Nervous System- Sensory Systems-.txt

• Sense organ or specialized receptors allow for transduction (conversion of some form of environmental signal to neural signal)
• Pathway to cortex through spinal nerves or cranial nerves

• Type of stimulus
• Determined by types of neurons activated

• Where the stimulus is located on the body or in the environment
• Usually determined by location of neurons that are activated by stimulus

Usually determined by number of activated neurons or frequency of action potentials

• Phasic receptors: activated by change in stimulus (when stimulus begins AND ends), adapt quickly
• Tonic receptors: respond as long as stimulus is present

• Thermoreceptors (hot and cold)
• Photoreceptors (light)
• Nociceptors (pain)
• Chemoreceptors (chemicals)
• Mechanoreceptors (vibration, touch, pressure, and stretch)

• Exteroreceptors (stimulus outside body)
• Interoreceptors (stimulus in internal organs)
• Proprioceptors (position of the body)

• General (receptors located throughout the body)
• Special (receptors in special sense organ)

Each sensory neuron responds to a very specific stimulus like somatosensory, olfactory, gustatory, visual, and auditory neurons

• Bigger dendritic field = bigger receptive field
• Bigger receptive field + fewer sensory neurons = decreased ability to determine location of stimulus

• Touch stimuli deform skin and underlying sensory endings
• Stretch in the sensory endings causes Na+ channels to open, depolarization and action potential generation

• A different mechanism for each type of taste (sour, salty, sweet, bitter and umami)
• Sour and salty tastants can enter cell and depolarize it
• Sweet, bitter, and umami have separate receptors on taste cells

Odorant binds to its receptor, leads to depolarization

Note that olfactory system is the ONLY sensory system in which all input doesn't go through thalamus

• Photoreceptors release Glu in dark which inhibits bipolar cells thus no activation of ganglion cells
• Photoreceptors stop releasing Glu in light. Bipolar and ganglion cells are active

Ganglion cells receiving input from rods have larger receptive fields (= poor spatial discrimination)

• Some ganglion cells decussate in optic chiasm
• Synapse in thalamus, then go to occipital lobe

• Processing simple to complex
• V1 cell active with light in certain location
• IT call only active when viewing specific face