Special senses - Sight and Sound Flashcards
Which of the five senses is NOT a special sense?
TOUCH
The rest of the senses have a specialized organ that detects the stimuli, but touch is not specialized because there are touch receptors everywhere!!
What is the sense organ for sight?
Eyes
What is the sensory layer for sight?
Retina
What is the stimulus for sight?
Photons
What are the receptor cells for sight?
Photoreceptors
Where does photoreception occur?
Retina
Describe the structural components of the eye?
Anterior cavity
Aqueous humour
Posterior cavity
Vitreous humour
Cornea
Lens
Retina
Where is the anterior cavity of the eye and which humour does it contain?
Between lens and cornea
- containing aqueous humour
Where is the posterior cavity of the eye and which humour does it contain?
Between lens and the back of the eye
- containing vitreous humour
Compare aqueous humour to vitreous humour
Aqueous humour is more fluid-like, a salt solution
Vitreous humour is gel-like, more solid
The both o them are responsible for maintaining the shape of the eye, cushioning
What are some accessory structures in the eye?
- eyelashes
- eyelid
- pupil
- iris
How do accessory structures in the eye participate in physical protection?
- protect the eyes
- keep it lubricated
- keeps out foreign substances
How do accessory structures in the eye participate in controlling access of light?
- iris plays a significant role in controlling access of light
- can dilate or constrict to allow more or less light into the eye
in darkness, dilator layer causes pupil dilation (widens to allow more light)
in light, sphincter layer constricts pupil (allows less light into the eye)
What is the iris and its functions?
An accessory structure(?) of the eye that consists of two smooth muscle components
- controls access of light
- has a radial pattern in the muscle that contracts in darkness to open up pupil
Dilator layer = pupil dilation
Sphincter layer = pupil constriction
What is the cornea?
A special fibrous layer of connective tissue
What is the retina?
The sensory layer of the eye found at the back
What is the pupil?
A hole
- absence of the iris muscle
- allows light to come in to the sensory layer
How is light brought to a focal point?
Via the LENS
- the lens refracts light and brings light into focus
- changing the shape of the lens changes how we can bend light coming into our eyes
What is acommodation?
the bending of light/changing the shape of the lens to reach the focal point
What is the ciliary body?
Two smooth muscle layers that is connected to the lens via connective tissue
What is the function of the ciliary body?
Participate in accommodation - changing the distance focal point by controlling the shape of the lens
For close vision: What kind of accommodation is required?
Ciliary muscle contraction
= lens ROUNDED
For distant vision: What kind of accommodation is required?
Ciliary muscle relaxed
= lens FLATTENED
Describe the layers of the retina?
The retina is a multi-layered sheet of neurons
Where are photoreceptor neurons found in the retina?
Found in the outer layer of the retina, farthest from the path of incoming light
Describe the path of travel for photons when they get to the retina
- Incoming light must pass through several layers of cells before it can reach the photoreceptors
- retinal ganglion cells
- bipolar cells - Once the photon reaches the photoreceptors, it transduced and the info is relayed in the opposite direction
- Relayed info/neural signals goes in the opposite direction back to the cells so that it can travel to the brain
Every photoreceptor only receive slight originating from a distinct point in visual space (receptor field)
Anything outside of the field is not going to be detected - you cannot see that stimulus
What are the two important features of the central retina
- MACULA (fovea centralis)
- OPTIC DISC
What is the macula/fovea centralis?
The darkened region of the retina
- has lots of photoreceptors
- is the focal point
What is the optic disc?
The lightened region marking the start of the optic nerve
- axons gather here and pass through to the optic nerve
- because there is a lot of axons, there is a lot of myelination happening, which gives it the white light colour
- all nerve tissue and blodd vessels go through the optic disc, leaving no room for photoreceptors in the optic disc
Where is the macula and optic disc in relation to each other?
The optic disc marks the beginning of the optic nerve, while the macula is just above the optic disc/optic nerve
How do the macula and optic disc compare in function?
The macula is in charge of being the FOCAL POINT containing lots of photoreceptors
While the optic disc is PACKED WITH AXONS, BLOOD VESSELS, NERVE TISSUE to the optic nerve that there is no room for photoreceptors (passage way)
Explain the blindspot in terms of the anatomy of the retina
Focal point = MACULA
If your macula is focused on the black circle, at a circle point the x is going to be in a receptive field of the optic disc, but since there are no photoreceptors in that region, the optic nerve is informally the blindspot
What is the function of photoreceptors?
