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Sensory Physiology Summary Sheet.docx

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Physiology 1021
John Ciriello

Sensory Physiology Summary Sheet NERVOUS SYSTEM Central Nervous System  Brain + Spinal Cord  Cerebrum: o 2 hemispheres o contralateral sensation and movement  Cerebellum “ring a BELL – motor control” o Two hemispheres o Ipsilateral motor control  Brain Stem: o Most primitive part of the brain o Life functions  Spinal Cord o Info to and from the brain Peripheral Nervous System  Somatic System  Spinal Nerves (voluntary)  Visceral System (Autonomic Nervous System) o Parasympathetic + Sympathetic The BRAIN: Forebrain  Telencephalon  Diencephalon Midbrain (Mesencephalon)  Tectum  Tegmentum Hindbrain  Metencephalon  Myelencephalon Grey Matter = Cell body White Matter = Axons The SPINAL CORD:  31 segments x 2 spinal nerves per segment = 62 Spinal Nerves  Dorsal root = sensory (Dolphin’s have a DORSAL fin, and they are SENSITIVE animals)  Ventral root = motor  5 REGIONS: “Breakfast at 8, lunch at 12 dinner at 5” o Cervical – 8 spinal segments o Thoracic – 12 o Lumbar - 5 o Sacral – 5 o Coccygeal – 1 Each spinal segments receives sensory input from particular regions of body o On the skin surface: DERMATOME  None on the face – 12 cranial nerves relay info of face o Neurons/Axons:  Afferent  info TO a place (sensory to CNS)  Efferent  Info FROM a place (motor info from CNS to target) Meninges: Cover the brain  Outer to Inner: o Dura Mater o Arachnoid – CSF in subarachnoid space  CSF: Produced by – Choroid Plexus  Ventricular system o Pia Mater LOBES of the Cerebral Cortex: SOMATOSENSATION:  Unique: Receptors are not concentrated like retina or cochlea Cutaneous Sensations  Touch  Proprioception – limb positioning  Kinesthesis – sense of limb movement  Skin: o Two types:  Hairy  Glabrous – hairless o Two Layers:  Epidermis – outer  Dermis – inner Mechanoreceptors:  Sensitive to physical distortion of skin – bend, stretch…  Distinguished by location and structure o Merkel’s Disc – Slow adapting, Smallin size o Meissner’s Corpuscles – Fast adapting, Smallin size o Ruffini’s Endings – Slow adapting, large in size o Pacinian Corpuscles – Fast adapting, LARGEST o Merk Ruffini (Mark Ruffalo – slow) o M&M’s are SMALL candies Thermoreceptors:  Respond to specific change in temperature PATHWAYS to the brain: Immediate SYNAPSE PRIMARY Somatosensory Cortex:  Somatotopy: o Particular bodily regions over represented in the brain o Hands, Lips, way larger  Smaller cortical neurons = higher sensitivity (fingers) PLASTICITY:  Changes in cortical maps from increase/decrease stimuli  Amputations o Lose a finger – neurons used from neighboring fingers  Training PAIN:  Nociceptors VISION: Retinal Targets:  Lateral Geniculate Nucleus (LGN)  Superior Colliculus (SC) – Tectum – Midbrain  Pretectum – Pupillary Constriction  Hypothalamus – suprachiasmatic nucleus – sync. Of diurnal rhythms with day-night cycle Light:  Stimulus for vision  EM Spectrum o Wavelengths – short: gamma, long: radio o Visible light – humans: 400-700nm Acuity:  Capacity to resolve fine spatial details  Three Factors: o Stimulus o Eye o Central visual pathways  Snellen Acuity: Eye Chart o 20/20 – normal o 20/40 – lower o 20/15 – higher o 20/200 – legally blind The EYE: Pupil Iris – colour – regulates pupil size Cornea: clear sheet in front pupil/iris Sclera: white of eye Conjunctiva – inside eyelid Aqueous Humor: between cornea &lens Vitrous Humor – between lens and retina Retinal Cells:  5 basic cell types: o photoreceptors  light sensitive o bipolar cells o ganglion cells  output neurons o horizontal cells o amacrine cells  Layers: o Nuclear: Cell bodies are o Plexiform: Synapses and axons are o Six Layers:  Ganglion cell layer (nuclear)  Inner plexiform  Inner nuclear  Outer plexiform  Outer nuclear
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