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Biology Edexcel Sophie > Topic 8 Grey Matter > Flashcards

Topic 8 Grey Matter Flashcards

1
Q

What is the largest part of the brain?

A

The cerebrum

The cerebrum is involved in vision, learning, thinking, emotions, and movement.

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2
Q

What are the two halves of the cerebrum called?

A

Cerebral hemispheres

The cerebrum is divided into the right and left cerebral hemispheres.

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3
Q

What is the thin outer layer of the cerebrum called?

A

Cerebral cortex

The cortex has a large surface area and is highly folded to fit into the skull.

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4
Q

What functions does the cerebrum control?

A
  • Vision
  • Learning
  • Thinking
  • Emotions
  • Movement

Different parts of the cerebrum are involved in different functions.

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5
Q

Where is the hypothalamus located?

A

Just beneath the middle part of the brain

The hypothalamus plays a critical role in homeostasis.

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6
Q

What is one key function of the hypothalamus?

A

Thermoregulation

The hypothalamus maintains body temperature at the normal level.

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7
Q

What does the hypothalamus produce that affects the pituitary gland?

A

Hormones

The pituitary gland is located just below the hypothalamus.

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8
Q

Where is the medulla oblongata located?

A

At the base of the brain, at the top of the spinal cord

The medulla oblongata is critical for automatic control of vital functions.

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9
Q

What vital functions does the medulla oblongata control?

A
  • Breathing rate
  • Heart rate

These functions are essential for survival.

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10
Q

What type of imaging technique uses radiation to visualize the brain?

A

Computed Tomography (CT)

CT scans show dense structures in the brain as light areas.

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11
Q

What can CT scans help diagnose?

A

Medical conditions related to the brain

They can reveal damaged brain structures.

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12
Q

What imaging technique produces detailed images without radiation?

A

Magnetic Resonance Imaging (MRI)

MRI scans provide high-resolution images of the brain.

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13
Q

Which part of the brain is responsible for coordinating movement and balance?

A

The cerebellum

The cerebellum is located underneath the cerebrum and also has a folded cortex.

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14
Q

Fill in the blank: The cerebellum is important for _______.

A

Coordinating movement and balance

Proper functioning of the cerebellum is crucial for motor control.

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15
Q

What is the main function of a CT scanner?

A

To produce cross-section images of the brain using X-rays

CT scans show major structures in the brain but do not indicate their functions directly.

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16
Q

What type of images do CT scans produce?

A

Cross-section images of the brain

CT scans can show damaged or diseased areas of the brain.

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17
Q

How do CT scans help in medical diagnosis?

A

They show damaged or diseased areas, such as bleeding after a stroke

Blood shows up as a lighter color on a CT scan due to different density.

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18
Q

What is a significant risk associated with CT scans?

A

They use X-rays, which can cause mutations in DNA

The risk of developing cancer from a CT scan is very low.

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19
Q

What technology do MRI scanners use to produce images?

A

Strong magnetic fields and radio waves

MRI scanners provide higher quality images compared to CT scans.

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20
Q

What advantage do MRI scans have over CT scans?

A

Higher quality images for soft tissue and better resolution between tissue types

MRIs can clearly differentiate between normal and abnormal brain tissue.

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21
Q

What can MRI scans reveal about brain tumors?

A

The size and location of the tumor

Tumor cells respond differently to magnetic fields than healthy cells, appearing lighter on the scan.

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22
Q

Fill in the blank: CT scans show _____ areas of the brain.

A

damaged or diseased

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23
Q

True or False: MRI scans can indicate brain function directly.

A

False

Brain function can only be inferred by examining damaged areas.

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24
Q

What can be inferred if a CT scan shows a patient can’t see?

A

The damaged area involved in vision

This inference is based on the relationship between structure and function.

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25
Q

What is the primary use of CT scans in medical diagnosis?

A

To identify bleeding and its extent in the brain

This helps determine which blood vessels are damaged and related brain functions affected.

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26
Q

What does an MRI scan provide?

A

A detailed, high resolution picture of the brain’s structure

MRI scans can also be used to research brain function.

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27
Q

How does an fMRI scan work?

A

It measures brain activity by detecting changes associated with blood flow

Active areas of the brain are highlighted during specific tasks.

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28
Q

What can MRI scans show in terms of medical diagnosis?

A

Damaged or diseased areas of the brain and conditions caused by abnormal activity

Some conditions may not have an obvious structural cause.

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29
Q

What is the purpose of using an fMRI scan before and during a seizure?

A

To pinpoint which part of the brain is not functioning properly

This assists in determining the cause of the seizure.

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30
Q

What does a PET scan use to show brain activity?

A

Radioactive material

A radioactive tracer is introduced into the body and absorbed into the tissues.

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31
Q

How does a PET scan build a map of radioactivity?

A

By detecting the radioactivity of the tracer

Different tracers can be used for various metabolic studies.

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32
Q

What is a common tracer used in PET scans?

A

Radioactively labelled glucose

It is used to examine glucose metabolism in the brain.

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33
Q

What condition can PET scans help study?

A

Alzheimer’s disease

They show reduced metabolism in certain brain areas.

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34
Q

True or False: PET scans can show if areas of the brain are unusually inactive or active.

A

True

This helps in studying disorders that affect brain activity.

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35
Q

Fill in the blank: MRI scans can help assess suspected _______ in the brain.

A

bleeding

MRI scans provide detailed information about bleeding.

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36
Q

What type of information can a doctor get from an MRI scan regarding bleeding?

A

Information about the location and extent of the bleeding

This is crucial for effective treatment.

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37
Q

What brain function is typically investigated using an fMRI scan?

A

Movement of body parts

For example, moving the left hand activates specific brain areas.

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38
Q

What is the primary advantage of using fMRI over traditional MRI?

A

It allows real-time observation of brain activity during tasks

This provides insights into functional areas of the brain.

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39
Q

Which side of the brain controls the left side of the body?

A

The right side

This is why the right side is active when the left hand moves.

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40
Q

What is habituation?

A

Habituation is a type of learned behavior where an animal reduces its response to an unimportant stimulus after repeated exposure over time.

It helps animals conserve energy and focus on more critical survival activities.

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41
Q

Why is habituation important for animals?

A

Habituation increases the chance of survival by allowing animals to differentiate between important and unimportant stimuli.

This helps them avoid wasting energy on non-threatening stimuli.

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42
Q

Give an example of habituation in prairie dogs.

A

Prairie dogs use alarm calls to warn others of a predator but have habituated to humans, no longer making alarm calls when they see them.

