Chapter 8 Flashcards

Aδ fiber
A moderately large, myelinated, and therefore fast-conducting axon, usually transmitting pain information. See Table 8.2. Compare C fiber.
acupuncture
The insertion of needles at designated points on the skin to alleviate pain or neurological malfunction.
adaptation
1. In the context of evolution, a trait that increases the probability that an individual will leave offspring in subsequent generations. 2. In the context of sensory processing, the progressive loss of receptor sensitivity as stimulation is maintained. See Figure 8.7.
adequate stimulus
The type of stimulus for which a given sensory organ is particularly adapted. Light energy, for example, is the adequate stimulus for photoreceptors.
analgesia
Absence of or reduction in pain.
anterolateral system
Also called spinothalamic system. A somatosensory system that carries most of the pain information from the body to the brain. See Figure 8.23. Compare dorsal column system.
attention
Also called selective attention. A state or condition of selective awareness or perceptual receptivity, by which specific stimuli are selected for enhanced processing. See Figure 8.12.
C fiber
A small, unmyelinated axon that conducts pain information slowly and adapts slowly. See Table 8.2. Compare Aδ fiber.
capsaicin
A compound synthesized by various plants to deter predators by mimicking the experience of burning. Capsaicin is responsible for the burning sensation in chili peppers.
cingulate cortex
Also called cingulate gyrus or cingulum. A region of medial cerebral cortex that lies dorsal to the corpus callosum.
coding
The rules by which action potentials in a sensory system reflect a physical stimulus.
congenital insensitivity to pain
The condition of being born without the ability to perceive pain.
cool-menthol receptor 1 (CMR1)
Also called TRP8. A sensory receptor, found in some free nerve endings, that opens an ion channel in response to a mild temperature drop or exposure to menthol. See Figure 8.22.
dermatome
A strip of skin innervated by a particular spinal root. See Figure 8.16.
dermis
The middle layer of skin, between the epidermis and the hypodermis. See Figure 8.4.
dorsal column nuclei
Collection of neurons in the medulla that receive somatosensory information via the dorsal columns of the spinal cord. These neurons send their axons across the midline and to the thalamus.
dorsal column system
A somatosensory system that delivers most touch stimuli via the dorsal columns of spinal white matter to the brain. See Figure 8.15. Compare anterolateral system.
dynorphins
One of three kinds of endogenous opioids. Enkephalins and endorphins are the other two. See Table 4.1.
endogenous opioids
A family of peptide transmitters that have been called the body’s own narcotics. The three kinds are enkephalins, endorphins, and dynorphins. See Table 4.1.
endorphins
One of three kinds of endogenous opioids. Enkephalins and dynorphins are the other two. See Table 4.1.
enkephalins
One of three kinds of endogenous opioids. Endorphins and dynorphins are the other two. See Table 4.1.
epidermis
The outermost layer of skin, over the dermis. See free nerve ending
An axon that terminates in the skin without any specialized cell associated with it and that detects pain and/or changes in temperature. See Figure 8.4.
gastrin-releasing peptide (GRP)
A neuropeptide that stimulates neurons in the dorsal horn to provide the sensation of itch.
glutamate
An amino acid transmitter, the most common excitatory transmitter. See Table 4.1.
hypodermis
Also called subcutaneous tissue. The innermost layer of skin, under the dermis.
labeled lines
The concept that each nerve input to the brain reports only a particular type of information.
marijuana
A dried preparation of the Cannabis sativa plant, usually smoked to obtain THC.
Meissner’s corpuscle
A skin receptor cell type that detects light touch. See Figures 8.4, 8.13.
Merkel’s disc
A skin receptor cell type that detects light touch. See Figures 8.4, 8.13.
migraines
Intense headaches, typically perceived from one half of the head, that recur regularly and can be difficult to treat.
naloxone
A potent antagonist of opiates that is often administered to people who have taken drug overdoses. It blocks receptors for endogenous opioids.
neuropathic pain
Pain caused by damage to peripheral nerves; often difficult to treat.
nociceptor
A receptor that responds to stimuli that produce tissue damage or pose the threat of damage.
opiates
A class of compounds that exert an effect like that of opium, including reduced pain sensitivity. See Table 4.1, under “Opioid peptides.” Compare opioids.
opioid receptor
A receptor that responds to endogenous and/or exogenous opioids.
opioids
A class of peptides produced in various regions of the brain that bind to opioid receptors and act like opiates. See Table 4.1.
