Biol 102 Sensory Mechanisms Lecture Notes

Sensory Mechanisms: Chapter 12,
Lecture 32
Receptors Receive and Convert Stimuli

  Stimulus: sensory input that causes some change within or
outside the body

– Heat, pressure, sound waves, light, chemicals

  Receptor: structure that detects stimulus and

converts its energy into another form
  Different kinds of receptors
– Mechanoreceptor – Thermoreceptor – Pain receptor
– Chemoreceptor
– Photoreceptor

1. Receptors Are Classified according to Stimulus
 Mechanoreceptors
– Respond to mechanical energy (sound waves change

in fluid pressure, stretching, gravity)
 Thermoreceptors
– Respond to heat or cold

 Pain receptors
– Respond to tissue damage or excessive heat or

pressure (tissue damage, excessive pressure and temperature)

, Receptors Are Classified according to Stimulus

 Chemoreceptors
– Respond to presence of chemicals
 Photoreceptors – Respond to light
CNS Interprets Nerve Impulses Based on Origin and
Frequency

  Nerve impulses are transmitted from receptors to specific
portions of brain
  Stronger stimuli
1. Activate a greater number of receptors
2. Trigger a greater frequency of action potentials in sensory
neurons
1. Some Receptors Adapt to Continuing Stimuli
 Some Inputs are Ignored  Sensory adaptation

o – Sensor neuron stops sending impulses even though the
original stimulus is still present

o – Allows the CNS to concentrate on important stimuli and
ignore noncritical ones to maintain homeostasis
 Receptors that adapt
– Light touch, pressure, and smell receptors

 Receptors that do not adapt
– Pain, joint, and muscle monitoring receptors
Somatic Sensations and Special Senses Provide Sensory
Information

 Somatic sensations