Physiology Of Olfaction And Gustation Flashcards
What are Ordorants?
They are airborne molecules and they give off vapor they reach the olfactory breceptors by being inhaled through the nose and through mouth the vapors circulate the throat
What is Olfaction?
It is the sense of smell and involves olfactory receptors responding to chemical stimuli
Made possible by the olfactory bulbs and olfactory membrane
What two layers make up the olfactory membrane?
Olfactory epithelium and Lamina propria
What is the olfactory epithelium?
Yellowish pigmented epithelium in the roof of the nasal cavity near the septum smell is detected by the olfactory chemoreceptors which are specialized endings of bipolar neurons that convert olfactory stimuli into nerve impulses
What does the olfactory epithelium contain?
Olfactory sensory neurons
Supporting cells
Basal stem cells
What does the olfactory epithelium cover?
Cribriform plate
Superior portion of the perpendicular plate
Superior nasal conchae of ethmoid bone
What does the lamina propria contain?
Areolar tissue
Blood vessels
Nerves
Olfactory glands
What are the purpose of the secretions of the olfactory glands?
They absorb water and form an think pigmented mucus that coats surface if the olfactory organs
What is the description of the olfactory sensory neurons?
The Cillian is unmyelenated and they contain olfactory receptors
A single axon passes through cribriform plate of the ethmoid bone and enter the olfactory bulbs
What is olfactory discrimination?
Can distinguish thousands of chemical stimuli and cns interprets smells by pattern of receptor activity
Where does olfactory reception occur?
On the surface membranes of the olfactory cilia
How does odorant discrimination occur?
Oforants interact with odorant binding proteins on the membrane surface and adenylyl cyclase activates and this is an enzyme that converts ATP to cAMP
CAMP will open sodium channels in the Plasma membrane which will depolarize
Sufficient depolarization occurs an action potential is triggered in the axon and information is relayed to CNS
How many odorant can activate olfactory receptors?
4 odorants
What do the axons leaving the olfactory epithelium do?
Collect into 20 or more bundles
Penetrate the cribriform plate of ethmoid bone and will reach the olfactory bulbs of the cerebrum where it will synapse in the Golmeruli
How does transmission of olfactory signal to olfactory bulb occur?
The axons of the receptors cells penetrate the cribriform plate and form the olfactory nerve
They synapse on Mitral cells in the olfactory bulb which is superior to cribriform plate
The axons of Mitral cells travel the olfactory tract to reach olfactory cortex and the limbic system
What are the olfactory pathways ?
They travel along the olfactory tract to reach olfactory cortex,hypothalamus and portions of limbic system
Arriving information reaches information centers without first synapsing the thalmus
What is Gustation?
It is the sense of taste
It has Gustatory Receptors which are distributed on tongue and potions of pharynx and larynx
What are taste buds?
They are taste receptors and specialized epithelial cells
What is the lingual papillae?
The superior surface of the tongue which are special projections
What are the 4 types of the lingual papillae?
Filliform-Provides friction that helps move objects around and dors not contain taste buds
Fungiform-contains 5 taste buds
Foliate
Circumvallate -contains 100 taste buds each
What do the taste buds contain?
Basal cells
Gustatory cells
What is Gustatory discrimination?
Where dissolved chemicals contact taste hairs and bind to receptir proteins of the Gustatory cell and diffrent tastes involves different receptor mechanisms
What do the sweet and sour receptors involve?
Chemically gated ion channels and stimulation produces depolarization of cell(Receptor potential)
These receptor potentials are graded
What do the bitter,sweet, and umami stimuli involve?
G proteins which are called gustucins protein complexes and use second messengers to produce their effects
What is the end results of taste receptors stimulation?
Release of NT by receptor cells and dendrites of sensory affarents wrapped by receptor membrane and they generate AP in affarent fiber and the Aps obey all or none
What is signal transduction?
Binding a tastant with a receptor cell and alters cells ionic channels to produce depolarizing receptor potential and the potential releases an NT and initiates AP with terminal endings of affarent nerve fibers with which receptor cells synapse
Signals conveyed via synaptic stops in brain stem and thalamus to cortical gustatory area
What are the Gustatory pathways?
The taste buds are innervated by the facial,glossophryngeal,vagus nerves
Sensory affarent fibers carried by these cranial nerves synapse in solitary nucleus of medulla oblongata and axons of postsynaptic neurons enter medial lemniscus
Where neurons join axons that carry somatic sensory information on touch pressure and proprioception after synapse in thalamus the information is projected on the Gustatory cortex and perception of taste is produced
Neurons in the trigeminal cranial nerve provides information about texture of food and taste related information
