BIO 360 - Exam 2 - Chapter 10 Outline Flashcards
The hairs on our arms help somatosensory receptors sense movement in the air millimeters above the skin surface. Accessory structures often enhance the information-gathering capability of the sensory system.
One receptive field is associated with one sensory neuron (the primary sensory neuron in the pathway), which in turn synapses on one CNS neuron (the secondary sensory neuron). (Primary and secondary sensory neurons are also known as first-order and second-order neurons.) Receptive fields frequently overlap with neighboring receptive fields.
Only olfactory information is not routed through the thalamus. The sense of smell, a type of chemoreception, is considered one of the oldest senses, and even the most primitive vertebrate brains have well-developed regions for processing olfactory information. Information about odors travels from the nose through the first cranial nerve[p. 283] and olfactory bulb to the olfactory cortex in the cerebrum.
The CNS must distinguish four properties of a stimulus:
(1) its Modality or nature
(2) its Intensity
(3) its Location
(4) its Duration
Population coding for intensity occurs because the threshold for the preferred stimulus is not the same for all receptors. Only the most sensitive receptors (those with the lowest thresholds) respond to a low-intensity stimulus. As a stimulus increases in intensity, additional receptors are activated. The CNS then translates the number of active receptors into a measure of stimulus intensity.
Once adaptation of a phasic receptor has occurred, the only way to create a new signal is to either:
(1) increase the intensity of the excitatory stimulus
(2) remove the stimulus entirely and allow the receptor to reset.
the specificity of sensory pathways is established in five ways:
(1) Each receptor is most sensitive to a particular type of stimulus.
(2) A stimulus above threshold initiates action potentials in a sensory neuron that projects to the CNS.
(3) Stimulus intensity and duration are coded in the pattern of action potentials reaching the CNS.
(4) Stimulus location and modality are coded according to which receptors are activated or (in the case of sound) by the timing of receptor activation.
(5) Each sensory pathway projects to a specific region of the cerebral cortex dedicated to a particular receptive field. The brain can then tell the origin of each incoming signal.
Thermoreceptors use a family of cation channels called transient receptor potential (TRP) channels to initiate an action potential. TRP channels also play a key role in the transduction of painful or irritating stimuli (discussed next) and provide a link between thermal sensation and pain.
For example, vanilloid receptors ( TRPV1 channels) respond to damaging heat from a stove or other source, as well as to capsaicin, the chemical that makes hot chili peppers burn your mouth. At the opposite end of the temperature spectrum, researchers have identified a related channel, TRPM8, that responds both to cold and to menthol, one reason mint-flavored foods feel cool.
The details of taste receptor cell signal transduction, once believed to be relatively straightforward, are more complex than scientists initially thought.
Sweet, bitter, and umami tastes are associated with activation of ______________ receptors.
Salty and sour transduction mechanisms both appear to be mediated by _____ ______.
G protein-coupled / ion channels
Hearing is our perception of the energy carried by sound waves, which are pressure waves with alternating peaks of compressed air and valleys in which the air molecules are farther apart (Fig. 10.16a). The classic question about hearing is, “If a tree falls in the forest with no one to hear, does it make a noise?” The physiological answer is no, because noise, like pain, is a perception that results from the brain’s processing of sensory information. A falling tree emits sound waves, but there is no noise unless someone or something is present to process and perceive the wave energy as sound.