This demonstrates that they do not perceive humans as a threat.

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43
Q

What happens to an animal’s response to an unimportant stimulus when habituation occurs?

A

The animal learns to ignore the unimportant stimulus, leading to a reduced response over time.

This allows them to engage in other survival activities, such as feeding.

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44
Q

How can you demonstrate habituation in a snail?

A

Gently brush something soft across the snail’s skin and time how long it takes for the snail to fully extend its tentacles again after being touched.

Repeating this process will show quicker re-extension if habituation has occurred.

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45
Q

What physiological changes occur during habituation?

A

Fewer electrical impulses are sent to effectors due to reduced calcium ion influx and decreased neurotransmitter release.

This results in a lower chance of reaching the action potential threshold on the postsynaptic membrane.

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46
Q

Fill in the blank: Habituation allows animals to conserve energy by _______.

A

[ignoring unimportant stimuli]

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47
Q

True or False: Habituation means that animals become less alert to all stimuli.

A

False

Animals remain alert to important stimuli that could threaten their survival.

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48
Q

What is the effect of repeated exposure to a stimulus on neurotransmitter release during habituation?

A

Repeated exposure decreases the amount of neurotransmitter released from vesicles into the synaptic cleft.

This results in fewer signals sent to effectors.

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49
Q

Why do snails still react to unfamiliar stimuli even after habituation?

A

Snails remain alert to unfamiliar stimuli, which may pose a threat, leading to a withdrawal response.

This shows that habituation does not mean complete unresponsiveness.

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50
Q

What is the visual cortex?

A

An area of the cerebral cortex at the back of the brain that receives and processes visual information.

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51
Q

What are ocular dominance columns?

A

Grouped neurones in the visual cortex that receive information from either the left or right eye.

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52
Q

What are the two types of ocular dominance columns?

A
  • Left ocular dominance columns
  • Right ocular dominance columns
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53
Q

How are ocular dominance columns arranged?

A

In an alternating pattern (left, right, left, right) across the visual cortex.

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54
Q

Who studied the visual cortex and how?

A

Hubel and Wiesel used animal models to study the electrical activity of neurones in the visual cortex.

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55
Q

What did Hubel and Wiesel find about ocular dominance columns in kittens?

A

The stitched-up eye was blind, and the columns for the open eye were larger than normal.

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56
Q

What happens when one eye is stitched shut in young kittens?

A

The ocular dominance columns for the stitched-up eye become smaller, and those for the open eye expand.

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57
Q

What were the results of stitching shut an adult cat’s eye?

A

The adult cat’s eye did not go blind, and ocular dominance columns remained the same.

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58
Q

What do Hubel and Wiesel’s experiments suggest about visual cortex development?

A

The visual cortex develops normal ocular dominance columns only if both eyes are stimulated early in life.

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59
Q

What is the critical period in visual development?

A

A period in early life when exposure to visual stimuli is essential for proper visual cortex development.

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60
Q

What did scientists find about cataracts in infants?

A

Cataracts must be removed within the first few months for normal visual system development.

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61
Q

What happens to adults with cataracts when they are removed?

A

Normal vision returns immediately because the visual system is already developed.

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62
Q

Fill in the blank: Hubel and Wiesel’s experiments provide evidence for a _______ in humans.

A

[critical period]

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63
Q

True or False: The human visual cortex has ocular dominance columns.

A

True

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64
Q

What occurs to synapses during the critical period?

A

Synapses that are not used are removed from the visual cortex.

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65
Q

What is the significance of visual stimuli during the critical period?

A

They are crucial for the proper organization of the visual cortex.

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66
Q

What did Hubel and Wiesel’s experiments demonstrate about visual stimulation?

A

They showed that lack of visual stimulation can lead to blindness in the non-stimulated eye.

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67
Q

What are some arguments against using animal models in experiments?

A
  • Animals are different from humans
  • Different species may have varying brain structures
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68
Q

What are alternative methods to study visual development in humans?

A
  • Observing cataracts
  • Studying children with visual impairments
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69
Q

What are ocular dominance columns?

A

They are structures in the visual cortex that process visual information from each eye.

Ocular dominance columns are essential for understanding how the brain processes visual stimuli.

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70
Q

Where in the brain are ocular dominance columns found?

A

In the visual cortex.

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71
Q

What is the significance of visual stimulation during the critical period of development?

A

Visual stimulation is necessary for the proper organisation of neurones in the visual cortex.

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72
Q

What happens to synapses that receive visual stimulation during the critical period?

A

They are retained.

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73
Q

What happens to synapses that do not receive visual stimulation during the critical period?

A

They are removed.

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74
Q

What is the consequence of a lack of visual stimulation during the critical period?

A

The visual cortex will not develop properly as many synapses will be destroyed.

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75
Q

List two arguments against using animals in medical research.

A
  • Animals may experience pain and distress
  • Animals are different from humans, so drug effects may vary.
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76
Q

List two arguments for using animals in medical research.

A
  • Research has led to significant medical breakthroughs
  • Animal experiments are only conducted when absolutely necessary.
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77
Q

True or False: Hubel and Wiesel conducted their experiments on humans.

A

False.

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78
Q

What ethical issues arise from using animals in medical research?

A

Concerns about animal rights and the potential for causing pain and distress.

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79
Q

Fill in the blank: Proper organisation of the visual cortex involves the elimination of unnecessary _______.

A

[synapses].

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80
Q

What do Hubel and Wiesel’s experiments provide evidence for?

A

A critical period in the development of the visual system.

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81
Q

What is a critical period in the context of visual system development?

A

A specific time frame during which visual stimulation is crucial for proper development.

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82
Q

What kind of pattern are ocular dominance columns arranged in?

A

A striped pattern corresponding to the input from the left and right eyes.

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83
Q

Describe one piece of evidence that suggests a critical ‘window’ exists for human visual system development.

A

Evidence from animal studies, such as those by Hubel and Wiesel, indicates a period where visual input is essential.

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84
Q

What alternatives exist to using animals in research?

A
  • Cultures of human cells
  • Computer models to predict effects.
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85
Q

What did Hubel and Wiesel’s experiments on kittens and monkeys reveal?

A

They provided significant insights into the development of the visual cortex.

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86
Q

Fill in the blank: The visual cortex is organized during the critical period based on _______ stimulation.

A

[visual].

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87
Q

What role do painkillers and anaesthetics play in animal experiments?

A

They minimize pain and distress to the animals.

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88
Q

What is brain development?

