Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biology - Unit 6 > Chapter 14 - Response to Stimuli > Flashcards

Chapter 14 - Response to Stimuli Flashcards

1
Q

Define stimulus

A

A detectable change in the environment that can be detected by an organisms. It is either internal in multicellular organisms or external in any organism

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

Define receptor

A

A specialised organ or cell that detects changes in the environment

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

Define response

A

As a result of the stimulus detected by the receptor, a change is caused which may be movement or a change in behaviour to increase chance of survival

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

Define taxes

A

A directional response that involves movement in a specific direction towards or away from a stimulus. Positive taxes is towards a stimulus and negative taxes is away from a stimulus

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

Give three examples of taxes

A

Algae move towards light (positive phototaxis)
Earthworms move away from light (negative phototaxis)
Bacteria move towards glucose (positive chemotaxis)

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

Define kinesis

A

A form of non-directional response from an unfavourable area to a favourable one by change of speed

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

When is kinesis important?

A

When the stimulus is less directional and no clear gradient is produced

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

How does kinesis work?

A

Organism moves into unfavourable area and increases movement to increase likelihood of moving into favourable area and vice versa

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

Define tropism

A

The directional growth of a plant in response to a directional stimulus

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

Give two examples of tropism

A
  • Plant shoots growing towards light (positive phototropism) and away from gravity (negative gravitropism)
  • Plant roots growing away from light (negative phototropism) and towards gravity (positive gravitropism)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

State the three factors plants respond to and describe why

A

Light as needed for photosynthesis
Gravity as need water and must be firmly anchored
Water as needed for photosynthesis and other metabolic processes

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

What are plant growth factors?

A

Hormones that affect growth and the tissues that release them

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

Define the sequence that leads from a stimulus to a response

A

Stimulus - Receptor - Coordinator - Effector - Response

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

What is indoleacetic acid?

A

A plant hormone that is a type of auxin responsible for controlling plant cell elongation

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

Where is indoleacetic acid produced?

A

The tips and shoots of flowering plants

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

Summarise phototropism in a flowering plant

A
  • Cells in top produce IAA which is transported down shoot
  • Initially evenly distributed
  • Light causes movement of IAA from light side to dark side
  • Greater concentration of IAA on dark side
  • Causes elongation of shoot cells
  • Elongates faster than light side so tip bends towards light
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Summarise gravitropism in a flowering plant

A
  • Cells in tip of root produce IAA which is transported along the root
  • Initially evenly distributed
  • Gravity influences movement of IAA from upper side to lower side of root
  • Greater of concentration on lower side of root
  • IAA inhibits elongation of root cells
  • Elongate less than upper side
  • Root bends towards the force of gravity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why does IAA have a greater effect on cells that are not fully matured?

A

Mature cells develop greater rigidity and hence do not respond

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

What is the acid growth hypothesis

A

The explanation of how IAA increases plasticity of cells:

  • Active transport of hydrogen ions from cytoplasm into cell wall space
  • Causes cell wall to become more plastic allowing elongation by expansion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the central nervous system

A

A division of the nervous system comprised of the brain and spinal chord

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

What is the peripheral nervous system

A

A division of the nervous system made up of pairs of nerves that originate from the brain or spinal chord

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

What can the peripheral nervous system be divided into?

A
  • Sensory neurones which carry impulses from receptors to the central nervous system
  • Motor neurones which carry nerve impulses away from the central nervous system to effectors
23
Q

The motor neurone system can be divided into what?

A
  • Voluntary nervous system which carries nerve impulses to skeletal body muscles under conscious control
  • Autonomic nervous system which carries nerve impulses to glands, smooth muscle and cardiac muscle under subconscious control
24
Q

What is the spinal chord?

A

A column of nervous tissue that runs along the back inside the vertebral column for protection

