KIN 103 (Chp: 10 - Senses) Flashcards
Smell - olfaction (what is it?)
Smell - olfaction
- Strong link between smell, memory, and emotion
- Olfactory sensory neurons
○ In the olfactory epithelium in the nasal cavity
○ Primary sensory neurons are in the nasal cavity
Odorants bind to odorant receptors, G-protein-cAMP-linked membrane receptors
Olfactory sensory neurons (What are they?)
Olfactory sensory neurons in the olfactory epithelium in nasal cavity are the receptors and the primary sensory neurons for smell
Olfactory pathway (What does it consist of?)
- Olfactory neurons in epithelium
- Cranial nerve I
- Olfactory bulb
- Olfactory cortex
- cereberal cortex and limbic system
What are the two unique features of the olfactory pathway?
Two unique things about the olfactory pathway
- They do not cross over
- They do not go through the thalamus
Where do the olfactory epithelium synapse?
with the olfactory bulb just above the cribriform plate
How long do Olfactory cells live for?
They only last for about 2 months before they are replaced
How did covid impact olfactory cells?
in covid 19 the supporting cells get infected causing the loss of smell
Taste buds and Transduction
Taste: four types
- Sour (with H+ ions)
- Salty (with Na+ ions)
- Sweet (nutritious foods)
- Bitter (toxic)
- Umami (protein)
- (Umami: Japanese for delicious, enhances flavor)
What ion is used in all taste cells?
Calcium is used in all taste cells
What taste senses use ATP?
- Sweet, umami, bitter: uses ATP
What is taste a product of?
WHEN WE TASTE THINGS IT IS A COMBINATION OF EVERYTHING THAT COMES TOGETHER
Synesthesia
Seeing sounds, tasting words
What are the ears two functions?
The ear is a sense organ that is specialized for two functions: hearing and equilibrium.
What is hearing?
Hearing is our perception of the activation of receptors in our cochlea by the energy carried by sound waves.
What is sound?
Sound is the brains interpretation of the frequency, amplitude and duration of sound waves.
Frequency
Frequency (Wavelength) = pitch
- Low frequency - low pitch
- Human range: 20-20,000Hz
Amplitude
Amplitude = intensity
- High amplitude = loud sound
- Measured in decibels
○ 10dB increase = 10x increase
○ Normal conversation = 60 dB
○ Rock concert 120+ dB
Hearing (steps 1-3)
- Sound waves strike the tympanic membrane and become vibrations
- The sound wave energy is transferred to the three bones of the middle ear, which vibrate.
- The staples is attached to the membrane of the oval window. Vibrations of the oval window create fluid waves within the cochlea
- The sound wave energy is transferred to the three bones of the middle ear, which vibrate.
Hearing (steps 4-6)
- Fluid waves push on the flexible membranes of the cochlear duct. Hair cells bend and ion channels open, creating electrical signals that alters neurotransmitter release
- Neurotransmitter release into sensory neurons create action potentials that trave through the cochlear nerve to the brain
- Energy from the waves transfers across the cochlear duct into the tympanic duct and is dissipated back into the middle ear at the round window
cochlear duct
The center of the membrane
Basilar membrane
The outside that is filled with little hairs
- Most flexible at the distal end
○ Can sense low frequency
- More stiff at the proximal end
○ Can sense high frequency
The higher the pitch the shorter
it travels down the basal
membrane
Organ of Corti
The middle layer in the ear
Stereocilia (what is it?)
The top of the hair cells are modified into Stereocilia of different heights
How is sound produced in the hair cells?
Rhythmic blending of the stereocilia by sound waves causes action potentials to be produced
- bending to short side = inhibition
- bending to long side = excitation
- no bending occuring = action potentials fired but no sound occurs
Loudness (how is it represented in hearing?)
Loudness = related to the frequency of action potentials
Ear neuron pathways
Primary sensory neurons project to medulla oblongata in the brainstem
Main pathway synapses in nuclei in midbrain and thalamus then projects to auditory cortex
Hearing loss (3 types) (Conductive)
Conductive: no transmission through either external or middle ear (ear wax )
Hearing loss (3 types) (Central)
Central: damage to neural pathway between ear and cerebral cortex or damage to cortex itself (uncommon, stroke)
Hearing loss (3 types) (Sensorineural)
Sensorineural: damage to structures of inner ear
(most common, old age, damage to hair cells, loud noises)
Cochlear implants (how do they work?)
they are inserted into the basilar membrane and stimulate the action potentials
Vestibular apparatus (What is it?)
