Special senses Flashcards
What are the General senses receptors?
- Chemoreceptors
- Mechanoreceptors
- Thermoreceptors
- Nociceptors
- PHOTORECEPTORS→melanocytes found to contain rhodopsin, which responds to light
What are the Special senses receptor types?
- Chemoreceptors
- Mechanoreceptors
- Photoreceptors
What is the purpose/what are Receptors?
- In order to detect a stimulus, there must be a receptor –
something to receive the information - Receptors are:
- Sensory nerve endings or
- Specialized cells adjacent to sensory nerves
What are sensory pathways?
- A stimulus (light, sound, taste, etc) generates a receptor
potential - Receptor potentials can be weak or strong, unlike action
potentials which are all-or-none - The receptor potential triggers an action potential in the sensory nerve
- Action potential travels to the brain where it is ”sensed”
What are Mechanoreceptors?
Mechanoreceptors: detect changes in pressure or movement;
-Ex. pressure receptors in skin, proprioceptors in muscles and joints
What are Thermoreceptors?
Thermoreceptors: detect temperature change
What are Nociceptors?
Nociceptors: detect pain
What are Chemoreceptors?
Chemoreceptors: detect changes in chemical concentrations;
- Ex. taste buds and olfactory receptors
What are Photoreceptors?
Photoreceptors: detect light energy;
-Ex. the eye
Where are special senses located?
*Special senses are localized and confined to the head region
- The receptors are specialized receptor cells
How is Taste (Gustation) recepted?
- Taste receptors are found taste buds in the mucosa of the mouth and pharynx
- Taste buds are found on tongue, posterior palate, pharynx, inside of cheeks, posterior wall of pharynx, and the epiglottis
- Most taste buds are found in papillae on tongue
What are the types of the papillae that contain taste buds?
Papillae that contain taste buds:
* Vallate (circumvallate) papillae
- Inverted “V” on back of tongue
* Fungiform papillae
- Scattered throughout surface of tongue
* Foliate papillae
- Posterolateral surface of tongue
What are the components of taste buds?
*Each papilla has many taste buds (except filiform papillae)
*Each taste bud is made of 50-100 epithelial cells:
- Gustatory epithelial cells (taste)
– Have long microvilli called gustatory hairs that extend through taste pore
- Basal epithelial cells (replace old and damaged cells every 7-10 days)
What are the components of taste?
*Dissolved molecules in saliva enter taste pore
*Molecules bind to receptors on gustatory hair cells
*Action potentials are generated, sensory neurons stimulated, signals sent to CNS
*Types of tastes:
- Sweet
- Sour
- Salty
- Bitter
- Umami
*These different tastes occur all over the tongue (taste map is incorrect)
How do smell and taste work together?
*Flavor = combination of taste, smell, and texture
*Smell and taste work hand-in hand
- Food has less taste when you have a cold
- Good smells stimulate appetite; bad smells do not
What is the Gustatory Pathway in brain?
*Taste receptors→sensory nerve fibers in cranial nerves →brainstem →thalamus →gustatory cortex (insula)
What is Olfaction (Smell)?
*Olfactory receptors are in the olfactory epithelium (pseudostratified columnar) that covers superior nasal concha and the superior part of nasal septum
*Millions of bipolar neurons = olfactory sensory cells
*Olfactory stem cells
- Continually form new olfactory sensory neurons
What are the components of Olfactory Receptors?
- Each bipolar olfactory neuron
- Has an apical dendrite that is near surface of epithelium
– Has olfactory cilia (hairs)—location of chemoreceptors - Mucus traps and dissolves molecules from inhaled air
- Chemical binds to chemoreceptor and activates olfactory sensory neuron
- Extensions of sensory neurons = filaments of olfactory nerve
- Enter CNS through cribriform plate of ethmoid bone
- Synapse with mitral cells in olfactory bulb at glomeruli
What is olfaction?
*Extensions from mitral cells relay olfactory information via olfactory tract to
1. Limbic system
- Smells elicit emotions and memories
2. Primary olfactory cortex in temporal lobe
What is Chemical Sense Disorders?
