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Flashcards in chapter 5: the sensorimotor system Deck (80):
1

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

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stimulus

a physical event that triggers a sensory response

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labeled lines

the concept that each nerve input to the brain reports only a particular type of information

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generator potential

a local change in the resting potential of a receptor cell that mediates between the impact of stimuli and the initiation of action potentials

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sensory transduction

the process in which a receptor cell converts the energy in a into a change in the electrical potential across its membrane

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Pacinian corpuscle or lamellate corpuscle

a skin receptor cell type that detects vibration and pressure

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threshold

the stimulus intensity that is just adequate to trigger an action potential at the axon hillock

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Meissner's corpuscle or tactile corpuscle

a skin receptor cell type that detects light touch, responding especially to changes in stimuli

9

Merkel's disc

a skin receptor type that detects light touch, responding especially to edges and isolated points on a surface

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Ruffini corpuscle

a skin receptor cell type that detects stretching of the skin

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free nerve ending

an axon that terminates in the skin and has no specialized cell associated with it; detect pain and/or changes in temperature

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range fractionation

the means by which sensory systems covers wide range of intensity values as each sensory receptor cell specializes in just one part of the overall range of intensities

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somatosensory system

a set of specialized receptors and neural mechanisms responsible for body sensations touch as touch and pain

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receptive field

the stimulus region and features that affect the activity of a cell in a sensory system

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adaptation

the progressive loss of receptor sensitivity as stimulation is maintained

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phasic receptor

a receptor in which the frequency of action potentials drops rapidly as stimulation is maintained

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tonic receptor

a receptor in which the frequency of action potentials declines slowly or not at all as stimulation is maintained

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central modulation of sensory information

the process in which higher brain centers, such as the cortex and thalamus, suppress some sources of sensory information and amplify others

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dorsal column system

a somatosensory system that delivers most touch stimuli via the dorsal columns of spinal white matter to the brain

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dermatome

a strip of skin innervated by a particular spinal nerve

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thalamus

the brain regions at the top of the brainstem that trade information with the cortex

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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

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non primary sensory cortex

for a given sensory modality, the cortical regions receiving direct projections from primary sensory cortex for that modality

also called second sensory cortex

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primary somatosensory cortex or somatosensory 1 (S1)

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, is in the parietal lobe

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polymodal neuron

a neuron upon which information from different sensory systems converges

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synesthesia

a condition in which stimuli in one modality evoke the involuntary experience of an additional sensation in another modality

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pain

the discomfort normally associated with tissue damage

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nociceptor

a receptor that responds to stimuli (e.g., pain or changes in temperature) that produce tissue damage or pose the threat of damage

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transient receptor potential 2 (TRP2)

a receptor, found in some free nerve endings, that opens its channel in response to rising temperatures

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A delta (Ad) fiber

a moderately large, myelinated, and therefore fast-conducting axon, usually transmitting pain information

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C fiber

a small, unmyelinated axon that conducts pain information slowly and adapts slowly

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anterolateral system or spinothalamic system

a somatosensory system that carries most of the pain information from the body to the brain

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substance P

a peptide transmitter that is involved in pain transmission

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neuropathic pain

pain that persists long after the injury that started it has heard; caused by damage to peripheral nerves and is often difficult to treat

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cingulate cortex

a region of medial cerebral cortex that lies dorsal to the corpus callosum; also called cingulum

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analgesia

absence of or reduction in pain

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endorphin

one of three kinds of endogenous opioids, used as a painkiller

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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

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naloxone

a potent antagonist of opiates that is often administered to people who have taken drug overdoses; it binds to receptors for endogenous opioids

40

placebo effect

relief of a symptom, such as pain, that results following a treatment that is known to be ineffective or inert

41

acupuncture

the insertion of needles at designed points on the skin to alleviate pain or neurological malfunction

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movement

a single relocation of a body part, usually resulting from a brief muscle contraction; less complex than an act

