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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?

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?

A

Pacemaker

Located at top of right atrium

25
Q

What does the Atrioventricular (AV) node do?

A

Helps delay the impulse to allow the atria to finish their contraction before ventricles contract.

26
Q

Where is the Bundle of His located?

A

The septum

27
Q

Why does the impulse in the heart need to be delayed?

A

Ensures enough time for blood to pass through and valves to close

28
Q

What does myogenic mean?

A

Can create its own impulse

29
Q

What 2 sections is the autonomic nervous system split into?

A

Sympathetic = fight or flight

Parasympathetic = rest and digest

30
Q

What is the medulla oblongata and what does it contain?

A

Contains the cardioregulatory centre

It receives information from chemoreceptors and baroreceptors

31
Q

What happens when there is a decrease in blood pH?

A

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
Q

What happens when an increase in blood pressure occurs?

A

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
Q

What is the retina?

A

Located at the back of the eye

Tissue made entirely of receptor cells

34
Q

What are the 2 different photoreceptor cells?

A

Cone cells

Rod cells

35
Q

What are cone cells?

A

Provide colour vision in high light intensity

Mostly concentrated in the fovea where best vision is found

Provide high visual acuity

36
Q

What are the 3 different types of cone cells?

A

Red sensitive

Blue sensitive

Green sensitive

37
Q

What is the trichromatic theory of colour vision?

A

3 types of cone cells

Red sensitive
Blue sensitive
Green sensitive

38
Q

What are rod cells?

A

Provide low visual acuity

Work in low light intensity

Lack colour perception

39
Q

How do cone cells have high visual activity?

A

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
Q

How to rod cells allow for low light vision?

A

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
Q

How does a Pacinian corpuscle produce a generator potential in response to a specific stimulus?

A

Pressure stretches membrane

Sodium ion gates open

Sodium ions enter causing depolarisation

Change in membrane potential

42
Q

What is a stretch-mediated sodium channel?

A

Special type of sodium channel that changes its permeability to sodium when it changes shape

43
Q

Why do brightly coloured objects often appear grey in dim light?

A

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
Q

Why is it easier to see a star in the sky by looking slightly to the side of it rather than directly at it?

A

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
Q

What is the process by which by which sodium ions pass through the gated channels?

A

Facilitated diffusion

46
Q

Why can’t we see colours in dim light?

A

Rod cells work in low light intensities, cone cells do not

They lack colour perception

47
Q

If a constant stimulus is applied to a receptor it stops responding. Suggest the advantage of this.

A

Allows noticeable things to be identified

48
Q

What are 2 stimuli that may result in a change of heart rate?

A

Blood pressure

Blood pH

49
Q

How is a resting potential of -70mV maintained in the sensory neurone when no pressure is applied?

A

Membrane more permeable to K+ and less permeable to Na+

Na+ actively transported out and K+ in

50
Q

How does applying pressure to the Pacinian corpuscle produce changes in membrane potential?

A

Applying pressure causes membrane to become distorted

Na+ channels in membrane open so Na+ moves in

Greater pressure move channels open

51
Q

How is a membrane potential the same whether a medium or heavy pressure is applied?

A

All or nothing principle

Once passed threshold all Na+ channels open

52
Q

What are advantages of a simple reflex?

A

Rapid

Protect against damage to body tissue

Doesn’t have to be learnt

53
Q

What is saltatory comduction?

A

Schwann cells insulate axon

Depolarisation only occurs in nodes of ranvier

Faster than if entire length of membrane had to be depolarised

54
Q

What controls a change in heart rate?

A

Medulla oblongata

55
Q

How does stimulation of chemoreceptors during exercise results in a change in heart rate?

A

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
Q

How does the connection of rod cells to neurons in the retina allow us to see objects in dim light?

A

Several rods have connections with one bipolar cell

Summation of generator potentials all together

Excess threshold

Individual generator potentials don’t exceed threshold

57
Q

How does the refractory period ensure that nerve impulses are kept separate from one another?

A

No opening of Na+ voltage gated channels to allow influx of sodium ions causing depolarisation

Biology (25 decks)

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