Physiology of Perception

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Physiology of Perception

• Sensation and Perception chapter 2

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Physiology of Perception

• The central nervous system (CNS) consists of the
  brain and spinal cord.
• We are a long way from understanding how the
  brain works, though there is much we do know
• Music and all other aspects of the world are
  represented in the brain in terms of mental or
  neural codes electrical signals
• CNS 2 types of cells neurons and glial
• Our brain is responsible for mental functions
  such as memory, thoughts, language and
  perceptions

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Physiology of Perception

• Neurons are cells that form the communication and
  information processing network of the nervous
  system. They generate electrical signals called
  nerve impulses.
• Physiological research to determine how
  individual neurons respond to stimuli in the
  environment to understand how our experience
  relates to this neural code.
• It is the properties of our perceptual systems
  (visual, auditory, touch, olfactory and taste)
  that determine what we experience (see, hear,
  feel, smell and taste)

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Human brain the primary receiving areas for the
senses
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Basic structure of the brain

• Primary receiving areas the first areas in the
  cerebral cortex to receive the signals initiated
  by each senses receptors
• Modular organisation specific functions are
  served by specific areas of the cortex e.g. the
  primary receiving areas for each of the senses
• Other areas in addition to the primary receiving
  areas are also associated with each sense the
  brain is not completely modular in function.

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Neurons
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Neurons

• Around 100 billion neurons in the brain
• Cell body - works to keep the cell alive
• Dendrites - receive electrical signals from
  other neurons
• Axon or nerve fibre conducts electrical signals
• Many different types of neurons e.g. receptors,
  motor neurons
• In response to a stimulus neurons generate action
  potentials / nerve impulse
• The action potential travels down the axon

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Neurons and action potential

• The function of the action potential is to
  communicate information e.g. an increase in the
  rate of nerve firing may carry information about
  the intensity of a stimulus
• it travels all the way down the axon without
  decreasing in amplitude
• important because it enables neurons to transmit
  signals over long distances.
• Spontaneous activity
• Lab work on this

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Neural Communication

• How is information transmitted between neurons?
• Across a small space between neurons called a
  synapse involves molecules called
  neurotransmitters
• Action potentials do not travel across a synapse
  - they trigger a chemical process that bridges
  the gap between the sending neuron (presynaptic
  neuron) and the receiving neuron.

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The visual system

• We see objects when light is reflected from the
  objects into our eyes
• Main elements of the eye cornea, lens (focusing)
  and retina (transduction)
• Focused light stimulates the receptors that line
  the back of the eye in a structure called the
  retina
• 2 types of visual receptors rods and cones
• The visual pigments in these receptors react to
  light and initiate electrical signals in a
  network of neurons that leave the back of the eye
  as the optic nerve.
• The optic nerve conducts these signals toward the
  brain

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The eye
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Light

• Light is the stimulus for vision
• A band of energy within the electromagnetic (EM)
  spectrum called visible light.
• The energy within the EM spectrum is
  characterised by its wavelength
• The wavelength of visible light is associated
  with colour
• Light - as a wave or as a stream of particles
  called photons (1 photon 1 packet of light
  energy)

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EM spectrum
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Focusing images on the retina

• Cornea fixed focus about 80 of the eyes
  focusing power
• Lens variable focus remaining 20 of the eyes
  focusing power it changes its shape to adjust
  focus for objects at different distances
• Accommodation focusing process of the eye
  changing the shape of the lens (demonstration
  page 31)
• Near point distance at which your lens can no
  longer adjust to bring a close object into focus
  (it increases as we get older presbyopia).

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The Retina

• The rods and cones are the light receptors
• Distribution of rods and cones in the retina
  only cones in the fovea, both rods and cones in
  the peripheral retina
• Blind spot area on the retina where there are
  no receptors location of the optic nerve
• Blind spot demonstration (print outs)

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