Special Senses Flashcards
- Stimuli
- Sensation
- 2 types of receptors
- Stimuli: Sensory information that our bodies are constantly exposed to
- Sensation: Our conscious awareness to these stimuli
2 classes;
- General senses receptors: temp, pain, touch, stretch & pressure
- Special senses receptors: gustation, olfaction, vision, equilibrium & auditory
3 types of stimulus origin receptors
- Exteroceptors
- found in skin or mucous membranes (nasal, oral vagina, anal)- “external receptors”
- Interoceptors
- found in walls of viscera - detect stretching, oxygen depravation, temp & pressure
- Proprioceptors
- found in muscles, tendons & joints
- detect body and limb movement, muscle contraction and stretching and changes in capsule struct
Modality of Stimulus (6)
- several classes of receptors based on stimulating agent
1. Chemoreceptors: detect specific molecules dissolved in fluid
2. Thermoreceptors: detect changes in temp
3. Photoreceptors: Detect changes in light intensity, colour & movement of light
4. Mechanoreceptors: detect physical deformation due to touch, pressure, vibration and stretch
5. Baroreceptors: detect pressure changes w/in body structures
6. Nociceptors: detect tissue damage and pain
How does sensation occur?
- Sensory receptors respond to environmental stimuli
- Nerve impulses travel to cerebral cortex and sensation (conscious perception of stimuli) occurs
- sensory adaptation = decrease in stimulus response - can occur w/ repetitive stimuli (i.e. odour)
Flow chart of sensation process
Stimulus -> sensory receptor -> nerve impulses along sensory fibre -> spinal cord -> brain
Receptive fields
- Entire area through which the sensitive ends of a receptor cell are distributed
- Smaller the receptive field = more sensitive and precise receptor is to location & nature of stimulus
Tactile Receptors
- what they are
- location
- 2 types
-Most numerous type of receptor
-are mechanoreceptors that react to touch, pressure and vibration stimuli
-located in dermis and subcutaneous layer
2 types;
1. Unencapsulated: endings not wrapped in CT or glial cells
2. Encapsulated: endings wrapped in CT or glial cells
Types of Unencapsulated Tactile receptors (3)
- Free Nerve Ending: widespread in deep epidermis & papillary layer of dermis
- detect pressure, change in temp, pain, touch - Root hair plexus: surrounds hair follicles in reticular layer of dermis
- detect movement of hair - Tactile Disc: stratum basale of epidermis
- detect light touch, textures and shapes
Types of Encapsulated tactile receptors (4)
- Krause Bulb: mucous membranes of oral, nasal, vagina and anal cavity
- detect light pressure and low-frequency vibration - Lamellated corpuscle: dermis, subcutaneous tissue, synovial membranes and some viscera
- detect deep pressure and high-frequency vibration - Ruffini Corpuscle: Dermis and subcutaneous layer
- detect continuous deep pressure and skin distortion
- Tactile corpuscle: Dermal papillae (esp. lips, palms, eyelids, nipples and genitals)
- detect fine, light touch and texture
Clinically significant types of pain (2 types)
- Phantom pain: sensation associated w/ part of body that has been removed
- sensory cell bodies from limb remain alive as part of dorsal spinal root
- also called phantom limb syndrome
-Referred pain: occurs when impulses form certain viscera, such as heart or appendix, are perceived as originating in dermatome of skin instead of the organ
Taste Receptors
- how many
- 5 main tastes
- 4 types of tongue papillae
- 4000 taste buds located primarily on tongue of adults
- 5 main types; sweet, sour, salty, bitter and umami (savoury)
- 80-90% of what we perceive as taste is actually due to sense of smell
- Are 4 types of tongue papillae: filiform, fungiform, vallate & foliate
Olfaction
- what detects smell
- 3 layers of it
- sense of smell
- Paired olfactory organs w/in nasal cavity
- Olfactory epithelium has 3 layers;
1. Olfactory receptor cells
2. Supporting cells
3. Basal cells
Smell receptors
- apical end