25
What are the properties of a reflex action
Rapid, short-lived, localised and involuntary
26
Define reflex arc
The nerve pathway in the body taken by an action potential leading to a rapid, involuntary response to a stimulus
27
Define reflex
An involuntary response to a sensory stimulus
28
Summarise the reflex arc
- Stimulus - Receptor detects this - Sensoru neurone passes impulse to spinal chord - Coordinator (intermediate neurone) links sensory neurone to motor neurone - Motor neurone carries impulse from spinal chord to effector - Effector such as muscle contracts - Response caused
29
Why are reflex arcs important?
- Involuntary so do not require decision making, allowing a more rapid and sometimes more complex response - Protect body from harm as do not need to be learnt - Fast as neurone pathway short with few synapses
30
What can artificial IAA hormones be used as?
Herbicides by causing the plant to grow itself to death
31
Define effector
A cell tissue, organ or system that carries out a response
32
Define coordinator
Connects information between receptor and appropriate effector
33
What is the pacinian corpuscle
A type of receptor that responds to mechanical pressure
34
What are the two features of the pacinian corpuscle?
- Specific to a single type of stimulus - Produces a generator potential by acting as a transducer (transduces mechanic energy of stimulus into generator potential)
35
Where do pacinian corpuscles occur?
Fingers, soles of feet and on external genitalia. They also occur in ligaments and tendons
36
Why are pacinian corpuscles located in tendons?
To enable the organism to know which joints are changing direction
37
Summarise the structure of a pacinian corpuscle
Sensory neurone lays in the centre of tissues with each tissue layer separated by gel
38
What is a stretch mediated sodium channel
A sodium channel whose permeability changes when deformed
39
Define transducer
Cells that convert a non electrical stimulus into an electrical signal
40
Define generator potential
Depolarisation of the membrane of a receptor cell due to stimuli
41
Summarise how a pinion corpuscle works
- Resting state means channels too narrow for sodium - Pressure applied causing membrane around neurone to deform - Widens sodium channels - Influx causes depolarisation and hence generator potential - Creates an action potential
42
Summarise rod cells of the eye
- Cannot distinguish between wavelengths of light so see black/white - More numerous than cone cells - Many link to one bipolar neurone (retinal convergence) resulting in low visual acuity - Greater chance of generator potential as many to one (spatial summation) - One type - Sensitive to low intensity light - More at the periphery of the retina and absent at the fovea
43
How do rod cells create a generator potential and what does this allow?
- Pigment in rod cells called rhodopsin must be broken down - There is enough energy from low level light to enable this - Hence rod cells can respond to low intensity light
44
Summarise cone cells
- Three types for different wavelengths of light (colour) - Fewer number that rod cells - Fewer at periphery of retina and concentrated at fovea - Good visual acuity due to each cell have one bipolar neurone but only respond to high intensity light
45
Why are rod cells located at the retinal periphery and cone cells at the fovea?
Fovea is opposite pupil where light intensity high and hence cone cells located here. Rod cells at retinal periphery as light intensity low
46
What are the two divisions of the autonomic nervous system?
Sympathetic - stimulates effectors and speeds up activity | Parasympathetic - Inhibits effectors and so slows down activity
47
Define sinoatrial node
An area of heart muscle in the right atrium that controls and coordinates contraction of the heart
48
Distinguish between myogenic and neurogenic muscles
Myogenic muscles contract from within whereas neurogenic muscle contracts due to nervous impulses from the outside
49
Summarise the sequence of events that controls heart rate
- Wave of electrical excitation spreads from SAN across atria causing them to contract - Atrioventricular septum is nonconductive and prevents the wave crossing to the ventricles - Wave of excitation enters second group of cells called atrioventricular node between atria - This conveys electrical excitation between ventricles along fibres called purkyne tissue which collectively make the bundle of His - Bundle of His conducts wave through atrioventricular septum to the base of ventricles - Wave of excitation released from Purkyne tissue causing both ventricles to contract form the bottom of the heart upwards
50
What is the medulla oblongata?
Area of the brain that causes change in heart rate. It has two centres: - One increases heart rate and is linked to the SAN by the sympathetic nervous system - One decreases heart rate which is linked to the senatorial node by the parasympathetic nervous system
51
What are the two receptors that detect changes in the heart?
Chemoreceptors and pressure receptors
52
Summarise how control by chemoreceptors work
- When blood has higher CO2 conc, pH lower - Chemoreceptors in wall of carotid arteries detect this and increase frequency of nerve impulses to medulla oblongata - This increases frequency of nerve impulse via sympathetic nervous system to SAN increasing production of electrical waves - Increased blood flow leads to more CO2 removed from lungs - pH falls and chemoreceptors reduce frequency of nerve impulses - Medulla oblongata reduces impulses to sinoatrial node
53
How do pressure receptors in the heart operate when blood pressure is too high
- Pressure receptors in the carotid arteries and aorta transmit more nervous impulses to centre of medulla oblongata that decreases heart rate - Impulses sent to SAN via parasympathetic nervous system to decrease heart rate
54
How do pressure receptors in the heart operate when blood pressure is too low
- Pressure receptors in the carotid arteries and aorta transmit more nervous impulses to centre of medulla oblongata that increases heart rate - Impulses sent to SAN via sympathetic nervous system to increase heart rate

Biology - Unit 6 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions