special senses

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Flashcard Set: The Special Senses

Topic: General Senses

Front: What are the five traditionally listed special senses?

Back: Vision (Sight), Smell (olfaction), Taste, Touch, Hearing.

Front: What additional sense, found in the ear, is also considered a special sense?

Back: Equilibrium (Balance).

Topic: Taste (Gustation)

Front: Where are taste buds primarily found?

Back: In papillae on the tongue mucosa.

Front: What are the three types of papillae found on the tongue?

Back: Filiform, fungiform, and circumvallate.

Front: Which types of tongue papillae contain taste buds?

Back: Fungiform and circumvallate papillae.

Front: Approximately how many taste buds are there, and how many cells does each contain?

Back: Approximately 10,000 taste buds; each has 40-100 epithelial cells.

Front: What are the 3 major types of epithelial cells within a taste bud and their functions?

Back:

* Supporting Cells: Separate and insulate receptor cells.

* Receptor (Gustatory) Cells: Deal with taste detection.

* Basal Cells: Stem cells that produce new receptor cells.

Front: What are the five basic taste sensations?

Back: Sweet, Salt, Sour, Bitter, Umami.

Front: What types of substances typically elicit a SWEET taste?

Back: Sugars, saccharin, alcohol, and some amino acids.

Front: What types of substances typically elicit a SALT taste?

Back: Metal ions (like sodium chloride).

Front: What types of substances typically elicit a SOUR taste?

Back: Hydrogen ions (acids).

Front: What types of substances typically elicit a BITTER taste?

Back: Alkaloids such as quinine and nicotine.

Front: What typically elicits an UMAMI taste?

Back: The amino acid glutamate (found in savory foods like meat broth, aged cheese).

Front: What must happen for a chemical to be tasted (activation)?

Back: It must be dissolved in saliva, diffuse into the taste pore, and contact the gustatory hairs of receptor cells.

Front: How quickly does taste adaptation occur?

Back: Adapts rapidly in 3-5 seconds and completely in 1-5 minutes.

Front: What is taste transduction?

Back: The process where the stimulus energy (chemical taste) is converted into a nerve impulse, usually involving an influx of ions into the receptor cell.

Front: Which two cranial nerves carry taste information, and from which parts of the tongue?

Back:

* Facial Nerve (VII): Anterior two-thirds of the tongue.

* Glossopharyngeal Nerve (IX): Posterior one-third of the tongue.

Front: What digestive reflexes can taste trigger?

Back: Increasing secretion of saliva and gastric juice.

Front: How significant is the sense of smell to the perception of taste?

Back: Taste is heavily influenced by smell (often cited as 80%). Blocked olfactory receptors make food taste bland.

Front: What other sensory receptors in the mouth influence taste perception?

Back: Thermoreceptors (temperature), mechanoreceptors (texture), and nociceptors (pain/irritation).

Topic: Smell (Olfaction)

Front: What is the primary organ of smell, and where is it located?

Back: The olfactory epithelium, covering the superior nasal concha.

Front: What type of neurons are olfactory receptor cells, and what key feature do they have?

Back: They are bipolar neurons with radiating olfactory cilia (which contain the receptors).

Front: What types of cells are found in the olfactory epithelium besides receptor cells?

Back: Supporting cells (cushion receptors) and Basal cells (stem cells for regeneration).

Front: What does the olfactory epithelium detect? What covers it to aid this?

Back: Detects chemicals in solution. It's covered by mucus which traps airborne molecules and dissolves them.

Front: What two physical states/properties must a substance have to be smelled?

Back:

* Must be in a gaseous state (volatile) to enter the nasal cavity.

* Must be water-soluble to dissolve in the olfactory epithelium mucus.

Front: Briefly describe the physiology of smell detection.

Back: An odorant molecule binds to protein receptors on olfactory cilia -> opens ion channels -> generates an action potential -> signal sent to the olfactory bulb.

Front: Describe the olfactory pathway after the olfactory bulb.

Back: Impulses travel down the olfactory tract to the thalamus -> frontal lobe (for conscious interpretation) OR to the hypothalamus/limbic system (for emotional responses to odor).

Front: What is anosmia, and what is a common cause?

Back: Loss of the sense of smell ("without smells"). Can be caused by head injuries that damage olfactory pathways.

Front: What are uncinate fits?

Back: Olfactory hallucinations (experiencing smells that aren't actually present), often preceding epileptic seizures.

Topic: Vision (Sight) - Accessory Structures

Front: What are the functions of the eyebrows?

Back: Shade the eyes from sunlight and prevent perspiration from dripping into the eyes.

Front: What is another term for eyelids? What muscle opens the eye?

Back: Palpebrae. The levator palpebrae superioris muscle raises the upper eyelid.

Front: What is the function of eyelashes?

Back: Trigger reflexive blinking when touched, protecting the eye.

Front: What is the conjunctiva? Where is it found? What causes "bloodshot" eyes?

Back: A transparent mucous membrane. Lines the eyelids (palpebral conjunctiva) and covers the anterior surface (white part) of the eyeball (bulbar conjunctiva). It's vascular; irritation or inflammation causes its blood vessels to dilate, resulting in bloodshot eyes.

Front: What does the lacrimal apparatus consist of?

Back: The lacrimal gland and the ducts that drain lacrimal secretions (tears).

Front: What do lacrimal glands secrete? What protective substances are in tears?

Back: Secrete tears. Tears contain mucus, antibodies, and lysozyme (an enzyme that destroys bacteria).

Front: Describe the path of tears across and out of the eye.

Back: Secreted by lacrimal gland -> released via superolateral excretory ducts -> spread across eye -> enter lacrimal puncta medially -> drain into the nasolacrimal duct -> empty into the nasal cavity.

Topic: Vision - Structure of the Eyeball

Front: What is the outermost layer of the eye called? What are its two parts?

Back: The Fibrous Tunic. Composed of the posterior, opaque Sclera and the anterior, transparent Cornea.

Front: What are the functions of the sclera?

Back: Protects the eyeball and provides an anchoring site for the extrinsic eye muscles.

Front: What is the primary function of the cornea?

Back: Allows light to enter the eye; major part of the eye's light-bending apparatus.

Front: What is the middle layer of the eye called? What are its three regions?

Back: The Vascular Tunic (Uvea). Regions: Choroid, Ciliary Body, and Iris.

Front: Describe the choroid. What is its main function?

Back: A dark brown, vascular membrane forming the posterior part of the uvea. Its blood vessels supply nutrients to all eye tunics, and its pigment helps absorb excess light.

Front: Describe the ciliary body. What muscle does it contain, and what structure does it control?

Back: A thickened ring of tissue surrounding the lens. Contains smooth muscle bundles (ciliary muscles). It anchors the suspensory ligaments that hold the lens in place; ciliary muscle contraction/relaxation changes lens shape for focusing.

Front: What is the iris? What is the pupil?

Back: The iris is the colored part of the eye. The pupil is the central opening in the iris that allows light to enter the inner eye.

Front: How does the iris control the amount of light entering the eye?

Back: In bright light/close vision: Circular muscles contract, pupil constricts.

In dim light/distant vision: Radial muscles contract, pupil dilates.

Front: How can emotional states affect pupil size?

Back: Pupils can dilate when observing appealing subject matter or during problem-solving/high mental effort; often linked to sympathetic nervous system activity.

Front: What is the innermost layer of the eye? What are its two main layers?

Back: The Sensory Tunic, or Retina. Composed of an outer Pigmented layer and an inner Neural layer.

Front: What is the function of the pigmented layer of the retina?

Back: Absorbs light that passes through the neural layer, preventing it from scattering and reflecting back, which would cause visual confusion. Also stores Vitamin A for photoreceptors.

Front: What key cell types are found in the neural layer of the retina?

Back: Photoreceptors (rods and cones) that transduce light energy, Bipolar cells, Ganglion cells, and interneurons (Amacrine and Horizontal cells) that process visual information.

Front: Where do ganglion cell axons run, and what structure do they form when leaving the eye?

Back: They run along the inner surface of the retina and converge to leave the eye as the Optic Nerve.

Front: What is the optic disc? Why is it called the "blind spot"?

Back: The site where the optic nerve exits the eyeball. It lacks photoreceptors (rods and cones), so light focused on this spot cannot be seen.

Topic: Vision - Photoreceptors and Internal Structures

Front: What are the two types of photoreceptor cells in the retina?

Back: Rods and Cones.

Front: Describe the function of Rods.

Back: Respond to dim light (high sensitivity), used for peripheral and night vision. Perceive input only in gray tones. Many rods converge onto a single ganglion cell, resulting in fuzzy, less detailed images.

Front: Describe the function of Cones.

Back: Respond to bright light (low sensitivity), provide high-acuity color vision. Found in the macula lutea, concentrated in the fovea centralis. Each cone (or few cones) synapses with a single ganglion cell, resulting in detailed vision.

Front: What structure divides the internal eye into anterior and posterior segments?

Back: The Lens.

Front: Describe the lens. What is a key property related to focusing? Is it vascular?

Back: A transparent, biconvex, flexible structure. It can change shape (accommodation) to precisely focus light on the retina. It is avascular (lacks blood vessels).

Front: How does the lens change with age? What condition can result?

Back: It becomes thicker, denser, and less elastic with age, impairing its ability to focus on close objects (presbyopia).

Front: What is a cataract? What are common causes?

Back: Clouding of the lens that obstructs vision. Can be caused by aging (lens thickening), diabetes mellitus, heavy smoking, or prolonged exposure to intense sunlight.