Photoceptors are in charge of phototransduction = the conversion of photons to membrane potential signals
What are the two types of photoreceptors?
Rods and cones
What is the function of the opsin protein?
Absorb light and activate retinal
- retinal (11-cis retinal and 11-trans retinal) molecules change shapes
- retinal shape changes cause changes in the shape of the opsin, activating the protein
- once the protein is activated it can absorb photons
What are the two types of retinal in an eye?
11-cis retinal (curved)
11-trans retinal (linear)
both of which come are derivatives of vitamin A
Describe the structural components of rod photoreceptors:
Rods have an inner and outer segment
- phototransduction begins in the outer segment with proteins + retinal
The outer segment is mad of membranous discs that contain opsin proteins
Are cones or rods more common in the peripheral retina?
Rods are the most common in the peripheral retina
Are cones or rods more common in the fovea centralis?
Cones are the most common in the fovea centralis
Describe the intensity, wavelength, and location of rod photoreceptors
Mediate vision in LOW LIGHT
- have a high sensitivity (can be activated when there is a low level of stimulus)
- low acuity = high convergence
- because of all the convergence, you cannot pinpoint which photoreceptor is being activated = not good at distinguishing stimulus space
- have one wavelength at which light absorption of maximized
Describe the intensity, wavelength, and location of cone photoreceptors
Have three types of cones to allow for colour vision
- activated at higher levels of light (low sensitivity)
- has different cone types that have different wavelengths in which they absorb maximal light
- one cone synapses with one bipolar neuron, relayed to the brain where the brain can process info/determine where the stimulus came from
What are the three types of cone photoreceptors?
Three types of cones allow for seeing colour
S-cone (blue)
M-cone (green)
L-cone (red)
S-cone
blue
M-cone
green
L-cone
red
Rod and Cones have:
______ SENSITIVITY
________ ACUITY
RODS: low light
HIGH SENSITIVITY
LOW ACUITY
CONES: colour vision (not good in dim light)
LOW SENSITIVITY
HIGH ACUITY
How is neurotransmitter release different in the darkness or lightness?
All photoreceptors release neurotransmitters constantly in the DARKNESS and become HYPERPOLARIZED during photon transduction
When does NT release occur?
IN DARKNESS
- depolarized
- NT are being released
- quite depolarized in the dark
- no light stimulus but the membrane is depolarized and NT is coming in
When doesn’t NT release occur?
IN LIGHT
- hyperpolarized because of the activation of opsin
- once light comes in and activates opsin, opsin triggers a series of enzymes that lead to the release of special proteins from Na+ ion channels that INACTIVATE Na+ channels
- stops depolarization because Na+ channels are closing
- ion channel become inactivated
- NO NT release
Will lightness or darkness have the highest amount of NT released from photoreceptors?
Darkness
Will lightness or darkness have the lowest amount of NT released from the fovea?
Lightness
From the retina, where is visual information relayed to?
Visual information from the retinas is relayed through the THALAMUS to PRIMARY VISUAL CORTEX (V1)
What is optic chiasm
The part of the brain where the optic nerves cross and is therefore of primary importance to the visual pathway
left side = processed by the right side
right side = processed by the left side
Membrane
Photoreceptors(cone/rod)
Bipolar cells
Cones and rods form synapses with bipolar neurons
Bipolar neurons form synapses with retinal ganglion cells
Axons go through optic disc/optic nerve to get to brain
**How are IPSPs generated in sign-inverting synapses?
In darkness, we get NT release
NT release stimulates bipolar cell
Bipolar cell will hyperpolarize = inhibitory
Where does nasal information cross?
Crosses at the optic chiasm = meaning that anything you see from the left side is processed by the right side, and everything you see from the right side is processed by the left side
Where does temporal information cross?
It doesn’t!
Anything you see is going to be processed on the same side that you see it
What is the sense organ for hearing?
ears
What is the sensory layer for hearing?
cochlea
What is the stimulus for hearing?
pressure waves
What are the receptor cells for hearing?
hair cells
What is hearing?
