Nervous System Lecture Notes: Sensory Receptors - PDF

Nervous System, Cont. Stimulation of sensory receptors and sensory neurons Objectives Describe how various types of sensory receptor cells stimulate sensory neurons Explain the causes of some sensory disorders Identify regions of cortical neural input from cranial...

Nervous System, Cont. Stimulation of sensory receptors and sensory neurons Objectives Describe how various types of sensory receptor cells stimulate sensory neurons Explain the causes of some sensory disorders Identify regions of cortical neural input from cranial vs spinal sensory neurons  Sensory Reception Each sense = “modality” General Receptors throughout body Special Specific organs for reception Eye, inner ear, tongue, nose Transduction Mechanoreceptor Chemical s Pressure Vibration Gustation  Vallate papillae  ½ of Gustation (Taste) all tastebuds w/ ~250 each Sweet Salty 5 sub Sour modalities Bitter Umami Papillae on tongue Taste buds Gustatory receptor cells Saliva chemicals Salty & Sour Salty Salt crystals  Na+ + Cl- High Na+ outside of receptor cells Diffusion into cells  Depolarization Release NTs Sour H+ concentration Same mechanism as in salty taste Sweet and Bitter Sweet G protein receptors Second messenger cascade  depolarizes the cell Ca2+ channel activated  release of neurotransmitter Bitter G protein receptors cAMP IP3 & DAG Depolarize or hyperpolarize Taste buds near posterior tongue Alkaloids Bitter plant products (coffee, hops, etc.) Toxic to some organisms – antibacterial Umami L-glutamate Protein-rich foods MSG G protein mechanism After Receptor Cell Depolarization… NTs released  sensory neurons Graded potentials Action potentials Facial (ant. 2/3) cranial nerve Glossopharyngeal cranial nerve (post. 1/3) Vagus nerve Gag reflex Olfaction Olfaction Chemical stimuli Superior nasal cavity Molecules dissolve in mucus Bind to transport proteins Transport to receptor dendrites Bipolar neurons G protein mechanism Graded potentials Mitral cells  olfactory Olfaction Olfactory tract Cerebral cortex (inferior & middle temporal)  Limbic system Does not synapse in thalamus before cortex Toxic chemicals can damage Neurons replaced Basal cells Anosmia Loss of sense of smell Trauma leads to damaged olfactory nerve Frontal lobe and ethmoid bone Temporary anosmia Respiratory infections, inflammation Allergies Toxic chemicals (e.g., formalin) Mild loss of taste Neurons repair less with age Elderly & salt Audition Audition Sound waves  action potential Auricle  ear canal Tympanic membrane Malleus  incus  stapes Vestibule  cochlea Audition – Inner Ear Fluid filled Scala vestibuli Scala tympani Fluid waves Bend basilar membrane Location based on frequency Audition Cilia Bend towards longest Open ion channels Depolarize hair cell  Cochlear nerve  Thalamus  Temporal lobe  Interpretation Pushed up against tectorial membrane High K+ Vibrating Basilar membrane  Frequency Response of the Basilar Membrane of the Cochlea Auditory Pathways in the Brain Depolarize hair cell  Cochlear nerve Pons inferior colliculus  Thalamus Temporal lobe  Interpretation 20 Vision - Reception Structure and Location of the Visual Pigments Hyperpolari ze  no NT release Release from inhibitio n Cis-retinal Trans- retinal 22  Rods Cone s Low light can hyperpolarize rods (not cones) takes > 1 rod to activate 1 bipolar cell  > 1 bipolar to activate one ganglion cell  effects on visual acuity of low light and peripheral vision? 23 Stop and think… What taste sensations rely on concentration gradients of stimuli? What are two ways tumors can result in anosmia? Next: Exam 1