A

How the brain grows and how neurones connect together.

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89
Q

What are measures of brain development?

A

Measures include the size of the brain, the number of neurones, and the level of brain function (e.g. speech, intelligence).

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90
Q

What is the nature-nurture debate?

A

The argument about whether nature or nurture influences brain development the most.

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91
Q

Why is it difficult to investigate the effects of nature and nurture?

A

Genetic and environmental factors interact, making it hard to know which one is the main influence.

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92
Q

What are two key factors that complicate the study of nature and nurture?

A

The existence of many different genes and various environmental factors.

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93
Q

What is one method scientists use to investigate brain development?

A

Animal experiments.

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94
Q

How do animal experiments help study nurture?

A

By studying the effects of different environments on genetically similar animals.

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95
Q

What do studies on rats raised in stimulating environments suggest?

A

Nurture plays a big role in brain size and the development of problem-solving skills.

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96
Q

What do studies suggest about rats reared in isolation?

A

They exhibit brain abnormalities similar to those found in schizophrenic patients, indicating the influence of nurture.

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97
Q

What effect does the absence of the Lgli gene have on mice?

A

It leads to enlarged brain regions and fluid buildup in their brains, suggesting nature’s role in brain development.

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98
Q

What is the significance of twin studies in understanding brain development?

A

They allow comparison of brain development between genetically identical individuals raised in different environments.

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99
Q

What do IQ scores of identical twins suggest?

A

Nature plays a big role in intelligence.

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100
Q

What is a limitation of comparing identical twins raised separately?

A

They still share the same environment in the womb, complicating the separation of environmental and genetic factors.

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101
Q

What does the comparison between identical and non-identical twins help determine?

A

It helps to cancel out environmental influences and assess the role of nature.

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102
Q

What does the higher incidence of stuttering in identical twins suggest?

A

Nature plays a significant role in developing the speech area of the brain.

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103
Q

What does the lack of difference in reading ability between identical and non-identical twins suggest?

A

Nurture plays a big role in reading ability.

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104
Q

Fill in the blank: The _______ is the argument about whether nature or nurture influences brain development the most.

A

nature-nurture debate.

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105
Q

What are the two main influences on brain development?

A

Nature and nurture

Nature refers to genetic factors, while nurture refers to environmental influences.

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106
Q

What do cross-cultural studies reveal about brain development?

A

Differences in brain development are more likely due to nurture, while similarities are more likely due to nature

Cross-cultural studies compare children from different cultures to assess the impact of upbringing.

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107
Q

What abilities are newborn babies born with?

A

Crying, feeding, and recognizing a human face

These abilities suggest that nature plays a significant role in these functions.

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108
Q

True or False: Newborn babies have the ability to speak.

A

False

This indicates that nurture plays a significant role in the ability to speak.

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109
Q

How does brain damage affect children’s brain development?

A

Children can still develop functions despite brain damage, suggesting nurture plays a role

Studies indicate that children with brain damage can eventually reach language milestones similar to those without damage.

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110
Q

Fill in the blank: The brain of a newborn baby has been affected a bit by the _______.

A

environment in the womb

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111
Q

What can scientists study by comparing children with and without brain damage?

A

The development of specific functions

This comparison helps determine if development is influenced more by nature or nurture.

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112
Q

What happens to language development in children aged 1-3 with brain damage?

A

They show a delay in major language milestones

However, by age 5, their language skills can become comparable to those without damage.

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113
Q

What is the significance of determining whether characteristics are influenced more by nature or nurture?

A

It helps in figuring out how to improve brain function by changing the environment

Understanding the influence can guide interventions for developmental issues.

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114
Q

What is meant by ‘nature’ in the context of brain development studies?

A

Genetic factors that influence brain functions

Nature encompasses inherited traits and biological predispositions.

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115
Q

Describe two other types of studies that could be used to research nature and nurture on brain development.

A

Twin studies and adoption studies

These studies help isolate genetic influences from environmental ones.

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116
Q

What are neurotransmitters?

A

Chemicals that transmit nerve impulses across synapses.

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117
Q

How are depression and serotonin levels related?

A

Depression is linked to a low level of serotonin.

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118
Q

What is Parkinson’s disease?

A

A brain disorder that affects motor skills.

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119
Q

What neurotransmitter is associated with Parkinson’s disease?

A

Dopamine.

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120
Q

What happens to neurons in the brain of a person with Parkinson’s disease?

A

Neurons that control movement are destroyed.

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121
Q

How do selective serotonin reuptake inhibitors (SSRIs) work?

A

They increase serotonin levels by preventing its reuptake at synapses.

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122
Q

What is L-dopa used for?

A

To treat the symptoms of Parkinson’s disease.

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123
Q

Why can’t dopamine be directly administered to treat Parkinson’s disease?

A

Dopamine can’t enter the brain.

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124
Q

What does L-dopa get converted into in the brain?

A

Dopamine.

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125
Q

What is the effect of increased dopamine levels in the brain?

A

More nerve impulses are transmitted across synapses, improving movement control.

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126
Q

What is MDMA commonly known as?

A

Ecstasy.

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127
Q

How does MDMA affect serotonin levels?

A

It increases serotonin levels by inhibiting its reuptake and triggering its release.

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128
Q

What is the primary effect of MDMA on mood?

A

Mood elevation.

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129
Q

Fill in the blank: A low level of the neurotransmitter _______ is linked to depression.

A

serotonin.

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130
Q

True or False: L-dopa directly replaces serotonin in the brain.

A

False.

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131
Q

What are the symptoms caused by a lack of dopamine in Parkinson’s disease?

A

Tremors and slow movement.

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132
Q

What enzyme converts L-dopa into dopamine?

A

Dopa-decarboxylase.

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133
Q

Fill in the blank: MDMA binds to and blocks the _______ proteins on the presynaptic membrane.

A

reuptake.

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134
Q

What is the Human Genome Project (HGP)?

A

A 13-year project that identified all of the genes found in human DNA.

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135
Q

Where is the information obtained from the Human Genome Project stored?

A

In databases.

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136
Q

How do scientists use the databases from the Human Genome Project?

A

To identify genes and proteins involved in disease.

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137
Q

What is an example of a drug being developed using information from the Human Genome Project?

A

A drug that inhibits an enzyme helping cancer cells to spread.

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138
Q

What do common genetic variations identified by the HGP affect?

A

The effectiveness of some drugs.

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139
Q

What are personalized medicines?

A

Drugs designed to be tailored to people with specific genetic variations.

