Responding to Change Random Retrieval

What is the role of phosphocreatine in muscle contraction?

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

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

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?

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.

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

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

Name part A on the above diagram.

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

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

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

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:

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

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

What has happened at stage 5?

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

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

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

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

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