Vestibular apparatus: provides information about movement and position in space
Semicircular canals (posterior canal)
○ Tilt of head (left to right)
Semicircular canals (superior canal)
○ Tilt of head (forward and back)
Semicircular canals (horizontal canal)
○ Rotation of head (left to right)
The Christa (what is it?)
The Christa: sensory receptor for semicircular canals, located in the ampulla (enlarged chamber, “bottle”)
What occurs within the semicircular canals?
The semicircular canals sense rotational acceleration
- When the head turns one way it pushes the endolymph the opposite way
Otolith organs (what are they?)
Otolith organs (utricle and saccule)
- Sensory receptor is the macule (a gel above the hairs)
- They are crystals that move in response to gravitational forces
Galvanic vestibular stimulation
Galvanic vestibular stimulation: activates the nerves from the vestibular system and initiates movements through involuntary postural reflexes
Vision
Vision is the process through which light reflected from objects is translated into a mental image.
Three steps
Three steps
- Light enters the eye and is focused on by the retina
- Photoreceptors in the retina transduce light energy into electrical signals
- Electrical signals are processed into visual images along pathways in the brain
Parts of the eye
Zonules: attach lens to ciliary muscle
Sclera: is connective tissue
Fovea: region of sharpest vision
Macula: the center of the field of vision
Neural pathway for vision (5 parts)
- optic nerve
- optic chiasm (crossover of nerves)
- optic tract
- thalamus
- occipital lobe
Pupillary reflex (what is it?)
Pupillary reflex: standard part of neurological examination
- light hitting retina of one eye activates photoreceptors and constricts pupils of both eyes via reflex through the midbrain (consensual reflex)
What control papillary constriction?
cranial nerve three
Concave and convex (what is the difference)
Concave lens: spreads light
Convex lens: converges light
How does the eye adjust for close and far objects?
The closer an object is the less parallel the light rays are
Accommodation
Accommodation is the process by which the eye adjusts the shape of the lens to keep objects in focus
Presbyopia
As we age the lens stiffens and we lose accommodation (presbyopia), making it difficult to focus on near objects requiring reading glasses (>40 yrs).
How do the ciliary muscles work?
- when they relax they flatten the lens
- when they contract they round the lens
Hyperopia
Difficulty seeing near objects (cornea too flat)
- focal point falls behind the retina
Myopia
Difficulty seeing far objects
(cornea too curved)
- focal point falls before the retina
Astigmatism
Astigmatism: abnormal shaped lens results in distorted images.
Rods and cones (what is the difference?)
Rods = non colour vision
Cone = colour vision
When an image comes into our eye what happens to it?
It is upside down from how it should be when it passes through the lens
Rhodopsin (what is it?)
Rhodopsin is the visual pigment for rods
- Converts light energy into a change in membrane potential
- Combination of opsin and retinal
How many pigments do cones have?
Cones have 3 pigments sensitive to different wavelengths (red, green, blue)
Phototransduction in rods (step 1-3)
- in darkness rhodopsin is inactive and ion channels are open, there is tonic release of neurotransmitters
- light energy activates rhodopsin and opsin and retinal unbind, second messanger process closes ion channels and hyperpolarizes membrane. This causes less neurotransmitter release and a graded potential dependent on intensity of light
- after this opsin and retinal recombine and end stimulation
Visual fields (how are they combined?)
Rod -> bipolar cell -> ganglion cells
Ganglion cell receptive fields (on-center, off-surround)
the ganglion is:
- excited by light in the center of the field
- inhibited by light in the outside of the field
Ganglion cell receptive fields (off-center, on-surround)
The ganglion is
- Excited by light in the outside of the field
- inhibited by light on the inside of the field
What does the retina use for distinction
- The retina uses contrast for distinction instead of absolute light intensity
How do we distinguish what is 3D and what is 2D
- objects in the visual field in which the two eyes overlap (binocular zone) are seen in 3D
- objects in the visual field of only one eye are only seen in 2D
How are the neurons in the thalamus and visual cortex organized?
- the organization of neurons in the thalamus and visual cortex are arranged in a topographic map which corresponds to the visual fields of the eye
