Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A level Biology > 5.5 plant and animal responses > Flashcards

5.5 plant and animal responses Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

define tropic

A

directional response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define nastic

A

Non directional response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why do plants respond to stimuilus

A

predation
growth
increase photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are three chemical defenses

A

tannins
alkaloids
pheromones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe tannins

A

toxic to microorganisms and larger herbivores and make the leaf taste bad

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe alkaloids

A

feeding deterrent as they taste bitter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe pheromones

A

chemicals which released by one individual can affect the behaviour or physiology of another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the different types of tropic response

A

Phototropism
geotropism
chemotropism
thigmotropism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define phototropism

A

Shoots grow towards light enabling them to photosynthesise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define geotropism

A

Roots grow towards pull of gravity anchoring them in soil and helps them take up water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define chemotropism

A

On a flower pollen tubes grow down the style attracted by chemicals in the ovary where fertilisation takes place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Define thigmotropism

A

Shoots of climbing plants such as ivy wind around other plants or solid structures to gain support

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Give an example of a nastic response

A

thigmonastic - response to touch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why are plant hormones called hormones if they dont come from a gland

A

The are chemical messengers specific to a tissue and receptor and initiate a response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the action of cytokinins

A

promote cell division and expansion
delay leaf senescence
overcome apical dominance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the action of abscisic acid

A

inhibit seed germination and growth
cause stomatal closure when water availability is low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the action of auxins IAA

A

Promote cell elongation
inhibit growth of lateral shoots
inhibit leaf fall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the action of gibberellins

A

promote seed germination and growth of stems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Give the action of ethene

A

Promote fruit ripening

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How do hormones move around the plant

A

active transport
diffusion
mass flow in sap or xylem vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Define apical dominance

A

inhibition of lateral buds further down the shoot by chemicals produced by the apical bud at the tip of a plant shoot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe the investigation into apical dominance

A

Auxin was applied to a cut shoot and lateral buds did not grow then auxin transport inhibitor was applied below the apex and lateral buds grew

The conclusion was that low levels of auxin promotes growth of lateral buds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What other chemicals are involved in apical dominance

A

Abscisic acid inhibits bud growth and high auxin levels keep abscisic acid levels high

Cytokinins promote bud growth and candirectly overcome apical dominance - when the apex is removed cytokinins spread around more evenly in the plant rather than all being in the tip

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the relationship between gibberellins and pea plants

A

Higher levels of GA1 in tall pea plant were homozygous dominant for the Le allele whereas the short plants where homozygous recessive

The Le gene was found to produce the enzyme which converted GA20 to GA1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the action of gibberellins in seed germination

A

When the seed absorbs water the embryo releases gibberellin which stimulates the production of amylase which breaks down starch into glucose for respiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What did Darwins experiments confirm

A

The shoot tip was responsible for phototropic responses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What experiments did darwin do

A

Cut tip
cover tip with opaque and transparent caps
cover base of shoot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What did Boyson-Jensen confirm

A

That water and solutes need to be present to move auxin from the shoot tip for phototropism to happen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What experiments did boyson - jensen do

A

Slice the tip of plant shoot and place agar block - lent to light
slice the tip of plant shoot and place mica - grew straight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is the effect of auxin in shoot growth

A

inhibits root growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what are some commercial uses of auxins

A

used to prevent leaf and fruit drop and promote flowering

producing seedless fruit

used as herbicides by promoting shoot growth and causing the plant to buckle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What are some commercial uses of cytokinins

A

they delay leaf senescence and used to prevent yellowing of lettuce leaves

used in tissue culture to help mass produce plants by promoting shoot and bud growth from small pieces of tissue taken from the parent plant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What are the commercial uses of gibberellins

A

fruit production
brewing
sugar production
plant breeding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

How are gibberellins used in fruit production?

A

they can delay senescence in citrus
they can act with cytokinins and improve apple shape
can make grape stalks elongate making grapes less compact and bigger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

How are gibberellins used in brewing

A

adding gibberellin can speed up the process of when barley seed produce amylase enzymes from the aleurone layer so more maltose is produced
malt is needed to make beer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

How are gibberellins used in sugar production?