- olfactory pathways
- Depends on 10-20 million olfactory cells in roof of nasal cavity
- at apical end of olfactory receptor cells are free nerve endings called olfactory hairs (project through mucous lining)
- hairs contain receptors for airborne molecules - axons from bipolar neurons of nasal mucosa pass through foramina of cribriform plate and enter olfactory bulbs
- neurons w/in olfactory bulbs project axon bundles called olfactory tracts to the olfactory cortex of temporal lobe
3 layers of Eye wall
- Fibrous tunic
- vascular tunic
- Retina
Layers of eye wall; Fibrous tunic
-2 regions
- Composed of 2 regions;
1. Cornea: transparent, avascular; receives oxygen and nutrients from lacrimal fluid and aqueous humor
2. Sclera: makes up majority of fibrous tunic; considered white of eye- allows for the attachment of extrinsic eye muscles to eye
Layers of eye; Vascular tunic
-3 parts
Composed of 3 regions;
- Choroid: largest area; contains vast network of capillaries that supply nutrients and oxygen to retina
- Ciliary Body: Composed of ciliary muscles & ciliary processes
- suspensory ligaments extend from ciliary body & attach to lens
- when ciliary muscle contract or relax shape of lens changes to focus incoming light into retina
- Iris: Pigmented part of eye
- inner margin = pupil (allows light to pass on to retina)
- diameter of pupil determined by 2 sets of muscles (Sphincter pupillae muscles - constriction; Dilator pupillae muscles - dilation)
Retina
- what it is
- 2 layers and what they contain
-internal layer of eye wall
2 layers;
-Pigmented layer: attaches to choroid; absorbs light energy that passes through retina and provides photoreceptors w/ vitamin A
-Neural layer: houses photorecetors and other associated neurons
Vision
- Receptors for vision reside in eye
- are photoreceptors that are capable of detecting light, colour and movement
Accessory structures of the eye (5)
-what they do
- Conjunctiva: stratified squamous epithelium that lines anterior surface of eye (not cornea) & inner surface of eyelid
- goblet cells to lubricate and moisten eye - Eyebrows: prevent sweat from dripping
- Eyelashes: prevent large foreign objects from contacting eyes
- Eyelids: Movable anterior protective covering for eye
- Tarsal glands: located within both eyelids; contain sebceous glands to prevent tear overflow and eyelids from sticking together
Accessory structures of eye;
- Palpebral fissure
- Medial and lateral commissures
- Lacrimal caruncle
- Palpebral fissure: opening between 2 eyelids
- Medial and lateral commissures: where eyelids unite at their medial and lateral borders
- Lacrimal caruncle: small, reddish structure at medial commissure that contains modified sweat glands
Optic Disc
- is the blind spot on retina
- located where ganglion cell axons exit retina to form optic nerve & renal arteries/veins enter and exit retina
- lacks photoreceptors
Fovea Centralis
- area of retina that contains highest proportion of cones and almost no rods
- sharpest area of vision
Anatomy of ear
- functions (2)
- 3 divisions
-functions in hearing and balance (equilibrium)
3 divisions;
- Outer ear: functions in hearing - filled w/ air
- Middle ear: functions in hearing - filled w/ air
- Inner ear: functions in hearing and balance; filled w/ fluid
External Ear
- Skin covered, funnel-shaped, elastic cartilage supported structure called auricle
- auricle leads to bony tube called external acoustic meatus - ends at tympanic membrane
- deep within external auditory meatus, glands produce waxlike secretion called cerument
Middle ear
- Air filled tympanic cavity, medial to tympanic membrane
- contains opening to auditory tube that connects to nasopharynx & 3 auditory ossicles (malleus, incus & stapes)
Inner Ear
- Located in spaces w/in petrous portion of temporal bone
- spaces = bony labyrinth
- within bony labyrinth = fluid-filled tubes and spaces called membranous labyrinth
- receptors for equilibrium housed within sensory epithelium lining of membranous labyrinth
