Chapter 6 - Audition & Mechanical Sense Flashcards
What is amplitude of a sound wave?
It’s intensity. The greater the amplitude, the louder the sound.
What is frequency?
The number of compressions per second (Hertz)
What is pitch?
Perception - sounds higher in frequency are higher in pitch.
What is timbre?
The tone quality or complexity.
What is pinna and where is it?
The out ear includes the pinna - flesh and cartilage attached to each side of the head.
What is the tympanic membrane?
The ear drum. It vibrates at the same frequency as the sound waves.
What does the tympanic membrane connect to?
Three tiny bones that transmit the vibrations to the oval window, a membrane of the inner ear.
What are the three tiny bones in the ear?
Hammer / malleus
Anvil / incus
Stirrup / stapes
How big is the tympanic membrane?
About 20 times bigger than the footplate of the stirrup that connects to the oval window.
What does the inner ear contain?
Cochlea.
What is the cochlea?
A snail-shaped structure that contains three long fluid filled tunnels (scala vestibuli, scala media, scala tympani).
What are the three fluid tunnels in the cochlea
Scala vestibuli
Scala media
Scala tympani
How does the stirrup impact on the cochlea?
The stirrup makes the oval window vibrate at the entrace to the scala vestibuli, setting in motion the fluid in the cochlea.
What are auditory receptors?
Hair cells. They lie between the basilar membrane of the cochlea on one side and the tectorial membrane on the other side. Vibrations displace the hair cells, opening ion channels in its membrane. The hair cells excite the cells of the auditory nerve - part of the eighth cranial nerve.
How do auditory receptors work?
Vibrations displace the hair cells, opening ion channels in its membrane. The hair cells excite the cells of the auditory nerve - part of the eighth cranial nerve.
What is place theory?
Basilar membrane resembles strings of a piano with each areas tuned to a specific frequency.
What is frequency theory?
Basilar membrane vibrates in synchrony with a sound, causing auditory nerve axons to produce an axon potential at the same frequency.
What is current theory?
Low-frequency sounds (up to 100 Hz) - frequency theory. For higher-frequency sounds - the neruon might fire every 2nd, 3rd or 4th or higher wave. It’s action potentials are phase-locked to the peaks of the sound waves. Other auditory neurons fire action potentials at different peaks to create a summed effect of the frequency of the sound wave.
What is the volley principle?
Auditory nerve produces volleys of impulses for sound up to about 4000/second even though no individual axon can approach that frequency.
How does the basilar membrane vary?
Stiff at the base to floppy at the apex. Hair cells respond to different frequencies along it.
What is amusia?
Tone deaf - can have difficulty recognising people being happy or sad in their voice.
What is absolute pitch?
Perfect pitch - early musical training is important
How does auditory information pass through the brain?
Information from the auditory system passes through subcortical areas, axons cross over in the midbrain so each hemisphere of the forebrain gets its information mostly from the opposite ear.
How are the auditory system and visual systems similar?
Organisation of the auditory cortex is strongly parallel to the visual cortex. “what” pathway - sensitive to patterns of sound in the anterior temporal cortex. “where” pathway - sensitive to sound location in the posterior temporal cortex and the parietal cortex.
What is the auditory what pathway?
sensitive to patterns of sound in the anterior temporal cortex.
What is the auditory where pathway?
sensitive to sound location in the posterior temporal cortex and the parietal cortex.
What does damage to the superior temporal cortex cause?
Patients are not able to tell the source of a sound is moving.
Where is the primary auditory cortex located?
Superior temporal cortex (area A1).
What does area A1 do?
Responds to imagined sounds as well as real ones. Damage to area A1 does not leave someone deaf but they have trouble with speech and music but they can identify and localise single sounds well.
What is the tonotopic map of sounds?
Cells in area A1 respond to a preferred tone.
What is conductive or middle-ear deafness?
Diseases, infections or tumorous bone growth can prevent the middle ear from transmitting sound waves properly to the cochlea. Can be corrected by surgery or hearing aides.
What is nerve deafness or inner-ear deafness?
Damage to part of the cochlea, hair cells or auditory nerve. Can be contained to part of the cochlea impairing certain frequencies. Nerve deafness can produce tinnitus - frequent or constant ringing in the ears.
What is tinnitus?
Frequent or constant ringing in the ears.
What causes hearning loss in old age?