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140
Q

How can doctors personalize a patient’s treatment?

A

By using genetic information to predict drug response.

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141
Q

True or False: The development of drugs for specific genetic variations may lead to a two-tier health service.

A

True

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142
Q

What might happen if a person’s genetic makeup indicates that an expensive drug will not be effective?

A

They might be refused the drug, even if it’s the only option available.

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143
Q

What ethical issue arises from the information held within a person’s genome?

A

It could be used by employers or insurance companies to discriminate.

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144
Q

How can revealing that a drug might not work for a person be psychologically damaging?

A

It could diminish their hope for treating a disease.

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145
Q

Fill in the blank: A disorder linked to a low level of serotonin is _______.

A

Parkinson’s disease

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146
Q

Describe one way that MDMA increases the level of serotonin in the brain.

A

MDMA releases more serotonin into the synaptic cleft.

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147
Q

Name a drug used to treat Parkinson’s disease.

A

Levodopa

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148
Q

Explain the role of dopamine in controlling movement.

A

Dopamine transmits signals that coordinate movement and balance.

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149
Q

Describe and explain the effects that Parkinson’s disease has on the brain.

A

It leads to the degeneration of dopamine-producing neurons.

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150
Q

Give three ethical issues surrounding the development of personalized medicines.

A
  • Increased research costs for drug companies
  • Potential discrimination based on genetic information
  • Psychological impact of knowing a drug won’t work
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151
Q

True or False: Chocolate can also increase serotonin levels.

A

True

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152
Q

What is the impact of genetic variations on asthma drugs?

A

Some asthma drugs are less effective for people with particular mutations.

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153
Q

What are genetically modified organisms (GMOs)?

A

Organisms that have had their DNA altered

GMOs are used in various applications, including drug production.

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154
Q

What types of drugs can be produced by genetically modified organisms?

A

Only drugs that are proteins

This includes various therapeutic proteins such as insulin.

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155
Q

What is the first step in genetically engineering microorganisms to produce drugs?

A

Isolating the gene for the protein using restriction enzymes

Restriction enzymes are enzymes that cut DNA at specific sequences.

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156
Q

What process is used to copy the gene for the drug?

A

PCR (Polymerase Chain Reaction)

PCR is a technique used to amplify a segment of DNA.

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157
Q

What are plasmids?

A

Small circular molecules of DNA

Plasmids are often used as vectors to transfer genetic material.

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158
Q

What is the role of plasmids in drug production using GMOs?

A

Plasmids are transferred into microorganisms to produce proteins

The modified microorganisms then divide and produce the useful protein.

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159
Q

Give an example of a drug produced from genetically modified bacteria.

A

Human insulin

Human insulin is used to treat Type 1 diabetes.

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160
Q

What is the first step in genetically engineering plants to produce drugs?

A

Inserting the gene for the protein into a bacterium

The bacterium acts as a vector to transfer the gene.

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161
Q

How does the bacterium modify the plant cell?

A

The bacterium inserts the gene into the plant cell DNA

This results in the plant cell becoming genetically modified.

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162
Q

What is a way the protein produced in genetically modified plants can be used?

A

Purified from the plant tissues or delivered by eating the plant

This method allows for the direct consumption of therapeutic proteins.

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163
Q

What is the first step in genetically engineering animals to produce drugs?

A

Injecting the gene into the nucleus of a fertilized animal egg cell

This process allows for the gene to be incorporated into the animal’s genome.

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164
Q

How is the gene expressed in genetically modified animals?

A

The egg cell is implanted into an adult animal

The animal grows with the gene present in every cell.

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165
Q

Where is the protein produced by genetically modified animals typically purified from?

A

The milk of the animal

This method is commonly used for proteins that can be secreted into milk.

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166
Q

True or False: Genetically modified plants can produce human insulin.

A

True

Some genetically modified plants have been engineered to produce insulin.

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167
Q

Fill in the blank: The bacterium used in plant genetic engineering is a _______.

A

vector

Vectors are essential for transferring genes into target cells.

168
Q

What is a genetically modified organism?

A

An organism whose genetic material has been altered using genetic engineering techniques.

169
Q

Describe how a genetically modified plant is created.

A

By introducing specific genes into the plant’s DNA, often using methods like agrobacterium-mediated transformation or gene guns.

170
Q

Describe how a genetically modified animal is created.

A

By incorporating foreign DNA into the animal’s genome, often through methods like microinjection or somatic cell nuclear transfer.

171
Q

What are the benefits of using genetically modified organisms (GMOs) in agriculture?

A

Benefits include higher yields, increased nutritional value, pest resistance, reduced pesticide use, and lower costs.

172
Q

How can GMOs help reduce the risk of famine and malnutrition?

A

By producing crops that are higher in nutrition and yield, making food more available.

173
Q

What is an example of a human protein produced from genetically modified organisms?

A

Human insulin produced from genetically modified bacteria.

174
Q

Fill in the blank: Vaccines produced in _______ tissues don’t need to be refrigerated.

A

plant

175
Q

What is a concern regarding herbicide-resistant crops?

A

They may interbreed with wild plants, creating ‘superweeds’ resistant to herbicides.

176
Q

What are some risks associated with the use of GMOs?

A

Potential transmission of genetic material, unforeseen consequences, and ethical concerns regarding animal modification.

177
Q

True or False: Human proteins from genetically modified organisms can cause allergic reactions.

A

False

178
Q

What is a potential benefit of producing drugs using genetically modified plants and animals?

A

It could make drugs more affordable, especially for people in poor countries.

179
Q

Discuss the long-term impacts of using GMOs.

A

There may be unforeseen consequences and concerns about ecological balance.

180
Q

What is the role of enzymes in industrial processes related to GMOs?

A

Enzymes produced from GMOs can be used in large quantities at reduced costs.

181
Q

Fill in the blank: Some people believe it’s wrong to _______ animals purely for human benefit.

A

genetically modify

182
Q

How has treatment for Type 1 diabetes changed with GMOs?

A

It has shifted from using cow insulin to human insulin produced by genetically modified bacteria.

183
Q

What is a stimulus?

A

Any change in the internal or external environment

184
Q

What do receptors do?

A

They detect stimuli

185
Q

What are effectors?

A

Cells that bring about a response to a stimulus

186
Q

Give two examples of effectors.

A
  • Muscle cells
  • Gland cells (e.g., pancreas)
187
Q

How do receptors communicate with effectors?

A

Via the nervous system or the hormonal system

188
Q

What is the nervous system made up of?

A

A complex network of cells called neurones

189
Q

Name the three main types of neurones.

