Midterm 2 Flashcards
What is sensation?
Refers to how cells of the nervous system:
- detect stimuli in the environment (such as light, sound, heat, etc.)
- how they turn these signals into a change in membrane potential and neurotransmitter release
What is perception?
Refers to the conscious experience and interpretation of sensory information
What happens first: perception or sensation?
Sensation is the initial process and perception is making something of the sensation
What are sensory neurons/sensory receptors?
- Specialized neurons that detect a specific category of physical events.
- They accomplish this task with receptor proteins that they put on the membrane which are sensitive to specific sensory stimuli/specific features of the extracellular environment
List the specific sensory stimuli/specific features of the extracellular environment that receptor proteins are sensitive to?
- the presence of specific molecules (via chemical interactions)
- physical pressure
- temperature
- pH (acidity, basicity)
- electromagnetic radiation (light)
What kind of extra sensory stimuli/specific features of the extracellular environment are non-human animals’ receptor proteins sensitive to?
- Electrical and magnetic fields
- Humidity
- Water pressure
What happens if it gets too hot or too cold?
Ion channels open if it gets too hot or too cold and this triggers an action potential
What’s sensory transduction?
Process by which sensory stimuli are transduced (converted) into receptor potentials
What’s a receptor potential?
- Graded change in the membrane potential of a sensory neuron caused by sensory stimuli
- Sensory stimuli being detected by sensory neurons
What’s a sensory neuron?
Specialized neuron that detects a particular category of physical events (sensory stimuli)
Ex: photoreceptor cells transduce light into receptor potentials
What do all sensory neurons do and what do they don’t all do/have?
- All sensory neurons release neurotransmitters
- Not all sensory neurons have axons or action potentials
How do smaller cell sensory neurons, such as photoreceptor neurons, who don’t have action potentials release neurotransmitters?
- They release neurotransmitter in a graded fashion, dependent on their membrane potential
- The more depolarized they are, the more neurotransmitter (ex: glutamate for photoreceptors) they release
What’s an example of a cell that is a sensory neuron who does not have an axon or action potentials?
Photoreceptor cells
What are opsins and what kind of metabotropic receptors are they?
- Receptor proteins that are sensitive to light -> they detect light
- Many opsins gain their sensitivity to light by binding to a molecule of retinal
- The opsins in our eye that transduce visual information are all inhibitory metabotropic receptors
What are the four different types of opsin proteins we use to detect light?
- Rhodopsin
- Red cone opsins
- Green cone opsins
- Blue cone opsins
What are the four different types of photoreceptor cells we have and what do they express?
- Rod cells (express rhodopsin)
- Red cone cells (express red cone opsin)
- Green cone cells (express green cone opsin)
- Blue cone cells (express blue cone opsin)
How many of the different types of opsins does each photoreceptor cell in our eye contain?
Each photoreceptor cell in our eye contains only one of these types of opsins
What’s a photoreceptor cell?
- Sensory neuron responsible for vision
- These cells transduce electromagnetic energy from visible light into receptor potentials
What’s the retinal and what kind of wavelength of light does it interact with?
- Small molecule (synthesized from vitamin A) that binds to opsin proteins and changes its physical shape when it absorbs light
- In mammals, retinal is the actual molecule that absorbs the energy of photons
- The wavelength of light that retinal can interact with is dependent on the opsin protein that retinal is bound to
Where is the opsin protein located?
It is embedded in the membrane of photoreceptor cells
What happens when light hits one electron in the retinal molecule?
That electron absorbs the light and goes into a high-energy state
What does visible light refer to and how do we detect this light?
- It refers to electromagnetic energy that has a wavelength between 380 and 760 nm
- We detect this light using four kinds of photoreceptor cells (1 rod cell & 3 cone cells)
What kind of light are rod cells very sensitive to?
They’re very sensitive to all visible light
True or False? All light travels at different speeds
False, all light travels at the same speed
What does the wavelength of the light signify?
How much energy the light has
How do cone cells interact with light?
- They’re not particularly sensitive to light
- There are 3 different kinds of them, each sensitive to different wavelengths
- They encode color vision
As you move from Gamma rays to TV and Radio Waves, how does the wavelength and energy vary?
Gamma rays have small wavelengths but high energy and these get progressively bigger and stronger till’ Tv and Radio waves which have long wavelengths and lower energy
Which opsin in our eyes first evolved hundreds of million years ago?
The red cone cell (red cone opsin)
How does the detection of light vary with how many cone cells you have in your eyes?
