Q

Why do plants kept in the dark grow taller than those in the light

A

Auxin is more present in the dark

119
Q

Plant growth substances vs animal hormones

A

Hormones travel faster in animals
Synthesised in endocrine glands vs cells sites
Slow acting in plants vs fast acting in animals

120
Q

Why is temp controlled in investigations on effect of plant hormones

A

So temp does not affect results as temp affects enzyme activity

121
Q

Why are monkeys used for human research

A

Closely related
Both primates
Similar physiology

122
Q

Actions of parasympathetic nervous system

A 
Increases blood flow to digestive system, allows peristalsis 
Decreases HR 
Decreases airway diameter 
Sexual arousal 
Constricts pupils
123
Q

Why is glycogen found in striated muscle

A

Glycogenolysis
Glucose can undergo glycolysis to produce ATP
Energy storage

124
Q

Uses of mitochondria in muscular contraction

A

ATP attaches to ATPase on the myosin head
Hydrolysis to release ADP and Pi during power stroke, allows myosin heads pull the actin filaments
Needed for myosin head to detach
Protein synthesis
Ca 2+ pumps in SR

125
Q

Internal organs affected by SNS/PNS

A

Heart
Lungs
Liver
Intestines

126
Q

How is the heart affected in the PNS/SNS

A

Slow HR vs. fast HR

127
Q

How are the lungs affected by the PNS/SNS

A

Shallow breaths vs deep breaths

128
Q

How is the liver affected by the PNS/SNS

A

Glucose take up (glycogenesis) vs glucose used up (glycolysis)

129
Q

How is the stomach affected by the PNS/SNS

A

More peristalsis vs. less

130
Q

How does the SNS affect smooth muscle

A 
Alters blood flow to increase bp
Vasoconstriction 
Peristalsis slows down 
Relaxes in airways (increases diameter)
Pupils dilate
131
Q

How does the SNS affect cardiac muscle

A

Heart beats faster

Beats w/ more force

132
Q

How does SNS affect voluntary muscles

A

Glycogenolysis in muscles for priming
Diaphragm contracting faster
More blood flow to skeletal muscle –> respiration

133
Q

Long term effects of chronic stress

A

Cardiovascular problems due to high bp

Suppression of immune system leads to susceptibility to disease

134
Q

Photoperiodism

A

Plants’ sensitivity to a lack of light, affects several diff plant responses e.g. flowering

135
Q

Phytochrome

A

Light sensitive pigment that affects the sensitivity of plants to light
Exists in two forms, Pt and Pft

136
Q

How do plants prevent freezing

A

Cytoplasm and vacuole contain sap that lowers the freezing point
Produce biological molecules (excluding lipids) to prevent cytoplasm freezing or protect cells from damage if they do freeze

137
Q

Commercial uses of plant hormones

A 
Ethene to control ripeneing 
Hormone rooting powders and micropropagation 
Auxin to produce seedless fruit 
Cytokinins to prevent aging 
Gibberellins to improve size and shape
138
Q

Transverse tubules

A

Extensions into sarcolemma

139
Q

Factors affecting stomatal closure

A

Temperature

Water availability

140
Q

How does increases in temp affect stomata

A

Release of ABA decreases
Stomata open
Allows plant to cool through water evaporation

141
Q

How does decrease in water availability affect stomatal

A

Increased release of ABA
Stomata close
Reduces water loss through transpiration

142
Q

How do gibberellins cause stem elongation

A

Promote cell elongation - by loosening cell walls

Promote cell division - producing proteins that control the cell cycle

OCR A level Biology (25 decks)

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