A

spraying sugar canes with gibberellins stimulates growth between the nodes which is useful as sugar can stores sugar in the cells of the internodes making more sugar available from each plant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

How are gibberellins used in pant breeding

A

gibberellins can speed up the process of conifer trees becoming reproductively active by inducing seed formation on young trees

spraying with gibberellin synthesis inhibitors can make flowers short and stocky such as poinsiettas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What are some commercial uses of ethene

A

speeding up fruit ripening in apples tomatoes and citrus fruit

promoting fruit drop in cherries
make cucumbers not bitter by reducing chance of self pollination
promoting lateral growth in some plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

define the autonomic nervous system

A

part of the nervous system responsible for controlling the involuntary motor activities of the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Define the central nervous system

A

the central part of the nervous system composed of the brain and spinal cord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Define the peripheral nervous system

A

the sensory and motor nerves connecting the sensory receptors and effectors to the CNS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Define the somatic nervous system

A

the motor neurones under conscious control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What are the somatic and autonomic nervous systems part of

A

They branch from the peripheral nervous system into the motor system and then the autonomic and somatic nervous systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What can the autonomic nervous system be further split into

A

sympathetic and parasympathetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

efine sympathetic

A

fight or flight and prepares the body for activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Define parasympathetic

A

rest and digest - conserves energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

how does the sympathetic and parasympathetic systems differ in terms of ganglia

A

s - ganglia just outside CNS
p - Ganglia in the effector tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

how does the sympathetic and parasympathetic systems differ in terms of pre and post ganglionic neurones

A

s - short pre-ganglionic neurones and long post-ganglionic neurones
p - long pre-ganglionic neurones and short post-ganglionic neurones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

how does the sympathetic and parasympathetic systems differ in terms of neurotransmitters

A

s - noradrenaline
p - acetylcholine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What are the 4 main parts of the human brain

A

cerebrum - higher thought process - memory
cerebellum - movement and balance
hypothalamus and pituitary - organises homeostatic response
medulla oblongata - coordinates autonomic responses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

describe the structure of the cerebrum

A

has two cerebral hemispheres connected via a major tract of neurones called the corpus callosum and the outermosst layer consists of a thin layer of nerve cell bodies called the cerebral cortex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

what are the functions of the cerebrum

A

conscious thought
conscious actions
emotional responses
intelligence, judgement and reasoning

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

what three areas is the cerebral cortex subdivided into

A

sensory areas
association areas
motor areas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

what is the sensory area in the cerebral cortex responsible for

A

receiving action potentials indirectly from sensory receptors and the size of the regions are related to the sensitivity of the area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

what is the association area in the cerebral cortex responsible for

A

compare sensory inputs with previous experience and judge an appropriate response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

what is the motor area in the cerebral cortex responsible for

A

send action potentials to various effectors and the sizes of the regions are related to the complexity of the movements needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

What is the function of the cerebellum

A

involved with balance and the co-ordination of movement and fine control of muscular movement
e.g. tensing correct muscles when playing a musical instrument

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Where is the conscious decision to contract muscles initiated

A

cerebral cortex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

How are the cerebrum and the cerebellum connected

A

by the pons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

what is the action of the hypothalamus and pituitary complex

A

controlling homeostatic mechanisms in the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

how does the hypothalamus control homeostatic mechanisms in the body

A

it contains its own sensory receptors and acts by negative feedback to maintain a constant internal environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Give some examples of how the hypothalamus controls homeostatic mechanisms

A

temperature regulation - the hypothalamus detects changes in core body temperature and receives sensory input from temperature receptors in the skin and will initiate responses

osmoregulation - osmoreceptors in hypothalamus monitor water potential of blood and osmoregulatory centre initiates the response

63
Q

how are the hypothalamus responses mediated

A

via the pituitary gland

64
Q

How does the pituitary gland act

A

In conjunction with the hypothalamus

65
Q

What are the two lobes of the pituitary gland

A

posterior lobe
anterior lobe

66
Q

Describe the function of the posterior lobe in the pituitary gland

A

linked to the hypothalamus by neurosecretory cells
hormones manufactured in hypothalamus such as ADH pass down neurosecretory cells and are released into the blood via the pituitary gland