- 1 cone (red cone) = I see light or I don’t see light
- Once you have 2 cones you have colour
- Once you have 3 cones, you can differentiate the entire colour spectrum
What kind of light activates the blue cone opsin?
Purple light
What kind of light activates the red cone opsin?
Pure red light
Is there colour in the peripheral vision?
The peripheral vision isn’t used to detect colour but is only used to detect stimuli
What kind of wavelengths of light are blue cone opsins most sensitive to?
Blue cone opsins are most sensitive to short wavelengths
What kind of wavelengths of light are green cone opsins most sensitive to?
Green cone opsins are most sensitive to medium wavelengths
What kind of wavelengths of light are red cone opsins most sensitive to?
Red cone opsins are most sensitive to long wavelengths
What is colour perception a function of?
A function of the relative rates (ratio) of activity in the 3 types of cone cells
What determines the amount of activation of any cone?
Both on the wavelength of the light and the amount of it (its intensity)
Which of the 3 cone opsins is most sensitive to light?
- Green cone opsins are the most sensitive to light, so if shown 3 colors separately (blue, green & red) at the same intensity, people often say the green light is brighter
- Blue cones are the least sensitive to light
What happens when red and green light bulbs are too close together?
Our eyes have a harder time differentiating them, they end up just looking yellow to us
How is paint different from light?
- Paint doesn’t create light; it absorbs some and reflects some
- Paint is considered subtractive of light whereas light is considered additive of light
- 3 primary colours for paint: yellow magenta and cyan
- 3 primary colours for light: green, red and blue
- The colours of paint only subtract one coloured light at a time
- When mixed together, paint is black (absence of colour)
- When mixed together, light is white (all the colours all at once and all light bouncing off of white)
What are the 3 dimensions to our perception of light and color?
- Brightness (intensity)
- Saturation (purity of wavelength)
- Hue (dominant wavelength - colour)
What happens if brightness is 0%?
The image will be black and hue and saturation will have no impact
What happens if saturation is 0%?
You’ll find yourself in the middle of the color cone where there is no color (equal contribution from all wavelengths) which results in a black and white image
What is Protanopia?
- Colour vision deficiency
- Absence of the red cone opsin (1% of males)
- Visual acuity is normal because red cone cells get filled with green cone opsin
- Inherited
- People have trouble distinguishing colors in the green-yellow-red section of the spectrum
- Simple mutations of the red cone opsin (1% of males) produce less pronounced deficits in color vision
What is Deuteranopia?
- Colour vision deficiency
- Absence of the green cone opsin (1% of males) - Visual acuity is normal because green cone cells get filled with red cone opsin
- Inherited
- People have trouble distinguishing colors in the green-yellow-red section of the spectrum
- Simple mutations in of the green cone opsin (6% of males) produce less pronounced deficits in color vision
What’s Tritanopia?
- Colour vision deficiency
- Absence of the blue cone opsin (1% of the population)
- Blue cone cells don’t compensate for this in any way, but blue cone opsin is not that sensitive to light, so visual acuity is not noticeably affected
Why is colour blindness way more prominent among men?
Since they only have one X chromosome
What’s achromatopsia?
- True color blindness
- Typically caused by mutations in the g protein signaling cascade that is similar in all cone cells
What’s the cornea?
- The outer, front layer of the eye
- Focuses incoming light a fixed amount
What’s the iris?
A pigmented ring of muscles
What’s the conjunctiva?
- Mucous membranes that line the eyelid
- They’re fused with our eyes -> why you can’t get things behind your eye
What’s the lens?
- Consists of several transparent layers
- The shape of the lens can change to allow the eye to focus, a process known as accommodation
What’s the pupil?
- Regulates the
amount of light entering the eye - It’s an opening in the iris
How could mutations of the cornea affect your vision?
Cornea being too thick or thin will affect your vision
What’s the retina?
- The interior lining (furthest back part) of the eye
- Contains photoreceptor cells
What’s the fovea?
- The central region of the retina
- There’s very little compression of visual information in the fovea, so this is where we have the highest visual acuity
What’s the optic disk?
- Site of blind spot in eye
- The point at which the optic nerve exits through the back of the eye
- It has no receptors
How can photoreceptors in the fovea register the exact location of the input, which enables high resolution, color vision?
Because the fovea primarily contains cone cells, each of which connects to a single downstream collection of cells (a bipolar cell which in turn connect to a single ganglion cell)
What is foveal vision sensitive to?