Pacinian corpuscle
Also called lamellated corpuscle. A skin receptor cell type that detects vibration. See Figures 8.4, 8.5, 8.13.
pain
The discomfort normally associated with tissue damage.
periaqueductal gray
The neuronal body–rich region of the midbrain surrounding the cerebral aqueduct that connects the third and fourth ventricles; involved in pain perception.
phasic receptor
A receptor in which the frequency of action potentials drops rapidly as stimulation is maintained. Compare tonic receptor.
placebo
A substance, given to a patient, that is known to be ineffective or inert but that sometimes brings relief.
polymodal
Also called multisensory. Involving several sensory modalities.
primary sensory cortex
For a given sensory modality, the region of cortex that receives most of the information about that modality from the thalamus or, in the case of olfaction, directly from the secondary sensory neurons. Compare secondary sensory cortex.
primary somatosensory cortex (S1)
Also called somatosensory 1. The gyrus just posterior to the central sulcus where sensory receptors on the body surface are mapped. Primary cortex for receiving touch and pain information, in the parietal lobe. See Figures 8.10, 8.15. Compare secondary somatosensory cortex.
range fractionation
A hypothesis of stimulus intensity perception stating that a wide range of intensity values can be encoded by a group of cells, each of which is a specialist for a particular range of stimulus intensities. See Figure 8.6.
receptive field
The stimulus region and features that affect the activity of a cell in a sensory system. See Figures 8.9, 10.13, 10.15.
receptor cell
A specialized cell that responds to a particular energy or substance in the internal or external environment, and converts this energy into a change in the electrical potential across its membrane.
receptor potentials (or generator potentials)
A local change in the resting potential of a receptor cell that mediates between the impact of stimuli and the initiation of nerve impulses.
Ruffini’s ending
A skin receptor cell type that detects stretching of the skin. See Figures 8.4, 8.13.
secondary sensory cortex
Also called nonprimary sensory cortex. For a given sensory modality, the cortical regions receiving direct projections from primary sensory cortex for that modality. Compare primary sensory cortex.
secondary somatosensory cortex (S2)
Also called somatosensory 2. The region of cortex that receives direct projections from primary somatosensory cortex. Compare primary somatosensory cortex.
sensory pathway
The chain of neural connections from sensory receptor cells to the cortex.
sensory receptor organ
An organ specialized to receive particular stimuli. Examples include the eye and the ear.
sensory transduction
The process in which a receptor cell converts the energy in a stimulus into a change in the electrical potential across its membrane.
somatosensory
Referring to body sensation, particularly touch and pain sensation.
somatosensory 1
See primary somatosensory cortex.
somatosensory 2
See secondary somatosensory cortex.
specific nerve energies
The doctrine that the receptors and neural channels for the different senses are independent and operate in their own special ways, and can produce only one particular sensation each.
spinothalamic system
See anterolateral system.
stimulus (pl. stimuli)
A physical event that triggers a sensory response.
substance P
A peptide transmitter implicated in pain transmission.
tactile
Of or relating to touch.
thalamus (pl. thalami)
The brain regions at the top of the brainstem that trade information with the cortex. See Figures 2.12, 2.14.
threshold
The stimulus intensity that is just adequate to trigger an action potential at the axon hillock.
tonic receptor
A receptor in which the frequency of action potentials declines slowly or not at all as stimulation is maintained. Compare phasic receptor.
top-down process
A process in which higher-order cognitive processes control lower-order systems, often reflecting conscious control. Compare bottom-up process.
transcutaneous electrical nerve stimulation (TENS)
The delivery of electrical pulses through electrodes attached to the skin, which excite nerves that supply the region to which pain is referred. TENS can relieve the pain in some instances.
transient receptor potential 2 (TRP2)
A receptor, found in some free nerve endings, that opens its channel in response to rising temperatures. See Figure 8.22.
transient receptor potential vanilloid type 1 (TRPV1)
Also called vanilloid receptor 1. A receptor that binds capsaicin to transmit the burning sensation from chili peppers and normally detects sudden increases in temperature. See Figure 8.22.
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