Brain areas responsible for language comprehension have become less active. Can have a decrease in inhibitory neurotransmitters, making it more difficult to suppress the irrelevant sounds and attending to relevant ones.
What is sound localisation?
High frequencies - time of arrival differences - intensity between ears (loudness) low frequencies - phase differences.
What is the vestibular organ?
Located next to the cochlea, it monitors movement and directs compensatory movement of your eyes. It detects the direction of tilt and amount of acceleration of your head.
What does the vestibular organ consist of?
The saccule, utricle and 3 semicircular canals. They are modified touch receptors. Calcium carbonate particles called otoliths lie next to the hair cells. They push against the and excite them.
How does the vestibular organ work?
The semicircular canals are filled with a jellylike substance and lined with hair cells. Acceleration causes the jelly to push against the hair cells. Action potentials travel through the 8th cranial nerve to the brainstem and cerebellum.
What happens when a touch receptor is stimulated?
It opens sodium channels in the axon, starting an action potential.
What is the Pacinian corpuscle?
It detects sudden displacements or high-frequency vibrations on the skin. The onion-like outer structure provides mechanical support that resists gradual or constant pressure. A sudden or vibrating stimulus bends the membrane allowing sodium ions to enter.
What are Merkel disks?
They respond to light touch i.e. stroking of the skin.
How does information go from touch receptors to the brain?
Info from the touch receptors in the head enters the CNS via the cranial nerves. From below the head, it enters through the 31 spinal nerves to the brain.
What spinal nerves are there?
8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal nerve pairs.
What does a spinal nerve consist of?
A sensory and motor component. Each spinal nerve innervates a limited area of the body called a dermatome.
What is a dermatome?
An area of the body that a spinal nerve innervates.
How does sensory information travel through the brain?
The various areas of the somatosensory thalamus send their impulses to different areas of the primary somatosensory cortex, located in the parietal lobe. Various aspects of body sensation remain separated though to the cortex.
What does pain do?
It directs attention towards a danger. The PFC typically responds only briefly to new light, touch, or sound. With pain, it continues to respond as long as the pain lasts.
How does pain flow from the skin to the brain?
Pain sensations begin with bare nerve endings. Axons carrying pain information have no myelination and are therefore slow. Thicker and faster axons convey sharp pain, whereas thinner ones convey dull pain. The brain processes pain more rapidly.
What does the brain do when it receives a pain signal?
Mild pain releases the neurotransmitter glutamate. Stronger pain releases several neuropeptides including substance P and CGRP (calcitonin gene-related peptide).
What brain pathways are activated?
Painful stimuli activates a path that goes through the reticular formation of the medulla and then to several central nuclei of the thalamus, amygdala, hippocampus, PFC and cingulate cortex. These also respond to emotional associations. The path extends to the ventral posterior nucleus of the thalamus and then to the somatosensory cortex, which responds to painful stimuli, memories of pain and signals warning of impending pain.
Where do pain sensations cross sides?
Pain sensations cross the spinal cord immediately before travelling to the brain.
What does damage to the cingulate gyrus do to pain responses?
People with damage to the cingulate gyrus still feel pain but it doesn’t distress them.
How are emotional and physical pain similar?
Hurt feelings are similar to physical pain. Emotional pain causes increased activity in both the cingulate gyrus and sensory areas. Emotional pain can also be relieved by pain medication.
How brain does the brain stop pain?
The brain stops pain by opioid mechanisms. Opiates bind to receptors found in the spinal cord and periaqueductal grey area of the midbrain. The transmitters that attach to the same receptors as morphine are endorphins.
What is gate theory?
Spinal cord neurons that receive messages from pain receptors also receive input from touch receptors and from axons descending from the brain. These other inputs can close the “gates” for pain messages through releasing endorphins. Morphine does not affect large-diameter axons that convey sharp pain but does block thinner axons that convey dull pain.
How do placebos impact on pain?
Placebos can relieve pain or depression. Placebos produce a large effect on the emotional response to pain in the cingulate cortex. Distraction plus placebo relieves more pain.
Where do cannabinoids act?
In the periphery of the body rather than the CNS.
How does capsaicin impact on pain?
Capsaicin stimulates receptors for heat. When rubbed on a sore shoulder etc it produces a temporary burning sensation followed by a longer period of decreased pain. Capsaicin applied in high doses causes a build up of calcium in heat receptors and damages the mitochondria in those receptors.
