the vestibular system (end of chapter 7)

3 movements that affect the 3 semicircular canals

1. moving head forward and backwards (nodding) 2. moving head side to side (shaking head no) 3. moving head in a "maybe" way, bring ear closer to shoulder -liquid will move in these directions through one of 3 semicircualr canals

3 ways in which vestibular information is used

1. to control the eye muscles so that, in spite of changes in head postion, the eyes can remain fixed on the same point 2. reflex mechanisms for maintaining upright posture and balance 3. providing conscious awareness of the position and acceleration of the body

how many types of receptor cells are there (for olfaction)

400

cupula

a gelatinous mass that encapsulates stereocilia, which extends across the lumen of each semicircular canal at the ampulla, makes the stereocilia more efficient and sensitvie, long protein fibrous connections that encase stereocilia

how is salt taste detected

a mechanism by which ingested sodium ions enter channels in the receptor cell membrane, depolarizing the cell and stimulating the production of action potentials in the associated sensory neuron

ampulla

a slight bulge in the wall of each duct, contains lymph, connected to semicircular canal

how is bitter taste detected

associated with many poisonous substances; generate receptor potentials via a G-protein mediated second messenger pathways and ultimately evoke the negative sensation of bitter flavor

how many odorants can humans discriminate

at least 10,000, because different ordors elicit different patterns of electrical activity in several cortical areas; odorants/chemicals will activate some combination of the 400 receptors

basal cells

at the bottom of taste buds, differentiate to continually replace taste receptor cells damaged in the occasionally harsh environment of the mouth

what happens to your balance when your eyes are closed?

balance is severely effected and you are a lot less stable, vision is critical for balance

what is the frequency of action potentials in the afferent nerve fibers that synapse with hair cells related to

both the amount of force bending the stereocilia and the direction in which this force is applied

how is the identity of a particular odorant determined

by the activation of a precise combination of plasma membrane receptors, each of which is contained in a distinct group of olfactory receptor cells

otolith

calcium carbonate crystals that make the gelatinous substance heavier than the surrounding fluid; thought to be there to enhance the sensitivity of the system; helps bend the stereocilia

what happens when otoliths get stuck in semicircular canals

can cause serious case of vertigo

vestibular apparatus

consists of 3 membranous semicircular canals and two saclike swellings, the utricle and saccule, all of which lie in tunnels in the temporal bone on each side of the head

semicircular canals

detect angular acceleration during rotation if the head along 3 perpendicular axes

where does information pass from the olfactory bulbs

directly to the olfactory cortex and parts of the limbic system

olfactory receptor neurons

first cells in the pathways that give rise to the sense of smell, they lie in a small patch of epithelium called the olfactory epithelium in the upper part of the nasal cavity

how long do olfactory receptor neurons survive

for only about 2 months, so they are constantly being replaced by new cells produced from stem cells in the olfactory epithelium

where does a umami taste come from (savory/delicious)

glutamate and similar amino acids (common additive used to enhance flavors of asian food, MSG)

positions of hair cells in the utricle

hair cells point straight up when you stand and they respond when you tip your head away from the horizontal plane, or to linear accelerations in the horizontal plane

positions of hair cells in the saccule

hair cells project at right angles to those in the utricle, an they respond when you move from a lying to a standing position, or to vertical accelerations like those produced when you jump on a trampoline

how do stereocilia work

have mechanically gated ion channels, so when liquid moves back and forth, the stereocilia get bent and ion channels are opened and generate an action potential eventually

hairlike microvilli on taste cells

increase the surface area of taste receptor cells and contain integral membrane proteins that that transduce the presence of a given chemical into a receptor potential

nystagmus

large, jerky, back and forth movement of the eyes that can occur in response to unusual vestibular input in healthy people; it can also be a sign of pathology

what do the utricle and saccule provide information about

linear acceleration of the head, and about changes in head position relative to the forces of gravity

what are the receptors in the utricle and saccule

mechanoreceptors that are sensitive to the displacement of projecting hairs

what must first for us to detect an odorous substance?

molecules of the substance must first diffues into the air and pass into the nose region of the olfactory epithelium; once there, they dissolve in the mucus that covers the epithelium and then bind to specific odorant receptors on the cilia

what needs to happen first before food molecules enter the pores of the taste buds

must be disslved in liquid, either ingested or provided by secretions of the salivary glands

motion sickness

occurs when you experience unfamiliar patterns of linear and rotational acceleration and adpatation to them has not occured yet

why can we taste so many other things besides the 5 basic tastes?

