BIOL 1050H Lecture Notes - Lecture 6: Hair Follicle, Sensory Neuron, Receptive Field
Sensory Organs
Sensory information parameters
• Modality – light, temperature,
acoustic, chemical
• Location – receptive field
• Intensity – e.g., quantity
photons/ amplitude of pressure
• Duration – phasic (onset) vs.
tonic (continued APs) receptors
Sensory receptors: modality
• Some characteristics of stimuli in the environment:
• Temperature - thermoreceptors – warm and cold
receptors
• Light - photoreceptors - vision
• Chemical - chemoreceptors – olfaction and gustation
• Vibration, pressure - mechanoreceptors – tactile,
stretch, vestibular, auditory
• Electric field
• Magnetic field
Unencapsulated nerve endings
• Dendrites lacking connective tissue wrappings:
Free nerve endings • For pain and temperature
• Location: skin and mucous membrane
Tactile (Merkel) discs • For light touch and texture
• Location: associated with Merkel cells at base of epidermis
Hair receptors • Monitor movement of hair
• Location:dendrites coil around a hair follicle
Primary taste sensations
• Salty – electroytes - sodium, potassium
• Sweet – carbohydrates, fruit
• Sour – acidic (H+)
• Umami – protein
• Bitter - alkaloids
Document Summary
Sensory information parameters: modality light, temperature, acoustic, chemical, location receptive field, intensity e. g. , quantity photons/ amplitude of pressure, duration phasic (onset) vs. tonic (continued aps) receptors. Unencapsulated nerve endings: dendrites lacking connective tissue wrappings: Free nerve endings for pain and temperature: location: skin and mucous membrane. Tactile (merkel) discs for light touch and texture: location: associated with merkel cells at base of epidermis. Hair receptors monitor movement of hair: location:dendrites coil around a hair follicle. Primary taste sensations: salty electroytes - sodium, potassium, sweet carbohydrates, fruit, sour acidic (h+, umami protein, bitter - alkaloids. Taste (gustation: begins with action of chemical stimulants (tastants) on taste buds, 4,000 taste buds found mainly on tongue. Filiform: no taste buds sense food texture. Foliate: weakly developed sides of tongue: taste buds degenerate by age 3. Fungiform: a few taste buds (~3) at tips and sides of tongue.
