Introduction to Sensory Physiology and Perception

Question 1

What are the 3 parts of the CNS? What’s the role of each?

Answer 1

• Subconscious; Control of movement, Autonomic responses, Behavioural responses
• Perception; Decisions on sensation
• Arousal; Modulatory pathways controlling attention, Control sleep and wakefulness

Question 2

What are the 4 types of sensory receptors? What do they detect? What are they used for?

What is an Activation threshold?

What is a Perceptual threshold?

Answer 2

• 1. Photoreceptors; Detects Light for Vision
     
     2. Chemoreceptors; Detects Chemicals in air, Chemicals in saliva, Inflammatory chemicals for Smell, Taste, Injury
     3. Thermoreceptors, Detects Temperature for Head, Cold, Injury
     4. Mechanoreceptors, Detects Pressure on skin, Pressure/tension/stretch in MSS, Head movement, Gravity, Air pressure waves for Touch, Injury, Proprioception, Equilibrium, Hearing
• Minimum stimulus strength that depolarises receptor enough to produce action potentials
• Minimum stimulus that produces enough action potentials to be detected

Question 3

What is temporal receptor adaptation? What does it allow?

What is spatial receptor adaptation?

How does damage/disease affect the sensory receptors?

Answer 3

• Damping down responses to unchanging stimuli and highlights moments when stimulus strength changes; allows vigorous responses to small changes without saturation
• Lateral inhibition; damping down responses to lateral afferents when all are getting the same stimuli
  o Highlights locations where stimuli strength changes
• Damage disrupts inhibitory systems = Hypersensitivity

Question 4

Somatosensory Cortex:
How is visceral pain still felt, even though it isn’t represented in the sensory strip?

How does Phantom Limb occur?

What occurs with Epileptic activity?

What is Synaesthesia?

Answer 4

• Still felt via Referred pain
• Loss of limb but retention of afferents within the amputation stump; stimulation of afferents will cause sensation where the afferents use to be
• Inappropriate activity of somatosensory cortex = Phantom sensations across body
• Auditory input activates visual colour processing area; “sees” sound as colours