olfaction has a very big influence on taste

what is the only sensory system that does not synapse in the thalamus prior to reaching to cortex

olfactory system

what does each hair cell receptor have

one direction of maximum neurotransmitter release

lingual papillae

physical structure seen on the tongue that allow chemicals in your mouth to move down to the taste buds

what is in charge of postural control

primarily the vestibular system, but it also integrates a lot of sensory info, like vision, proproception, and touch

what do the cilia contain?

receptor proteins that provide binding sites for odor molecules

proprioception

sense of body awareness; refers to the fact that you can focus attention on something else but you are able to tell where your big toe is (perception of body parts) primarily due to muscle spindles; kinesthetic awareness

olfaction

sense of smell

where do some areas of the olfactory cortex send projections to

some regions of the frontal cortex

structure of mature olfactory receptor neurons

specialized affarent neurons that have a single, enlarged dendrite that extends to the surface of the epithelium; several long, nonmotile cilia extend from the tip of the dendrite and lie along the surface of the olfactory epithelium where they are bathed in mucus

taste buds

specialized sense organs for taste, the vast majority on the upper surface and sides of the tongue, arranged like organge slices around a hallow taste pore and are found in the walls of lingual papillae

epley maneuver

specific way you can dislodge otoliths, move head in specific directions

what do the receptor cells of the semicircular canals contain

stereocilia

how is sour taste detected

stimulted by foods with high acid content, such as lemons; hydrogen ions block potassium channels in the sour receptors, and the loss of hyperpolarzing potassium leak current depolarizes the recepotor cell

how is sweet taste detected

sweet receptors have integral membrane proteins that bind natural sugars like glucose and artificial sweetners; binding activates a G-protein coupled second messenger pathway that ultimately blocks potassium channles and thus generates a depolarizing receptor potential

5 taste submodalities

sweet, sour, salty, bitter and umami

gustation

taste

olfactory bulbs

the axons of the olfactory receptor cells synapse in this pair of brain structures which lie on the undersurface of the frontal lobes

vestibular labyrinth

the bony tunnels of the iner ear that house the vestibular apparatus and the cochlea, have a very complicated shape

bending of stereocilia

the fluid filling the duct is not attached to the skull and because of inertia, it tends to retain its original position -the movement of the ampulla is pushed against the stationary fluid which causes the bending of the stereocilia and the alteration in the rate of release of neurotransmitters from hair cells -the neurotransmitter crosses the synapse and activates the affarent neurons associared with the hair cells, initiating the propagation of action potentials toward the brain

what happens when a hair cell is bent in the direction of its maximum neurotransmitter release and the opposite direction

the receptor cell depolarizes and in the opposite direction it hyperpolarizes

what determines the direction in which stereocilia are bent and which hair cells are stimulated

the speed and magnitude of rotational head movements

why cant you smell when you have a cold

the thick mucus layer in the nose dilutes the chemicals or block them from entering the oflactory bulb

what is used to relay information about hair cell stimulation from the vestibular apparatus to nuclei within the brainstem

the vestibular branch of the vestibulocochlear nerve; info is transmitted via a polysynaptic pathway through the thalamus to a system of vestibular centers in the parietal lobe of the cerebral cortex

what are descending projections used for

they are sent from the brainstem nuclei tot he spinal cord to influence postural reflexes

what happens after the odorants are dissolved in mucus

they now act like ligands and active a G-protein-mediated pathway that increases cAMP, which opens nonselective cation channels and depolarizes the cell

where do pathways for taste in the central nervous system project

to the gustatory cortex, near the "mouth" region of the somatosensory cortex

where does the endolymph move from the cochlea

to the vestibular labryinth, your body will sense this movement as it lines up with movements in the body and head

how is umami taste detected

umami receptor cells depolarize via a G-protein coupled receptor mechanism

what converges to form the vestibulocochlear nerve

vestibular and cochlear branches

what leads to a good sense of posture and movement

vestibular information is integrated with sensory information coming from the joints, tendons, and skin

why aren't there otoliths in the cochlea/auditory system

vibrations are enough to start action potentials, no vibrations in this system

is there action potential activity even when your head isn't moving

yes, some neurotransmitter is alawys released at reast, the release increases or decreases from this resting state according to the direction in which the hair cells are bent

how do you test someones vestibular system

you must confuse your other systems (sensory systems) by using vibrations