THE SPECIAL SENSES. Introduction Vision

Transcription

1 THE SPECIAL SENSES Introduction Vision

2 RECEPTORS Structures designed to respond to stimuli Variable complexity

3 RECEPTORS: GENERAL PROPERTIES Transducers Receptor Potential Generator Potential

4 RECEPTORS Stimulus causing receptor potentials generator potential in afferent neuron Nerve impulse

5 SENSATION AND PERCEPTION Stimulatory Input Conscious Level = Perception Awareness = sensation

6 ADAPTATION Reduction in rate of impulse transmission when stimulus is prolonged

7 INFORMATION CONVEYED BY RECEPTORS Modality Location Intensity Duration

8 CLASSIFICATION OF RECEPTORS Stimulus Modality Chemoreceptors Thermoreceptors Nociceptors Mechanoreceptors Photoreceptors

9 CLASSIFICATION OF RECEPTORS Origin of stimuli Exteroceptors Interoceptors Proprioceptors

10 SPECIAL SENSES Vision Hearing Olfaction Gustation Vision and hearing involve special sensory structures

11 THE EYE AND VISION 70% of all sensory receptors are in the eye Nearly half of the cerebral cortex is involved in processing visual information Optic nerve is one of body s largest nerve tracts

12 VISION The eye is a photoreceptor organ Refraction Conversion (transduction) of light into APs Information is interpreted in cerebral cortex

13 Eyebrow Eyelid Eyelashes Site where conjunctiva merges with cornea Palpebral fissure Lateral commissure Eyelid Medial commissure (a) Surface anatomy of the right eye Figure 15.1a

14 Orbicularis oculi muscle Eyebrow Palpebral conjunctiva Cornea Eyelashes Bulbar conjunctiva Conjunctival sac Orbicularis oculi muscle (b) Lateral view; some structures shown in sagittal section Figure 15.1b

15 LACRIMAL APPARATUS Lacrimal gland and ducts that connect to nasal cavity Lacrimal secretion (tears) Dilute saline solution containing mucus, antibodies, and lysozyme Blinking spreads the tears toward the medial commissure Drain into the nasolacrimal duct

16 Lacrimal sac Lacrimal gland Excretory ducts of lacrimal glands Lacrimal punctum Lacrimal canaliculus Nasolacrimal duct Inferior meatus of nasal cavity Nostril Figure 15.2

17 EXTRINSIC EYE MUSCLES Six extrinsic eye muscles

18 Superior oblique muscle Superior oblique tendon Superior rectus muscle Lateral rectus muscle Inferior rectus Inferior oblique muscle muscle (a) Lateral view of the right eye Figure 15.3a

19 Muscle Lateral rectus Medial rectus Superior rectus Inferior rectus Inferior oblique Superior oblique Action Moves eye laterally Moves eye medially Elevates eye and turns it medially Depresses eye and turns it medially Elevates eye and turns it laterally Depresses eye and turns it laterally Controlling cranial nerve VI (abducens) III (oculomotor) III (oculomotor) III (oculomotor) III (oculomotor) IV (trochlear) (c) Summary of muscle actions and innervating cranial nerves Figure 15.3c

20 STRUCTURE OF THE EYEBALL Wall of eyeball contains three layers (tunics) Fibrous Vascular Sensory (retinal)

21 STRUCTURE OF THE EYEBALL Three layers 1) Fibrous tunic Sclera Cornea

22 Sclera Cornea Scleral venous sinus Fibrous Tunic Figure 15.4a

23 Corneal Edema

24 STRUCTURE OF THE EYEBALL Three layers 2) Vascular tunic (uvea) Choroid Ciliary body Ciliary processes Ciliary muscle Iris

25 Ciliary body Ciliary zonule (suspensory ligament) Sclera Choroid Iris Pupil Cornea Lens Scleral venous sinus VascularTunic Figure 15.4a

26 STRUCTURE OF THE EYEBALL Three layers 3) Retina Photoreceptor neurons Rods and Cones Bipolar neurons Ganglion neurons Optic nerve Optic disc

27 Ciliary body Ciliary zonule Cornea Iris Pupil Sclera Choroid Retina Macula lutea Fovea centralis Optic nerve Lens Scleral venous sinus Retina Central artery and vein of the retina Optic disc (blind spot) Figure 15.4a

28 Ganglion cells Bipolar cells Photoreceptors Rod Cone Amacrine cell Horizontal cell Pathway of signal output Pigmented Pathway of light layer of retina (b) Cells of the neural layer of the retina Figure 15.6b

29 Pathway of light Optic disc Neural layer of retina Pigmented layer of retina Choroid Sclera Central artery and vein of retina Optic nerve (a) Posterior aspect of the eyeball Figure 15.6a

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31 Blood supply to the retina