Physiology Unit 2
SENSORY PHYSIOLOGY Sensory System
• Sensory informa on – Conscious sensa ons – Unconscious sensa ons • Sensory processing – Transferring s mulus energy into a graded poten al (receptor poten al) – Then to an ac on poten al in an afferent neuron • Pa ern of ac on poten als is the code that provides informa on on the s mulus General Classes of Receptors
• Mechanoreceptors • Thermoreceptors • Photoreceptors • Chemoreceptors • Nociceptors Sensory Receptors
• Specialized endings of sensory neurons • Separate cells that signal the afferent neurons by releasing chemical messengers • The energy or chemical that ac vates a sensory receptor is a s mulus • The process by which a s mulus is transformed into an electrical response is sensory transduc on Receptor Poten al
• Sensory transduc on involves the opening/closing of ion channels Graded Poten al to Ac on Poten al
• The ini al ion movement generates local current that flows a short distance along the axon to a region where the membrane has voltage-gated ion channels an an AP can be generated • Usually the first Node of Ranvier Primary Sensory Coding
• Conver ng s mulus energy that conveys relevant sensory informa on to the CNS is coding – Type of energy it represents (modality) – Intensity – Loca on of the body affected Sensory Unit Sensory Modality
• Modali es – Temperature, taste, sound, touch • Submodali es of sensa on – Submodality of temperature: hot/cold – Submodali es of taste: sweet, bi er, salty, sour, umame – Submodality of sound: pitch, volume S mulus Intensity S mulus Dura on
• Rapid adapta on – Phasic receptors – Signal change – Rapid fading of sensa on – “on” and “off” response • Slow adapta on – Tonic receptors – Signal slow changes or prolonged events – Joint, muscle receptors for maintaining posture
Sensory Pathways
• A Sensory Pathway – A bundle of parallel, 3 neuron chains that run together – Also called ascending pathways – Non-specific – Specific – Most sensory pathways convey informa on from a single type of sensa on (mechanoreceptors, thermoreceptors, etc.) Specific Ascending Pathways
• Sensory pathways ascend to 1. Brainstem (RAS) 2. Thalamus 3. Final neurons in the pathway terminate in the specific sensory area of the cortex • Excep on: olfactory neurons branch to the limbic system rather than the thalamus Soma