Detail & color
What is peripheral vision sensitive to?
Dim light
Why is precise location and shape of input heavily impeded in the periphery?
Because collections of photoreceptors (primarily rods, which use the opsin rhodopsin) converge onto fewer and fewer downstream collections of neurons (bipolar and ganglion cells)
How many more bipolar cells does the periphery have compared to the fovea?
10 x the amount of bipolar cells
How large is our field of vision and how much of it can we accurately read?
- Our field of vision is 120º
- We can only read in 2º of our vision (with our fovea) everything else is too blurry to make out
Describe the primary characteristics of cones
- Most prevalent in the central retina; found in the fovea
- Sensitive to moderate-to-high levels of light
- Provide information about hue
- Provide excellent acuity
Describe the primary characteristics of rods
- Most prevalent in the peripheral retina; not found in the fovea
- Sensitive to low levels of light
- Provide only monochromatic information
- Provide poor acuity
What are orbits?
Bony sockets in the front of the skull where eyes are suspended
What holds the eye in place and allows it to move around?
Six extraocular muscles attached to the sclera
What are saccadic eye movements?
- Rapid, jerky shifts in gaze from one point to another
- Our eyes scan a scene by making saccadic movements
What are pursuit eye movements?
- Calmer eye movement
- They allow us to maintain an image of a moving object
What are the 3 neurons in the retina?
- Photoreceptor cells
- Bipolar cells
- Ganglion cells
What’s the function of photoreceptor cells as neurons in the retina?
Neurons responsible for the transduction of light; they project to bipolar cells
What’s the function of bipolar cells as neurons in the retina?
Neurons that relay information from photoreceptor cells to ganglion cells
What’s the function of ganglion cells as neurons in the retina?
- The only neurons in the retina that send axons out of the eye
- They receive information from bipolar cells and project to the rest of the brain; their axons give rise to the optic nerve, which leaves the retina through the optic disc
What’s the function of horizontal cells in the retina?
- Neurons that interconnect and regulate the excitability of adjacent photoreceptor and bipolar cells
- They adjust the sensitivity of these neurons to light in general (adjust the excitability)
What’s the function of amacrine cells in the retina?
- Neurons that interconnect and regulate the excitability of adjacent bipolar and ganglion cells - Many different types of amacrine cells, and each have different functions
What’s the order of the layers of the retina that light passes through?
- Ganglion cell layer
- Bipolar cell layer
- Photoreceptor cell layer
What kind of ion channels do photoreceptor cells have in addition to the regular leak potassium ion channels that all neurons have and how do these work?
- “leaky” sodium ion channels which are open in the dark (when the cells are at rest)
- In the dark, sodium continually enters through these ion channels, which depolarizes the photoreceptor cell membrane to -40 mV
- At this depolarized membrane potential, photoreceptor cells continuously release glutamate
- These channels close when the retinal portion of the retinal-opsin complex absorbs light, which hyperpolarizes the membrane to -70 mV
Do bipolar cells have action potentials?
Bipolar cells don’t have action potentials and release glutamate in a graded fashion dependent on their membrane potential
What are the 2 types of bipolar cells and describe how these function?
- OFF bipolar cells which express ionotropic glutamate receptors, so they are depolarized by glutamate. Because photoreceptor cells constantly release glutamate in the dark, OFF bipolar cells are more active (more depolarized) in the dark than in the light (release neurotransmitter in dark)
- ON bipolar cells only have inhibitory metabotropic glutamate receptors, so they are uncommonly inhibited by glutamate. Thus ON bipolar cells are more active (more depolarized) in the light vs the dark (release neurotransmitter in light)
Do retinal ganglion cells have action potentials?
- Yes, they’re typical neurons
- They have action potentials and are generally excited by glutamate
What’s the receptive field of a neuron involved in visual processing and how is it identified in animals?
- The area of visual space where the presence of light influences the firing rate (or activity) of that neuron
- As the animal maintains focus on a central fixation point, you shine light in different areas of visual space and see where in visual space a change in light alters the spiking activity of the neuron
Describe how retinal ganglion cells react to light in different ways in their receptive field
- Their receptive fields often have a “center-surround” organization and they are called ON or OFF cells, depending on whether they show increased or decreased spiking activity when light is presented in the center of their receptive field
- ON ganglion cells are excited by light in the center and are inhibited by light in the surround
- OFF cells are excited by light in the surround and are inhibited by light in the center
How does visual information get relayed to the brain?