67
Q

describe the function of the anterior lobe in the pituitary gland

A

produces its own hormones which are released into the blood in response to releasing factors (type of hormone) produced by the hypothalamus

68
Q

what do the hormones from the anterior lobe control

A

a number of physiological processes including response to stress, growth, reproduction and lactation

69
Q

What are the actions of the medulla oblongata

A

controls non skeletal muscle - cardiac and involuntary smooth muscle - by sending action potentials through the autonomic nervous system

70
Q

What centres does the medulla oblongata contain

A

cardiac
vasomotor
respiratory

71
Q

What is the cardiac centre in the medulla oblongata responsible for

A

regulating heart rate

72
Q

What is the vasomotor center in the medulla oblongata responsible for

A

regulating circulation and blood pressure

73
Q

What is the respiratory centre in the medulla oblongata responsible for

A

controlling rate and depth of breathing

74
Q

How do the centers in the medulla oblongata coordinate vital functions

A

they receive sensory information and coordinate vital functions by negative feedback

75
Q

What is a reflex action

A

responses to changes in the environment that do not involve any processing in the brain to coordinate the movement

76
Q

what is the blinking reflex

A

causes temporary closure of the eyelids to protect them from damage

77
Q

What type of reflex is the blinking reflex

A

cranial as it passes through part of the brain

78
Q

Why may blinking be stimulated

A

foreign object
sudden bright light
loud sounds

79
Q

Describe the corneal reflex

A

this reflex is mediated by a sensory neurone from the cornea which enters the pons then relay neurone and an action potential passes down the motor neurone causing the eye to blink

80
Q

What type of reflex is a corneal reflex

A

cranial reflex

81
Q

How can the corneal reflex be inhibited

A

e.g. contact lenses wearers can prevent the reflex and not blink
the myelinated neurones carry inhibitory action potentials faster than the non-myelinated neurone can carry an action potential so the inhibitory action potentials can prevent the formation of an action potential in the motor neurone

82
Q

describe optical reflexes

A

protects the light sensitive cells of the retina from damage

83
Q

Describe the knee jerk reflex

A

unexpected stretching of muscle spindles causes a contraction of the quadriceps to straighten the leg

84
Q

what kind of reflex is the knee jerk

A

spinal reflex

85
Q

What is different about the neuronal pathways of a knee jerk reflex

A

no relay neurone

86
Q

Why can the knee jerk reflex not be overridden

A

lack of relay neurone means the action potential cannot be inhibited as it relies on myelinated neurones carrying inhibitory action potentials to the synapse before the motor neurone is stimulated there is insufficient delay to enable inhibition

87
Q

Why do we have reflexes

A

they have survival value

88
Q

How does the brain coordinate responses to the effector

A

action potentials in the somatic nervous system
action potentials in sympathetic and parasympathetic parts of the autonomic nervous system
release of hormones via hypothalamus and pituitary gland

89
Q

What are some physiological changes caused by adrenaline

A

pupils dilate
heart rate and blood pressure increase
blood glucose levels rise
ventilation rate and depth increase
metabolic rate increases

90
Q

How does the cerebrum use sensory input to coordinate a response

A

inputs feed into the sensory are in cerebrum
cerebrum passes signals to association centres
if a threat is recognised the cerebrum stimulates the hypothalamus
hypothalamus increases activity in sympathetic nervous system and stimulates release of hormones from anterior pituitary gland

91
Q

Describe the role of the sympathetic nervous system in the fight or flight response

A

hypothalamus activates sympathetic nervous system and this either activates the adrenal medulla causing a secretion of adrenaline into the bloodstream or impulses activate glands and smooth muscles

this combines with neural activity to constitute a fight or flight response

92
Q

Describe the action of the anterior pituitary gland in the fight or flight response (CRH)

A

The hypothalamus secretes releasing hormones to stimulate the pituitary gland
corticotropin-releasing hormone (CRH) from the hypothalamus causes the release of adrenocorticotropic hormone (ACTH) which passes around the blood stream and stimulates adrenal cortex to release a number of corticosteroid hormones e.g. cortisol which metabolises carbohydrates

