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Brain&Behavior Ch 5
The Sensorimotor System
| Term | Definition |
|---|---|
| receptor cells | 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 |
| stimulus | a physical event that triggers a sensory response |
| labeled lines | the concept that each nerve input to the brain reports only a particular type of information |
| 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 |
| 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 |
| Pacian corpuscle or lamellated corpuscle | a skin receptor cell type that detects vibration and pressure. |
| threshold | the stimulus intensity that is just adequate to trigger an action potential at the axon hillock |
| Meissner's corpuscle or tactile corpuscle | a skin receptor cell type that detects light touch, responding especially to changes in stimuli |
| Merkel's disc | a skin receptor cell type that detects light touch, responding especially to edges and isolated points on a surface |
| Ruffini corpuscle | a skin receptor cell type that detects stretching of the skin |
| free nerve ending | an axon that terminates in the skin and has no specialized cell associated with it. |
| what do free nerve endings do? | detect pain and/or changes in termperature |
| range fractination | the means by which sensory systems cover a wide range of intensity values as each sensory receptor cell specialized in just one part of the overall range of intensities. |
| somatosensory system | a set of specialized receptors and neural mechanisms responsible for body sensations such as touch and pain |
| receptive field | the stimulus region and features that affect the activity of a cell in a sensory system |
| adaptation | the progressive loss of receptor sensitivity as stimulation is maintained |
| phasic receptor | a receptor in which the frequency of action potentials drops rapidly as stimulation is maintained |
| tonic receptor | a receptor in which the frequency of action potentials declines slowly or not at all as stimulation is maintained |
| 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. |
| dorsal column system | a somatosensory system that delivers most touch stimuli via the dorsal columns of spinal white matter to the brain |
| dermatome | a strip of skin innervated by a particular spinal nerve |
| thalamus | the brain regions at the top of the brainstem that trade information with the cortex |
| 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 |
| nonprimary sensory cortex | (secondary sensory cortex) for a given sensory modality, the cortical regions receiving direct projections from primary sensory cortex for that modality |
| 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, in the parietal lobe. |
| polymodal neuron | a neuron upon which information from different sensory systems converges |
| synesthesia | a condition in which stimulus in one modality evoke the involuntary experience of an additional sensation in another modality |
| pain | the discomfort normally associated with tissue damage |
| immediate, short-lasting pain causes us to... | withdraw from the source (reflexively) to prevent further damage |
| longer-lasting pain encourage behaviors such as... | sleep, inactivity, grooming, feeding, and drinking that promote recuperation |
| There is a widely used quantitative measure of pain perception. What are the three different dimensions of pain? | sensory-discriminative, motivational-affective, and overall cognitive evaluative |
| sensory-discriminative dimension | throbbing, gnawing, shooting |
| motivational-affective (emotional) dimension | tiring, sickening, fearful |
| cognitive evaluative dimension | no pain, mild, excruciating |
| pain pathway: __________ receptors get the initial message | peripheral |
| nociceptors | a receptor that responds to stimuli that produce tissue damage or pose the threat of damage (pain receptor) |
| peripheral mediation of pain: 1st step | injured cells release substances that stimulate nerve endings and also cause local inflammation |
| peripheral mediation of pain: 2nd step | information enters through the dorsal root and synapses on neurons in the dorsal horn. |
| peripheral mediation of pain: 3rd step | pain fivers release glutamate as a transmitter and substance P as a nueromodulator in the spinal cord. The dorsal horn cells then send info across the midline and up to the thalamus |
| capsaicin | chemical that makes chili peppers spicy hot |
| Studies of capsaicin has helped in what way? | they helped reveal the receptor that signals sudden increases in temp. (reason spicy foods seem to 'burn') |
| capsaicin is a type of TRPV1 (transient receptor potential vanilloid type 1). TRPV1's normal job is to... | report a rise in temperature to warn us of danger |
| TRP2 (transient receptor potential | a receptor, found in some free nerve endings, that opens its channel in response to rising temperature |
| compare TRPV1 and TRP2 | TRP2 detects even higher temps thatn does TRPV1, but does NOT respond to capsaicin. |