The detection of sound or pressure waves in the air
What are the three parts of the ear?
- Outer ear - tympanum (ear drum)
- Middle ear
- Inner ear
What is the tympanum?
The ear drum marking the end of the outer ear
The middle ear contains _________
Ossicles
What is the cochlea?
Its the spiral, sea looking thing inside the inner ear
Where does sound transduction occur?
Fluid of the inner ear at the cochlea (cochlear duct)
Describe the path of pressure waves to sound transduction
- Transfer waves coming into our ears
- Motion gets transferred through ear bones, interacting with inner ear at the oval window of cochlea
- Three layers that are connected at the tip of the cochlea, their vibrations can be transferred to the cochlear duct
- Cochlear duct = fluid-filled membrane containing cells that conduct sound waves (hair cells)
- Cochlear = spiral filled with fluid, water-glue like structure (cochlear duct), fluid filled = movement at receptor cells
What do hair cells do? Where are they located?
- mediate transduction
- have mobile hairs that are located within the cochlear duct
Are hair cells neurons or epithelial cells?
Epithelial cells
- cannot generate action potentials
- but are excitable
- mechanoreceptors
- can release NT
- hair cells form synapses with neurons
Describe the endolymph and perilymph of hair cells
Hair cells always have their bodies sitting in PERILYMPH, and their hairs extended into ENDOLYMPH (cochlear duct)
Differentiate kinocilium and stereocilia of hair cells
Kinocilium - displacement stimulates hair cell
Stereocilia - displacement inhibits hair cell
The cochlear duct is located between the scala __________and scala ________________
Scala vestibuli
Scala timpani
Hair cells for audition are found where?
Found in the spiral organ within the cochlear duct
- connected to both the basilar membrane and the tectorial membrane
Where is the basilar membrane?
Between the cochlear duct and the scala timpani
Where is the tectorial membrane?
Above the hair bundles of mechanosensory hair cells in the cochlea
How does the movement of hair cells relative to the tectorial membrane lead to membrane potential changes?
- All stereocilia are connected to the tectorial membrane (on the top)
- Depending on the movement of the stereocilia (inhibitory or not), it can either cause depolarization or hyperpolarization
(pushing the ion channels closed/open) - When pressure comes in, movement changes the shape of the basilar membrane (on the bottom) and as it changes, it pushes the hair cells against the tectorial membrane
- As the hair cells are moving relative to the tectorial membrane, it bends the hair in a direction the leads it to open the mechanically gated ion channels
How are mechanically gated ion channels opened/closed?
By force or pressure that pushes them open…
The basilar membrane starts [stiff/flexible] and becomes [stiff/flexible] as it spirals
The basilar membrane starts [stiff] and becomes [flexible] as it spirals
Why does the basilar membrane have different flexibilities along its length?
The basilar membrane has different flexibilities along its length so that sounds with different frequencies (pitches) cause movements in different parts of the membrane
If there is movement at the base of the basilar membrane, what kind of frequency wave was received?
HIGH FREQUENCY WAVES
If there is movement between the base/apex of the basilar membrane, what kind of frequency wave was received?
MEDIUM-FREQUENCY WAVES
If there is movement at the apex of the basilar membrane, what kind of frequency wave was received?
LOW-FREQUENCY WAVES
What kind of stimulus would cause the following
A) Soft sound?
B) Strong sound?
C) High pitched sound?
D) Medium pitched sound?
E) Low pitched sound?
A) Soft sound?
=> weak stimulus
B) Loud sound?
=> strong stimulus
C) High pitched sound?
=> higher frequency = closer to the base
D) Medium pitched sound?
=> medium frequency = in between the base/apex
E) Low pitched sound?
=> lower frequency = closer to the apex
The cochlea maps _______ not __________
The cochlea maps PITCH not SPACE
How does interaural time difference work?
Sounds are detected first by the ear nearest the stimulus
How does interaural level difference work?
The head creates a sound shadow for the farthest ear
What is tonotopy?
The organization of auditory information according to pitch (frequency)
How does auditory information make it to the hindbrain?
Afferent neurons relay auditory information from hair cells to the hindbrain, where it is processed before reaching the forebrain
Your reaction time is better based on hearing than sight: Why is that?
A shorter path/time for action potential transmission to reach the cerebral cortex