A
  • Sensory neurones
  • Motor neurones
  • Relay neurones
190
Q

What do sensory neurones do?

A

Transmit electrical impulses from receptors to the CNS

191
Q

What do motor neurones do?

A

Transmit electrical impulses from the CNS to effectors

192
Q

What do relay neurones do?

A

Transmit electrical impulses between sensory and motor neurones

193
Q

What happens when an electrical impulse reaches the end of a neurone?

A

Neurotransmitters take the information across to the next neurone

194
Q

What are electrical impulses also called?

A

Nerve impulses or action potentials

195
Q

What is the role of the CNS?

A

Processes information and sends impulses along motor neurones to effectors

196
Q

Fill in the blank: The brain unconsciously processes the information, so these responses are _______.

A

reflexes

197
Q

What do light receptors (photoreceptors) in dim light do?

A

Stimulate radial muscles to dilate pupils

198
Q

What do light receptors (photoreceptors) in bright light do?

A

Stimulate circular muscles to constrict pupils

199
Q

True or False: Hormones are substances released by glands into the bloodstream.

A

True

200
Q

What is the function of hormones?

A

Regulate various physiological processes

201
Q

What is an example of a stimulus that can trigger a hormonal response?

A

Low blood glucose concentration

202
Q

What is a stimulus?

A

Any change in the internal or external environment

203
Q

What do receptors do?

A

They detect stimuli

204
Q

What are effectors?

A

Cells that bring about a response to a stimulus

205
Q

Give two examples of effectors.

A
  • Muscle cells
  • Gland cells (e.g., pancreas)
206
Q

How do receptors communicate with effectors?

A

Via the nervous system or the hormonal system

207
Q

What is the nervous system made up of?

A

A complex network of cells called neurones

208
Q

Name the three main types of neurones.

A
  • Sensory neurones
  • Motor neurones
  • Relay neurones
209
Q

What do sensory neurones do?

A

Transmit electrical impulses from receptors to the CNS

210
Q

What do motor neurones do?

A

Transmit electrical impulses from the CNS to effectors

211
Q

What do relay neurones do?

A

Transmit electrical impulses between sensory and motor neurones

212
Q

What happens when an electrical impulse reaches the end of a neurone?

A

Neurotransmitters take the information across to the next neurone

213
Q

What are electrical impulses also called?

A

Nerve impulses or action potentials

214
Q

What is the role of the CNS?

A

Processes information and sends impulses along motor neurones to effectors

215
Q

Fill in the blank: The brain unconsciously processes the information, so these responses are _______.

A

reflexes

216
Q

What do light receptors (photoreceptors) in dim light do?

A

Stimulate radial muscles to dilate pupils

217
Q

What do light receptors (photoreceptors) in bright light do?

A

Stimulate circular muscles to constrict pupils

218
Q

True or False: Hormones are substances released by glands into the bloodstream.

A

True

219
Q

What is the function of hormones?

A

Regulate various physiological processes

220
Q

What is an example of a stimulus that can trigger a hormonal response?

A

Low blood glucose concentration

221
Q

What is a gland?

A

A group of cells that are specialised to secrete a useful substance, such as a hormone

Example: The pancreas secretes insulin.

222
Q

What are hormones?

A

‘Chemical messengers’ that can be proteins, peptides, or steroids

Example: Insulin is a peptide hormone, while progesterone is a steroid hormone.

223
Q

How are hormones secreted?

A

When a gland is stimulated by a change in concentration of a specific substance or by electrical impulses

224
Q

How do hormones travel in the body?

A

Hormones diffuse directly into the blood and are transported by the circulatory system

225
Q

What are target cells?

A

Cells that have specific receptors for a hormone, allowing them to bind and respond to it

226
Q

What is the role of effectors in hormonal communication?

A

Effectors are the target cells that respond to the hormone’s signal

227
Q

What happens when low blood glucose concentration is detected?

A

The pancreas releases the hormone glucagon into the blood

228
Q

What is the response of the liver to glucagon?

A

Target cells in the liver convert glycogen into glucose, releasing it into the blood

229
Q

What is a key difference between nervous and hormonal communication?

A

Nervous communication uses electrical impulses, while hormonal communication uses chemicals

230
Q

Which communication method has a faster response?

A

Nervous communication

231
Q

Describe the response duration of hormonal communication.

A

Long-lived response - hormones aren’t broken down very quickly

232
Q

Fill in the blank: Hormones travel at the _______ of blood.

A

[speed]

233
Q

True or False: Hormonal communication leads to a localized response.

A

False

234
Q

List two types of effectors.

A
  • Muscles
  • Glands
235
Q

What is the role of receptors in the human eye’s response to bright light?

A

They detect the change in light intensity and initiate a response

236
Q

What is one way nervous communication is different from hormonal communication?

A

Nervous communication is short-lived while hormonal communication is long-lived

237
Q

Give an example of a hormone and its function.

A

Insulin - regulates blood glucose levels

238
Q

What are receptors specific to?

A

One kind of stimulus

239
Q

What type of receptors are found on cell surface membranes?

A

Proteins

240
Q

What is the voltage across the membrane called?

A

Potential difference

241
Q

What generates the potential difference across the membrane?

A

Ion pumps and ion channels

242
Q

What triggers an action potential?

A

If the change in potential difference reaches the threshold level

243
Q

Fill in the blank: Light enters the eye through the _______.

A

Pupil

244
Q

What area of the retina contains many photoreceptors?

A

Fovea

245
Q

What is the blind spot?

A

Where the optic nerve leaves the eye with no photoreceptor cells

246
Q

What do photoreceptors convert light into?

A

An electrical impulse

247
Q

True or False: Rods provide color vision.

A

False

248
Q

Where are rods mainly found?

A

Peripheral parts of the retina

249
Q

Where are cones mainly found?

A

Packed together in the fovea

250
Q

What type of vision do rods provide?

A

Monochromatic vision

251
Q

What happens to light-sensitive pigments when light hits them?

A

They are bleached, causing a chemical change

252
Q

What type of neurone connects photoreceptors to the optic nerve?

A

Bipolar neurone

253
Q

Fill in the blank: The optic nerve carries impulses to the _______.

A

Brain

254
Q

What occurs when sodium ions diffuse into a rod cell?

A

The inside of the cell becomes depolarized

255
Q

What is the process called when light energy causes a change in photoreceptors?

A

Bleaching

256
Q

What happens to the neurotransmitter release when it is dark?

