Communication: Detection Of Sounds Flashcards
What is the function of the pinna?
The purpose of the pinna is to collect sound. It does so by acting as a funnel, amplifying the sound and directing it to the ear canal. In mammals like cats and dogs, it is obviously highly directional, but even in humans the pinna functions as a directional sound collector.
What is the function of tympanic membrane?
The tympanic membrane is a thin layer of tissue that separates the outer ear from the Middle ear. It functions by vibrating in response to percussions from compression. Sound waves in the air. These vibrations are translated into fluid waves by the ossicles in the middle ear.
What is the function of the ear ossicles?
The ossicles. The three tiniest bones in the body form the coupling between the vibration of the eardrum and the forces exerted on the oval window of the inner ear. Formally named the malleus, incus and stapes, they are commonly referred to in English as the hammer, anvil and stirrup.
What is the function of the oval window?
The oval window is a membrane-covered opening which leads from the Middle ear to the vestibule of the inner ear. Vibrations that come into contact with the tympanic membrane travel through the three ossicles and into the inner ear.
What is the function of the round window?
The stapes bone transmits movement to the oval window. As the stapes footplate moves into the oval window, the round window membrane moves out, and this allows movement of the fluid within the cochlea, leading to movement of the cochlear inner hair cells and thus hearing.
What is the function of the cochlea?
The cochlea transforms the sound in neural massage. The function of the cochlea is to transform the vibrations of the cochlear liquids and associated structures into a neural signal. This occurs at the organ of corti, which is located all along the cochlea.
What is the function of the auditory nerve?
The cochlear nerve, also known as the acoustic nerve, is the sensory nerve that transfers auditory information from the cochlea to the brain. It is one of the many pieces that make up the auditory system, which enables effective hearing.
outline the role of the Eustachian tube
The Eustachian tube connects the middle ear with the throat. Usually this opening is kept closed, but it opens when we swallow or yawn.
Air can pass through this opening, thus equalising the pressure between the middle ear and the atmosphere.
outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur
Sound waves are collected by the pinna and travel down the auditory canal to the tympanic membrane, which vibrates at the same frequency as the sound.
The first of the ossicles is attached to the tympanic membrane, and this bone begins to vibrate, amplifies the vibration and then passes the vibration on to the other two ossicles, which also amplify the vibration.
The last ossicle is attached to the oval window, which begins to vibrate and causes the fluid in the cochlea to vibrate.
The hair cells of the organ of Corti detect the vibration and pass a message to the brain via the auditory nerve.
Different sounds move the hair cells in different ways, thus allowing the brain to distinguish various sounds.
We can summarise as shown below:
describe the relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of different
Passing along the length of the cochlea is a ribbon-like structure, the organ of Corti. This has three main components: the basilar membrane, hair cells and the tectorial membrane.
The basilar membrane is composed of transverse fibres of varying lengths. Vibrations received at the oval window are transmitted through the fluids of the cochlea causing the transverse fibres of the membrane to vibrate at certain places according to the frequency.
High frequency sounds cause the short fibres of the front part of the membrane to vibrate and low frequency sounds stimulate the longer fibres towards the far end.
As the basilar membrane vibrates, the hairs of the hair cells are pushed against the tectorial membrane. This causes the hair cells to send an electrochemical impulse along the auditory nerve to the brain.
The region of the basilar membrane vibrating the most at any instant sends the most impulses along the auditory nerve.
The actual perception of pitch depends on the mapping of the brain. Nerves from particular parts of the organ of Corti stimulate specific auditory regions of the cerebral cortex of the brain. When a particular part of the cortex is stimulated, we perceive a sound of a particular pitch.
outline the role of the sound shadow cast by the head in the location of sound
Many animals can use their two ears to judge the position from which a sound comes. They can move each ear independently until each ear receives the maximum sound.
Humans cannot move their ears, but can locate the direction of a sound nevertheless. This is because the sound is heard more loudly by the ear nearest to it and also fractionally earlier.
The pinna is mostly skin and cartilage with some muscles attached to the back, which is what allows some animals to “wiggle” their ears.
The brain uses reflections from the twists and folds of the pinna to determine the direction of sounds. Sounds coming from the front and sides become enhanced as they are directed into the auditory canal while sounds from behind are reduced. This helps an animal to hear what they are looking at while reducing some of the distracting background noise.
outline and compare the detection of vibrations by insects, fish and mammals
Many insects have a pair of membranes, called the tympanic membranes, located on the abdomen or legs. The tympanic membranes act in a similar way to eardrums by vibrating when sound waves reach them. Sensory cells called mechanoreceptor cells detect the vibrations and send a message to the brain.
Many insects also have hairs on the exterior of the body which vibrate in response to sound waves of specific frequencies, depending on the stiffness and length of the hairs. The hairs are often tuned to frequencies of sounds produced by the same or other species. These hairs may be used to detect mates or predators.
Fish do not have external ears, but have internal ears located near the brain. There is no eardrum or cochlea, but the semicircular canals are present. Vibrations of water caused by sound waves are conducted through the skeleton of the head to the inner ear. Hair cells in the semicircular canals vibrate in response and send a message to the brain.
Fish also detect low frequency vibrations with the lateral line system. This consists of a long fluid-filled canal which runs just under the skin down each side of the fish. There are pores at frequent intervals which connect the canals to the exterior. Vibrations in the surrounding water are transmitted to the fluid in the canals, and are detected by groups of sensitive cells called neuromasts. These neuromasts have hairs which project into the canal fluid and detect vibrations by a mechanism similar to that used in the cochlea of the mammalian ear. Messages from the neuromasts are sent to the brain.
Fish also have an air-filled swim bladder, located in the abdomen, which vibrates in response to sound or vibrations. Some fish have a series of bones which conduct vibrations from the swim bladder to the inner ear.
