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Biology > Section 6- Response to stimuli > Flashcards

Section 6- Response to stimuli Flashcards

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1
Q

What do vertebrates have that provide rapid, automatic responses to stimuli?

A

Reflex arcs

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2
Q

What is the process of stimulus to response?

A

Impulse passes across a synapse to a relay neuron

Across another synapse

Travels to an effector via the motor neuron

Effector initiates the response

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3
Q

What are tropisms?

A

Growth response in a plant

Reponses are controlled by specific control factors

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4
Q

What is an example of a specific growth factor that controls tropisms?

A

Auxins

Indole acetic acid (IAA)

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5
Q

What is a photoropism?

A

Growth of a plant towards or away from light

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6
Q

What is the process of positive phototropism?

A

Grow towards lights

IAA is produced in shoot tip and diffuses into the growing region

In presence of light is moves to the dark side

IAA disrupts hydrogen bonds between microfibrils in cellulose allowing cells to elongate and divide

Leads to unequal growth

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7
Q

What is gravitropism?

A

Plants response to gravity

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8
Q

What is the process of positive gravitropism?

A

Grow towards gravity

IAA made in the tips of the roots diffuses into the growing region

Dense organelles amyloplasts sink to the bottom of the roots

Moves IAA with them

IAA inhibits growth causing the root to bend downwards

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9
Q

What are amyloplasts and when are they used?

A

Storage vesicles of starch

Sink to bottom of roots during positive gravitropism

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10
Q

What is an example of a positive and negative phototropism?

A

Positive: Shoots of plant growing towards lights

Negative: Roots growing away from the light

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11
Q

What is a taxis?

A

Directional movement responses to a directional stimulus

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12
Q

What is an example of a positive phototaxis?

A

Moth flying towards light

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13
Q

What would be an example of a negative phototaxis?

A

Worm burrowing underground

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14
Q

What is a kineses?

A

A kinetic response is a non-directional response

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15
Q

How does the strength of a stimulus affect the rate of movement?

A

Bigger stimulus causes the animal to move faster

Make more frequent turns

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16
Q

What is the kinesthetic response when an organism is in favourable conditions?

A

Organism slows down and turns less frequently

Increases chances of remaining in favourable environment

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17
Q

What is the difference between taxis and kinesis?

A

Taxis is a directional movement response to a directional stimulus

Kinesis is a non-directional response

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18
Q

What is the Pacinian corpuscle?

A

Pressure receptor found in the skin tissue of mammals

One of many receptors in the skin that each detect just one stimulus

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19
Q

What does the Pacinian corpuscle consist of?

A

Series of plasma membranes that enclose the end of a sensory neurone

Membranes are called lamellae

Within the final lamellae are lots of sodium ions

In lamellae and the axon membrane are stretch-mediated carrier proteins for sodium ions

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20
Q

What happens when pressure is applied to the lamellae in the Pacinian corpuscle?

A

The membranes become distorted

Carrier proteins open allowing sodium ions to move by facilitated diffusion into the axon

Potential difference (voltage) is altered across the membrane = GENERATOR POTENTIAL

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21
Q

In the Pacinian Corpuscle, the bigger the stimulus…

A

The more stretch-mediated carrier proteins open

More sodium ions enter the axon by facilitated diffusion, so the change in potential difference is larger

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22
Q

In the Pacinian Corpuscle, if the generator potential is big enough to pass through the threshold

A

Then an ‘action potential’ (nerve impulse) will be generated

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23
Q

How is the cardiac cycle controlled?

Study These Flashcards
A
  1. Impulse starts in SinoAtrial (SA) node
  2. Impulse travels through atria walls
  3. Both atria contract
  4. Cardiac impulse reaches Atrioventricular (AV) node
  5. Impulse spreads down Bundle of His
  6. Impulse spreads around ventricle walls through purkinje fibres
  7. Causes ventricles to contract
24
Q

What is the SinoAtrial (SA) node and where is it located?