A

No information is sent to the bipolar neurone

257
Q

What happens to sodium ions when it’s light?

A

They cannot diffuse into the cell

258
Q

What are receptors?

A

Proteins found in the nervous system that detect stimuli

259
Q

What happens during active transport regarding sodium ions?

A

Sodium ions (Na+) are pumped out of the cell

260
Q

What occurs when sodium ions diffuse back into the cell?

A

The cell membrane is said to be depolarised

261
Q

What is released when an inhibitory neurotransmitter is released?

A

No action potentials in the bipolar neurone

262
Q

What triggers the release of neurotransmitters in rod cells?

A

Light energy causing the breakdown of rhodopsin

263
Q

What is the process called when rhodopsin breaks apart into retinal and opsin?

A

Bleaching

264
Q

What happens when sodium ion channels close in rod cells?

A

Sodium ions cannot diffuse back in

265
Q

What is the result of sodium ions building up outside the rod cell?

A

The cell membrane becomes hyperpolarised

266
Q

What does hyperpolarisation of the rod cell lead to?

A

Stops releasing neurotransmitters

267
Q

What occurs when the bipolar neurone is no longer inhibited?

A

It depolarises

268
Q

What is the outcome if the change in potential difference reaches the threshold?

A

An action potential is transmitted to the brain via the optic nerve

269
Q

Fill in the blank: ‘Depolarised’ means there’s not much _______ in charge across the membrane.

A

difference

270
Q

What type of channels are sodium channels?

A

Cation channels

271
Q

What do photoreceptors convert light into?

A

Electrical signals

272
Q

When it’s dark, is a bipolar neurone inhibited or uninhibited?

A

Inhibited

273
Q

What is rhodopsin?

A

A light-sensitive pigment that’s broken apart by light energy when rod cells are stimulated

274
Q

What is the bundle of neurones that links the eye to the brain?

A

Optic nerve

275
Q

True or False: Action potentials are sent along the bipolar neurone when it is inhibited.

A

False

276
Q

What is the blind spot?

A

Area in the retina where no photoreceptors are present

277
Q

What do neurones carry in the form of action potential?

A

Nerve impulses

Neurones carry nerve impulses to other parts of the body.

278
Q

What are the main extensions of a neurone that connect to other neurones?

A

Dendrites and axons

Dendrites carry impulses towards the cell body, while axons carry impulses away.

279
Q

What is the primary function of motor neurones?

A

Carry nerve impulses from the CNS to effector cells

Motor neurones have many short dendrites and one long axon.

280
Q

What is the structure of sensory neurones?

A

One long dendron and one short axon

The cell body is located in the middle of the neurone.

281
Q

What do relay neurones do?

A

Transmit action potentials through the CNS

They connect sensory neurones to motor neurones.

282
Q

What is the resting potential of a neurone?

A

-70 mV

This is the voltage across the membrane when the neurone is at rest.

283
Q

What creates and maintains the resting potential in a neurone?

A

Sodium-potassium pumps and potassium ion channels

These structures regulate ion concentrations across the neurone membrane.

284
Q

What is the function of sodium-potassium pumps?

A

Move three sodium ions out for every two potassium ions in

This process requires ATP and is an example of active transport.

285
Q

What happens to sodium ions in a neurone’s resting state?

A

They cannot diffuse back in

The membrane is not permeable to sodium ions.

286
Q

What causes the outside of a neurone to be positively charged?

A

More positive ions outside than inside

This difference in charge is due to the action of sodium-potassium pumps.

287
Q

Fill in the blank: The membrane of a neurone is _______ at rest.

A

Polarised

288
Q

What is the term for the rapid change in a neurone’s membrane potential triggered by a stimulus?

A

Depolarisation

This process is essential for the propagation of action potentials.

289
Q

True or False: The outside of the neurone is negatively charged at rest.

A

False

The outside is positively charged compared to the inside.

290
Q

What happens during repolarisation?

A

Potassium ions diffuse out of the neurone

This process restores the resting potential.

291
Q

What is hyperpolarisation in the context of neurones?

A

An overshoot of the resting potential

This occurs when the membrane potential becomes more negative than the resting state.

292
Q

What is depolarisation in a neurone?

A

A process where sodium ion channels open, allowing sodium ions to diffuse into the neurone, making the inside less negative.

Depolarisation occurs when the potential difference reaches the threshold of around -55 mV.

293
Q

What happens during repolarisation?

A

Sodium ion channels close and potassium ion channels open, allowing potassium ions to diffuse out of the neurone.

This process helps return the membrane potential towards its resting state.

294
Q

What is hyperpolarisation?

A

A phase where potassium ion channels are slow to close, leading to an overshoot where the potential difference becomes more negative than the resting potential.

This can result in a potential difference of less than -70 mV.

295
Q

What is the resting potential of a neurone?

A

The state where the ion channels are reset and the sodium-potassium pump maintains the membrane potential until the neurone is excited again.

The resting potential is typically around -70 mV.

296
Q

What is the refractory period?

A

The recovery phase after an action potential during which the neurone cannot be excited again due to closed ion channels.

Sodium channels are closed during repolarisation and potassium channels are closed during hyperpolarisation.

297
Q

What causes the change in potential difference during an action potential?

A

The opening and closing of voltage-gated sodium and potassium channels in response to changes in membrane potential.

This process is essential for the transmission of action potentials along the neurone.

298
Q

What are the roles of sodium and potassium channels in action potentials?

A

Sodium channels facilitate depolarisation, while potassium channels facilitate repolarisation and hyperpolarisation.

Both types of channels are voltage-gated and open at specific voltages.

299
Q

Fill in the blank: The sodium-potassium pump helps maintain the neurone’s _______.

A

resting potential

300
Q

True or False: Potassium ions diffuse into the neurone during depolarisation.

A

False

During depolarisation, sodium ions diffuse into the neurone.

301
Q

What is the threshold potential for depolarisation in a neurone?

A

-55 mV

302
Q

How does hyperpolarisation affect the neurone’s potential?

A

It makes the potential difference more negative than the resting potential.

This occurs due to the slow closure of potassium channels.

303
Q

What happens after an action potential in terms of ion channels?

A

Ion channels reset, and the sodium-potassium pump restores resting potential.

This process is crucial for preparing the neurone for the next potential action.

304
Q

What is the potential difference across the membrane during resting potential?

A

-70 mV

305
Q

Name the two main types of ion channels involved in action potentials.

A
  • Sodium ion channels
  • Potassium ion channels
306
Q

What is the process called when sodium ions enter a neurone and diffuse sideways?

