Ch. 5 Flashcards
Chapter 4 of The Mind's Machine
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
Stimuli
A drug that enhances the excitability of neurons
Labeled Lines
The concept that each nerve input to the brain reports only a particular type of information
Receptor Potential
Also called generator potential. A local change in the resting potential of a receptor cell in response to stimuli, which may initiate an action potential
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. Other definition: converting the signal from environmental stimuli into action potentials that our brain can understand
Pacinian Corpuscle
Also called lamellated corpuscle. A skin receptor cell type that detects vibration and pressure
Meissner’s Corpuscles
Also called tactile corpuscle. A skin receptor cell type that detects light touch, responding especially to changes in stimuli
Merkel’s Discs
A skin receptor cell type that detects light touch, responding especially to edges and isolated points on a surface
Ruffini Corpuscles
A skin receptor cell type that detects stretching of the skin
Free Nerve Endings
An axon that terminates in the skin and has no specialized cell associated with it. Can detect pain, itch, heat, and cold stimuli
What stimuli are going to be more ephasized?
A good deal of selection and analysis takes place along sensory pathways. The brain receives a highly filtered representation of the external world, in which stimuli that are critical for survival are strongly emphasized at the expense of less important stimuli
Somatosensory System
A set of specialized receptors and neural mechanisms responsible for body sensations such as touch and pain
More cells are allocated to the spatial representation of what?
sensitive, densely innervated sites, like the lips
Receptive Field
The stimulus region and features that affect the activity of a cell in a sensory system. A region of space in which a stimulus will alter that neuron’s firing rate
Sensory Adaptation
The progressive loss of receptor response as stimulation is maintained. Ex. clothes on skin
Phasic Receptors
A receptor in which the frequency of action potentials drops rapidly as stimulation is maintained
Tonic Receptors
A receptor in which frequency of action potentials declines slowly or not al all as stimulation is maintained. Ex. pain receptors- they maintain a high level of activity to avoid further injury
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 to the brain via the dorsal columns of spinal white matter
Dermatome
A strip of skin innervated by a particular spinal dorsal root
How does sensory information travel to the brain?
Sensory info travels from the sensory surface to the highest levels of the brain, and each sensory system has its own distinctive pathway from the periphery to successively higher levels of the spinal cord and/or brain
What is the relationship of the thalamus and sensory information?
Information reaches the thalamus before being relayed to the cortex. Information about each sensory modality is sent to a separate division of the thalamus. One way for the brain to suppress particular stimuli is for the cortex to direct the thalamus to emphasize some sensory information and suppress other information
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
Also called secondary sensory cortex. For a given sensory modality, the cortical regions receiving direct projections from primary sensory cortex for that modality
Primary Somatosensory Cortex
Also called somatosensory 1 or S1. Primarily the postcentral gyrus of the parietal lobe, where sensory inputs from the body surface are mapped
Where is the somatosensory 1 located in each hemisphere?
the postcentral gyrus (the long strip of tissue that lies just posterior to the central sulcus dividing the parietal lobe from the frontal lobe)
What parts of the body have large representations in S1?
parts of the body where we are especially sensitive to touch, like hands and fingers
Polymodal Neutons
A neuron upon which information from more than one sensory system converges
Synesthesia
A condition in which stimuli in one modality evoke the involuntary experience of an additional sensation in another modality
Pain
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
In the McGill Pain Questionnaire, what are the three different dimensions of pain?
- The sensory-discriminative dimension (e.g., throbbing, gnawing, shooting)
- The motivational-affective (emotional) dimension (e.g., tiring, sickening, fearful)
- An overall cognitive-evaluative dimension (e.g., no pain, mild, excruciating)
Nociceptors
A receptor that responds to stimuli that produce tissue damage or pose the threat of damage (free nerve endings specialized to detect damage)
What in the body prevents individuals to not feel pain?
A mutation in a particular gene (SCN9A) the encodes a voltage-gated sodium channel expressed in free nerve endings that serve as nociceptors. Without this channel, pain fibers cannot produce the action potentials that ordinarily signal tissue damage
Transient Receptor Potential Vanilloid Type 1 (TRPV1)
receptor that reveals sudden increases in temperature (the reason spicy foods seems to burn). Found in C Fibers
Transient Receptor Potential Type M3 (TRPM3)
A receptor, found in some free nerve endings, that opens its channel in response to rising temperatures. Found in A Delta (Aδ) Fibers
A Delta (Aδ) Fibers
A moderately large, myelinated, and therefore fast-conducting axon that usually transmits pain information. Action potentials in these fibers reach the spinal cord very quickly
C Fibers
A small, unmyelinated axon that conducts pain information slowly and adapts slowly
Anterolateral System
Also called spinothalamic system. A somatosensory system that carries most of the pain information from the body to the brain
How does information about pain reach the brain?
Nerve fibers carrying information about pain and temperature 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. Each hemisphere receives its input from the contralateral side of the body
Substance P
A peptide transmitter that is released alone with the excitatory transmitter glutamate. Substance p selectively boosts pain signals and remodels pain pathway neurons
Cingulate Cortex
Also called cingulum. A region of medial cerebral cortex that lies dorsal to the corpus callosum (part of the limbic system). The extent of activation in the cingulate cortex correlates with how much discomfort different people report in response to the same mildly painful stimulus.
Neuropathic Pain
Pain that persists long after the injury that started it has healed. Neurons continue to directly signal pain, and amplify the pain signal, in the absence of any tissue damage.
Phantom Limb Pain
Example of neuropathic pain where people experience great pain that seems to come form an amputated limb
Analgesia
Absence of or reduction in pain
Naloxone
A potent antagonist of opioids that is often administered to people who have taken drug overdoses
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. Applied to nerves around the injury sites to relieve pain.
