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Wright BIO 1150 - Sensory System
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BIO 1150 1st Edition Lecture 15Topic Discussed: Sensory SystemsSensory neurons transmit info to the central nervous system• Sensation is based on neural input to brain• Sensory systems have accessory structures associated with sensory neuronsRetina- houses cells that work with light, it is a “piece of brain in the eye”Sensory neurons- transducers• Converts one form of energy into anotherPhotoreceptors-visual sensory receptors• Variations, they are not identical (rods and cones are the two types)• Rods and cones work with different degrees of light• Backmost layer of retinaLight is absorbed by molecules in membrane• Electromagnetic radiation (light) can interact with biomolecules in a variety of waysRhopsin-visual pigment, composed of retinal and opsin• Light energy changes molecule shape, enzymes restore rhopsin to original shape• The shape change promotes series of reactions• Uses G protein intermediate• G-protein-hormone triggered 2nd messengerLight exposure• Causes a cascade of events (phosphodiesterase is an enzyme involved in this cascade)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• This results in ion channel closure• Change in membrane voltage leads to a change in neurotransmitter release• Absence of neurotransmitter sends a signal to the brain• Neurotransmitter release induces action potentials in the optic nerve neuron• Rods/cones send signals to bipolar to ganglia cellsMultiple components of the sensory stimulus may be encoded by separate mechanisms • Can distinguish color, brightness etc.Color- encoded by relative activation of cone photoreceptors with pigments sensitive to specific ranges of wavelength• “adequate stimulus”- stimulus that can activate a particular receptor• Humans- are lucky to see colorSensory receptors- filters• They don’t only respond to particular aspects of the environment • Range of wavelengths that we can see is limited by the responsiveness of our conesVisible light is only a small part of electromagnetic spectrumSome animals can sense ranges of stimuli that we can’t • Insects see in UV• Fish/birds can sense earth’s magnetic fieldsSenses- not really accurate representing the world • We acclimate or respond to inputs• Dark adaptation- sensitivity changes in the presence of constant stimulationSenses in the head transmit their signals via cranial nerves• There are 12 cranial nerves and are part of the peripheral nervous system• Cranial nerve #2- optic nerve- transmits visionBlind spot- part of retina “hole” where you can’t see• Axons of retinal ganglion cells form optic nerve• Axons end in lateral geniculate nucleus of thalamusRetina-topic representation- map of retina in different parts of brainConscious perception of sensory stimulus- in cerebral cortex • Vision perceived when stimulation reaches regions of occipital lobePathways to cortex-multisynaptic (several neuron sequence)• Each region of synapses (brain nucleus) serves as a site of integration• Between nuclei, crossing of axons= bilateral representationOptic chiasm- where nerves cross (pathways)Balance-sensorySenses are “projected”Brain-“parallel processor”• Divides vision into


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Wright BIO 1150 - Sensory System

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