| TRP2 receptors are found on __ _____ fibers | A delta fibers |
| A delta fiber | a moderately large, myelinated, and therefore fast-conducting, axon, usually transmitting pain info |
| In contrast, nerve fibers that possess TRPV1 receptors consist of thin, unmyelinated fibers called __ fibers | C fibers |
| C fiber | a small, unmyelinated axon that conducts pain info slowly and adapts slowly |
| Pain pathway: special _______ pathways carry bain info to the brain | neural |
| nerve fibers carrying info about pain and temp send their axons to enter the dorsal horns of the spinal cord, where they synapse onto spinal neurons that project across the midline to the opposite side and then up toward the thalamus of the brain. forms? | anterolateral, or spinothalamic, system |
| the anterolater system is distinct from the dorsal column system, but like that system, each hemisphere receives its inputs from the ___________ side of the body | contralateral |
| ascending pain pathways in the CNS: 1st step | pain info is carried by rapidly conducting myelinated A delta fibers and slowly conducting unmyelinated C fibers |
| ascending pain pathways in the CNS: 2nd step | axons of dorsal horn neurons cross the midline and ascend the spinal cord in the anterolateral quadrant |
| ascending pain pathways in the CNS: 3rd step | pain info is provided to various brainstem sites, which control pain- related behavior such as vocalization |
| ascending pain pathways in the CNS: 4th step | pain info is distributed to many thalamic and cortical areas |
| ascending pain pathways in the CNS: 5th step | cingulate cortex is especially activated by pain information |
| within the spinal cord, the arriving pain fibers release excitatory transmitter glutamte along with a peptied, ______ __, that selectively boosts pain signals and model pain pathway neurons | substance P |
| substance P | a peptide transmitter that is involved in pain transmission |
| mice lacking substance P can still feel _____ pain but cannot feel _____ pain | intense, mild |
| sometimes pain persist long after the injury that started it has healed. This neuropathic pain is a disagreeable example of ______________, where neurons continue to directly signal pain and amplify the pain signal, in the absence of tissue damage | neuroplasticity |
| neuropathic pain | pain that persists long after the injury that started it has healed. It is caused by damage to the peripheral nerves and is often difficult to treat |
| phantom limb pain | patients experience great pain that seems to come from a limb that was previously amputated |
| phantom limb pain is notoriously difficult to treat. One approach that has met with some success involves using a _______ to... | mirror, to trick the brain into believing it is controlling the missing limb and allow the brain to recalibrate the pain signal |
| pain info is eventually integrated in the ________ ______ | cingulate cortex |
| cingulate cortex | a region of medial cerebral cortex that lies dorsal to the corpus callosum |
| pain control: a dominant model of pain transmission is called the gate control theory. what does this theory hypothesize? | that spinal "gates" control the signal that gets through to the brain. If this is right, then effective pain relief may depend on finding ways to keep the gates closed, cutting of pain signal |
| analgesia | absence of or reduction in pain |
| analgesic drugs are highly effective. The ______ have been known for centuries to relieve pain sensations | opiates |
| analgesic drugs: opiate drugs and enogenous opioids do what? | bind to specific receptors in the brain to reduce pain |
| analgesic drugs: researchers have found that the action of opioids binding to receptors to reduce pain is especially pronounced in the brainstem region called the ____________ ____ | periaqueductal gray; one possibility is brainstem system activates the pain gating mechanism of the spinal cord, blocking the tramission of pain signals |
| analgesic drugs: epidural, or intrathecal injection | injecting opiates directly into the spinal cord |
| electrical stim: 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. |
| electrical stim: We know the TENS acts at least in part by releasing ________ ______, because administration of naloxone partially blocks this analgesic action | endogenous opiods |
| electrical stim: naloxone | potent antagonist of opiates that binds to receptors for endogenous opioids |
| Placebos: placebo effect | relief of symptom that results following a treatment that is known to be ineffective or inert |
| Placebos: brain imaging indicates that ______ and placebos activate the same brain regions | opioids |
| Placebos effectively control pain... | in some people, but not all |
| activation of endogenous opioids: acupuncture | the insertion of needles at designated points on the skin to alleviate pain or neurological malfunction |
| acupuncture: in those people for whom acupuncture is effective, a release of __________ may be an important part of the process | endorphins |