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reflex

a simple, highly stereotyped, and unlearned response to a particular stimulus (e.g., an eye blink in response to a puff of air)

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act

complex behavior, as distinct from a simple movement

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motor plan

a plan for a series of muscular contractions, established in the nervous system prior to its execution; also called motor program

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electromyography (EMG)

the electrical recording of muscle activity

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closed-loop motor control

a control mechanism that provides a flow of information from whatever is being controlled to the device that controls it

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open-loop motor control

a control mechanism in which feedback from the output of the system is not provided to the input control

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ballistic

referring to a rapid muscular movement that is generally fully preprogrammed and thus not susceptible to error correction during execution

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antagonist

a muscle that counteracts the effect of another muscle

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synergist

a muscle that acts together with another muscle

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skeletal muscle

a muscle that is used for movement of the skeleton, typically under our conscious control

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striate muscle

a type of muscle that has a striped appearance; it is generally under voluntary control

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motoneuron

a neuron that transmits neural messages to muscles (or glands); also called motor neuron

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neuromuscular junction

the region where the motoneuron terminal and the adjoining muscle fiber meet; the point where the nerve transmits its message to the muscle fiber

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acetylcholine (ACh)

a neurotransmitter that is produced and released b parasympathetic postganglionic neurons, by motoneurons, and by neurons throughout the brain

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final common pathway

the motoneurons of the spinal cord, so called because they receive and integrate all motor signals from the brain and then direct movement accordingly

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proprioception

body sense; information about the position and movement of the body that is sent to the brain

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muscle spindle

a muscle receptor that lies parallel to a muscle and sends impulses to the central nervous system when the muscle is stretched

60

intrafusal fiber

any of the small muscle fibers that lie within each muscle spindle

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Golgi tendon organ

any of the receptors within tendons that send impulses to the central nervous system when a muscle contracts

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stretch reflex

the contraction of a muscle in response to stretch of that muscle

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pyramidal system or corticospinal system

the motor system that includes neurons within the cerebral cortex and their axons, which form the pyramidal tract

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extrapyramidal system

a motor system that includes the basal ganglia and some closely related brainstem structures; axons of this system pass into the spinal cord outside the pyramids of the medulla

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primary motor cortex (M1)

the apparent executive region of the initiation of movement; primarily the precentral gyrus

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precentral gyrus

the strip of frontal cortex, just in front of the central sulcus, that is crucial for motor control

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nonprimary motor cortex

frontal lobe regions adjacent to the primary motor cortex that contribute to motor control and modulate the activity of the primary motor cortex

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supplementary motor area (SMA)

a region of nonprimary motor cortex the receives input from the basal ganglia and modulates the activity of the primary motor cortex

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premotor cortex

a region of nonprimary motor cortex just anterior to the primary motor cortex

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plegia

paralysis, the loss of the ability to move

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paresis

muscular weakness, often the result of damage to motor cortex

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apraxia

an impairment in the ability to carry out complex movements, even though there is no muscle paralysis

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mirror neuron

a neuron that is active both when an individual makes a particular movement and when that individual sees another individual make the same movement

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basal ganglia

a group of forebrain nuclei, including caudate nucleus, globus pallidus, and putamen, found deep within the cerebral hemispheres

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cerebellum

a structure located at the back of the brain, dorsal to the pons, that is involved in the central regulation of movement

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ataxia

a loss of movement coordination, often caused by disease of the cerebellum

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decomposition of movement

difficulty of movement in which gestures are broken up into individual segments instead of being executed smoothly; it is a symptom of cerebellar lesions

78

Parkinson's disease

a degenerative neurological disorder, characterized by tremors at rest, muscular rigidity, and reduction in voluntary movement, caused by loss of the dopaminergic neurons of the substantia nigra

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substantia nigra

a brainstem structure in humans that innervates the basal ganglia and is named for its dark pigmentation

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Huntington's disease

a genetic disorder, with onset in middle age, in which the destruction of basal ganglia results in a syndrome of abrupt, involuntary writhing movements and changes in mental functioning