Front: What fills the posterior segment of the eye (behind the lens)? What are its functions?

Back: Vitreous humor (a clear, gel-like substance). Functions: transmits light, supports the posterior surface of the lens, holds the neural retina firmly against the pigmented layer, contributes to intraocular pressure.

Front: What fills the anterior segment of the eye (in front of the lens)? What are its two chambers?

Back: Aqueous humor (a clear fluid similar to blood plasma). Chambers: Anterior chamber (between cornea and iris) and Posterior chamber (between iris and lens).

Front: What are the functions of aqueous humor? How is it drained?

Back: Supplies nutrients and oxygen to the lens and cornea, carries away metabolic wastes. Drains continuously via the Canal of Schlemm (scleral venous sinus).

Topic: Vision - Optics and Photoreception

Front: What happens to light when it passes from one transparent medium to another at an angle?

Back: Its speed changes, and it refracts (bends).

Front: How does a convex lens (like the eye's lens) affect parallel light rays?

Back: It bends the light rays so they converge at a single point called the focal point.

Front: What is the orientation of an image formed on the retina by the eye's lens system?

Back: It is upside down and reversed left to right. (The brain interprets it correctly).

Front: What is photoreception?

Back: The process by which the eye detects light energy.

Front: What do rods and cones contain that allows them to detect light? How are these arranged?

Back: They contain visual pigments (photopigments, e.g., rhodopsin in rods) located within stacked, disk-like infoldings of the plasma membrane. These pigments change shape when they absorb light.

Front: From where does the neural retina receive its blood supply?

Back: Two sources:

* The outer third (including photoreceptors) receives blood from the Choroid.

* The inner two-thirds receives blood from the Central Artery and Central Vein of the retina, which enter/exit through the optic nerve.

Topic: Vision - Eye Movement

Front: How many extrinsic (extraocular) muscles control the movement of each eye? Name the two groups.

Back: Six muscles: Four Rectus muscles (Superior, Inferior, Lateral, Medial) and Two Oblique muscles (Superior, Inferior).

Front: Which three cranial nerves innervate the extrinsic eye muscles?

Back: Oculomotor (III), Trochlear (IV), and Abducens (VI).

Topic: The Ear - Hearing and Balance

Front: What are the three major areas of the ear?

Back: Outer Ear, Middle Ear, and Inner Ear.

Front: Which parts of the ear are involved only with hearing?

Back: Outer Ear and Middle Ear.

Front: Which part of the ear functions in both hearing and equilibrium?

Back: Inner Ear.

Topic: The Ear - Outer Ear

Front: What is the external, visible part of the ear called? What is its function and composition?

Back: Auricle or Pinna. Composed of elastic cartilage covered by skin. Function is to direct sound waves into the external auditory canal.

Front: What is the tube extending from the auricle to the eardrum? What lines it and what glands are present?

Back: External auditory meatus (canal). Lined with skin containing hairs, sebaceous (oil) glands, and ceruminous glands (which secrete cerumen/earwax).

Front: What structure forms the boundary between the outer and middle ear?

Back: Tympanic membrane (eardrum).

Topic: The Ear - Middle Ear

Front: What is the middle ear also known as? Describe its general characteristics.

Back: Tympanic cavity. It's a small, air-filled, mucosa-lined cavity within the temporal bone.

Front: What structures border the middle ear laterally and medially?

Back: Laterally: Tympanic membrane (eardrum). Medially: Bony wall containing the Oval Window and Round Window (openings to the inner ear).

Front: What is the superior portion of the middle ear cavity called?

Back: Epitympanic recess.

Front: What tube connects the middle ear to the nasopharynx? What is its crucial function?

Back: Pharyngotympanic (Auditory or Eustachian) tube. Its function is to equalize the pressure in the middle ear cavity with the external air pressure, allowing the eardrum to vibrate freely.

Front: Name the three tiny bones (ear ossicles) found in the middle ear, in order from the eardrum to the oval window.

Back: Malleus (hammer), Incus (anvil), Stapes (stirrup).

Front: What is the function of the ear ossicles?

Back: To transmit the vibratory motion of the eardrum to the oval window, amplifying the pressure/force of the sound waves.

Front: Which two small skeletal muscles are found in the middle ear, and what is their function?

Back: Tensor tympani (attached to malleus) and Stapedius (attached to stapes). They contract reflexively in response to loud sounds to dampen vibrations and protect the inner ear.

Topic: The Ear - Inner Ear

Front: What is the complex system of tunnels within the temporal bone called? Name its three regions. What fluid fills it?

Back: Bony (osseous) Labyrinth. Regions: Vestibule, Cochlea, and Semicircular Canals. Filled with Perilymph.

Front: What structure lies suspended within the bony labyrinth? What fluid fills it?

Back: Membranous Labyrinth (a series of interconnected sacs and ducts). Filled with Endolymph (a potassium-rich fluid).