| acupuncture, then, resembles _______ | placebos |
| ___________ events can produce significant analgesida | stressful (ex. wounded soldiers who feel no pain for some time after their injuries occur) |
| analgesia strategies fall into four categories... | psychogenic, pharmocological, stimulation, and surgical pain relief |
| pharmacological pain relief includes... (4) | opiates, spinal block, anti-inflammatory drugs, and cannabinoids |
| stimulation pain relief includes... (3) | TENS/mechanical, acupuncture, and central gray |
| surgical pain relief includes... (4) | cutting peripheral nerve cord, rhizotomy (cutting dorsal root), cord hemisection, and frontal lobotomy |
| psychogenic pain relief includes... (4) | placebo, hypnosis, stress, and cognitive |
| behavior requires movements that are precisely _________ and _______ | programmed and monitored |
| movement | a single relocation of a body part, usually resulting from a brief muscle contraction; less complex than an act |
| reflex | a simple, highly stereotyped, and unlearned response to a particular simulus |
| acts | complex behavior, as distinct from a simple movement |
| early discoveries suggested that reflexes are the basic units of behavior. The flaws of this perspective became apparent and researchers realized that acts require a _______ ____ | motor plan |
| motor plan | a plan for a series of muscular contractions, established in the nervous system prior to its execution |
| researchers can track the simple movements that make up an act by using electromyography (EMG). What is this? | electrical recording of muscle activity |
| in motor planning by the nervous system, a trade-off between _____ and _________ is apparent | speed and accuracy |
| closed-loop motor control | feedback info is obtained through sensory monitoring of the movement as it is being performed, and is used for error correction while the movement is being made |
| open-loop motor control | no feedback info affects the execution of the movement, and the activity is considered preprogrammed |
| closed-loop motor control maximizes _______ while open-loop motor control maximizes _______ | accuracy, speed |
| ballistic | referring to a rapid muscular movement that is generally fully preprogrammed and thus not susceptible to error correction during execution |
| the neuromuscular system is organized according to a distinct hierarchy: (6) | skeletal system/ skeletal muscles, spinal cord, brainstem, primary motor cortex, nonprimary motor cortex, and other brain regions (cerebellum and basal ganglia via the thalamus) |
| neuromuscular hierarchy: (1) skeletal system and the muscles attached to it determine what? | which movements are possible |
| neuromuscular hierarchy: (2) spinal cord controls controls what? | skeletal muscles in response to motor commands from the brain, or in direct response to sensory inputs (reflexes) |
| neuromuscular hierarchy: (3) brainstem integrates and transmits what? | integrates motor commands from higher levels of the brain and transmits them to the spinal cord. (also relays sensory info about the body from the spinal cord to the forebrain) |
| neuromuscular hierarchy: (4) what is initiated in the primary motor cortex? | main commands for action |
| neuromuscular hierarchy: (5) areas adjacent to the primary motor cortex, the nonprimary motor cortex, provide additional source of motor commands by acting... | acting indirectly via primary motor cortex and through direct connections to lower levels of the motor hierarchy |
| neuromuscular hierarchy: At the very top of the movement hierarchy is the ________ ______, which is crucial to the conscious formulation of behavioral plans | prefrontal cortex |
| neuromuscular hierarchy: (6) other brain regions- the cerebellum and basal ganglia, via the thalamus, modulate what? | the activities of the other parts of the control system |
| a complex neural system controls ________ to create ________ | muscles, behavior |
| ________ and the ________ work together to move the body | muscles and skeleton |
| around a joint, different muscles are arranged in reciprocal fashion, connected to the bone by ______ | tendons |
| what does it mean when we say the muscles are arranged in reciprocal fashion? | when one muscle group contracts, it stretches the other group (antagonist) |
| muscles: antagonist | a muscle that counteracts the effect of another muscle |
| muscles: synergist | a muscle that acts together with another muscle |
| skeletal muscles | muscles that have a striped appearance and are typically under our conscious control |
| skeletal muscles are used for... | the movement of the skeleton |
| skeletal muscles have a striped appearance due to overlapping layers of contractile proteins called _____ and ____ | myosin and actin |
| skeletal muscles are said to be made of _______ muscle | striate (generally under voluntary control) |
| contraction of the muscle increases the overlap of actin and myosin filaments within _______ ______ | muscle fibers (as they slide past each other the muscle shortens) |
| most muscles consists of a specific mixture of two types of fiber: | slow-twitch fibers and fast-twitch fibers |
| slow-twitch fibers contract with _____ intensity and fatigue ________ | low, slowly |
| fast-twitch fibers contract with _____ intensity and fatigue ________ | high, quickly |
| muscles contract because ___________ of the spinal cord and brainstem send action potentials along their axons and axon collaterals to terminate at specialized synapses called _____________ _______ | motoneurons, neuromuscular junctions |
| neuromuscular junction | region where motoneuron terminal and the adjoining muscle fiber meet; the point where the nerve transmits its message to the muscle fiber |
| the production of action potential by a motoneuron triggers the release of the neurotransmitter ___________ at all of the motoneuron's axon terminals | acetylcholine (ACh) |
| motor unit | motoneuron together with all of the muscle fibers it innervates |
| how do the fibers respond to the release of acetylcholine (ACh)? | by triggering the molecular events that cause actin and myosin to produce contration |
| faciculation | "jumping nerves" caused by misfiring motor unit |
| neuroscientists refer to motoneurons as the 'final common pathway' because... | they receive and integrate all motor signals from the brain and then direct movement accordingly |
| sensory ________ from muscles, tendons, and joints govern movement | feedback |
| proprioception | body sense; information about the position and movement of the body that is sent to the brain |
| What are the two special proprioceptors that monitor muscle length and muscle tension? | muscle spindles and Golgi tendon organs |
| proprioceptors: muscle spindle | muscle receptor that lies parallel to a muscle and sends impulses to the CNS when the muscle is stretched |
| a muscle spindle is basically a capsule, buried within the other fiber of the muscle, that contains a special kind of muscle fiber called an ___________ fiber | intrafusal |
| intrafusal fiber | any of the small muscle fibers that lie within each muscle spindle |
| proprioceptors: Golgi tendon organ | any of the receptors within tendons that send impulses to the CNS when a muscle contracts |
| stretch reflex | the contraction of a muscle in response to stretch of that muscle |
| what is an example of a stretch reflex? | knee jerk |
| the spinal cord ______ "automatic responses and ________ inputs from the brain | mediates, receives |
| the lowest level of hierarchy is the spinal cord, where relatively simple circuits produce reflexive behavioral responses to sensory stimuli. a straightfoward example is the ______ reflex | stretch (ex: dropping a load into the outstretched hand) |
| ex. dropping a book into outstretched hand: (1st) a weight dropped into the hand causes what? | stretching of the biceps muscle |
| ex. dropping a book into outstretched hand: (2nd) the stretch does what? | excites the muscle spindle, which sends action potentials to the dorsal spinal cord |
| ex. dropping a book into outstretched hand: (3rd) the action potentials do what? | synapse onto motoneurons in the spinal cord that cause the biceps to contract, restoring the arm to the original position |
| ex. dropping a book into outstretched hand: (4th) What else do the muscle fibers excite? | interneurons that inhibit triceps motoneurons, causing the triceps to relax when the biceps contracts |
| although the muscles of the head are controlled by the brain (cranial nerves) the muscles of the rest of the body are controlled by commands from the brain via the spinal cord. The brain sends these commands to the spinal cord through two major pathways: | the pyramidal system and the extrapyramidal system |
| the pyramidal (or coricospinal) system consists of... | neuronal cell bodies within the cerebral cortex and their axons, which pass through the brainstem, forming the pyramidal tract to the spinal cord |
| in a cross section of the ________, the tract is a pyramid shape on each side of the midline | medulla |
| Because the left and right pyramidal tracts each cross over to the other side, the right cortex controls the _____ side of the body while the left cortex controls the _____. | left, right |
| Lesions anywhere in the pyramidal tract will cause ________ in the muscular targets of the damaged axons | paralysis |
| many of the axons of the pyramidal tract originate from the neurons in the ________ _________ _______ | primary motor cortex (M1) |
| many other pathways run from the forebrain to the brainstem and spinal cord. Because these tracts are outside the pyramids of the medulla, they and their connections are lumped together as the _____________ ________. | extrapyramidal system |
| extrapyramidal system | 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 |
| Lesions of the extrapyramidal system do not prevent the movement of individual joints and limbs, but interfere with.... | spinal reflexes and with systems that regulate and fine-tune motor behavior |
| motor cortex _____ and _______ movements- and more | plans and executes |
| primary motor cortex (M1) | the apparent executive region for the initation of movement; primarily the precentral gyrus |
| the primary motor cortex of humans-M1- is a major source of _____ forming the pyramidal tract | axons |
| like S1, the primary somatosensory cortex, M1 occupies a single large cortical gyrus: the __________ gyrus, located immediately in front of the central sulcus | precentral gyrus |
| like S1, M1 is organized as a map of the ____________ side of the body | contralateral |
| Just anterior to M1 are cortical regions, collectively known as _________ ______ ______, that make additional crucial contributions to motor control | nonprimary motor cortex |
| nonprimary motor cortex | front lobe regions adjacent to the primary motor cortex that contribute to motor control and modulate the activity of the primary motor cortex |
| the nonprimary motor cortex can contribute to behavior directly through... | communication with lower levels of the motor hierarchy in the brainstem and spinal cord systems |
| the nonprimary motor cortex can contribute to behavior indirectly through... | M1 |
| the traditional account of nonprimary motor cortex emphasizes two main regions: | supplementary motor area (SMA) and the premotor cortex |
| supplementary motor area (SMA) | region of nonprimary motor cortex that receives input from the basal ganglia and modulates the activity of the primary motor cortex |
| premotor cortex | region of nonprimary motor cortex just anterior to the primary motor cortex |
| the supplementary motor area (SMA) seems important for what? | the initiation of movement sequences, especially when they're being executed according to an internal preprogrammed plan |
| in contrast, the premotor cortex seems to be activated when what? | when motor sequences are guided by external events |
| evidence is mounting that the premotor cortex is not a single system, but really a mosaic of different units, controlling groups of motor behaviors that cluster together into major categories This organization reinforces what idea? | the idea that motor and premotor areas mostly map behaviors, rather than mapping specific movements, as in M1 |
| strokes or other injuries in motor areas of the cortex tend to result in __________ or __________ | paralysis or weakness |
| plegia | paralysis, the loss of the ability to move |
| paresis | muscular weakness, often the result of damage to motor cortex |
| damage to nonmotor zones of the cerebral cortex, such as some regions of parietal or fronal association cortex, produces more-complicated changes in motor control, such as apraxia. What is apraxia? | an impairment in the ability to carry out complex movements, even though there is no muscle paralysis |
| 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 |
| extrapyramidal systems ________ and ____-_____ motor commands | regulate and fine-tune |
| two of the most important sources of extrapyramidal fibers are the _______ __________ and the _________ | basal ganglia, cerebellum |
| the basal ganglia are especially important for movements performed by ____________, in contrast to those guided by sensory control | memory |
| the cerebellum appears to help establish he fine-tune neural programs for _______ movements | skilled (especially the kinds of rapid, repeated movements that become automatic. |
| the basal ganglia and the cerebellar systems thus make distinct but _____________ contributions to regulating motor behavior | complimentary |
| damage to extrapyramidal systems impairs _________ | movement |
| ataxia | a loss of movement coordination, often caused by disease of the cerebellum |
| the exact consequences of cerebellar damage depend on the part of the cerebellum that has been damaged, but common motor symptoms include what? | characteristic abnormalties of gait and posture, especially ataxia of the legs |
| decomposition of movement | difficulty of movement in which gestures are broken up into individual segments instead of being executed smoothly |
| what are symptoms of cerebellar lesions? (3) | decomposition of movement, difficulties with gaze and visual tracking of objects |
| two diseases that target the basal ganglia reveal important aspects of extrapyramidal contributions to motor control: | parkinson's disease and huntington's disease |
| Parkinson's disease | a degenerative neurological disorder, characterized bu tremors at rest, muscular rigidity, and reduction in voluntary movement, caused by loss of the dopaminergic neurons of the substantia nigra |
| substantia nigra | brainstem structure in humans that innervates the basal ganglia and is named for its dark pigmentation |
| 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 |
| damage to the basal ganglia in Parkinson's disease causes ______ movements, and damage to the basal ganglia in Huntington's disease cause _________ movements | slowing of, excessive |
Created by:
cmccartney2
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