Olfactory disorders are most common (compared to taste disorders)
* Anosmia = absence of smell
- Blow to head/whiplash
- Colds/allergies
- Zinc deficiency
* Uncinate fits = olfactory hallucinations
- Brain disorders
Components of vision?
Vision
*Humans use vision as our dominant sense
*70% all sensory receptors in our body are located in our eyes
What are the Accessory Structures of the Eye?
- Eyebrows
- Shade eyes from sunlight
- Prevent sweat from running into eyes
- Palpebrae = eyelids
- Have eyelashes at free margin
– Keep foreign objects out of eye
– Very sensitive→blinking reflex - Sebaceous glands in palpebrae
–Lubricate surface of eye
– Those associated with eyelashes can get infected = sty
- Have eyelashes at free margin
- Palpebral fissure
- Space between eyelids
- Lacrimal caruncles
- Pink raised portion; medial angle
Surface Anatomy of the Eye?
Conjunctiva
* Transparent mucous membrane
* Covers inner surface of eyelids and anterior surface of eyeball (except cornea)
* Conjunctivitis (very contagious)
Tear Production
Lacrimal apparatus is made of the lacrimal gland and ducts that drain lacrimal fluid
* Lacrimal gland
- Superolateral region of the orbit
- Serous cells produce lacrimal fluid = tears
– Contains mucus, antibodies, and lysozyme (destroys bacteria)
- Fluid washes irritants away from eye surface
Tear Drainage
Tears move across eye, enter puncta
* Drain into lacrimal canaliculi, then
* Lacrimal sac →
* Nasolacrimal duct →
* Nasal cavity
What is the Extrinsic Eye Muscles?
*Movement of each eye is controlled by 6 extrinsic eye muscles
*Skeletal muscles
*Attach to outer surface of the eyeball (sclera)
What is Strabismus?
*Strabismus = misaligned eyes (cross-eyed)
*Caused by a problem with one or more of extrinsic eye muscles
*Eyes do not align properly
*Some results:
- Double vision
- Lack of stereoscopic (3-D) vision
- Amblyopia (reduced vision in the weaker eye “lazy eye”)
What are the layers of the eye?
3 tunics (= layers)
*Fibrous tunic (outermost)
*Vascular tunic
*Sensory tunic (innermost)
What is the Fibrous Tunic?
*Outermost layer
*Extension of dura mater
*Provides protection and mechanical support
*Avascular
*Parts
- Sclera (dense irregular CT→opaque)
- Cornea (dense regular CT→transparent)
*Sclera is covered by conjunctiva
- Mucous membrane (stratified columnar with goblet cells)
What is Vascular Tunic?
*Middle tunic
Parts
* Choroid: vascular, dark surface absorbs excess light
* Iris is made of smooth muscle
- Contracts and enlarges to regulate light entry to eye ball →pupil changes size
- Melanocytes (brown pigment, eye color)
What makes eyes darker in color?
Darker colored eyes have more pigment in anterior region of iris. Light eyes have little to no pigment in the anterior region.
What is the ciliary body of the Vascular Tunic?
Ciliary body
* Ciliary muscle
- Smooth muscle
*Suspensory ligaments
*Controls the shape of the lens (which focuses light onto the back surface of the eye)
*Capillaries within produce aqueous humor
What is Accommodation?
- The lens changes shape when looking at things up close = accommodation
- Close objects (parasympathetic control)
- Ciliary muscle contracts
- Suspensory ligaments slacken
- Lens becomes round
- Distant objects (sympathetic control)
- Ciliary muscle relaxes
- Suspensory ligaments become taut
- Lens is flattened
- With age, the lens becomes less elastic →presbyopia
- Bifocals or reading glasses are needed
What is Sensory Tunic?
*Innermost tunic
*Two layered structure:
1. Pigmented layer (next to choroid)
* Single epithelial layer, contains melanin granules
* Absorbs light
* Nourishes neural layer
2. Neural layer (in contact with lumen of eye)
* Three types of neural cells
- Photoreceptor cells
- Bipolar cells
- Ganglion cells
