Chapter 16 - Special Senses Flashcards
What is the difference between sensation and perception relating to senses?
Sensation - the raw form in which a receptor sends information to the brain
Perception - the way your brain interpret this information
What are the special senses receptor types and what does each sense?
- Nociceptors - respond to pain / tissue damage
- Thermoreceptors - respond to temperature
- Mechanoreceptors - respond to mechanical stimuli (touch and sound)
- Chemoreceptors - respond to chemical substances (taste and smell)
- Photoreceptors - respond to light energy (eyes/vision)
How is temperature senses? What functions as the sensor?
Thermoreceptors - respond to temperature
–Free nerve endings
Class of chemicals which stimulates pain receptors…
bradykinins
What important job do bradykinins perform?
activates cascade reactions leading to healing
What chemicals have the ability to block pain?
- Enkephalins (opioid) - bind to the same receptor as morphine
- Serotonin - stimulates the release of enkephalins
- Endorphins (opioid) - similar to morphine
What is the descending analgesic pathway? In what two ways does it function?
Descending Analgesic Pathway - relieves pain after pain has “done its job”
- Stops pain signal
- –Secretes serotonin into inhibitory spinal interneuron (stimulates release of enkephalins)
- –Secretes enkephalins onto postsynaptic neuron - Hyperpolarizing effect (nerve inhibition)
- –Synapses with presynaptic neurons –> opens Cl- channels (inhibits entire nerve causing the pain signal)
Where are the olfactory receptors located?
Form the olfactory epithelium, at the upper portion of the nasal cavity.
How are odorants sensed?
Odorants - stimulate olfactory hairs, which stimulate olfactory receptors
- -Over 10,000 types
- -Patterns of activation represent different smells
What are the the parts of an olfactory receptor?
- Olfactory bulb
- Olfactory epithelium (full of olfactory receptors, made by basal stem cells)
- Supporting cells - physical support, nourishment, electrial insulation, and detoxification
- Cilia (hairs) - project from the tip to sense odorants
How many different odors are we able to distinguish?
10,000
What is taste “multi-sensual”?
All flavors are combinations of the 5 gustatory receptor tastes.
What are the 5 gustatory receptor tastes?
- Sour (acids)
- Sweet (sugars)
- Bitter (alkaloids) - natural aversion to bitter tastes because they are found in toxins + rotten foods
- Salty (metal salts)
- Umami (amino acids) - “meaty” taste, often found in Japanese cuisine
Describe the structure of the eye.
- Fibrous tunic - outer layer
- –cornea
- –sclera - Vascular tunic - middle layer
- –area of blood supply, hence “vascular”
- –Choroid - contains blood vessel that nourish retina
- –Ciliary body - secretes aqueous humor
- –Ciliary muscle - pulls on lens for focusing, “squinting”
- –Lens - focuses the image on the retina
- –Iris - dilates / constricts to control the amount of light coming through the pupil - Retina
- –Photoreceptor layer - contains rods + cones
- –Bipolar cell layer - rods + cones synapse with bipolar cells
- –Ganglion layer - axons extend posteriorly to optic disc –> exit through the optic nerve
How do rods + cones differ in structure?
Hint: Photopigments
RODS
- Rhodopsin (opsin protein) + vitamin A (retinol)
- Forms:
- –Cis form - purple
- –Trans form - clear
CONES
- 3 different opsin proteins (that respond to blue, green, and red-orange light) + vitamin A (retinol)
- -Individual cones only contain one photopigment
How do rod cells sense light?
Light causes…
1. Some rhodopsin molecules to split
—Dim light - rods split and recombine (dynamic process)
—Bright light - rods become nonfunctional (takes 40 mins from bright to dim light for rods to function maximally)
2. Rhodopsin to go from Cis form –> Trans form (bleached)
—Cis form - secretes glutamate, which inhibits bipolar cells (allows you to see in the dark)
> Light exposure causes rod to release less glutamate, removing the inhibition of the bipolar cell
—-Trans form - light activates bipolar cell —> creates a local potential –> ganglia depolarizes (releases Na+, becomes excitatory),
> Rod now BLEACHED
What are the structure of the outer, middle, and inner ear?
OUTER
- Auricle
- External acoustic meatus - part of ear where sound passes throught and alters pressure on tympanic membrane
- Ceruminous glands - produces wax
MIDDLE -Tympanic cavity -3 Auditory ossicles > malleus > incus > stapes -Tensory tympani and stapedius muscles -Pharyngotympanic tube - equalizes pressure
INNER EAR
-Labyrinth - complex system of chambers and tubes
-Cochlea - fluid-filled chamber where hearing is sensed
-Semicircular canals - connected to the…
> vestibule
> round window - relieves pressure by bulging in and out in response to vibrations from the stapes
Explain the sound pathway
- Sound vibration causes a portion of the basilar membrane (of the cochlea) to vibrate –> bends stereocilia in that area
- Tip link of stereocilia is pulled to open ion channel –> K+ ions flood in, depolarizing cell
- Depolarization releases neurotransmitters –> stimulates a nearby sensory nerve
- Stimulated sensory nerve sends a signal to the brain
Explain how the orientation of the Utricle and Saccule allow for the detection of static equilibrium. Where in the inner ear are these structures located?
Static equilibrium - senses the position of the head (standing, lying down, etc.)
-Occurs in the vestibule, which contains otolith organs
> Utricle - has verticle macula
> Saccule - has horizontal macula
(Macula = patches of hair cells)
Describe the location and structure of the sense organs for dynamic equilibrium.
Dynamic equilibrium - detects motion
-Occurs in the 3 semicircular canals
> Ampulla - at the base of each canal
> Crista ampullaris - sensory organ of rotation, contains stereocilia that position themselves in fluid
—-Movement of fluid puts pressure on the crista ampullaris, moving the hair cells
> Cupula - dome-shaped mass that hair cells extend up into