Visual information is relayed from retinal ganglion cells (RGCs) to the thalamus (the lateral geniculate nucleus) to area V1 in the cerebral cortex (primary visual cortex) which is found in the occipital lobe, which then travels through the visual association cortex and goes to the temporal lobe and the parietal lobe
Describe simple cells
Simple cells in primary visual cortex are sensitive to lines of light, and their receptive fields are typically organized in a center-surround fashion.
How much of the cerebral cortex is dedicated to processing visual information?
20-25%
Describe the visual association cortex?
- Part of the occipital lobe that surrounds primary visual cortex
- Each area of the visual association cortex responds to particular features of the visual environment, such as particular shapes, locations, movements, and colors
- Each region forms one or more independent maps of the visual field
Describe the receptive field of neurons in the Primary Visual Cortex
- Neurons in V1 have larger receptive fields than the retinal ganglion cells
- They are most activated when a line of light in a particular orientation is detected in the receptive field
- This is because they are trying to identify areas where there are sharp transitions between light and dark (or between two colors) and are hence trying to identify borders, edges, corners
- Trying to identify objects and their relative position in space
- This activity done through Top-Down processing
What kind of visual processing does the temporal lobe (ventral stream) do?
- Involved in identifying form (shape)
- It encodes “what” the object is and its color
- Most of the information is coming from the fovea, most of it coming from cone cells, that are detecting what colours
What kind of visual processing does the parietal lobe (dorsal stream) do?
- Involved in identifying spatial location
- It encodes “where” objects are, if they are moving, and how you should move to interact with or avoid them
What’s monocular vision?
Some primary visual cortex neurons respond to visual input from just one eye
What’s binocular vision?
Most primary visual cortex neurons respond to visual input from both eyes
What’s depth perception?
- Many monocular cues can be used to estimate depth, such as relative size, amount of detail, relative movement as we move our eyes, etc.
- These are the cues we use to appreciate depth when looking at a 2 dimensional image
What’s stereopsis?
Perception of depth that emerges from the fusion of 2 slightly different projections of an image on the 2 retinas
What’s retinal disparity?
- The difference between the images from the two eyes, which results from their horizontal separation - It improves the precision of depth perception, which is particularly helpful when trying to plan movements to interact with objects in space
What is Agnosia?
- Deficit in the ability to recognize or comprehend certain sensory information, like specific features of objects, persons, sounds, shapes, or smells, although the specific sense is not defective nor is there any significant memory loss
- Relates to a problem/damage in some sensory association cortex…not to problems with the sensory neurons themselves or with primary sensory areas
- Problems with comprehending the stimuli and not detecting it
What’s Akinetopsia?
- Deficit in the ability to perceive movement
- Type of visual agnosia caused by damage in an area of the dorsal visual stream (in the parietal lobe of the cerebral cortex)
What’s Cerebral Achromatopsia?
- Visual agnosia caused by damage to the ventral visual stream (temporal lobe) -> not genetic mutation
- People will deny having any perception of color and say everything looks dull or drab, and that it is all just “shades of grey”
- Lose the ability to remember the colour of things from before
What’s Prosopagnosia?
- Failure to recognize particular people by sight of their faces; caused by damage to the fusiform gyrus (fusiform face area)
- Can detect other people from the smell or sound of them so they don’t notice anything’s wrong
Why are most of the visual pathways bidirectional?
- Their axons go both ways
- Top-down processing
- Descending neural activity from the top areas reflect predictions about what the input is most likely be in the next moment (based on previous experience)
- Descending information cancels out the correctly predicted ascending information, so the only information that actually ascends are errors in visual predictions
What’s the predictive coding theory of perception?
- Each level of the visual network (except the lowest level, which represents the image) attempts to predict the responses at the next lower level via feedback connections
- What propagates up is the prediction error signal, which is used to improve future predictions
Which axons leave the eye?
Only the axons of retinal ganglion cells
What’s the function of the superior colliculi?
Visual information is used here to control fast visually-guided movements (visual reflexes)
What’s the function of the hypothalamus with visual information?
Visual information is used here to control circadian rhythms (such as sleep-wake cycles)
What’s the function of the somatosensory system?
It provides information about touch, pressure, temperature, and pain, both on the surface of the skin and inside the body
What are the 3 interacting somatosensory systems?
- the exteroceptive system (cutaneous/skin senses)
- the interoceptive system (organic senses)
- the proprioceptive (kinesthesia) system
What’s the function of the exteroceptive system?
