Flashcards in Chapter 3 Deck (47):
-the sense of taste
-taste and smell are closely related
-ex: when we talk about certain tastes like lemon, strawberry etc, we often mean doors
Are there less or more receptors in taste compared to olfaction?
Five primary taste classes
-from the Japanese word "pleasant savoury taste", it is the fifth and most recently characterized taste category
How are taste receptors organized?
into discrete classes of sensation
-groups of 50 cells
Where do taste buds come from?
on the sides of papillae
Where are the main gustatory papillae found on the tongue?
Molecule that stimulates taste receptors on tongue and gives rise to sensation of taste
How do tastant gain access to taste receptors?
molecules of a tastant have to permeate the papillae and buds
The "tongue map"
-is the idea that certain tastes are detected only by certain parts of the tongue
-this is a myth
Typical lifespan of taste cells?
only a few weeks
Inotropic taste receptors
typical salty taste
What is a sour taste related to?
-acidity, in particular hydrogen ions
What are the two additional tastes?
-because of sensory adaptation, brief or intermediate tests are best
-ex: in rodents, some methods of testing either discriminate or prefer a certain taste usually takes a few seconds of licking
Innate or learned?
New born infants accept and suck on an artificial sweet coated nipple, although they will reject a bitter coated nipple.
Thus: the basic accept/reject functions of sweet and bitter are innate
Can tastings ingested by pregnant mothers affect an infants postnatal diet?
Yes, certain foods ingested by a pregnant mother may be transmitted into amniotic fluid and affect an infants postnatal preferences and diet
the acceptability on the basis of its taste
Palatability and taste coding
palatable substances are often consumed in higher amounts than non-palatable
the perception of a stimulus (in this context smell or taste) as the internal state changes
What affects the rating of pleasantness of a tastant?
if one is asked to rate pleasantness of a food multiple times while they eat their rating of pleasantness will decrease as the meal proceeds
Sensory specific satiety
describes a related phenomenon, namely that satiety for one particular food does not mean satiety for all foods
What is palatability dependent on?
the tastant and its concentration
Gastrointestinal (G.I) tract
-also called the food tube
-is a tube that connects the mouth to the anus
-if straightened out would be 20 feet long
Role of a G.I tract?
Detect and selectively absorb desired nutrients to fuel cells of the body
How many neurones are associated with the G.I tube?
-more than 200 neurones
-those 200 neurons form the enteric nervous system
Enteric nervous system
-a set of neurones involved in the various sensory and motor functions of the G.I tract
-is also known as the "Gut Brain"
-specialized in the walls of the G.I tract that secrete hormones in response to stimulation by specific nutrients
-these cells express chemosensory receptors that send sensory information
Two major signals to the brain
1-action potential in sensory afferents of the vagus nerve
2-specific hormones are released into the bloodstream as a result of specific enteroendocrine cell stimulation
2 tiny regions that have a weak blood-brain barrier
-the area postrema
-the arcuate nucleus
What are the reasons for sweating while you eat
sweating while you eat spicy foods happen because of a benign action of capsaicin in the mouth (salivary glands) occurs, triggering facial sweat
Behavioural satiety sequence
a sequence of behaviours that normally occur immediately after the end of a meal
Which is the most studied of all the gut hormones?
What is the action of Cholecystokinin (CCK)?
A hormone released from cells in the upper part of the digestive tract in response to stimulation by food
What are two other satiety hormones?
-Peptide YY (PYY)
-the only gut hormone found to increase hunger
-released from cells in the stomach and sparks a state of hunger
2 main hormones released by pancreas
-peptide hormone secreted by beta cells of the pancreas
-serves to promote storage of absorbed nutrients as glycogen and triglycerides
-peptide hormone released by alpha cells of the pancreas
-functioning to raise glucose levels by breaking down stored glycogen into glucose
Primary stimulus to insulin release?
-is a rise in blood glucose as carbohydrate containing meals get absorbed into the blood
Other chemical triggers for insulin?
-this takes several minutes after a meal for food to begin being absorbed
-insulin is released immediately
-the result of this is a neural signal to the pancreas
-a symptom of untreated diabetes is high blood sugar which is also referred to as hyperglycaemia
What happens if hyperglycaemia goes untreated?
-can lead to neuropathy (damage to neurones)
-also vascular collapse which deteriorates the retina and causes blindness
Type 1 diabetes
-early in life
-typically caused by lack of insulin