Pacinan Corpuscle

• What is a stimulus?

  A detectable change in the environment
• Why is the ability to respond to stimuli important for organisms?

  It increases their survival rate
• What are the two key sections of the nervous system?

  Central and peripheral nervous systems
• What does the central nervous system consist of?

  Brain and spinal cord
• What components make up the peripheral nervous system?

  Receptor cells, sensory neurons, motor neurons
• What is the role of receptors in the nervous system?

  They detect stimuli and trigger responses
• How many key receptors are mentioned in the AQA specification?

  Three key receptors
• What are the two types of photoreceptors mentioned?

  Rods and cones
• What happens when a stimulus is large enough?

  It establishes a generated potential
• What is required for an action potential to be initiated?

  Influx of sodium ions above -55 mV
• What occurs if the stimulus is not strong enough?

  No action potential is generated
• What type of stimulus does the pacinian corpuscle respond to?

  Pressure
• Where are pacinian corpuscles mainly found?

  In the skin, especially fingers and feet
• What is the structure of the pacinian corpuscle?

  A sensory neuron wrapped in connective tissue
• What is found between the layers of the pacinian corpuscle?

  A viscous gel
• What type of channel proteins are in the sensory neuron of the pacinian corpuscle?

  Stretch mediated sodium ion channels
• When do the sodium ion channels in the pacinian corpuscle open?

  When they are deformed and stretched
• What happens when pressure is applied to the pacinian corpuscle?

  Sodium ions diffuse into the neuron
• What is the resting potential of a neuron?

  -70 millivolts
• What threshold must be reached for an action potential to occur?

  -55 millivolts
• What occurs when enough sodium ions diffuse into the neuron?

  An action potential is generated
• What is the process of how the pacinian corpuscle generates an action potential?

  1. Pressure applied to pacinian corpuscle
  2. Stretch mediated sodium channels open
  3. Sodium ions diffuse into neuron
  4. Inside becomes more positive
  5. If threshold of -55 mV is reached, action potential occurs
• What are the components of the nervous system and their roles?

  • Central Nervous System:
  • Brain and spinal cord
  • Coordinates responses
  • Peripheral Nervous System:
  • Receptor cells, sensory neurons, motor neurons
  • Detects stimuli and transmits signals
• What are the characteristics of stretch mediated sodium ion channels?

  • Closed unless deformed
  • Open when pressure is applied
  • Allow sodium ions to diffuse in
• What happens during the resting state of a neuron?

  • No pressure applied
  • Sodium channels are closed
  • Resting potential is maintained at -70 mV
• What is the significance of the pacinian corpuscle in the nervous system?

  • Detects pressure stimuli
  • Initiates action potentials
  • Contributes to sensory perception