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Flashcards in Special Senses Deck (26):
1

-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;
1. General senses receptors: temp, pain, touch, stretch & pressure
2. Special senses receptors: gustation, olfaction, vision, equilibrium & auditory

2

3 types of stimulus origin receptors

1. Exteroceptors
-found in skin or mucous membranes (nasal, oral vagina, anal)
-"external receptors"
2. Interoceptors
-found in walls of viscera - detect stretching, oxygen depravation, temp & pressure
3. Proprioceptors
-found in muscles, tendons & joints
-detect body and limb movement, muscle contraction and stretching and changes in capsule struct

3

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

4

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)

5

Flow chart of sensation process

Stimulus -> sensory receptor -> nerve impulses along sensory fibre -> spinal cord -> brain

6

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

7

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

8

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

9

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

10

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

11

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

12

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

13

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

14

3 layers of Eye wall

-Fibrous tunic
-vascular tunic
-Retina

15

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

16

Layers of eye; Vascular tunic

-3 parts

Composed of 3 regions;
1. Choroid: largest area; contains vast network of capillaries that supply nutrients and oxygen to retina
2. 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
3. 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)

17

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

18

Vision

-Receptors for vision reside in eye
-are photoreceptors that are capable of detecting light, colour and movement

19

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

20

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

21

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

22

Fovea Centralis

-area of retina that contains highest proportion of cones and almost no rods
-sharpest area of vision

23

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

24

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

25

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)

26

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