Audition, Vestibular System, Olfaction, Taste Flashcards
What does the vestibular system do?
Detects and represents changes in head and body position relative to gravity (spinny)!
When we are walking, our vestibular system is sensing all the sloshing and changes in visual field, and making eye muscle adjustments in order to stay foveated.
What does the audition system do?
IDing pressure-created waves generated by vibrating air molecules. Physical force.
What are the general principles of Audition?
- System concerned with location and identity of stimuli. WHERE and WHAT?
- Topography and spatial representation assessed based on quantitative aspects of stimuli, generating a COMPUTATIONAL MAP. Not a distinct point-to-point such as in somatosensory perception and vision. Here, our brain actually TELLS us where the thing is.
What are the general principles of Vestibular Sensation?
- Concerned primary with CHANGE - acceleration and direction of movement relative to space/gravity.
- Regulates ongoing movement of eyes, head, posture to cope with changes in body position and movement through space. Very key for locomotion and stable vision.
How does sound wave get transduced into chemical signal and then action potential?
Vibration on the round window at front of the cochlea vibrates the fluid in the cochlea, which moves little stepwise groups of hair. The tips of the hairs have K+ channels that are connected to each other, hair to hair, and are closed until the tallest hairs moves and pulls on the other hairs and the K+ channels through the connections, and the K+ channels open, depolarizing the cell, allowing Ca++ to enter, emitting vesicles with neurotransmitter to afferent nerve cell to start an action potential to the brain.
How does the vestibular system get its message to the brain?
Similar to the fluid and hair cells in the cochlea, there are fluid and hair cells in the vestibular apparatus. The fluid sloshes around, with similar effect on the hair cells, and so the CHANGE in the movement of the fluid (speeds up, slows down, changes direction), elicits distinct changes in the POSITIONS of the hair cells.
How is auditory information relayed to the brain?
From cochlea, auditory nerves synapse at rostral medulla, up to midpons where some stay on same side and some cross to other side and synapse, travel up through pons/midbrain to posterior caudal midbrain and synapse at the inferior colliculus, up through thalamus and out to primary auditory cortex.
How is vestibular information relayed to the brain?
Scarpa’s ganglion gets info from the body in the rostral medulla and synapses with two paths, both go up through the abducens nucleus in the pons, where the path leading to the opposite side of body is excited and same side of body is inhibited at synapse; some of these cells send axons directly to lateral rectus muscles of eyes and some go further up through the omedial longitudinal fasciulus (crossover), to the midbrain, where they synapse with efferent nerves at the oculomotor nucleus, which then goes and sends signals to the medial rectus muscles of the eyes.
What are the chemical senses?
Olfaction (airborne) and gustation (ingested, water soluble).
What are a few general principles of chemosensation?
- Identification of stimuli.
- Abundance of stimuli.
- Not so much topography - where is stimuli.
- Relies on G-protein receptor mechanisms to transduce messaging.
- Molecular DIVERSITY in receptor proteins gives specificity, not cool patterns of signals as in audition or vision.
- Receptors turn over constantly throughout life.
- Age-related functional decline.
Tell me the components of the olfactory system. NOW!
Olfactory bulb
Cribiform plate (the bony plate between the brain cavity and the sinus cavity)
Olfactory nerves leading up from the olfactory epithelium
Airborne chemicals.
Describe the molecular mechanism of Odor Transduction.
Odorant (chemical) molecule binds to G-protein coupled receptor, activating via phosphorylation the G-protein; activated G-protein goes to active adenylate cyclase, activating cAMP; cAMP opens Na+/Ca++ channels; Ca++ connects with CAM and that complex opens Cl- channels to let Cl- out of the cell; other Ca++ filters out through Na+/Ca++ exchanger. This ultimately causes a massive depolarization of the cell membrane.
Where in the brain does gustatory sense get all sorted out? How does the information get there?
PERIPHERAL PATHWAY: From taste buds to afferent cells through Cranial nerves VII, IX, X to nucelus of solitary tract, then becomes the
CENTRAL PATHWAY: afferent nerves up through pons to ventral posterior medial nucleus of THALAMUS and synapses and out laterally to the gustatory complex.
How does taste transduction happen?
Taste buds are NOT NERVE CELLS. They are collections of lots of cells, some of which have receptors to the chemicals. Taste buds have pores with microvilli to let chemicals of taste in. Salts and acids go directly through channels, while sweet, bitter, umami flavors through Gprotein/second messenger systems. The salts and acids tend to only cause depolarization that ultimately brings in Ca++, but the Gprotein pathway signals either do this OR directly act on the endoplasmic reticulum to emit Ca++. The Ca++ causes vesicles with neurotransmitters to exit, and the neurotransmitter (serotonin), starts the action potential in the gustatory afferent nerve.
