Lecture 6 Flashcards
What do senses respond to?
They respond to biologically relevant stimuli, this system is very specialised and evolution has allowed us to interpret the stimuli.
Define sound waves
Define frequency
Define amplitude
Define sound
Periodic compressions of air causing vibrations, this can be measured by looking at frequencies and amplitude.
The number of compressions per time which relates to pitch, the higher the frequency, the higher the pitch.
The intensity of the sound wave which relates to loudness.
A sound is when a complex set of acoustic information is transferred.
How does our ear detect sound?
We have a pinna which is the outer ear and a tympanic membane which is the ear drum and is very thin. There are instruments within the ear, there’s the hammer and the anvil. They receive the sound information. After this, there’s the cochlea which consists of 3 fluid filled tunnels. It’s snail shaped and it distinguishes frequencies. The vibrations displace the hair cells in the cochlea which sends information to the auditory nerve. The auditory nerve allows the sound information to leave the ear and enter the cochlea nucleus at the bottom of the brain. A crossover then occurs and information from the left ear goes to the right side of the brain and vice versa. The information then enters the primary auditory cortex.
How to we distinguish between frequencies?
Because we can interpret pitch. This happens in the basilar membrane in the cochlea which is stiff at the base of the shell like structure and floppy in the middle. There are two different theories of how the process occurs. The place theory believes that each area of the membrane responds to a specific pitch but this wouldn’t work as the areas are too tightly linked. Then there’s the frequency theory which states that states that the frequency of nerve impulses are in sync with pitch, however, the neurons wouldn’t be quick enough for this. The current view is that it’s a combination of both. In the primary auditory cortex, neighbouring cells respond to neighbouring frequencies.
What happens if the primary auditory cortex is damaged?
It wouldn’t cause deafness but it would affect sound processing like speech.
What happens if the middle of the ear is damaged?
You could get conductive deafness which is when the bones in the middle ear are damaged (hammer, anvil etc.). This can happen at any age due to disease/tumours and so on. You could also get nerve deafness which is when the cochlea, hair cells and auditory nerve are damaged. This can be inherited or can develop because of pre-natal problems.
How can we locate sounds?
Both ears receive different information; there’s a difference in time of arrival, difference in intensity and a phase difference (when the sounds waves to each ear aren’t in sync).
What is our hearing range?
What can dolphins hear that we can’t?
Elephants?
20 Hz to 20 KHz.
Ultrasounds (high pitch).
Infrasounds (low pitch).
Discuss vestibular sensation
It’s an organ in the ear that helps us balance. The organ detects the position and movement of the head. It consists of three semi-circular canals next to the inner ear. The canals are filled with a jelly like substance and are lined with hair cells. When our head moves, so does the jelly like substance, this causes the calcium carbonate particles called otoliths in the jelly to move against the hair cells, sending a signal to the cerebellum. The three canals are for each type of movement, up and down/left to right/forwards and backwards.
Discuss the system of tasting
Taste buds are grouped in papillae. Different people have different amounts of fungiform papillae, the more you have, the more sensitive you are to taste, these are called super tasters. A single taste bud has about 50 receptors which act like neurons. They release neurotransmitters to excite nearby neurons. However, they’re replaced unlike neurons as they are modified skin cells (10-14 days). The nerves report the information to the medulla in the nucleus of the tractus solitarius. This information then divides into two and goes to different areas. The information to do with touch/texture goes to the somatosenosry cortex. The information to do with taste goes to the insula aka the primary taste cortex.
What are the 4 types of primary taste?
There are many types of primary taste but traditionally there’s sweet salty sour and bitter. Recently they’ve found glutamate taste receptors aka fast food, showing that there’s many types of primary taste
Why do we taste and smell?
To obtain information on the chemical environment via physical contact. The chemical systems like taste and smell have evolved more readily as the system isn’t complex and chemical information is just as vital. There is information in the chemical environment that can’t be obtained in any other way. It’s important so we can detect toxic substances and bad food.
What is a vomeronasal organ?
An olfactory organ that can detect pheromones in the environment. Humans don’t have this. It allows you to detect the odourless chemical that alters your behaviour sexually. Humans have a few receptors would could explain co-cycling of women’s menstrual cycles.
How do we smell?
We smell via olfactory receptor cells in the nasal cell. There’s hundred of types for many different chemicals which is different to taste buds. Then there is the olfactory bulb which processes the information from the limbic system.
What is Huntington’s disease?
What about Parkinson’s?
Both a neurodegenerative diseases, neurons in the brain die.
When you ave Huntington’s your arms jerk and you get facial tremors. It also correlates with psychological disorders like depression, anxiety and hallucinations. It’s strongly genetic and begins in the basal ganglia then spreads to the cerebellum.
Parkinson’s, you get rigidity, slow movement and difficulty initiating physical activity. There is a correlation with cognitive disorders like imagining movements or events. It begins in the substantia nigra which causes decreased dopamine activity and therefore decreased stimulation of the motor cortex. There is evidence for genetics as well as exposure to toxins.
