Special Senses BMS 111

Flowchart nodes

• Special Senses     *Special Sensory Receptors -Localized- confined to the head region -Receptors are specialized receptor cells- not free ending sensory neurons

• 1. Taste (gustation)   -Receptors classified as chemoreceptors -respond to chemicals

• 5. Balance (equilibrium) -The ear- receptor organ for hearing and equilibrium -Composed of three main regions 1. External ear- hearing 2. Middle ear- hearing 3. Internal ear- hearing and equilibrium

• 4. Hearing (audition) -The ear- receptor organ for hearing and equilibrium -Composed of three main regions 1. External ear- hearing 2. Middle ear- hearing 3. Internal ear- hearing and equilibrium

• 3. Sight (vision) -Visual organ is the eye -70% of all sensory receptors are in the eye -40% of the cerebral cortex in involved in processing the visual information ​​

• 2. Smell (olfaction)   -Receptors classified as chemoreceptors  -respond to chemicals

• Taste receptors

• Located in taste buds -most are found on the surface of the tongue

• Most taste buds occur in projections of the tongue mucosa called papillae -3 types of papillae

• Filiform papillae -on the anterior part of the tongue, roughens tongue, enabling it to grasp and manipulate food during chewing

• Fungiform papillae -scattered over the entire surface of the tongue

• Vallate papillae -arranged in and inverted v near the back of the tingue  

• -each taste bud has 50-100 epithelial cells 

• Three major cell types in taste buds

• Gustatory epithelial cells (the sensory receptor cells)

• Supporting Cells

• Basal Epithelial Cells

• Have long microvilli that extend through a taste pore   -Microvilli contain taste receptors

• Innervated by three cranial nerves

• Facial Nerve -Anterior 2/3 of tongue

• Glossopharyngeal -Posterior 1/3 of tongue

• Vagus Nerve -Epiglottis

• -Olfactory sensory receptors are part of the olfactory epithelium  -located in the roof of the nasal cavities

• Sensory cells in the olfactory epithelium are ciliated neurons

• Cilia contain receptor proteins

• Axons of olfactory sensory cells

• Gather into bundles- filaments of the olfactory nerve

• Pass through the skull

• Synapse with neurons on the olfactory bulb

• Axons from these neurons project to the limbic region, where smells elicit emotions, and to the cerebral cortex where conscious preception of odor occurs

• Conjunctiva: thing membrane covering inside of eyelids and white of eye   Conjunctivitis: Irritation of the conjunctiva- often by bacteria or viruses. referred to as "pink eye"

• Lacrimal Apparatus: Lacrimal glad- tear duct

• Extrinsic eye muscles: -control movement of eyes and hold eyes in orbit -muscles insert on the eyeball

• Innervation of extrinsic eye muscles

• Occulomotor Nerve: Medial Rectus Lateral Rectus Superior Rectus Inferior Oblique

• Trochlear Nerve: Superior Oblique

• Abducens Nerve: Lateral Rectus

• Strabismus -eyes do not align in the same direction -caused by weakness or paralysis of extrinsic eye muscles -Should be corrected as early as possible because disuse will cause pathways within the brain to degenerate

• Layers of the eye

• Vascular layer:

• Inner Layer

• The fibrous layer -Most external layer of the eyeball

• Sclera -Posterior five-sixths of the tunic

• Cornea -anterior one-sixth of the fibrous tunic

• -White, opaque region -Provides shape and an anchor for eye muscles

• Allows light to be transmitted into the eyeball

• Choroid: Where blood vessels come in

• Ciliary body: shapes the lens

• Iris: Light regulator

• Retina: -Innermost/ deepest layer -picks up light and sends to optic nerve -contains photoreceptors

• Optic Nerve: runs from the eye to the brain to send visual stimulus to the brain

• Composed of two layers

• Pigmented layer: Single layer melanocytes

• Neural layer: Sheet of nervous tissue

• Photorecptors

• Cone Cells: -Operate best in bright light -Enable high-acuity, color vision

• Rod Cells: -More Sensitive to light -Allow vision in dim light

• Outer (External) Ear:

• The auricle (pinna) -helps direct sound

• External acoustic canal (meatus) -Directs sound to the tympanic membrane -lined with skin (contains hair, sebaceous glands, and ceruminous glands)

• Tympanic Membrane -Forms the boundary between the external and middle ear

• Middle Ear: -ear ossicles- transmit vibrations from tympanic membrane to oval window

• Ear ossicles  -transmit vibrations from tympanic membrane to oval window

• Malleus: attaches to the eardrum

• Incus: between the malleus and stapes

• Stapes: Vibrates against the oval window

• Oval window (deep to stapes)

• Round window

• Pharyngotympanic (auditory) tube

• Entrance to mastoid antrum in the epitympanic recess

• The Inner (Internal) ear

• Bony labyrinth -a cavity consisting of three parts

• Semicircular canals: -Equilibrium: rotational (angular) acceleration of the head

• Vestibule-Utricle and saccule -Equilibrium: linear acceleration of head (gravity)

• Cochlea -Hearing

• Vestibular nerve -Equilibrium

• Cochlear Nerve -Hearing

• 2 main parts

• Semicircular Canals -Equilibrium

• Cochlea (snail) ​​​​​-hearing