Receptors, Eye, Pacinian Corpuscle & Chemo/Baro Receptors

Question 1

How does the Pacinian Corpuscle work (3)

Answer 1

• Increased pressure deforms changes stretch-mediated sodium (ion) channel;
• Sodium ion channel proteins open and sodium ions diffuse in;
• Depolarisation leading to generator potential

Question 2

Explain how the fovea increases the detail of an image (2)

Answer 2

• High (visual) acuity
• Each / single cone is connected to a single bipolar/ neurone

Question 3

Explain how the connection of several rods to a single bipolar cell (Retinal convergence) influences visual acuity (2)

Answer 3

• (Spatial) Summation means cannot distinguish between stimuli from different rod cells linked to same bipolar cell
• Decreases acuity

Question 4

Explain how the connection of several rods to a single biopolar cell (Retinal convergence) influences sensitivity (2)

Answer 4

• (Summation of) sub-threshold stimuli produces threshold stimulation;
• Increases sensitivity

Question 5

The heart controls and coordinates the regular contraction of the atria and ventricles
Describe how

Answer 5

• SAN - AVN - bundle of His/Purkyne fibres
• Impulses/electrical activity (over atria)
• Atria contract
• Non-conducting tissue (between atria and ventricles)
• Delay (at AVN) ensures atria empty/ventricles fill before ventricles contract
• Ventricles contract from apex upwards

Question 6

Describe what is meant by the term threshold

Answer 6

• When threshold has been reached;
• (Threshold or above) causes maximal response / all or nothing principle;

Question 7

Explain why increased cardiac output is an advantage during exercise.

Answer 7

• Higher cardiac output - Increases O2 supply (to muscles);
• Increases glucose supply (to muscles);
• More ATP produced by oxidative phosphorylation / more energy release / more aerobic respiration / actively respiring muscles
• Increases CO2 removal (from muscles) / lactate removal;
• Increases heat removal (from muscles) / for cooling;
• Delays the formation of lactate

Question 8

The rate of ATP consumption of a de-myelinated neurone is greater than that of a myelinated neurone when conducting impulses at the same frequency.

Explain why.

Answer 8

• Greater entry of sodium ions / greater exit of K+
• in de-myelinated neurone;
• Ref. to active transport / ref. to ion pumps;

Question 9

Exercise causes an increase in heart rate.

Describe the role of receptors and of the nervous system in this process.

Answer 9

1. Chemoreceptors detect rise in CO2 / H+ / acidity / carbonic acid /f all in pH
   OR
   Baro / pressure receptors detect rise in blood pressure;
2. Send impulses to cardiac centre/medulla;
3. More impulses to SAN;
4. By sympathetic (nervous system for chemoreceptors / CO2)
   OR
   By parasympathetic (nervous system for baro / pressure receptors / blood pressure);