A&P CHAPTER 15 PT.1

polynesian-smino (manifesting) (15.1-15.3)

special senses

convey specific stimuli from specialized sensory organs in discrete locations of the head. differ from general senses in stimuli detected, structure of sensory receptors, and location of sensory nerves

transduction

when a physical or chemical stimulus is converted into an action potential that can be interpreted by the brain. special senses do this with stimuli such as light, chemicals, or sounds in the environment

olfaction

sense of smell/detection of odorants (chemicals) in the air. bypasses the thalamus.

olfactory epithelium

small patch of specialized epithelium located in the superior region of each nasal cavity. contains olfactory neurons, basal cells, and supporting cells

olfactory neurons

modified bipolar neurons that detect odorants. also known as chemoreceptors. consist of an apical modified dendrite, a cell body, and a basal axon. the modified dendrite projects into the roof of the nasal cavity. neurons are bundled into groups of 10-100 and travel through tiny holes in the cribriform plate of ethmoid bone to reach CNS.

olfactory cilia

increases surface area available for odorant detection. extend into a layer of mucus produced by olfactory glands.

olfactory nerve

formed by bundled groups of axons from olfactory neurons. axons terminate by synapsing on other neurons called mitral cells

olfactory bulb

structure located in the brain just superior to the ethmoid bone and inferior to the frontal lobe of the brain.

basal cells of olfactory neurons

stem cells that develop into olfactory neurons. ensure continual replacement of these neurons.

supporting cells of olfactory neurons

columnar cells that support and surround the olfactory neurons. Contain a pigment that gives the olfactory epithelium its color

olfactory tract

axons that exit the olfactory bulb; travel to other regions of the CNS for interpretation

step 1 of activation of olfactory receptors

binding of an odorant to its receptor, which activates a G-protein

step 2 of activation of olfactory receptors

the activated G-protein triggers the enzyme adenylate cyclase to convert ATP into cAMP

step 3 of activation of olfactory receptors

cAMP opens ion channels that allow sodium and calcium ions to enter the cell

olfactory pathway

olfactory stimuli are transmitted to the CNS and delivered to various regions of the brain

step 1 of the olfactory pathway

The axons of olfactory neurons (making up the olfactory nerve) carry olfactory stimuli to the olfactory bulb in the CNS.

step 2 of the olfactory pathway

An olfactory stimulus travels from the olfactory bulb to the primary olfactory cortex in the temporal lobe.

primary olfactory cortex

located in the inferomedial temporal lobe near the optic chiasma, is responsible for awareness and identification of an odor.

taste buds

Clusters of receptor cells and supporting cells on the tongue that detect taste sensation. each is contacted by sensory neurons that transmit stimuli to the central nervous system. typically located on the lateral surfaces of the papillae.

papilae

Finger-like protrusions on the surface of the tongue, some of which contain taste buds.

vallate papillae

largest and are dome-shaped; each contains hundreds of taste buds

fungiform papillae

mushroom-shaped and each contains only a few taste buds.

foliate papillae

ridges on the sides of the tongue and contain taste buds only in childhood.

filiform papillae

long, thin cylinders scattered across the tongue. lack taste buds but have sensory nerve endings that detect the texture and temperature of food.

gustatory cells

specialized epithelial cells with microvilli that contain receptors detecting different tastes. microvilli are found on the apical surface of the cell and project into a small pocket on the surface of the papilla, called the taste pore. basal end of each cell forms a synapse with the receptive endings of a sensory neuron that carries taste stimuli into the CNS via the facial, glossopharyngeal, or vagus nerve.

basal cells of taste buds

stem cells that differentiate into new gustatory cells, which have a lifespan of only 10-14 days

supporting cells of taste buds

surround the gustatory cells. They provide physical support but have no role in taste sensation.

sweet taste

mostly due to simple sugars such as glucose and fructose

sour taste

produced by hydrogen ions, as found in the citric acid of lemon juice.

salty taste

presence of metal ions such as sodium and potassium ions.

bitter taste

imparted by many different compounds, including alkaloids such as those found in coffee, many plant poisons, and rancid foods. humans are most sensitive to this taste, which serves a protective function

umami taste

often associated with meat or broth, is produced by glutamate or other amino acids.

step 1 of activating a taste receptor

Changes in ion movements depolarize the gustatory cell’s plasma membrane

step 2 of activating a taste receptor

Depolarization of the membrane opens voltage-gated calcium ion channels, and calcium ions enter the cell.

step 3 of activating a taste receptor

The calcium ions trigger the release of neurotransmitters, which produce an action potential in the axon of the sensory neuron

step 1 of gustatory pathway

Axons of the facial, glossopharyngeal, and vagus nerves carry taste stimuli from the tongue into the CNS.

step 2 of gustatory pathway

Axons of these three nerves terminate in the solitary nucleus in the medulla oblongata by synapsing on central sensory neurons

step 3 of gustatory pathway

Axons from the solitary nucleus synapse on neurons in the thalamus, which then send the taste signals to the primary gustatory cortex in the parietal lobe.

primary gustatory cortex

integrates incoming stimuli, leading to awareness and identification of a particular taste.