the ear has another function besides hearing, what is it?
balance/equlibrium
chemoreceptors that responds to chemicals in the internal environment
Interoceptors
Chemoreceptors that respond to chemical changes in external environment
externoreceptors
what are the three stages that chemoreceptors take to sense something?
detection
amplification
signaling
why are smell and taste related?
their brain functions overlap in the insula
what are the three cells of the olfactory epithelium
olfactory receptors--The neurons have non-motile cilia that don’t move but dip directly into the mucus where the odorant is dissolved
The supporti ngcells in the apical side (Bowman’s Glands) secrete mucus and enzymes that oxidize hydrophobic, volatile odorants and make them less lipid soluble and less penetrate the membrane and enter the brain
The basal cells--undifferentiated stem cells which help to regenerate the neurons once they are lost or when they are degraded
each olfactory receptor neuron expresses only ___ ____ of olfactory receptor protein
one kind
Input from all neurons expressing the same receptor is collected by a single dedicated acceptor called _____ of the olfactory bulb
glomerulus
what CN is the olfactory epithelium innervated by
CN 1 (olfactory)--carries the information from olfactory receptors cells to the olfactory bulb
CN 5 (trigeminal)--detects noxious or painful stimuli such as ammonia
**if the cribriform plate (where the olfactory bulb is) is damaged the sense of smell can be reduced or gone BUT the detection of ammonia and other painful stimuli won't be because its not CN1 that detects theses it is CN 5 and that is NOT in the cribriform plate
Adapt by about 50% in the ___ ____ or so after stimulation but adapt very slowly thereafter
Complete insensitivity to strong odors occurs in about ____ ____
Reduced sensitivity involves an adaptation process in the ___ ____ ____
first second
one minute
central nervous system
where are the three areas the axons in the olfactory tract can go
1. cerebral cortex primary olfactory area of temporal lobe
2. from primary olfactory area to frontal lobe
3. limbic system and hypothalamus
inability to detect odor
Anosmia
decreased ability to detect odors
hyposmia
Distorted identification of smell
dysosmia
altered perception of smell in the presence of an odor, usually unpleasant
parosmia
perception of smell without an odor present
phantosmia
inability to classify or contrast odors although able to detect odors
agnosia
"-osmias" are smell disorders and most of these are caused by damages of the _____
brain
Smell and Taste disorders can be ____ or ____ or _____
total (all odors/tastes)
partial (affecting several/tastes)
specific (only one or select few odors/tastes)
The following are characteristics of:
Modified epithelial cells with surface folds called microvilli
Plasma membrane of microvilli contain receptor sites that bind selectively with chemical molecules
taste receptor cells
What are the three types of papilla that taste buds are located one
circumvillate (form a V shape on the back of the tongue)--MOST TASTE BUDS HERE
fungiform (on the flat anterior surface of the tongue)
foliate (on the lateral surfaces of the tongue
which taste buds degenerate in early childhood?
foliate
what is the function of the microvilli in the taste bud
they provide receptor surface for taste
what are interwoven around taste cells and what are they stimulated by?
taste nerve fibers
stimulated by taste receptor cells
the taste nerve fibers invaginate into the cell membranes with many vesicles formed beneath. These vesicles are believed to contain...
Neurotransmitters that is released through cells to excite nerve fiber endings
at low taste substance concentration --> taste buds usually responds to ____ of the five taste stimuli
one
at high taste substance concentration --> taste buds are excited by ____ _ ____of the five taste stimuli
two or more
the ______ of the taste chemical dictates the amount of taste and taste stimulations
concentration
what depolarizes a taste cell?
the substance binding to the taste cell (which has a negatively charged membrane)
Five primary tastes
salty
sweet
sour
bitter
umami
what are the following tastes due to
salty
sour
bitter
sweet
umami
salty-- NaCl
sour--H+
bitter--drugs and other chemicals
sweet--CHO
umami--Meat
the more ___ the food, the stronger the sour reaction becomes
acidic
what are the two classes of substances that particularly to cause bitter taste
1) long chain organic substances that contain nitrogen
2) alkaloids (many of the drugs in medicine such as quinine, caffeine, strychnine, and nicotine)
**alkaloids are important because many deadly toxins found in poisonous plants are alkaloids
Some substances taste sweet at first than bitter later--> example:
saccharin
T/F: sweet taste is caused by one single class of chemicals
FALSE!! it is not caused by any single class of chemicals
Some of the chemicals that cause this sensation include, sugars, glycols, alcohol, aldehydes, ketones, amides, esters, some amino acids, some small proteins, sulfonic acids, halogenated acids, and inorganic salts of lead and beryllium
most of the chemicals that contribute to sweet tastes are
ORGANIC
Slight changes in the chemical structure such as adding simple ___ can change the chemical from sweet to ____
radical
bitter
umami is the dominating taste of food containing
L-glutamate
What is L-glutamate toxicity?