It responds to external stimuli applied to the skin (e.g. touch)
What’s the function of the interoceptive system?
It provides information about conditions within the body and is responsible for efficient regulation of its internal milieu (e.g. heart rate, breathing, hunger, bladder)
What’s the function of the proprioreceptive system?
It monitors information about the position of the body, posture and movement (e.g., the tension of the muscles inside the body)
What are the different types of external stimuli that cutaneous senses (skin) encode?
- Pressure (touch)
- Vibrations
- Temperature
- Pain
What is skin pressure caused by?
Mechanical deformation of the skin
When do skin vibrations occur?
When we move our fingers across a rough surface
What is skin temperature caused by?
Produced by objects that heat or cool the skin
What is pain on the skin caused by?
Can be caused by many different types of stimuli, but primarily tissue damage
What are the different layers of the skin called?
- The outermost layer of skin -> Epidermis, where its cells get oxygen from the air, not the blood
- The middle layer is called dermis
- The deepest layer is called the hypodermis (or subcutaneous, “below the skin”)
What’s glabrous skin?
- “Hairless” skin (palm of hands and feet) which are very sensitive parts of our skin and have particular kinds of sensory neurons
What do free nerve endings primarily respond to?
- Temperature and Pain
- May confuse the two when there are sharp temperature changes (ex: sticking cold hand in warm water will feel like it’s burning sensation)
What are the different corpuscles in the skin and what do they respond/ are sensitive to?
- Ruffini corpuscules -> sensitive to stretch and the kinesthetic sense of finger position and movement
- Pacinian corpuscles -> respond to skin vibrations
- Meissner’s corpuscles (only in glabrous skin) -> detect very light touch and localized edge contours (brail-like stimuli)
What are the two categories of thermal receptors?
Those that respond to warmth and those that respond to coolness
Describe thermal receptors
- Information is poorly localized, and the axons that carry it to the CNS are unmyelinated or thinly myelinated
- Some of the receptor proteins that are sensitive to temperature can also be activated by certain ligands ex: capsaicin molecules activate heat receptors and menthol molecules activate cold receptors
Describe pain receptors
- Mediated by free nerve endings in the skin
- Many types of pain receptor cells (usually referred to as nociceptors, or “detectors of noxious stimuli”)
- One type is the high-threshold mechanoreceptors (pressure receptor cells), which are free nerve endings that respond to intense pressure, like something striking, stretching, or pinching the skin
- Other types of free nerve ending appear to respond to extreme heat (or the presence of chemicals such as capsaicin, the active ingredient in chili peppers)
What is Phantom Limb?
- A form of pain sensation that occurs after a limb has been amputated
-Amputees report that the missing limb still exists and that it often hurts (cold, itchy, hot, hurts)
What causes phantom limb and what’s the treatment?
- One idea: phantom limb sensation is due to confusion in the somatosensory cortices (primary and association)
- The brain gets nonsense signals (in part from the cut axons) and it has difficulty interpreting them
- Treatment: behavioural therapy where they put a mirror and gives the brain an opportunity to reconceptualize
How do axons from skin, muscles and internal organs enter the CNS and what are 2 main pathways
- Enter the CNS via spinal nerves
- 1st pathway: Poorly localized information (crude touch, temperature, and pain) immediately crosses over in the spinal cord and the first synapse is there. This information then ascends to the thalamus through the spinothalamic tract.
- 2nd pathway: highly localized information (ex: fine touch) ascends ipsilaterally through the dorsal column of the spinal cord. The first synapse in this pathway is in the medulla. From there the information crosses over to the contralateral side as it ascends to the thalamus
- Both pathways then get bundled together in the midbrain before synapsing in the thalamus. From there, information goes to primary somatosensory cortex in the parietal lobe
What is the somatotopic map of the body surface?
- Map that highlights the relationship between cortical stimulations and body sensations
- Also referred to as somatosensory homunculus (“little man”)
What’s tactile agnosia?
- Occurs from damage to somatosensory association cortex
- Patients with tactile agnosia have trouble identifying objects by touch alone and may confuse the object with another one
- However, these patients can often draw objects that they are touching, without looking, and they can sometimes identify objects from their drawings
- They can identify the objects by sight
What happens when a tasted molecule binds to a taste receptor protein?
