Neurones and Receptors

  • Created by: Rachelezy
  • Created on: 13-02-20 10:44

Types of Receptors (Basics)


  • Detect changes in light


  • e.g. Pacinian Corpuscle detect mechanical stimuli in the form of pressure and vibration
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Pacinian Corpuscle

Pacinian Corpuscle:

  • Found in joints, tendons, and ligaments (also fingers, soles of feet and external genitalia)
  • Contain a single sensory neurone located in lamellae (connective tissue) which forms layers separated by a gel.

Contains stretch mediated sodium channels in the cell surface membrane:

  • When not under pressure, these channels are closed - Under pressure these become deformed
  • They open and allow the rapid influx of sodium ions to occur.
  • Positive charge on the sodium ions changes the membrane potential, causing the membrane to become depolarised
  • Results in a generator potential being generated which goes on to create an action potential in the axon.
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Photoreceptors in the eye (Overview)


  • Light receptors in the eye
  • Light enters through the pupil and amount of light entering is controlled by muscles in the iris.
  • Lens of the eye focuses the light on the retina (this is where photoreceptors are located, more specifically the fovea)
  • Nerve impulses then carried via the optic nerve to the brain

Blind Spot - Point where the optic nerve leaves the eye (no photoreceptor cells are located here)

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Photoreceptors in the eye (Rod and Cone Cells)

Cone Cells:

  • Involved in colour vision
  • Present at the greatest density in the fovea
  • Contain the pigment iodopsin
  • Not sensitive to light so require quite bright light to work
  • Contains three different primary pigments (red, blue and green)
  • Provide good visual acuity as each cone cell has its own synapse via a bipolar neurone which connects to the optic sensory neurone

Rod Cells:

  • Mainly concentrated in highest density outside of the fovea
  • Very sensitive to light - are stimulated by low light conditions
  • Provide low visual acuity because more than one rod cell shares the same synapse with a bipolar cell - multiple rods have to be stimulated in order for a generator potential to occur.
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Simple Reflex Arc

Stimulus --> Receptor --> Sensory neurone --> Intermediate (relay) Neurone --> Motor Neurone --> Effector --> Response

Sensory Neurone - Carries nerve impulse from the receptor to the spinal cord

Intermediate (relay) Neurone - Located entirely in spinal cord and relays the nerve impulse from sensory neurone to the motor neurone

Motor Neurone - Carried nerve impulse from the spinal cord to the effector (can be a muscle or gland)

Reflex that bypasses the brain

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