A

Wave of depolarisation

307
Q

What happens to sodium ion channels in the next region of the neurone when an action potential occurs?

A

They open and sodium ions diffuse into that part

308
Q

What effect does the refractory period have on action potentials?

A

Prevents overlap and ensures they are discrete impulses

309
Q

True or False: The refractory period allows action potentials to travel in both directions.

A

False

310
Q

What is the relationship between the size of a stimulus and the frequency of action potentials?

A

A bigger stimulus causes more frequent impulses

311
Q

Fill in the blank: Local anaesthetics work by binding to _______ in the membrane of neurones.

A

Sodium ion channels

312
Q

What is the effect of local anaesthetics on action potentials?

A

They prevent action potentials from being conducted

313
Q

What does reaching the threshold in a neurone signify?

A

An action potential will always fire with the same change in voltage

314
Q

What is the outcome if the threshold is not reached in a neurone?

A

An action potential won’t fire

315
Q

How does the refractory period contribute to the directionality of action potentials?

A

It ensures action potentials are unidirectional

316
Q

What analogy is used to describe the wave of depolarisation in neurones?

A

A Mexican wave travelling through a crowd

317
Q

What occurs during the refractory period regarding ion channels?

A

Ion channels are recovering and can’t be opened

318
Q

How does a small stimulus compare to a big stimulus in terms of action potential?

A

A bigger stimulus causes them to fire more frequently

319
Q

What is the term for the potential when a neurone is at rest?

A

Resting potential

320
Q

What is the primary effect of sodium ions rushing into a neurone?

A

Causes depolarisation

321
Q

What does the term ‘discrete impulses’ refer to in the context of action potentials?

A

Separate action potentials that do not overlap

322
Q

What is the myelin sheath?

A

An electrical insulator made of Schwann cells

323
Q

What are the nodes of Ranvier?

A

Tiny patches of bare membrane between Schwann cells

324
Q

What is the role of sodium ion channels at the nodes of Ranvier?

A

They are concentrated at the nodes and allow sodium ions to enter

325
Q

How does depolarisation occur in myelinated neurones?

A

It only happens at the nodes of Ranvier

326
Q

What is saltatory conduction?

A

The ‘jumping’ of impulses from node to node

327
Q

How does the conduction velocity relate to impulse speed?

A

A high conduction velocity means the impulse is travelling quickly

328
Q

What happens in a non-myelinated neurone?

A

The impulse travels as a wave along the whole length of the axon membrane

329
Q

Fill in the blank: In a myelinated neurone, the impulse _______ from node to node.

A

[jumps]

330
Q

True or False: Impulses travel faster in myelinated neurones than in non-myelinated neurones.

A

True

331
Q

What is one function of Schwann cells?

A

To form the myelin sheath around neurones

332
Q

What is the effect of a bigger stimulus on the size of an action potential?

A

It does not affect the size of the action potential

333
Q

What characterizes multiple sclerosis?

A

Damage to the myelin sheaths of neurones

334
Q

How fast can shrimps conduct nerve impulses?

A

Faster than 200 ms

335
Q

What is a synapse?

A

A junction between a neurone and another neurone, or between a neurone and an effector cell.

An effector cell can be a muscle or gland cell.

336
Q

What is the tiny gap between cells at a synapse called?

A

The synaptic cleft.

337
Q

What does the presynaptic neurone contain at the synapse?

A

A synaptic knob filled with synaptic vesicles containing neurotransmitters.

338
Q

What triggers the release of neurotransmitters into the synaptic cleft?

A

An action potential arriving at the end of a neurone.

339
Q

What happens when neurotransmitters bind to receptors on the postsynaptic membrane?

A

They might trigger an action potential, cause muscle contraction, or cause hormone secretion.

340
Q

True or False: Synapses allow impulses to travel in both directions.

A

False.

341
Q

How are neurotransmitters removed from the synaptic cleft?

A

They are taken back into the presynaptic neurone or broken down by enzymes.

342
Q

Name two examples of neurotransmitters.

A
  • Acetylcholine
  • Dopamine
343
Q

What role does acetylcholine play in the body?

A

It is involved in muscle contraction and the control of heart rate.

344
Q

What causes calcium ions to diffuse into the synaptic knob?

A

The arrival of an action potential that stimulates voltage-gated calcium ion channels to open.

345
Q

What is exocytosis in the context of neurotransmitter release?

A

The process by which vesicles fuse with the presynaptic membrane and release neurotransmitters into the synaptic cleft.

346
Q

What happens to calcium ions after they diffuse into the synaptic knob?

A

They are pumped out afterwards by active transport.

347
Q

What is the function of mitochondria in synaptic knobs?

A

They produce ATP, which is needed for active transport and the movement of vesicles.

348
Q

Fill in the blank: The influx of calcium ions into the synaptic knob causes synaptic vesicles to move to the _______.

A

presynaptic membrane.

349
Q

What is the role of neurotransmitter receptors on the postsynaptic membrane?

A

To bind neurotransmitters and initiate a response in the postsynaptic cell.

350
Q

What ensures that synaptic transmission is unidirectional?

A

The presence of receptors only on the postsynaptic membranes.

351
Q

What is a synapse?

A

A synapse is the junction between two neurons where information is transmitted.

352
Q

What name is given to the tiny gap between the cells at a synapse?

A

Synaptic cleft

353
Q

How do synapses ensure that nerve impulses are unidirectional?

A

Neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron.

354
Q

What is synaptic divergence?

A

Synaptic divergence occurs when one neuron connects to many neurons, allowing information to be dispersed.

355
Q

What is synaptic convergence?

A

Synaptic convergence occurs when many neurons connect to one neuron, amplifying information.

356
Q

Fill in the blank: The neurotransmitter diffuses across the synaptic cleft and binds to specific _______.

A

[receptors]

357
Q

What happens to sodium ion channels in the postsynaptic neuron when the neurotransmitter binds to receptors?

A

Sodium ion channels open.

358
Q

What causes depolarization in the postsynaptic membrane?

A

The influx of sodium ions.

359
Q

What is generated if the threshold is reached in the postsynaptic membrane?

A

An action potential.

360
Q

True or False: The neurotransmitter remains in the synaptic cleft to prolong the response.

A

False

361
Q

What is summation at synapses?

A

Summation is the additive effect of neurotransmitter released from many neurons or one neuron stimulated repeatedly.

362
Q

What is the role of synaptic knobs?

A

Synaptic knobs contain mitochondria that produce ATP for active transport and movement of vesicles.