- Produces a change in membrane potential (either directly or through g protein signaling cascades)
- Different tastes relate to the activation of different types of taste receptor proteins
Describe taste buds
- Taste buds consist of groups of 20 to 50 taste receptor cells
- Each taste bud is sensitive to a particular type of taste because all the cells in a taste bud express the same taste receptor protein
- Taste receptor cells do not have traditional action potentials. They release neurotransmitter in a graded fashion
- Taste receptor cells are replaced about every 10 days (dying all the time) due to being exposed to hostile environment
What are the 6 different categories of taste receptors and how are they detected ?
- sweetness (sugar) -> detected with a single metabotropic receptor
- umami (glutamate - found in high protein foods) -> detected with a single metabotropic receptor
- bitterness (a variety of different molecules) -> detected with 50 different metabotropic receptors
- saltiness (ions) -> detected with an ion channel that is highly permeable to sodium
- sourness (pH level; also detects carbonation) ->
detected with an ion channel that is highly permeable to hydrogen channels - fat (fatty acids) -> detected with metabotropic receptors and fatty acid transporters
Which taste receptor cells are instinctively rewarding/reinforcing?
- Sugar and umami taste receptor cells
- Direct stimulation of them (or their downstream structures in the cerebral cortex) is inherently reinforcing
Which taste receptor has a different type of receptor for every one of its tasting molecules?
- Bitterness
- Bitter taste is unique
Which taste receptor cells are instinctively aversive?
- Bitter taste receptor cells
- People often grow to appreciate some bitter taste cell activity at low concentrations (as an acquired taste)
What activates both salt and umami receptors?
MSG (monosodium glutamate)
Where is the primary gustatory cortex located?
In the insula lobe of the cerebral cortex
What happens to mice when we switch their sugar receptor genes with bitter receptor genes?
They can’t taste sugar anymore and begin to enjoy the bitterness
What are the molecules that the olfactory system is specialized for identifying?
- Odorants
- They are volatile substances
- Most of them are lipid soluble fats and of organic origin, however many substances that meet these criteria have no odor
- The receptor proteins that transduce odorants into a change in membrane potential are metabotropic g protein-coupled receptors
Why are dogs much better at smelling than humans?
- Because most odorants are resting on the ground and to detect them you have to sniff and this gust of wind will get them to go up and bind to receptors
- Dogs are smell-oriented and are always sniffing the ground and are closer to the ground
What’s Olfactory epithelium?
- The tissue of the nasal sinus that sits underneath the skull (the cribriform plate) and contains olfactory receptors cells
How do olfactory cells function?
- Each olfactory cell expresses only one type of olfactory receptor protein
- Olfactory receptor cells synapse in glomeruli in the olfactory bulb, which in turn sends axons into the brain
- Each glomerulus processes information from just one type of olfactory receptor cell (expressing a particular type of olfactory receptor protein)
- Each glomerulus processes a distinct odor
Are odors hardwired to be good or bad to humans?
Odors are largely not hard wired to be innately good or bad. Whether we like or dislike an odor is related to learned associations
How is olfactory information relayed to the brain?
It goes directly to primary olfactory cortex in the temporal lobe and the amygdala
What are pheromones?
- Molecules released by one animal to signal something to another member of the same species
- Behavioural responses to pheromones are largely innate (hard-wired from birth)
What are functions of pheromones in many animals, especially insects?
- attract or repel other members of the same species
- signal attractiveness and sexual receptivity
- mark a path to follow (as seen in ants)
- signal danger
Describe what sound waves are
- When an object vibrates, its movement causes the molecules of air surrounding it to alternately condense and rarefy (pull apart) -> governed by diffusion of air molecules
- These fluctuations in air pressure travel away from the source as a sound wave at
approximately 700 miles/hour - Something vibrating really slow is a low note and something vibrating very fast is a high note
How do sound waves affect our ears?
- Changes in air pressure from sound waves move the eardrum in and out
- High amplitude movement will determine how far in or out our eardrum is going
What are the 3 dimensions of sound?
- Loudness
- Pitch (tone)
- Timbre
What does the loudness of sound correspond to?
Corresponds to the amplitude or intensity of the molecular vibrations
What does the pitch/tone of sound correspond to?
- Corresponds to the frequency of the molecular vibrations
- Measured in hertz (Hz) or cycles per second
What does the timbre of sound correspond to?
- Corresponds to the complexity of the sound wave
- We use timbre to help identify the source of the sound wave (through learning processes) -> which instrument made the sound
- The specific mixture of frequencies that different instruments emit when the same note is played
What’s the pinna?
- The outer ear
- Sound is funnelled through it
