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Audition and other chemical senses

35 important questions on Audition and other chemical senses

Describe the general principles of sensory processing (4).

1. Reception - stimulus to receptor
2. Transduction - Receptor to neuron
3. Encoding - neuron to brain
4. Perception - interpretation of the stimulus in the brain

Describe sensory adaptation.

A gradual decrease in sensitivity of a sensory system to a constant stimulus. Ex. Being "noseblind" to a constant smell.

What are the 3 jobs of the auditory sense, hearing?

Detect sound, locate source, and recognize source.

Describe pitch as it relates to audition.

Pitch corresponds to wavelength; a higher frequency means a higher pitch; measured in hertz (Hz)

Describe loudness as it relates to audition.

Loudness corresponds to amplitude (larger amplitude = louder noise); measured in decibels (dB)

Describe timbre as it relates to audition.

Timbre corresponds to the complexity of a sound (think pure tone/complex tone).

What are the parts of the outer ear and their functions?

- Pinna, ear canal, and tympanic membrane (outer part of eardrum)
- function of outer ear is to funnel sounds to the eardrum

What are the parts of the middle ear and their functions?

- inner part of tympanic membrane/eardrum,
- ossicles (malleus, incus, stapes) - transmit waves from eardrum to inner ear
- oval window - tunnel into the cochlea
- middle ear functions to amplify sound energy

What are the parts of the inner ear and their functions?

- main function is to take sound waves and turn them into neural activity to be processed by the brain.
- cochlea - fluid filled, spiral shaped cavity involved in auditory transduction --> sound waves disturb the fluid
- round window - allows fluid to move in the cochlea
- organ of corti - contains the basilar membrane and hair cells; is where sound is transduced
- hair cells - auditory receptor cells anchored to the base of the basilar membrane --> injury to hair cells can cause hearing loss

Describe the difference between inner hair cells and outer hair cells.

Inner hair cells are responsible for hearing. Outer hair cells help discriminate frequencies and increase sensitivity to sounds. They synapse with dendrites of bipolar cells who bring auditory info to the brain. Linked to each other by tip links.

Describe the hair cell pathway.

- sound waves move through the cochlea and vibrate the basilar membrane, which moves auditory hair cells, causing K+ and Ca2+ channels to open, depolarizing the hair cell. Causes synapses with dendrites of bipolar neurons, which bring auditory information to the brain.

Describe the auditory pathway (cochlea to brain)

Auditory info sent from cochlea to cochlear nuclei (medulla), then the superior olivary nuclei, then the inferior colliculi (midbrain), then the medial geniculate nucleus (MGN) of the thalamus, then the primary auditory cortex.

Describe tonotopic mapping.

All levels of the auditory pathway have tonotopic organization --> they are arranged in a map according to the frequencies to which they respond.

Describe the regions of the auditory cortex.

- Core region- primary auditory cortex; sends info to:
- belt region - first level of auditory association cortex; surrounds primary auditory cortex; sends info to:
- parabelt region- highest level of auditory association cortex

Describe the difference between the anterior and posterior streams (audition).

- Anterior stream - analysis of complex sound (what)
- Posterior stream - sound localization (where)

Describe how pitch perception works (place coding vs rate coding).

- Moderate to high frequencies = place coding (perceiving pitch depending on where the basilar membrane is activated).
- Low frequencies = rate coding (processing pitch based on the rate of neurons firing).

Describe what a cochlear implant is/how it works.

An intervention for people who are deaf due to hair cell loss. Implant surgically placed in inner ear, stimulating auditory nerve, and external device worn near the ear, converts sound to electric impulses.

Describe the two components of the vestibular sense.

1. Vestibular sacs - sense direction and speed of linear acceleration, sense head tilt
2. Semicircular canals - sense direction an speed of head rotation.

Describe the important parts and functions of the vestibular sacs.

The vestibular sacs are important parts of the inner ear responsible for detecting changes in the head's position and movements. They help maintain balance and spatial orientation by sending signals to the brain about the body's position in relation to gravity.
- utricle - horizontal head movement
- saccule - vertical head movement

Describe the function of the semicircular canals.

