7.3 The Chemical Senses

Question 0

In a system relying on the ____ principle, each receptor would respond to a limited range of stimuli, and the meaning would depend entirely on which neurons are active.

Answer 0

labeled-line

Question 1

A ____ ____ enables a small animal to find food, avoid certain kinds of danger, and even locate mates.

Answer 1

chemical sense

Question 2

In a system relying on the ____ ____ principle, each receptor would respond to a wider range of stimuli, and a given response by a given axon means little except in comparison to what other axons are doing.

Answer 2

across-fibre pattern

Question 3

Each taste and smell stimulus excites several kinds of neurons, and the meaning of a particular response by particular neuron depends on the context of responses by other neurons. In short, nearly all perceptions depend on the pattern across an ____ of axons.

Answer 3

array

Question 4

Taste results from the stimulation of the ____ ____, the receptors on the tongue.

Answer 4

taste buds

Question 5

Where is other senses remain seperate throughout the cortex, taste and smell axons converge onto many of the same cells in an area called the ____ cortex.

Answer 5

endopiriform

Question 6

That convergence of axons enables taste and smell to combine their influences on ____ ____.

Answer 6

food selection

Question 7

The taste receptors for taste are not true neurons but modified ____ ____.

Answer 7

skin cells

Question 8

Like neurons, ____ ____ have excitable membranes and release neurotransmitters to excite neighbouring neurons, which in turn transmit information to the brain.

Answer 8

taste receptors

Question 9

Like skin cells, however, taste receptors are gradually sloughed off and replaced, each one lasted about _______.

Answer 9

10 to 14 days

Question 10

Mammalian taste receptors are in taste buds located in _____ on the skin surface of the time. a given ____ may contain up to 10 or more taste buds, and each taste bud contains about 50 receptors.

Answer 10

papillae

Question 11

Traditionally, people in Western society have described ____, ____, ____, and ____ as the primary tastes.

Answer 11

sweet, sour, salty, and bitter

Question 12

A phenomenal, called ____, reflects the fatigue of receptors sensitive to sour tastes. Where a second sour taste seems less sour because of the first.

Answer 12

adaptation

Question 13

You experience a little _____ – reduced response to one taste after exposure to another. E.g. a sour taste following a salty, sweet, or bitter taste.

Answer 13

cross-adaptation

Question 14

Several types of evidence to suggest a fifth taste receptor, which is ____, as an monosodium glutamate (MSG). The tongue has a glutamate receptor that resembles the brains glutamate receptors.

Answer 14

glutamate

Question 15

Glutamate tastes somewhat like unsalted chicken broth. English-language had no word for this taste, so English-speaking researchers adopted the Japanese word ____.

Answer 15

umami

Question 16

In addition to the fact that different chemicals excite different receptors, they produce different ____ of action potentials.

Answer 16

rhythms

Question 17

Chemicals used to test taste are ____ (sweet), ____ (salty), ____ (sour), and ____ (bitter). Abbreviated as S, N, H, Q.

Answer 17

sucrose, NaCl (table salt), HCI (hydrochloric acid), and quinine

Question 18

The saltiness receptor is simple. Recall that a neuron produces an action potential when sodium ions cross its membrane. A ____ receptor, which detects the presence of sodium, simply permits sodium ions on the tongue to cross its membrane.

Answer 18

saltiness

Question 19

Sweetness, bitterness, and umami receptors resemble the ____ synapses. After a molecule binds to one of these receptors, it activates a G-protein that releases a second messenger within the cell.

Answer 19

metabotropic

Question 20

Bitter taste used to be a puzzle because bitter substances include a long list of dissimilar chemicals. It turns out that we have not one bitter receptor but a family of ___ or more.

Answer 20

25

Question 21

One consequence of having so many bitter receptors is that we detect a greater variety of ____ ____. The other is that because each type of bitter receptor is present in small numbers, we can’t detect very low concentrations of bitter substances.

Answer 21

dangerous chemicals

Question 22

Taste coding in the brain. Information from the receptors in the anterior two thirds of the tongue travels to the brain along the ____ ____, a branch of the seventh cranial nerve (the facial nerve).

Answer 22

chorda tympani

Question 23

Taste information from the ____ tongue and the throat travels along branches of the ninth and tenth cranial nerves.

Answer 23

posterior

Question 24

The taste nerves project to the nucleus of the ____ ____ (NTS), a structure in the medulla.

Answer 24

tractus solitarius

Question 25

From the NTS, information branches out, reaching the ____, the lateral ____, the ____, the ventral-posterior ____, and two areas of the cerebral cortex.

Answer 25

pons, hypothalamus, amygdala, thalamus