93
Q

Describe the action of the anterior pituitary gland in the fight or flight response (TRH)

A

Thyrotropin-releasing hormones (TRH) causes the release of thyroid stimulating hormone (TSH) which stimulates the thyroid gland to release more thyroxine which increases metabolic rate and makes cells more sensitive to adrenaline

94
Q

What are the three types of muscle

A

involuntary - smooth
involuntary - cardiac
voluntary - skeletal

95
Q

what kind of pairs are muscles arranged in

A

antagonistic pairs - one contracts the other relaxes

96
Q

where is smooth muscle found

A

found in the walls of tubular structures such as blood vessels and the bronchioles

97
Q

describe smooth muscle

A

consists of individual cells tapered at both ends
each cell contains a nucleus and bundles of actin and myosin

98
Q

What is smooth muscle contraction controlled by

A

the autonomic nervous system

99
Q

describe cardiac muscles

A

long fibres which branch to form cross bridges and the cells are joined by intercalated disks

100
Q

What is the purpose of intercalated discs

A

specialised cell surface membranes fused to produce gap junctions that allow free diffusion of ions between cells

101
Q

Describe how the structure of the cardiac muscles aids the heart

A

the cross bridges help to ensure that electrical stimulation spreads evenly over the walls of the chambers it also ensures that the contraction is a squeezing actionrather than one dimensional

102
Q

How are some muscles in the heart fibres adapted

A

purkyne tissue are modified to carry electrical impulses
heart muscle is myogenic and can initiate its own contractions

103
Q

Where can skeletal muscle be found

A

joints in the skeleton
intercostal muscles

104
Q

Describe skeletal muscles

A

it is made up of a large bundle of long cells called muscle fibres and each fibre is multi nucleate and is surrounded by a membrane called the sarcolemma
the cell cytoplasm is known as the sarcoplasm and is specialised to contain many mitochondria and an extensive sarcoplasmic reticulum

105
Q

Describe the arrangement of muscle fibres in skeletal muscle

A

They arranged into a number of myofibrils which are contractile elements
they are then divided into sarcomeres which contain protein filaments called actin and myosin

106
Q

describe how the sarcolemma is specialised

A

folds inwards across the muscle fibres and stick into the sarcoplasm called T tubules and they help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre

107
Q

what is the function of sarcoplasmic reticulum

A

stores and releases calcium ions that are needed for muscle contraction

108
Q

Describe the stimulation of contraction

A

action potentials arriving at the end of the axon cause calcium ion channels to open and calcium ions flood in causing vesicles of acetyl choline to fuse with the plasma membrane and diffuse across the gap and fuse with receptors in the sarcolemma

this opens sodium ion channels causing sodium ions to enter the muscle fibre causing a depolarisation and a wave of depolarisation spreads along the sarcolemma and down transverse tubules into the muscle fibre

109
Q

How do you investigate muscle stimulation

A

an electromyograph (EMG) electrodes detect action potentials in the motor neurone

110
Q

What is creatine phosphate

A

a compound in muscle that acts as a store of phosphates and can supply phosphates to make ATP rapidly

111
Q

describe the structure of myofibril

A

contain bundles of thick and thin myofilaments
thin filaments (I band) which are aligned to make up the light band these are held together by the Z line (light band)
thick filaments make up the dark band (A band)

thick and thin filaments overlap but where there is no overlap is called the H zone
Sarcomere - distance between two Z lines

thick and thin filaments are surrounded by sarcoplasmic reticulum

112
Q

What is the distance between 2 Z lines called

A

sarcomere

113
Q

What is the H zone comprised of

A

mostly myosin as this is where no overlap occurs

114
Q

Describe the thin filaments in myofibrils

A

they are actin and consists of 2 chains of actin subunits twisted around each other
wound around the actin is a molecule of tropomyosin which are globular molecules of troponin
Each troponin complex consists of three polypeptides one binds to actin one to tropomyosin and the third to calcium when its available
Actin filaments have binding sites for myosin heads called actin-myosin binding sites

