Topic 6 errors

The fovea of the eye of an eagle has a high density of cones. An eagle focuses the image of its prey onto the fovea

Explain how the fovea enables an eagle to see its prey in detail. Do not refer to colour vision in your answer (2)

1. cones connect to a singluar neurone

2. cones send seperate sets of impulses to the brain / optic nerve

3. high visual acuity

The retina of an owl has a high density of rod cells. Explain how this enables an owl to hunt its prey at night. Do not refer to rhodopsin in your answer. (3)

1. high sensitivity to light

2. several rods connected to single neurone / spatial summation

3. enough neurotransmitters to reach / overcome threshold

explain how applying pressure to the Pacinian COrpuscle produces changes in membrane potential recorded by microelectrode P

1. (Pressure causes) membrane / lamellae to become deformed / stretched;

2. Sodium ion channels in membrane open and sodium ions move in;

3. Greater pressure more channels open / sodium ions enter

Membrane potential is sme whether heavy or medium pressure was applied to finger tip.

Why (2)

1. All or nothing principle

2. threshold has been reached