Study These Flashcards
A

Pacemaker

Located at top of right atrium

25
What does the Atrioventricular (AV) node do?
Helps delay the impulse to allow the atria to finish their contraction before ventricles contract.
26
Where is the Bundle of His located?
The septum
27
Why does the impulse in the heart need to be delayed?
Ensures enough time for blood to pass through and valves to close
28
What does myogenic mean?
Can create its own impulse
29
What 2 sections is the autonomic nervous system split into?
Sympathetic = fight or flight Parasympathetic = rest and digest
30
What is the medulla oblongata and what does it contain?
Contains the cardioregulatory centre It receives information from chemoreceptors and baroreceptors
31
What happens when there is a decrease in blood pH?
It is detected by the chemoreceptors More action potentials sent to the acceleratory centre of the cardioregulatory centre of the medulla oblongata More action potentials sent down sympathetic nervous system to sinoatrial node Generates impulse at faster rate
32
What happens when an increase in blood pressure occurs?
Detected by barrow receptors More action potentials sent to the acceleratory region of the cardioregulatory centre of the medulla oblongata More action potenials sent down parasympathetic nervous to sinoatrial node Less frequent impulses to be generated
33
What is the retina?
Located at the back of the eye Tissue made entirely of receptor cells
34
What are the 2 different photoreceptor cells?
Cone cells Rod cells
35
What are cone cells?
Provide colour vision in high light intensity Mostly concentrated in the fovea where best vision is found Provide high visual acuity
36
What are the 3 different types of cone cells?
Red sensitive Blue sensitive Green sensitive
37
What is the trichromatic theory of colour vision?
3 types of cone cells Red sensitive Blue sensitive Green sensitive
38
What are rod cells?
Provide low visual acuity Work in low light intensity Lack colour perception
39
How do cone cells have high visual activity?
Each cone cell is connected to a single bipolar cell This is connected to a single neuron in the optic nerve When light strikes cone cell an action potential is triggered that tells brain exactly where light source is (provided stimulus is intense enough to pass generator potential)
40
How to rod cells allow for low light vision?
Generator potentials can add together multiple rod cells that connect to 1 neuron Allows low light vision Brain cannot determine exactly where light source is Visual acuity reduced
41
How does a Pacinian corpuscle produce a generator potential in response to a specific stimulus?
Pressure stretches membrane Sodium ion gates open Sodium ions enter causing depolarisation Change in membrane potential
42
What is a stretch-mediated sodium channel?
Special type of sodium channel that changes its permeability to sodium when it changes shape
43
Why do brightly coloured objects often appear grey in dim light?
Only rod cells are stimulated by low light intensities Rod cells cannot distinguish between different colour of light Object is perceived only in a mixture of black and white
44
Why is it easier to see a star in the sky by looking slightly to the side of it rather than directly at it?
Looking at one side means light from star is focused toward the outer regions of the retina Mostly rod cells Stimulated by low light intensities so star is seen
45
What is the process by which by which sodium ions pass through the gated channels?
Facilitated diffusion
46
Why can't we see colours in dim light?
Rod cells work in low light intensities, cone cells do not They lack colour perception
47
If a constant stimulus is applied to a receptor it stops responding. Suggest the advantage of this.
Allows noticeable things to be identified
48
What are 2 stimuli that may result in a change of heart rate?
Blood pressure Blood pH
49
How is a resting potential of -70mV maintained in the sensory neurone when no pressure is applied?
Membrane more permeable to K+ and less permeable to Na+ Na+ actively transported out and K+ in
50
How does applying pressure to the Pacinian corpuscle produce changes in membrane potential?
Applying pressure causes membrane to become distorted Na+ channels in membrane open so Na+ moves in Greater pressure move channels open
51
How is a membrane potential the same whether a medium or heavy pressure is applied?
All or nothing principle Once passed threshold all Na+ channels open
52
What are advantages of a simple reflex?
Rapid Protect against damage to body tissue Doesn't have to be learnt
53
What is saltatory comduction?
Schwann cells insulate axon Depolarisation only occurs in nodes of ranvier Faster than if entire length of membrane had to be depolarised
54
What controls a change in heart rate?
Medulla oblongata
55
How does stimulation of chemoreceptors during exercise results in a change in heart rate?
Increase in Co2 from respiration Decrease in blood pH which is detected by chemoreceptors in carotid More impulse to medulla oblongata More impulses along sympathetic nervous system to the SAN increasing heart rate
56
How does the connection of rod cells to neurons in the retina allow us to see objects in dim light?
Several rods have connections with one bipolar cell Summation of generator potentials all together Excess threshold Individual generator potentials don't exceed threshold
57
How does the refractory period ensure that nerve impulses are kept separate from one another?
No opening of Na+ voltage gated channels to allow influx of sodium ions causing depolarisation

Biology (25 decks)

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