115
Q

describe thick filaments

A

consists of a bundle of myosin molecules and each molecule has two protruding heads at the end of each molecules
these heads are mobile and bind to the actin when the binding sites are exposed
Each myosin head has a binding site for actin and ATP

116
Q

What lead to the sliding filament hypothesis

A

during contraction the light band and H zone get shorter therefore the Z lines move l=closer together so the thick and thin filaments slide past each other leading to this theory

117
Q

What is the action of troponin and tropomyosin

A

These proteins help myofilaments move past each other

118
Q

How can the thick and thin filaments bind

A

Actin filaments have binding sites for myosin heads called actin-myosin binding sites

Each myosin head has a binding site for actin and ATP

119
Q

What is the mechanism of muscle contraction

A

the sliding action is caused by movement of myosin heads, when the muscle is stimulated the tropomyosin is moved aside exposing the binding sites on the actin, the myosin heads attach to the actin and move causing the actin to slide past the myosin

120
Q

Describe the control of contraction

A

the received action potential is carried to the sarcoplasmic reticulum which stores calcium ions and causes the release of calcium ions into the sarcoplasm

the calcium ions bind to the troponin which alters the shape pulling the tropomyosin aside exposing the binding site on the actin

myosin heads bind to the actin forming cross bridges between filaments

the myosin heads move pulling the actin filament past the myosin filament

The myosin heads detach from the actin and can bind again further up the filament

121
Q

What happens once contraction occurs

A

the calcium ions are rapidly pumped back into the sarcoplasmic reticulum allowing the muscles to relax

122
Q

What is the role of ATP in muscle contraction

A

it supplies energy for contraction, part of the myosin head acts as ATPase and can hydrolyse ATP releasing energy

123
Q

Describe the role of ATP in muscle contraction

A

the myosin head attaches to the actin filament forming a cross bridge

the myosin head tilts backwards causing the thin filament to slide past the myosin filament this is the power stroke and during the power stroke ADP and Pi are released from the myosin head

After the power stroke a new ATP molecule attaches to the myosin head breaking the cross bridge

The myosin head then returns to its original position and the atp is hydrolysed releasing the energy required to make this reaction occur and the myosin head can now make a new cross-bridge further along the actin filament

124
Q

How is the supply of ATP maintained

A

Aerobic respiration
anaerobic respiration
creatine phosphate

125
Q

What enzyme is involved when using creatine

A

creatine phosphotransferase

126
Q

How much longer does creatine phosphate prolong a contraction

A

ATP available in muscle tissue is only enough to support 1-2 seconds worth of contraction and the supply of creatine phosphate is sufficient enough to prolong it for a further 2-4 seconds

127
Q

Why is the circulation caused by the heart pumping important

A

transport of oxygen and nutrients
removal of waste products
transport of urea from liver to kidneys
distribute heat around the body

128
Q

why does the requirement of cells and tissues vary

A

varies according to level of activity

129
Q

how can heart action be modified

A

raising or lowering the heart rate
altering the force of contractions of the ventricular walls
altering stroke volume (volume of blood pumped by minute)

130
Q

describe the difference between atrial and ventricular muscle

A

the atrial muscle has a higher myogenic rate than ventricular muscle

131
Q

Why is a coordination mechanism in the heart essential

A

the two chambers must contract in a coordinated fashion or the action of the heart will be ineffective

132
Q

What is called the hearts pacemaker

A

SAN sinoatrial node

133
Q

describe the action of the SAN

A

it initiates a wave of excitation that usually overrides the myogenic action of the cardiac muscle
the SAN is a region of tissue that can initiate an action potential which travels as a wave of excitation over the atrial walls through the AVN and down purkyne fibres to the walls of the ventricles to contract

134
Q

what hormone does the heart respond to and why

A

adrenaline which increases heart rate

135
Q

How is the heart controlled at rest

A

by the SAN which has a set frequency varying from person to person typically 60-80 per minute

