Bio10004 2024 Special Sensory Overview PDF

Department of Health Sciences and Biostatistics Anatomy and Physiology Bio10004-2024 Overview of Special senses and Clinical Disorders Dr. Greg Davis Copyright notice Learning objectives 1.Describe the sensory organs of smell and their neural pathways 2.Desc...

Department of Health Sciences and Biostatistics Anatomy and Physiology Bio10004-2024 Overview of Special senses and Clinical Disorders Dr. Greg Davis Copyright notice Learning objectives 1.Describe the sensory organs of smell and their neural pathways 2.Describe the sensory organs of taste and their neural pathways 3.Identify the internal and accessory structures of the eye and explain their function and neural pathways 4.Describe the structures of the external, middle and inner ear and explain their roles in hearing and equilibrium and neural pathways Sensory organs of smell Learning objectives Describe the sensory organs of smell and their neural pathways Olfaction (sense of smell) Olfactory organs are in the nasal cavity reaches the olfactory epithelium Olfactory hairs Carries odorant molecules highly modified neurons Olfactory receptors cilia extend to the mucus lining the epithelial surface Chemicals dissolved in the interact with odorant-binding receptor proteins mucus Can distinguish 2000-4000 different odours How we smell Olfactory pathways “Olfactory nerve” (cranial nerve NI) – Bundle of olfactory receptor axons – penetrate the cribriform plate, – enter the cranium Synapse in the olfactory bulb of the cerebrum Axons leave the olfactory bulb – travel along the olfactory tract to the olfactory cortex. sensory organs of taste Learning objectives Describe the sensory organs of taste and their neural pathways Sense of taste Provides information about food and liquid consumed Five primary taste sensations – Saltiness, taste of sodium ions (Na+), e.g. table salt NaCl – Sourness, taste of acidity (excess of H+ ions), e.g. lemon – Bitterness, taste of bitter chemicals, e.g. dark chocolate – Sweetness, taste of sugars, e.g. glucose – Savouriness (umami), taste of amino acids and nucleotides, e.g. beef, soy sauce, Parmesan cheese Strongest when integrated with olfactory sensations Papillae contain taste buds Taste receptor cells Sensory organs of vision Learning objectives Identify the internal and accessory structures of the eye and explain their function and neural pathways  Vision Humans rely on vision more than on any other special sense Vision enables the immediate observation of distant objects Visible light is electromagnetic radiation with a wavelength of approximately 400–700 nm – Light with a smaller wavelength is known as ultraviolet – Light with a larger wavelength is known as infrared The eye and face Fig. 9-10a in Martini: Essentials 6th ed. Structure of the eye Iris is a thin, annular structure in the eye, responsible for controlling the diameter and size of the pupil, thus the amount of light reaching the retina. Eye colour is defined by that of the iris. Retina The retina is a thin layer of tissue that lines the back of the eye on the inside. It is located near the optic nerve. The function of the retina is to receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition. Retina The retina is a thin layer of tissue that lines the back of the eye on the inside. It is located near the optic nerve. The function of the retina is to receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition. View of retina In the centre of the retina is the optic nerve, From the centre of the optic nerve (disc) radiates the major blood vessels of the retina. To the left of the disc, can be seen the slightly oval-shaped, blood vessel-free reddish spot, the fovea, which is at the centre of the area known as the macula. Photoreceptors: rods and cones Auditory system (sense of hearing) Learning objectives Describe the structures of the external, middle and inner ear and explain their roles in hearing and equilibrium and neural pathways Auditory system (sense of hearing) Our sense of hearing enables us to detect and interpret sound waves Sound waves enter our body via the ears The inner ear is shared between two sensory modalities: hearing and equilibrium Both are based on mechanoreceptors (hair cells) Cranial nerve VIII (vestibulocochlear nerve) serves both hearing and equilibrium Sound waves Hearing 20 Hz -20 kHz Best around 1 kHz The ear Anatomy: external ear External ear Auricle (pinna) External acoustic meatus (ear canal) Tympanic membrane (eardrum) Earwax: also called cerumen, is made by the sebaceous glands to protect the ears. The ear wax has both lubricating and antibacterial properties. Untreated build up can lead to hearing loss, irritation, pain in the ear, dizziness. Anatomy: middle ear Middle ear – Tympanic cavity contains auditory ossicles (ear bones) Malleus (hammer) Incus (anvil) Stapes (stirrup) Anatomy: inner ear Internal ear serves both hearing and equilibrium Anatomy: inner ear Cochlea contains the cochlear duct – Oval window is connected to the base of stapes – Round window separates the perilymph of cochlear chambers from air-filled middle ear Anatomy: inner ear Semicircular ducts convey information about the rotational movements of the head The passage and reception of sound