363
Q

Describe the sequence of events from the arrival of an action potential at the presynaptic membrane to the generation of a new action potential at the postsynaptic membrane.

A

1) Action potential arrives at presynaptic membrane. 2) Neurotransmitter is released into synaptic cleft. 3) Neurotransmitter binds to postsynaptic receptors. 4) Sodium channels open, causing depolarization. 5) If threshold is reached, a new action potential is generated.

364
Q

What is a response in plants?

A

Plants respond to stimuli to increase their chances of survival.

365
Q

Why do plants need to respond to stimuli?

A

To increase their chances of survival by adapting to environmental changes.

366
Q

What is a tropism?

A

A tropism is a plant’s growth response to a directional stimulus.

367
Q

What is a positive tropism?

A

Growth towards the stimulus.

368
Q

What is a negative tropism?

A

Growth away from the stimulus.

369
Q

What is phototropism?

A

The growth of a plant in response to light.

370
Q

How do shoots and roots respond to light in phototropism?

A
  • Shoots grow towards light (positively phototropic)
  • Roots grow away from light (negatively phototropic)
371
Q

What is geotropism?

A

The growth of a plant in response to gravity.

372
Q

How do shoots and roots respond to gravity in geotropism?

A
  • Shoots grow upwards (negatively geotropic)
  • Roots grow downwards (positively geotropic)
373
Q

How do plants respond to stimuli without a nervous system?

A

Plants use growth factors, which are chemicals that speed up or slow down growth.

374
Q

Where are growth factors produced in plants?

A

In the growing regions of the plant, such as shoot tips and leaves.

375
Q

What is the role of auxins in plant growth?

A

Auxins stimulate shoot growth by promoting cell elongation.

376
Q

What effect do high concentrations of auxins have on roots?

A

They inhibit growth in roots.

377
Q

Name other important plant growth factors.

A
  • Gibberellins — stimulate flowering and seed germination
  • Cytokinins — stimulate cell division and differentiation
  • Ethene — stimulates fruit ripening and flowering
  • Abscisic acid (ABA) — involved in leaf fall
378
Q

What are phytochromes?

A

Proteins that detect light and help regulate plant responses to light.

379
Q

What is the significance of different wavelengths of light for phytochromes?

A

They respond to different wavelengths, influencing plant growth and development.

380
Q

Fill in the blank: A _______ is a plant’s growth response to a directional stimulus.

A

tropism

381
Q

True or False: All plants respond to stimuli in the same way.

A

False

382
Q

What is the role of auxin in plants?

A

Auxin regulates growth and responses to stimuli in plants.

383
Q

What is the significance of IAA in plant growth?

A

IAA (Indole-3-acetic acid) is an important auxin that influences growth direction.

384
Q

How does IAA affect phototropism?

A

IAA moves to shaded parts of the plant, causing cells to elongate and the shoot to bend towards the light.

385
Q

How does IAA influence root growth in response to light?

A

IAA moves to the side of the root away from light, inhibiting growth on that side and causing the root to bend away.

386
Q

Define geotropism in relation to IAA.

A

Geotropism is the growth response of plants to gravity, where IAA accumulates on the underside, causing uneven growth.

387
Q

What are phytochromes?

A

Phytochromes are photoreceptors in plants that detect light.

388
Q

Where are phytochromes found in plants?

A

Phytochromes are found in leaves, seeds, roots, and stems.

389
Q

What light wavelengths do phytochromes absorb?

A

Phytochromes absorb red light at 660 nm and far-red light at 730 nm.

390
Q

What happens to phytochromes when exposed to red light?

A

P660 is quickly converted into PFR when exposed to red light.

391
Q

What occurs to phytochromes in darkness?

A

PFR is slowly converted back into PR in darkness.

392
Q

How do the levels of PR and PFR change throughout the day?

A

Daylight contains more red light, leading to higher levels of PFR compared to PR at night.

393
Q

Why do some plants flower in summer?

A

Differing amounts of PR and PFR regulate gene transcription involved in flowering, leading to summer blooms.

394
Q

Fill in the blank: Plants respond to stimuli to _______.

A

survive and adapt to their environment.

395
Q

What is a tropism?

A

A tropism is a growth response of a plant to a directional stimulus.

396
Q

True or False: IAA promotes growth on the side of the plant that is exposed to light.

A

False.

397
Q

What stimulates iris plants to flower?

A

High levels of PFR.

398
Q

What time of year would an iris flower?

A

In spring or summer when light levels are high.

399
Q

What is the role of auxin in plants?

A

Auxin regulates growth and responses to stimuli in plants.

400
Q

What is the significance of IAA in plant growth?

A

IAA (Indole-3-acetic acid) is an important auxin that influences growth direction.

401
Q

How does IAA affect phototropism?

A

IAA moves to shaded parts of the plant, causing cells to elongate and the shoot to bend towards the light.

402
Q

How does IAA influence root growth in response to light?

A

IAA moves to the side of the root away from light, inhibiting growth on that side and causing the root to bend away.

403
Q

Define geotropism in relation to IAA.

A

Geotropism is the growth response of plants to gravity, where IAA accumulates on the underside, causing uneven growth.

404
Q

What are phytochromes?

A

Phytochromes are photoreceptors in plants that detect light.

405
Q

Where are phytochromes found in plants?

A

Phytochromes are found in leaves, seeds, roots, and stems.

406
Q

What light wavelengths do phytochromes absorb?

A

Phytochromes absorb red light at 660 nm and far-red light at 730 nm.

407
Q

What happens to phytochromes when exposed to red light?

A

P660 is quickly converted into PFR when exposed to red light.

408
Q

What occurs to phytochromes in darkness?

A

PFR is slowly converted back into PR in darkness.

409
Q

How do the levels of PR and PFR change throughout the day?

A

Daylight contains more red light, leading to higher levels of PFR compared to PR at night.

410
Q

Why do some plants flower in summer?

A

Differing amounts of PR and PFR regulate gene transcription involved in flowering, leading to summer blooms.

411
Q

Fill in the blank: Plants respond to stimuli to _______.

A

survive and adapt to their environment.

412
Q

What is a tropism?

A

A tropism is a growth response of a plant to a directional stimulus.

413
Q

True or False: IAA promotes growth on the side of the plant that is exposed to light.

A

False.

414
Q

What stimulates iris plants to flower?

A

High levels of PFR.

415
Q

What time of year would an iris flower?

A

In spring or summer when light levels are high.

Biology Edexcel Sophie (8 decks)

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