Gives an in-depth look into sensory physiology. This introduces you to the general properties of the sensory system to ease you into the lecture before going into the key properties and pathways. You are then introduced to the 4 different types of receptors that make-up the sensory pathway, first w...
• Begins with stimulus = physical energy of different types acting on a sensory receptor cell
• (When physiologists talk about receptors, they sometimes mean the receptor cells themselves, and sometimes
receptor molecules in their membranes)
• Receptor cells may be neurones or epithelial cells — but they always connect with a neurone
• The receptor cells is a transducer which converts the external stimulus into an intracellular signal
1. SENSORY RECEPTORS
• Diverse
• Specific
2. SENSORY TRANSDUCTION
• Transduce physical and chemical signals to membrane potentials - receptor potential
• Generate action potentials in sensory neurons
3. SENSORY PATHWAY
• Transmit to the CNS via specific pathways
• For central integration and modulation of sensation
• Ranging from single modified neurones to complex organs (a human eye contains 126 million receptor neurons)
• Complex receptor organs have elaborate ACCESSORY STRUCTURES (e.g. The lens in the eye)
Integration of Physiological Systems Page 1
, Simple receptors Complex neural Most special senses
are neurons with receptors have receptors are cells
free nerve nerve endings that release
endings. They may enclosed in neurotransmitter onto
have myelinated connective tissue sensory neurons,
or unmyelinated capsules. This initiating an action
axons illustration shows potential. The cell
a Pacinian illustrated is a hair cell,
corpuscle, which found in the ear
senses touch
Type of Receptor Examples of Stimuli
Chemoreceptors Oxygen, pH, organic molecules (e.g. glucose)
Mechanoreceptors Pressure (baroreceptors), stretch (osmoreceptors), vibration,
acceleration, sound
Photoreceptors Lights (protons)
Thermoreceptors Heat or cold
1. MODALITY
• Example: red or green light
2. LOCATION
• Direct (touch receptors of skin) or indirect (direction of sound - computed by brain based on information from both
ears)
3. INTENSITY
• The graded receptor potential is proportional to the strength of the stimulus, and is translated into frequency of firing
in the connecting neurone
4. DURATION
• Tonic receptors = slowly adapting, remain activated as long as the stimulus is present (e.g. Pain receptors)
• Phasic receptors = rapidly adapting, activated when a stimulus first appears, but they deactivate if it remains
constant (e.g. Smell receptors)
Integration of Physiological Systems Page 2
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