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Response to Stimuli Flashcards

(56 cards)

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1
Q

How do organisms increase their chance of survival?

A

By responding to changes in their environment

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2
Q

What is a tropism?

A
  • Plant growth in response to directional stimulus

- can be towards (+) or negative (-)

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3
Q

What are the tropisms of the plant shoot?

A
  • Positive phototropism

- Negative geotropism

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4
Q

What are the tropisms for a plant root?

A
  • Negative phototropism
  • Positive geotropism
  • Positive hydrotropism
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5
Q

What are the advantages of the plant root tropisms?

A

leaves in most favourable position to capture light

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6
Q

What are the advantages of the plant root tropisms?

A
  • increase probability of roots growing in soil

- increase H2O and nutrient absorption

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7
Q

What are plant growth factors?

A
  • Regulate growth in response to directional stimuli

- Stages: mitosis and cell elongation

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8
Q

What does IAA stand for and what is it?

A

Indoleacetic Acid

An auxin which can cause cell elongation

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9
Q

How does IAA move thru the plant?

A

By diffusion

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10
Q

For phototropism in shoot tip, where does IAA accumulate?

A

The shaded side

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11
Q

How does IAA cause cell elongation?

A
  1. attaches to receptors on cell membrane
  2. causes release of H+ ions
  3. pH decreases
  4. hydrogen bonds in cellulose microfibrils disrupted
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12
Q

True or false: in roots, IAA increases cell elongation

A

False: in roots IAA inhibits growth

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13
Q

For geotropism in roots, where does IAA accumulate and why?

A

On the lower region to inhibit cell elongation, so top side can grow faster

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14
Q

Name 2 reasons why it is important for organisms to respond to stimuli?

A
  1. increase chance of survival

2. increase reproductive success (increase chance of beneficial alleles passes on)

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15
Q

What is taxis?

A

directional response

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16
Q

What is positive and negative taxis?

A 
\+ = towards stimulus 
- = away from stimulus
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17
Q

What are the actual names of the taxis for: water, light and chemical?

A

hydrotaxis, phototaxis and chemotaxis

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18
Q

What is kinesis?

A

non-directional response

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19
Q

How can you tell if the organism doesn’t favour the environmental conditions?

A

more rapidly the organism moves and with fewer turns

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20
Q

Receptors respond to only…

A

1 type of stimulus`

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21
Q

How is an action potential formed?

A

The generator potential exceeds the threshold

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22
Q

Receptors are transducers. What does that mean?

A

change one form of energy into an electrochemical impulse

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23
Q

The greater the stimulus….

Study These Flashcards
A

the greater the frequency of action potentials, and increase time that they go on for

24
Q

Describe briefly how the Pacinian Corpuscle works

Study These Flashcards
A
  1. lamellae deforms
  2. stretch mediated Na+ ion channels open
  3. Na+ opens diffuse thru
  4. depolarises the membrane causing a generator potential
25
Which eye receptor can sense colour and has high visual acuity?
Cone cell
26
where are rod and cone cells located in the retina?
Cone: fovea Rod: periphery
27
Which eye receptor is stimulated in low light and which is stimulated in high light intensity?
Low: rod high: cone
28
What is the name of the pigment that rod cells have?
Rhodopsin
29
What is the name of the pigment which cone cells have?
Iodopsin
30
Why do cone cells have high visual acuity?
each cell has own bipolar neuron and so separate signals sent to the brain so can distinguish which was stimulated
31
How can cone cells produce colour images?
- 3 types responding to different wavelengths | - different type of iodopsin which breaks down in presence of specific wavelength
32
Why are cone cells stimulated at high light intensities?
- own separate bipolar neuron so multiple cells can't be combined to exceed threshold - iodopsin need more energy to break down
33
Why do rod cells have low visual acuity?
- Many rod cells attached to a single bipolar neuron | - single impulse to brain so can't distinguish
34
How can rod cells respond to low light intensity?
- many rod cells connected to 1 bipolar neuron = increase chance of threshold exceeded - rhodopsin doesn't need lots of energy to break down
35
Define sensory neuron
carry nerve impulses from receptor towards CNS
36
Define motor neuron
Carry nerve impulses away from CNS to effectors
37
Define CNS
Made up of brain and spinal cord
38
Define the peripheral nervous system
made up of pairs of nerves that originate from either brain or spinal cord
39
Define the voluntary nervous system
40
What is the difference between the voluntary nervous system and the autonomic nervous system?
voluntary: conscious control autonomic: not voluntary
41
Name 3 reasons why the reflex arc is important
1. very rapid 2. reduce/avoid damage/injury 3. helps to maintain balance/posture
42
What is the autonomic nervous system?
Controls involuntary activities of internal muscles/glands (sympathetic and parasympathetic)
43
What does antagonistic mean?
Sympathetic and Parasympathetic nervous systems oppose one another
44
What is the parasympathetic nervous system?
Stimulates effectors = speeds up activity (in response to stressful stimuli)
45
What is the parasympathetic nervous system?
Inhibits effectors = slows down activity (in response to stimuli)
46
The importance of the parasympathetic nervous system (2)
1. helps conserve energy | 2. Replenishes body's reserves
47
What is the role of the Sinoatrial node?
Generates + sends out electrical waves across wall of atrium = atrium contracts
48
What is the role of the atrioventricular septum?
Non-conductive tissue that prevents electrical wave crossing to ventricles
49
What is the role of the atrioventricular node and why is there a short delay in sending an impulse?
- detects impulses from atria | - allow atria to finish contracting
50
Why is the electrical impulse sent from the apex up the ventricle walls?
Prevents blood pooling in the apex
51
The medulla oblongata has 2 centres:
- Acceleratory | - Inhibitory
52
How does the medulla oblongata increase heart rate?
Impulse sent to SAN via sympathetic system
53
How does the medulla oblongata decrease heart rate?
Impulse sent to SAN via parasympathetic system
54
What are chemoreceptors and where are they located?
- detect changes in the pH (due to CO2 conc.) | - located in the carotid arteries
55
Where are pressure receptors located?
in the carotid arteries and aorta
56
Pressure increases: ___________ system | Pressure decreases: ___________ system
increase: parasympathetic decrease: sympathetic

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