receptors exam questions Flashcards
Suggest and explain how the interaction between the muscles labelled in the diagram could cause the pupil to constrict (2 marks)
M1: circular muscles contract
M2: radial muscles relax
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 (3 marks)
M1: high visual acuity
M2: each cone is connected to a single neurone
M3: cones send separate sets of impulses to the brain
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 marks)
M1: high visual sensitivity
M2: several rods connected to a single neurone
M3: enough neurotransmitter to overcome threshold
Explain how the resting potential of -70mv is maintained in the sensory neurone when no pressure is applied. (2 marks)
M1: membrane more permeable to potassium ions and less permeable to sodium ions
M2: sodium ions actively transported out and potassium in
Explain how applying pressure to the pacinian corpuscle produces the changes in membrane potential recorded by microelectrode P. (3 marks)
M1: pressure causes membrane to become deformed
M2: sodium ion channels in membrane open and sodium ions move in
M3: greater pressure more channels open
The membrane potential at Q was the same whether medium of heavy pressure was applied to the finger tip. Explain why. (2 marks)
M1: threshold has been reached
M2: all or nothing principle
Multiple sclerosis is a disease in which parts of the myelin sheath surrounding neurones are destroyed. Explain how this results in slower responses to stimuli. (2 marks)
M1: no action potential
M2: more depolarisation over length of membrane.