If you eat a lot of processed food that has a very high level of L-glutamate you could get L-glutamate toxicity and that kills neurons and so the neurons that detect toxins are not there
this is because L-glutamate may be related to glutamate receptors expressed in neuronal synapses of the brain
Taste receptor types of the following tastes
salty
sweet
umami
bitter
sour
salty: taste receptor type 1
sweet: 2
umami: 2
bitter: 2
sour: 3
lower threshold for ___ taste then ___ taste
higher threshold for ___ and ___ taste
bitter, sour
salty, sweet
which three CN serve the taste buds?
facial--anterior 2/3 of the tongue
glossopharnygeal--posterior 1/3 of the tongue
vagus--throat and epiglottis
where do the taste signals (carried by the three CNs) synapse?
solitary nucleus in the medulla oblongata
From the medulla oblongata the sensory neurons can project to two places
1. thalamus
2. limbic system and hypothalamus
Where do axons project to in the thalamus
the cerebral cortex primary gustatory area of the parietal lob for conscious perceptions of taste
Ca is a non-specific ion so how does Ca activate different taste?
this is because the calcium comes from different sources and this activates different mechanisms and contributes to different perception of taste
inability to taste
ageusia
decreased ability to taste
hypoguesia
distorted ability to taste
dysgeusia
taste blindness--blind for certain substances such as
thiourea compounds
A substance frequently used to test taste blindness is
phenylthiocarbamide
If all tastants cause release of neurotransmitter from many gustatory cells, why do foods taste different?
Patterns of impulses in groups of first order neurons that synapse with the gustatory receptor cells
Different tastes elicit activation of different groups of neurons
Individual gustatory receptor can respond to more than one taste
There is an overlap between type ___ and type ___ because both of these cells are dependent on the ion influx and calcium influx into the cells
1 and 3
the point at which you perceive something as painful
pain threshold
the point at which the pain is so great that you can't take it anymore
pain tolerance
myelinated motor nerve that is high velocity
A alpha
what are the two pain nerves
A delta and C
myelinated and high velocity-->pain, heat and cold
When you hit your thumb--> its sharp and rapid pain
A delta Nerve
unmyelinated and very slow -->pain, autonomics
When you hit your thumb and the next day you have slow, throbbing/aching pain--> coming from these
C nerve
a theory that states there is a more or less localized sensation of discomfort, distress or agony, resulting from stimulation of specialized nerve endings
Specificity theory
there is a specific wiring for pain
A theory that states modulation of sensory input between small pain fibers (both c and A delta) and large neuronal fibers; result is a decrease in transmission at the synapse between primary and secondary afferent neuronal pathways.
gate control theory
the gate mechanism is an example of
presynaptic inhibition
T/F: Stimulation of large fiber (Alpha beta) inhibits small fibers (C and alpha delta) function being transmitted to second order neurons
True
modulation of pain neurophysiology at multiple ___ and ____ levels of the CNS
ascending and descending
anatomically, all pain receptors appear as
free nerve endings
three type of receptors
mechanical
thermal (hot and cold)
chemical (polymodal)
potassium, protons, serotonin, bradykinin, histamine, TNF-alpha, substance P are what type of mediators of nociceptor
activation
prostgladins, leukocytes, nerve growth factors, substance P, interleukin-1 and endotoxins are are what type of nociceptors mediators
sensitization
where is the primary afferent synapse?
dorsal horn of the spinal cord
3 sensory nucleus of the trigeminal nerve
nucleus oralis
nucleus interpolis
nucleus caudis
what the the transmitter for the primary afferent synapse?
substance P
what depletes the NT substance P?
Capsaicin
ascending pathway that is "fast" pain (sharp, bright, stinging), A delta fibers for mechanical and thermal pain transition to sensory cortex
neospinothalamic tract
ascending pathway that is "slow" pain (dull and aching); slow C fibers for chemical stimuli are transmitted to multiple areas of the medulla and mesencephalon thereby activating the thalamus and reticular activating system (RAS)
paleospinothalamic tract
descending pathways are associated with
endogenous modulators/inhibition of pain (analgesia)
The descending pathways that are associated with serotonergic and enkephalinergic pathways are located where? (3)
periadequductal grey
raphe magnus nucleus
dorsal horn of the spinal cord
Act as naturally occurring morphne-like peptides
Peptides are rapidly metabolism
Reversible with opioid antagonists