The semicircular canals are part of the inner ear and are responsible for detecting rotational movements of the head. This information is important for tasks such as walking, running, and even simple movements like turning the head. When cilia bend, ion channels open and K+ enters cilia, depolarizing the membrane and causing the excitation of vestibular neurons.

Describe the vestibular pathway.

The auditory nerve (cranial nerve) has 2 branches, one being the vestibular nerve; most vestibular nerve axons synapse on vestibular nuclei in medulla/brainstem --> projects to cerebellum, thalamus, spinal cord, brain stem, and cranial nerves.

What is the vestibulo-ocular reflex?

Allows maintenance of gaze at a fixed point while the head moves.

Describe the types of skin/skin receptors.

- Glabrous skin = hairless skin
- skin receptors
--> merkel's disks (touch sensitive; detect form and roughness)
--> ruffini corpuscles (touch sensitive; detect stretching)
--> meissner's corpuscle (touch sensitive; detect edges)
--> pacinian corpuscle (vibration sensitive)
--> free nerve endings (temperature sensitive)

What causes perception of cutaneous stimulation?

Thermoreceptors -
- respond to heat (located deep in the skin)
- respond to cool (located just beneath the epidermis)

What causes pain? What are the types of pain receptors?

Pain is produced by networks of free nerve endings in the skin.
3 types of pain receptors:
- intense pressure
- extreme heat, acid, capsacin
- pungent/chemical irritants

Name 3 perceptual/behavioral effects of pain.

1. Sensory component - perception of intensity of painful stimulus
2. Emotional component - unpleasantness
3. Long-term emotional responses to chronic pain

Describe how the perception of pain is "malleable".

- natural neural circuits can reduce pain when stimulated by different environmental stimuli
- "contagious" pain
- phantom limb pain
- pain can be reduced by a placebo

Describe the somatosensory pathway.

It starts with sensory receptors that detect touch, temperature, pain, and body position. These receptors send signals through sensory neurons to the spinal cord. In the spinal cord, the sensory information is relayed to the brainstem and then to the thalamus. Finally, the sensory signals are sent to the somatosensory cortex in the brain, where they are processed and interpreted to create our perception of touch, pressure, temperature, and pain.

Describe the 6 qualities of taste.

- bitter - "poison", almost universally avoided
- sour - may indicate spoiled, commonly avoided
- sweet - food detectors for safety
- salty - signal sodium chloride
- umami - savory, protein detectors
- fatty - detect fatty acids

Describe what taste buds are and their parts.

- papillae are the bumps you can see on your tongue.
--> fungiform papillae - anterior 2/3rds
--> foliate papillae - folds along back of tongue
--> circumvallate papillae - posterior 1/3rd
- your taste buds are located on the papillae, and each bud has 20-50 receptors. They have short life spans.

Describe how taste receptors work.

- taste molecules bind to taste receptors and cause changes in membrane permeability to ions which causes changes in membrane potential.

Describe the gustatory pathway.

Taste receptor cell stimulate axons of cranial nerves, which synapse on the nucleus of the solitary tract (in medulla), which projects to the ventral posteromedial nucleus of the thalamus, then to the gustatory cortex in insula and base of frontal cortex.

Describe transduction (olfaction).

When odorants bind to olfactory receptors, g proteins in the cell membrane open sodium channels; ions flow into the cilia, producing depolarizing receptor potentials.

How are we able to perceive so many different odors?

Odorant molecules bind to multiple receptors, each of which stimulate an olfactory neuron.

Describe the olfactory pathway.

The olfactory pathway starts when odor molecules enter the nose and stimulate specialized sensory cells called olfactory receptor neurons. These neurons then send signals to the olfactory bulb in the brain, which processes and interprets the information. From the olfactory bulb, the signals are relayed to other brain regions, including the limbic system and amygdala, which play roles in processing emotions and memories related to the smells.
- Note: Olfaction is the only sensory system that does not send sensory info to the thalamus before sending it to the cortex.

The question on the page originate from the summary of the following study material:

Physiology of Behavior | 9780134080918 | Neil R Carlson

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