Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Orbital Region General Sensation and Vision Generalized Sensation Physiology • Sensation –state of awareness of external and internal conditions of the body • Four conditions for sensation: – – – – 1. Adequate stimulus 2. Adequate receptor (transducer) 3. Conduction 4. Translation (interpretation) Brain’s Assumption in Translating Assumption: Source of light is from above Reversing X pattern; notice shading. How many triangles? Assumption: Straight lines should connect. Which dark line is larger? Assumption: perspective Characteristics of Sensation • Modality –ability to interpret nerve impulses differently • Projection –referral of sensation to point of origin • Adaptation –decrease in sensitivity of receptors to continued stimulation – Phasic (fast) – Tonic (slow) – Some receptors never adapt (pain, cold, etc.) • Afterimage –persistence of sensation after stimulus ceases Classification of Receptors • Type of Sensory Information Relayed – Exteroreceptors, Enteroreceptors, Proprioceptors • Type of Stimulus Transduced – Mechanoreceptors, Thermoreceptors, Chemoreceptors, and Nociceptors • Complexity of Receptor – Simple structure (usually single cell) –most general senses – Complex structure (many cells) –special senses General Senses • Cutaneous –skin receptors • Proprioception –sense of body position • Nociception –pain perception (chemoreceptors that perceive locally secreted warning hormones (prostaglandins)) Distribution of Cutaneous Receptors Sensitivity of Skin due to Receptive Fields Cutaneous Receptors Proprioceptors Muscle sensors Muscle spindles (Intrafusal fibers: -senses degree of length of muscle fibers and the rate of change in length Golgi Tendon organs –sense tension within tendon Relationship of Stretch to AP Referred Pain Illustrates projection. General Pathway of Perception Orbital Region Accessory Structures of the Eye Eyelid Lacrimal Apparatus Outer Eye Extrinsic Ocular Muscles Arrangement of Posterior Orbit Trochlear Optic Nerve Occulomotor Abducens Action and Innervation of Ocular Muscles Action and Innervation of Ocular Muscles Which cranial nerve is injured? Orbital Blood Supply Ophthalmic Middle Meningeal to Cavernous sinus Ophthalmic Internal Carotid Facial v. Eye Anatomy Aqueous Humor Flow (Canal of Schlemm) Glaucoma results from inadequate drainage of Aqueous Humor leading to increase pressure in the eye. Iris controls amount of light entering the eye. Distant Vision Near Vision (Accomodation) Near and Far-sightedness Astigmatism and Presbyopia • Astigmatism –results from imperfections in the resolving structures in the eye (lens and/or cornea) • Presbyopia is the loss of near vision with age; resulting from a decrease in elasticity of the lens. Increase lens opacity with age. Cataract Retina Cellular Arrangement Special Areas of Retina Blind Spot Optic Disc (blind spot) Optic N. Photoreceptors: Cones and Rods Three populations of cones Rod’s and Cone’s Photopigments Retinal Bleaching Visual Processing