136
Q

what can the frequency of excitation waves in the heart be altered by

A

by the output from the cardiovascular centre in the medulla oblongata

137
Q

How is the frequency of the excitation waves altered

A

nerves from the cardiovascular centre in the medulla oblongata of the brain supply the SAN and affect the frequency of contractions
nerves are controlled by autonomic nervous system

138
Q

what part of the nervous system are the nerves which alter frequency of excitation in the heart from

A

autonomic

139
Q

how does the action of the accelerans and vagus nerve differ

A

accelerans causes the heaert rate to increase whereas action potentials travelling down the vagus nerve reduce heart rate

140
Q

Describe what occurs when action potentials are sent down the accelerans nerve

A

Action potentials sent down the sympathetic accelerans nerve cause the release of the neurotransmitter noradrenaline at the SAN which increases heart rate

141
Q

Describe what occurs when action potentials are carried down the vagus nerve

A

they release the neurotransmitter acetylcholine which reduces heart rate

142
Q

what environmental factors can affect heart rate

A

inputs from the sensory receptors

143
Q

How do environmental factors affect heart rate

A

the interactions of inputs is coordinated by the cardiovascular centre to ensure that the output to the SAN is appropriate to the overall conditions

144
Q

give some examples of sensory inputs to the cardiovascular centre

A

stretch receptors in muscles
chemoreceptors in the carotid arteries, aorta and brain
stretch receptors in the walls of the carotid sinus

145
Q

Describe how stretch receptors in the muscle are able to effect heart rate

A

they detect movement of the limbs sending impulses to the cardiovascular centre informing it that extra oxygen may soon be needed leading to an increase in heart rate

146
Q

Describe how chemoreceptors in the carotid arteries have an effect on heart rate

A

the chemoreceptors in the carotid arteries, aorta and brain monitor the pH of the blood when excess CO2 reacts with water in blood plasma it produces a weak carbonic acid reducing the pH of the blood affecting the transportation of oxygen

the change in pH is detected by the chemoreceptors which send action potentials to the cardiovascular centre this will tend to increase the heart rate

147
Q

Describe what may occur if CO2 concentration in the blood falls

A

reduces the activity of the accelerator pathway therefore the heart rate declines

148
Q

Describe how stretch receptors in the carotid sinus affect heart rate

A

it a small swelling in the carotid artery which monitors blood pressure

If pressure rises too high the stretch receptors send action potentials to the cardiovascular centre leading to a reduction in the heart rate

149
Q

what must happen if the controlling mechanism of the heart rate fails

A

an artificial pacemaker must be fitted which delivers an electrical impulses to the heart muscle

an artificial pacemaker may be connected to the SAN directly or directly to the ventricle muscle

150
Q

Give an example of positive feedback caused by increasing heart rate

A

increasing heart rate may produce more carbon dioxide in the heart muscle which leads to a decrease in pH which will be detected by the chemoreceptors and tend to increase heart rate

151
Q

Describe how sensory input is used to prevent the heart rate rising too high during intense exercise

A

stretch receptors in the carotid sinus will detect an increase in blood pressure and if the pressure rises too high it will send action potentials to the cardiovascular centre in the medulla oblongata leading to a reduction in heart rate

152
Q

.How does auxin stretch cells

A

promoting active transport of H+ by an ATPase on the plasma membrane into the cell wall, the resulting low pH provides optimum conditions for wall loosening enzymes called expansins to work, these enzymes breaks bonds within the cellulose so the walls become less rigid and can expand as the cell takes in water

the H+ also interrupts the hydrogen bonds

153
Q

how are plant hormones involved in the leaf loss of deciduous plants

A

auxins inhibit leaf loss and are produced in young leaves not older ones
ethene stimulates leaf loss and is produced in ageing leaves and abscission layer develops at the bottom of the leaf stalk separating the leaf from the rest of the plant

154
Q

how are hormones involved in stomatal closure

A

abscisic acid binds to receptors on guard cell membranes causing calcium ions to enter through the now open channels to the cytosol

the increased concentration of calcium ions in the cytosol causes other ion channels to open and ions such as potassium leave the guard cell raising its water potential. Water then leaves the guard cell making it falcid and the stomata close

A level Biology (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions