Responding to Change

Category: Responding to Change

A stimulus is a change in the internal or external environment, which can be detected by a receptor, and an effect brought about by an effector. In this unit, we look at how different organisms detect and coordinate these responses.

Plants respond to stimuli via growth factors. At A Level, this is based around Indole Acetic Acid (IAA). the responses are slow, growth responses called tropisms. There have been many experiments on plant responses, and some of these are tested in here.

Animals ( such as many invertebrates) can have simple responses to stimuli that can enable a motile organism, to move to a favourable environment. These are either taxes , which are directional responses, or kineses, which are non-directional responses.

Nervous coordination includes the establishment and maintenance of a negative resting potential,and the generation of an action potential due to changes in membrane permeability to sodium and potassium ions. Once again, we extend GCSE basic understanding of synapses, to consider summation and inhibition too. Receptors are cells that detect specific stimuli, and cause the establishment of a generator potential. In a pacinian corpuscle, the stimulus is pressure. We also use the examples of rod and cone cells as receptors that detect light.

Skeletal muscle is an effector. The arrival of an action potential causes biochemical changes which results in cycles of actinomyosin bridge breaking and formation.

Homeostasis is the maintenance of a constant internal environment. Specifically we look at the control of blood glucose via insulin and glucagon. Also the action of adrenaline, and the second messenger model. We also look specifically at the control of water potential of the blood via ADH on the kidney.

Responses in Plants

1 / 20

Plant responses to stimuli are controlled by what?

Photosynthesis

Growth Factors

Action Potentials

2 / 20

What word describes the growth response of a plant to a stimulus?

Tropism

Trophism

Tropasm

3 / 20

What is a growth response to light called?

Flurotropism

Gravitropism

Phototropism

4 / 20

What response do roots have to light?

Negatively Geotrophic

Positively Phototrophic

Negatively Phototrophic

5 / 20

Which of the following is an example of a plant growth factor?

Indyacetic Acid

Indoleacetic Acid

Indayloacetic Acid

6 / 20

What affect does IAA have on shoot tips?

Mitosis

Elongation

Inhibition

7 / 20

How does IAA bring about this effect?

Stimulates reactions to increase the amount of cellulose in the cell wall, so it can grow.

Stimulates reactions to make the membrane more fluid.

Stimulates reactions which break the bonds between the cellulose molecules in the cell wall.

8 / 20

What effect does low concentrations of IAA have on root tissue?

Stimulates growth.

Inhibits growth.

Increases active transport.

9 / 20

What effect does high concentrations of IAA have on shoot tip tissue?

Stimulates growth.

Inhibits growth.

Increases active transport.

10 / 20

Which of the following is true?

If IAA is unevenly distributed, then growth is evenly distributed and the tissue grows straight. If IAA is evenly distributed, the growth is uneven and the tissue bends.

If IAA is evenly distributed, then growth is evenly distributed and the tissue grows straight. If IAA is unevenly distributed, the growth is uneven and the tissue bends.

11 / 20

In shoot tips which are lit from the side, where will the highest concentration of IAA be found?

The lit side ( illuminated)

The shaded side

Both sides evenly

12 / 20

In root tips growing parallel to the soil, where will the highest concentration of IAA be found ?

The upper surface

The lower surface

Both even

13 / 20

How does IAA become unevenly distributed?

Bright light destroys IAA.

Shade stimulates the production of IAA.

IAA moves away from light.

14 / 20

What does Darwin's experiment where he removed a shoot tip then replaced it show?

That the shoot tip is not needed for shoot growth.

That the shoot tip is responsible for shoot growth.

That growth is controlled below the shoot tip.

15 / 20

What does Darwin's experiment where he placed a black cover over the tip show?

That directional light on the tip effects the direction of growth.

That directional light does not effect direction of growth.

That aluminium foil is toxic to shoot tips.

16 / 20

What does Boysen and Jensen's experiment using agar show?

That gelatin blocks can stimulate growth.

That the tip can be removed and the shoot still grow normally.

That the signal produced by the plant can pass through gelatin.

17 / 20

Which of these statements about Went's experiment is NOT true?

That plant growth is probably caused by a chemical which can diffuse.

That a substance produced in the tip can move (diffuse) into gelatin, and then out again.

Gelatin blocks stimulate growth.

18 / 20

What does this experiment by Went show?

That uneven distribution of a chemical from a shoot tip controls growth.

That even distribution of a chemical from a shoot tip controls growth.

That gelatin controls growth.

19 / 20

What would be a suitable control for Went's experiment ?

The same experiment, but with a different species of plant shoot.

The same experiment but with a gelatin block without a shoot tip having been placed on it.

The same experiment, but with light coming from the opposite direction.

20 / 20

Mica is like thin glass, and is impermeable to most substances. What does Boysen Jensen's experiment inserting mica show ?

That chemicals diffuse down the shoot from the tip.

That chemicals move away from light.

That chemicals move away from light and diffuse down from the tip.

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Taxis and Kinesis

1 / 15

What is the definition of a stimulus?

A change in the internal environment.

A change in the external environment.

A change in the internal or external environment.

2 / 15

True or False : Kinesis is a directional response to a stimulus.

TRUE

FALSE

3 / 15

True or False : Taxis is when an organism either moves faster in harsh conditions or turns less in harsh conditions.

TRUE

FALSE

4 / 15

True or false : Kinesis is a random movement

TRUE

FALSE

5 / 15

True or false : Taxis is a directional movement

TRUE

FALSE

6 / 15

Flatworms turn more frequently in response to an increase in light intensity. Is this taxis or kinesis?

Taxis

Kinesis

7 / 15

True or False : Taxis is only ever away from a stimulus

TRUE

FALSE

8 / 15

Blow fly maggots have a light sensitive spot on their head, which they use to move away from light. Is this taxis or kinesis?

Taxis

Kinesis

9 / 15

Maggots follow a scent up a concentration gradient towards a food source. Is this taxis or kinesis?

Taxis

Kinesis

10 / 15

Woodlice are more stationary with increased humidity. Is this taxis or kinesis?

Taxis

Kinesis

11 / 15

Honey bees can detect the polarised light from the sun and use it to navigate even in cloudy weather. Is this taxis or kinesis?

Taxis

Kinesis

12 / 15

What piece of equipment do animal scientists use to investigate the effect of different stimuli on invertebrates?

Pooter

Pitfall Trap

Choice Chamber

13 / 15

In the above experiment on woodlice, what is the Independent variable?

Light Intensity

Number of woodlice

Length of time you leave the woodlice in the chamber

14 / 15

In the above experiment on woodlice, how would you make the method more valid?

Change the light intensity on the light side with each repeat.

Place each woodlice in the centre of the chamber at the start of each repeat.

Make the dark- side dark and damp.

15 / 15

In the above experiment, you hypothesised that a woodlouse responds by kinesis to a change in light intensity. What would be the best way to measure a response which shows kinesis?

By putting them on the lighter side, and seeing if they move to the darker side.

By counting how many woodlice are on the dark side after on minute.

By measuring how often each woodlice turns/ changes direction in one minute.

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138

Nerves: The Resting Potential

1 / 10

How can charged ions cross a plasma membrane?

a) Simple Diffusion
b) Facilitated Diffusion
c) Active Transport

a & b

b & c

a & c

2 / 10

When an neurone axon is at rest, what charge is the extra cellular fluid compared to the cytoplasm?

a) Simple Diffusion
b) Facilitated Diffusion
c) Active Transport

Positive

Negative

Neutral

3 / 10

Which word best describes the charge distribution across a resting axon plasma membrane?

Polarised

Depolarised

Hyperpolarised

4 / 10

Across a resting human neurone plasma membrane, what is the average potential difference?

+70mV

-70mV

-70V

5 / 10

The resting potential of a neurone is maintained in part, by the Sodium-potassium pump. But which of the following shows the correct movement of the ions?

2 sodium ions out, and 3 potassium ions in.

3 sodium ions in, and 2 potassium ions out.

3 sodium ions out, and 2 potassium ions in.

6 / 10

The plasma membrane of a neurone at rest is most permeable to which ions via facilitated diffusion?

Chlorine ions

Sodium Ions

Potassium Ions

7 / 10

In a resting neurone, why do potassium ions move out via ion channels?

Due to the greater concentration on potassium ions on the inside compared to the outside.

Due to the electrochemical gradient.

Due to the lower concentration on potassium ions on the inside compared to the outside.

8 / 10

Name protein B in the above diagram.

Sodium Ion Channel

Potassium Ion Channel

Sodium-potassium pump

9 / 10

Name protein A in the above diagram.

Sodium Ion Channel

Potassium Ion Channel

Sodium-potassium pump

10 / 10

Name protein C in the above diagram.

Sodium Ion Channel

Potassium Ion Channel

Sodium-potassium pump

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113

Nerves: Action Potentials

1 / 19

Stimulation ( either by a generator potential in a receptor cell or a neurotransmitter binding to a receptor on a postsynaptic membrane) caused which type of channel to open?

Sodium Leakage Channels.

Voltage Gated Sodium Channels.

Voltage Gated Potassium Channels.

2 / 19

After a stimulation has occurred, why do ions move out of an axon?

A Concentration Gradient exists.

Active transport occurs.

An Electrochemical Gradient exists.

3 / 19

What do we call the process happening at '3' on the above diagram?

Depolarisation

Polarisation

Repolarisation

4 / 19

What ion is moving during process '3' on the above diagram?

Sodium Ions

Potassium Ions

Phosphate Ions

5 / 19

Which direction are the ions moving during process 3 on the above diagram?

Into the cytoplasm

Out of the cytoplasm

6 / 19

Name the process happening at '4' on the above diagram?

Depolarisation

Polarisation

Repolarisation

7 / 19

Which ions are moving across the membrane during process '4'?

Sodium Ions

Potassium Ions

Phosphate Ions

8 / 19

What causes a change in the type of channels that are open at stage '4' ?

A change in potential difference.

The passage of 1.5ms since the stimulation occurred.

The generation of a second action potential.

9 / 19

Name stage 5 on the above diagram ( spell it carefully!)

10 / 19

What has happened at stage 5?

The voltage gated sodium channels stay open too long.

The voltage gated potassium channels stay open too long.

The voltage gated potassium channels close too soon.

11 / 19

Which of the events (A - F above) starts depolarisation? Type the letter in the box

12 / 19

Which of the events ( A- F above) requires ATP ? ( Type the letter in the box)

13 / 19

Put the above events ( A-F) in order for the passage an action potential.

D, C, B, E, A, F

C, B, E, A, F, D

E, A, C, B, F, D

14 / 19

The period of time after an action potential, when another action potential cannot pass along that section of a neurone is called the ____________ period ( Watch your spelling).

15 / 19

Why can't a second action potential pass immediately after the first ?

During this period the Sodium-potassium pump is not operational.

During this period the voltage gated sodium channels are locked shut.

During this period the potentil difference across the plasma membrane remains positive.

16 / 19

In order for an action potential to be triggered, a certain number of sodium channels must open, each setting a change in the potential difference.

What name is given to this change in potential difference that must be reached ? (Type your answer)

17 / 19

True or false: If more sodium channels are opened by a stimulus, then the action potential which is generated is bigger.

TRUE

FALSE

18 / 19

True or False: If too few sodium channels are opened by a stimulus on an neurone membrane, then no action potential is generated.

TRUE

FALSE

19 / 19

True or False: A stronger stimulus will generate more frequent action potentials.

TRUE

FALSE

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Nerves: Conduction Along Axons

1 / 15

After an action potential has fired, the refractory period acts as the following:

a) Prevents action potentials overlapping
b) Limit the frequency of action potentials
c) Limit the size of action potentials
d) Makes action potentials travel unidirectionally.

b, c, d

a,b,c,d

a, b, d

2 / 15

In the above diagram, which graph shows the correct effects of increasing a stimulus?

Neither

3 / 15

Many peripheral neurones (including motor neurones)have cells wrapped around the axon.

What are these cells called? ( type your answer- watch your spelling).

4 / 15

Cells wrapped around peripheral neurones contain a membrane with a high content of a fatty substance forming a sheath.

What is the name of this fatty substance? ( Type your answer).

5 / 15

What the the tiny gaps called labelled X on the above diagram? ( Type your answer)

6 / 15

What is the main function of the fatty substance wrapped around peripheral nerve axons?

Thermal Insulators

Electrical Insulators

Waterproof Layer

7 / 15

When an action potential is generated, there is a temporary reversal of the polarity of the neurone membrane at that point. Does this mean that:

The inside becomes more negative compared to the outside.

The outside becomes more negative compared to the inside.

The outside becomes more positive compared to the inside.

8 / 15

Once an action potential has been generated, what causes the next section of the axon membrane to become depolarised?

Some sodium ions diffuse through the cytoplasm, and cause voltage gated sodium channels to open.

Some potassium ions diffuse through the cytoplasm, and cause voltage gated potassium channels to open.

Voltage gated sodium channels are open all the time, so the sodium ions just diffuse out.

9 / 15

Once an action potential has been generated, why is the wave of depolarisation only in one direction?

Hyperpolarisation means potassium channels are working at capacity.

Sodium ions only ever diffuse away from the cell body.

The refractory period means that voltage gated channels are 'locked' closed.

10 / 15

Why is the speed of conduction faster on myelinated neurones?

The sheath creates a hydrostatic pressure, pushing the ions and therefore the action potential along.

The sheath keeps the axon warmer, therefore diffusion is faster.

Due to action potentials only occurring at the gaps between the sheath, so the impulse 'jumps' between them.

11 / 15

Name the term given to the 'jumping' of an action potential long a myelinated neurone.( Type in your answer)

12 / 15

True or False - The speed of conduction along an unmyelinated neurone is around 5 m/s ( jogging pace).

TRUE

FALSE

13 / 15

True or False - Axons with a narrower diameter have a faster speed of conduction.

TRUE

FALSE

14 / 15

Axons with a wider diameter axon have...

More sodium ions for diffusion.

More resistance to the flow of ions through the cytoplasm.

Less resistance to the flow of ions through the cytoplasm.

15 / 15

Why does an increase in temperature ( up to 40 degrees) cause an increase in the speed of conduction along a neurone?

Faster production of ATP.

Faster rate of enzymes.

Faster rate of diffusion of ions.

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Nerves: Synaptic Transmission

1 / 20

Using the diagram, name C

Synaptic Gap

Synaptic Cleft

Synaptic Space

2 / 20

Using the diagram, name E

Nervotransmitter

Synaptictransmitter

Neurotransmitter

3 / 20

Using the diagram, name D

Ligand Gated Ion Channel

Voltage Gated Ion Channel

Sodium-Potassium Pump

4 / 20

Using the diagram, name B

Synaptic Vesicle

Neurotransmitter vesicle

Myelin vesicle

5 / 20

On the diagram, F is a voltage gated ion channel on an excitatory synapse, but which type of ion does it allow through?

Sodium ions

Potassium ions

Calcium ions

6 / 20

On the diagram, which type of ion will D allow through when opened on an excitatory synapse?

Sodium ions

Potassium ions

Calcium ions

7 / 20

Put the following statements in order to explain what happens at an excitatory synapse:

a) Voltage gated calcium channels open.
b) Synaptic vesicles fuse with the pre-synaptic membrane
c) If threshold is reached, an action potential is generated
d) Calcium ions diffuse into the presynaptic neurone.
e) Arrival of an action potential
f) Neurotransmitters bind to receptors with associated sodium channels
g) Neurotransmitters diffuse across the cleft
h) Sodium ions diffuse into post synaptic membrane

a,d,c,g,f,h,c,b,e

e,d,b,a,g,f,h,c

e,a,d,b,g,f,h,c

8 / 20

True or False: Synapses can only transmit an impulse in one direction?

TRUE

FALSE

9 / 20

What reduces the concentration of neurotransmitter in a synapse after it has diffused across?

The neurotransmitter is actively reabsorbed whole, via endocytosis.

An enzyme breaks the neurotransmitter down.

Nothing, it just diffuses until a vey low concentration is reached.

10 / 20

Whether a synapse is excitatory or inhibitory depends on what?

The concentration of the neurotransmitter released.

The type of neurotransmitter released.

The concentration of calcium ions.

11 / 20

What effect do inhibitory synapses have on the post-synaptic membrane?

Depolarise

Repolarise

Hyperpolarise

12 / 20

If a neurotransmitter binds to the post synaptic membrane and causes potassium ion channels to open, would it be excitatory or inhibitory?

Excitatory

Inhibitory

13 / 20

If the concentration of neurotransmitter secreted is very low, then threshold may not be reached. What term describes the process of increasing neurotransmitter release? either by multiple presynaptic neurones forming a single synapse or increasing the frequency of neurotransmitter release. Type your answer

14 / 20

What term is used to describe when more than one presynaptic neurone releases its neurotransmitter onto single post-synaptic neurone? ( Type your answer carefully)

15 / 20

What term is used to describe when more than one presynaptic neurone releases its neurotransmitter onto single post-synaptic neurone? ( Type your answer carefully)

16 / 20

Dopamine is a neurotransmitter which has a role in numerous processes in the brain including pain relief. The release of dopamine can be stimulated by chemicals called endorphins produced in the brain. Endorphins attach to opioid receptors on presynaptic neurones that release dopamine. Morphine is a drug that has a similar structure to endorphins and can provide pain relief, explain how.

Morphine is a competitive inhibitor of endorphins, and blocks their binding.

Morphine attaches to opioid receptors, causing the receptors to secrete more dopamine.

Morphine attaches to the opioid receptors, causing more dopamine to be released from the synaptic vesicles.

17 / 20

GABA is a neurotransmitter released in some inhibitory synapses in the brain. GABA causes negatively charged chloride ions to enter postsynaptic neurones. Explain how this inhibits postsynaptic neurones

The post synaptic neurone becomes hyperpolarised , so more sodium ions are required to reach threshold.

The post synaptic neurone becomes less polarised , so less sodium ions are required to reach threshold.

18 / 20

Synaptic knobs contain mitochondria, which of the following is NOT a use of ATP in the presynaptic neurone?

To pump calcium ions out of the pre-synaptic membrane.

To make the vesicles fuse with the presynaptic membrane.

To reabsorb degraded neurotansmitter.

19 / 20

Doctors investigated two ways of measuring the effect of general anaesthetics. In one method they timed how long it took to stop blinking, and then repeated the investigation using a machine to record when brain activity showed they were unconscious. Blinking involves cholinergic synapses. Anaesthetic S is a similar shape to acetylcholine. Suggest how anaesthetic S stops the transmission across the synapse.

S acts as an agonist

S acts as an antagonist

S inhibits the enzymes that break down acetylcholine

20 / 20

The table shows the results on investigating how fast an anaesthetic works. Using the results from the machine, was there a significant difference between anaesthetics S and Q?

Yes

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Nerves: Receptors (Pacinian Corpuscles and Eye)

1 / 15

When a stimulus is detected by a receptor, it generates a potential difference across it's plasma membrane. What is the name of this potential difference?

Action potential

Generator potential

Receptor potential

2 / 15

Can the potential difference created by a receptor have different values depending on the size of the stimulus?

Yes

3 / 15

What is the stimulus detected by a Pacinian corpuscle? (type your answer)

4 / 15

Name part A on the above diagram.

Nodes of Ranvier

Motor Neurone

Sensory Neurone

5 / 15

Name part B on the above diagram (type your answer).

6 / 15

What type of sodium channels are opened when a Pacinian corpuscle is stimulated?

Voltage-gated Sodium Channels

Ligand-Gated Sodium Channels

Stretch-mediated Sodium Channels

7 / 15

When the layers of connective tissue are pressed, what happens to the neurone membrane?

It becomes more negative on the outside.

It becomes more positive on the outside.

It becomes more negative on the inside.

8 / 15

In order for an action potential to be generated in a Pacinian corpuscle, what must happen?

Enough sodium ions must diffuse out to reach threshold.

Enough sodium ions must diffuse in to reach threshold.

Enough potassium ions must diffuse in to reach threshold.

9 / 15

The diagram above shows a cross section of a human eye. Name layer A (Type your answer).

10 / 15

Layer B is the layer which contains the photoreceptor cells. What is it's name ? ( Type your answer).

11 / 15

Point C is the point where most colour sensitive photoreceptor cells are located. What is it called?

12 / 15

What is the structural adaptation which give cones high visual acuity compared to rod cells?

Single cone cells synapse with a single bipolar neurone.

Many cone cells can synapse with a single bipolar neurone.

The pigment in cones ( Photopsin) is more sensitive than that in rods (Rhodopsin).

13 / 15

What is the structural adaptation which gives rods high sensitivity compared to rod cells?

Single rod cells synapse with a single bipolar neurone.

Many rod cells can synapse with a single bipolar neurone.

The pigment in cones ( Photopsin) is less sensitive than that in rods (Rhodopsin).

14 / 15

The cone density is highest on the fovea in the centre of the retina. In a human fovea there are 150 000 cones per mm2. The diameter of a human fovea is 1.2 mm. Calculate the number of cones on the human fovea.

678584

239790

169646

15 / 15

When light falls on cells 1 and 2, only one spot of light is seen. But, when light falls on cells 2 and 3, two spots of light are seen. Say why?

1 & 2 share a neurone, and 2 and 3 share a neurone.

1 & 2 share a neurone, and 2 and 3 have separate neurones.

2 and 3 are both cone cells.

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Muscle Contraction

1 / 20

The image above shows a muscle fibre. Name organelle A

Microfibril

Myofibril

Sarcofibril

2 / 20

The image above shows a muscle fibre. Name organelle C

Plasma Membrane

Sarcoplasmic Reticulum

Sarcolemma

3 / 20

The image above shows a muscle fibre. Name organelle E

Sarcolemma

T Tubule

Sarcoplasmic Reticulum

4 / 20

The image above shows a muscle fibre. What is the function of organelle E?

Generation of ATP

Transmission of an action potential to all fibrils.

Storage and release of calcium ions.

5 / 20

In the above image, which type of protein makes up the myofilaments labelled C? type your answer in carefully.

6 / 20

In the above image, name the unit represented by B.

Sarcomere

Sarcometre

Sarcolemma

7 / 20

The muscle filament in the above diagram is relaxed, what would happen to the following zones when it contracts?

The I band gets shorter, the H zone gets longer, but the A band stays the same.

The I band gets shorter, the H zone gets shorter, but the A band stays the same.

The I band gets shorter, the H zone gets shorter, but the A band gets longer.

8 / 20

Which of the above diagrams represents either end of an 'A Band' in muscle?

9 / 20

Which of the above diagrams represents the myofilaments an 'M line' in muscle?

10 / 20

Which of the above diagrams represents the myofilaments a 'Z line' in muscle?

11 / 20

Which protein found in a myofilament has multiple globular heads? (Type your answer carefully).

12 / 20

Which protein blocks the actin-myosin binding site in a relaxed myofibril?

Troponin

Tropomyosin

Myosin

13 / 20

In the sliding filament theory, what causes the actin-myosin binding site to be exposed?

The hydrolysis of ATP.

An influx of calcium ions into the sarcoplasmic eticulum.

The release of calcium ions, out of the sarcoplasmic reticulum.

14 / 20

Name the molecule that carries out the function : Attaches to the Z line at the end of the sarcomere.

Actin

Myosin Tails

Myosin Heads

15 / 20

Breaks down ATP on myosin head

ATPase

ATP Synthase

Calcium ions

16 / 20

One role of ATP in muscle contraction is to provide the energy required for the 'powerstroke' of the myosin head. What is the other use of ATP in muscle contraction?

To 'reset' the myosin head.

To break the actin-myosin cross bridge.

To release Calcium ions.

17 / 20

One form of muscle disease is caused by a mutated allele of a gene. This leads to production of myosin molecules that are unable to bind to other myosin molecules. If myosin molecules are unable to bind to other myosin molecules, this prevents muscle contraction. Suggest why.

It cannot pull on the actin. The myosin filaments will just slide past each other.

The actin - myosin cross bridges will not form.

The actin - myosin cross bridges will not break.

18 / 20

What is the role of phosphocreatine in muscle contraction?

As a respiratory substrate to feed into glycolysis.

Hydrolysis of ATP

Phosphorylation of ATP

19 / 20

Which of the following are features of slow twitch muscle fibres:

A)Lots of aerobic respiration
B)Lots of mitochondria
C)Low levels of myoglobin

A & C

A & B

A, B & C

20 / 20

Which of the following is a feature of fast twitch muscle fibres when compared to slow twitch.

Fewer blood vessels

Higher numbers of mitochondria

Lower concentration of PCr.

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