The Somatic Nervous System - Sensory Organs PDF

The Somatic Nervous System - Sensory Organs Chapter 14  Describe different types of sensory receptors Describe the structures responsible for the special senses of taste, smell, hearing, balance, and vision Sensory...

The Somatic Nervous System - Sensory Organs Chapter 14  Describe different types of sensory receptors Describe the structures responsible for the special senses of taste, smell, hearing, balance, and vision Sensory Distinguish ow different tastes are transduced Perception: Describe the means of mechanoreception for hearing Objectives and balance List the supporting structures around the eye and describe the structure of the eyeball Describe the process of phototransduction  Sensory Receptors: structural types Free nerve endings Pain and temperature Encapsulated endings Pressure and touch Specialized Receptor cell Photoreceptors Sensory Receptors: Location Another way to classify receptor types: Exteroceptor Located near stimulus Interoceptor Internal organs Proprioceptor Near moving body part  Sensory Receptors: Functional Types Another way to classify: Chemoreceptor Chemical stimuli Osmoreceptors Solute concentrations Nociceptor Pain Mechanoreceptor Physical stimuli / sound / balance Thermoreceptor Temperature Photoreceptor Blausen.com staff (2014). "Medical gallery of Blausen Medical 2014". rods & cones for vision WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436 Sensory Modalities General sense Distributed throughout body Special sense Specific organ dedicated to it Modality Refers to how information is encoded  Gustation Sweet Dissolved glucose G protein-coupled receptors Salty Perception of Sodium in saliva Sour Hydrogen ion perception Bitter G protein- coupled receptors Depolarize or hyperpolarize Umami G protein-coupled receptors L-glutamate  Gustation Taste buds Within papillae Gustatory receptor cells Supporting cells Basal Cells Can activate Facial nerve Glossopharyngeal nerve Vagus nerve Olfaction Olfactory epithelium Olfactory receptor neurons Dendrites on apical surface Odorant molecules Airborne, pass over olfactory epithelial region Bind to proteins in mucus Transported to dendrites Graded potential Olfaction Axons extend: From basal surface to brain Connect to olfactory bulb Axons then split Olfactory cortex Inferior and medial area of temporal lobe Hypothalamus and Limbic system Long term memory / Emotion Accessory Eye Structures Accessory structures lacrimal gland (tears), lacrimal duct leads to the eye and conjunctiva. Four straight and two oblique extrinsic eye muscles. Eyelids, eyebrows, and eye lashes for protection. Eye Anatomy Tissue layers Fibrous tunic Sclera & Cornes Vascular tunic Choroid Ciliary Body Iris Neural tunic (Sensory Layer) Retina Pigmented Epithelium Rods & Cones Optic Nerve  Lens – biconvex, flexible structure to help focus light on the retina, held by suspensory ligaments which attach to ciliary muscles Rods and Cones 130 million rods vs. 6.5 million cones Rods are cylindrical stacks covered in proteins, they react to light, more rods the further from the fovea Cones sense color (blue, green, and red) and are concentrated in the fovea Eye/Vision Problems Hyperopia – eyeball is short, light focuses after the retina (farsightedness) Myopia – eyeball is long, light focuses before retina (nearsightedness) Diplopia – eyes don’t focus on same spot (double vision)  Vision is processed right to left, upper to lower, and is inverted, but the image is integrated to the proper positioning The ventral stream recognizes an objects significance, uses temporal lobe structures The dorsal stream locates objects in space and guides movements in response, uses parietal lobe structures and interacts with somatosensory cortical areas Ear Outer – auricle, external auditory meatus, external auditory canal with ceruminous glands, and tympanic membrane (ear drum) Middle – begins at tympanic membrane, 3 ossicles (malleus, incus, and stapes), and ends at oval window. Middle ear is filled with air unless there is an ear infection. Inner – passages in the temporal bone. Vestibule, cochlea (audition), and 3 semicircular ducts (equilibrium). Perilymph surrounds the membranous labyrinth and endolymph fills the membranous labyrinth. Auditory Tube Known as Eustachian tube Connects middle ear to the pharynx Allows air to enter or leave to equalize pressure Fluid can drain through tube during infections Cochlea Has 3 ducts – scala vestibule (attached to oval window), scala media (organ of Corti), and scala tympani (attached to round window). Vestibular and tympanic canals are filled with perilymph Scala media is filled with endolymph and is where sensory function occurs Each duct is separated my a membrane Organ of Corti attaches to the basilar membrane, has hair cells with stereocillia, and hairs are anchored to a tectorial membrane Can you Hear Me Now? Audition is a physical/mechanical sensation Sound waves cause tympanic membrane to vibrate, vibrations make ossicles move, perilymph moves basilar membrane which bends the hairs, and now channels can open for depolarization. Nerve signal can now be conducted through the vestibulocochlear nerve (CN VIII) to the brain Ossicles amplify the sound waves Sound High frequency for high pitch at the base (start) of the cochlea Intensity – more hair cells move because of louder sounds Hearing aid amplifies the sound if the system isn’t working well enough, but won’t do anything if hairs are compromised Cochlear implant – should conduct sound to nerve and used if hairs are no longer working  Equilibrium/Balance Static equilibrium is detected by mechanoreceptor in the vestibule If moving, cells slide in the 3 semi circular ducts and bend hairs to signal to the brain where the head is in space, filled with perilymph Depolarization Both auditory and balance work by mechanoreceptors Hair is pulled to open the channel and K+ rushes in (Not Na+) Balance is different in that hair cells bend one way causing depolarization and the opposite way causes hyperpolarization Review Questions What’s up next? 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