A sensory receptor is a specialized cell or cell process that monitors conditions in the body or the external environment



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Introduction

  • A sensory receptor is a specialized cell or cell process that monitors conditions in the body or the external environment.

  • Stimulation of the receptor directly or indirectly alters the production of action potentials in a sensory neuron.

  • The sensory information arriving at the CNS is called a sensation.

  • A perception is a conscious awareness of a sensation.

  • General senses

  • Special senses

  • Sensations of smell (olfaction), taste (gustation), balance (equilibrium), hearing, and vision

  • Specialized receptor cells that are structurally more complex than those of the general senses

Receptors

  • Receptor specificity — each receptor responds to one type of stimulus

  • Sensory Limitations

  • Humans do not have receptors for every possible stimulus.

  • Our receptors have characteristic ranges of sensitivity.

  • A stimulus must be interpreted by the CNS. Our perception of a particular stimulus is an interpretation and not always a reality.

The General Senses

  • Receptors for general senses classified by location:

  • Exteroceptors provide information about the external environment.

  • Proprioceptors monitor body position.

  • Interoceptors monitor conditions inside the body.

  • Receptors for general senses classified by type of stimulus:

  • Nociceptors = tissue damage

  • Thermoreceptors = change in temperature

  • Mechanoreceptors = physical distortion, contact, or pressure

  • Chemoreceptors = chemical composition of body fluids

Olfaction (Smell)

  • Olfactory organs

  • Nasal cavity

  • Olfactory epithelium

  • Bipolar olfactory receptors (N I)

  • Supporting cells

  • Basal cells (stem cells)

  • Olfactory glands (Bowman’s glands)

  • Blood vessels

  • Nerves (axons of N I)

Gustation (Taste)

  • Gustatory receptors are clustered in taste buds, which contain gustatory cells that extend taste hairs through a taste pore.

  • Three types of papillae (epithelial projections) on human tongue:

  • Filiform

  • Fungiform

  • Circumvallate

  • Four primary tastes:

  • Salty

  • Bitter

  • Sweet

  • Sour

  • Also water and umami (characteristic of broth)

Equilibrium and Hearing

  • The Ear

  • External ear

  • Middle ear

  • Auditory ossicles

  • Inner ear

  • Equilibrium
  • Cochlea

  • Hearing

Vision

  • Accessory Structures

  • Eye

  • Fibrous tunic

  • Vascular tunic

  • Neural tunic

  • Chambers of the eye



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