Placebo Effect
Relief of a symptom, such as pain, that results following a treatment that is known to be ineffective or inert
Acupuncture
The insertion of needles at designated points on the skin to alleviate pain or neurological malfunction. Reduces pain because of the expectation that the needles will relieve pain which induces a release of endogenous opioids
How can some individuals continue to fight or escape even when they should be feeling overwhelming pain?
Stress has been shown to activate both an opioid-dependent form of analgesia, which can be blocked by naloxone, and another, non-opioid analgesia system. These endogenous analgesic systems allow individuals to keep moving rather than be overwhelmed with pain
Movements
Contractions of muscles that provide our sole means of interacting with the world around us
Reflexes
simple, unvarying, and unlearned response to sensory stimuli such as touch, pressure, and pain
Acts
Complex behavior, as distinct from a simple movement. Ex. getting dresses walking, or speaking in a sentence
Motor Plan
A plan for a series of muscular contractions, established in the nervous system prior to its execution
Electromyography (EMG)
recording the electrical activity of muscles as they contract and the moment-to-moment positions of the body
What is the hierarchy of the neuromuscular system?
- Skeletal System
- Spinal Cord
- Brainstem
- Primary Motor Cortex
- Areas adjacent to the primary motor cortex (nonprimary motor cortex)
- other brain regions such as the cerebellum, basal ganglia, and the thalamus
What is the skeletal systems purpose in the neuromuscular system?
The skeletal system and the muscles attached to it determine which movements are possible.
What is the spinal cords purpose in the neuromuscular system?
The spinal cord controls skeletal muscles in response to motor commands from the brain or, in the case of simple reflexes, in direct response to sensory inputs.
What is the purpose of the brainstem in the neuromuscular system?
The brainstem integrates motor commands from higher levels of the brain and transmits them to the spinal cord. It also relays sensory information about the body from the spinal cord to the forebrain
What is the purpose of the primary motor cortex in the neuromuscular system?
Some of the main commands for action are initiated in the primary motor cortex
What is the purpose of the nonprimary motor cortex in the neuromuscular system?
Areas adjacent to the primary motor cortex, nonprimary motor cortex, provide an additional source of motor commands, acting indirectly via primary motor cortex and through direct connections to lower levels of the motor hierarchy. At the very top of the movement hierarchy is the prefrontal cortex, which is crucial to the formulation of behavioral plans.
What is the purpose of the other brain regions in the neuromuscular system?
Other brain regions—the cerebellum and basal ganglia, via the thalamus—modulate the activities of the other parts of the control system.
Antagonist Muscles
A muscle that counteracts the effect of another muscle. When one muscle group contracts, it stretches the other group
Synergists
A muscle that acts together with another muscle. Muscles that work together to move a limb in one direction
What are the two types of fibers that muscles consist of?
Slow-twitch fibers that contract with relatively low intensity but fatigue slowly, and fast-twitch fibers that contract strongly but fatigue quickly
Motor Neurons
A neuron that transmits neural messages to muscles
Neuromuscular Junctions
The region where the motor neuron terminal meets its target muscle fiber. It is the point where the nerve transmits its message to the muscle fiber
What does the production of an action potential by a motor neuron release?
the neurotransmitter acetylcholine (ACh) at all of the motor neuron’s axon terminals
Motor Unit
The motor neuron, together with all of the muscle fibers it innervates
What do the fibers do in response to the release of ACh?
triggering their own action potentials that cause actin and myosin to produce contraction
Final Common Pathway
The motor neurons of the brain and spinal cord, so called because they receive and integrate all motor signals from the brain to direct movement
Proprioception
The brain and spinal cord monitoring the state of the muscles, the positions of the limbs, and the instructions being issued by the motor centers. This collection of information is called proprioception.
Muscle Spindle
A muscle receptor that lies parallel to a muscle and sends impulses to the central nervous system when the muscle is lengthened. Contains intrafusal fiber
Intrafusal Fiber
Any of the small muscle fibers that lie within each muscle spindle
Golgi Tendon Organs
A type of receptor found within tendons that sends impulses to the central nervous system when a muscle contracts
Stretch Reflex
The contraction of a muscle in response to stretch of that muscle
What are the two major pathways that the brain sends commands to the spinal cord through?
pyramidal system and the extrapyramidal system
Pyramidal System
Also called corticospinal system. The motor system that includes neurons within the cerebral cortex and their axons, which form the pyramidal tract
What does the pyramidal system consist of?
neuronal cell bodies within the frontal cortex and their axons, which pass through the brainstem, forming the pyramidal tract to the spinal cord
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
Primary Motor Cortex (M1)
The apparent executive region for the initiation of movement. It is primarily the precentral gyrus. Major source of axons forming the pyramidal tract. Occupies a single large cortical gyrus (the precentral gyrus)
Precentral Gyrus
The strip of frontal cortex, just anterior to (in front of) the central sulcus, that is crucial for motor control
Motor homunculus
A figure drawn using the body proportions represented in M1
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
What are the two main regions of the nonprimary motor cortex?
supplementary motor area (SMA) and premotor cortex
Supplementary Motor Area (SMA)
A region of nonprimary motor cortex that receives input from the basal ganglia and modulates the activity of the primary motor cortex. Important for the initiation of movement sequences, especially when they’re bing executed according to an internal preprogrammed plan.
Premotor Cortex
A region of nonprimary motor cortex just anterior to the primary motor cortex. Seems to be activated when motor sequences are guided by external events
Plegia
Paralysis; loss of the ability to move
Paresis
Muscular weakness, often the result of damage to motor cortex
What is the result of strokes or other injuries in motor areas of the cortex?
plegia or paresis
What can happen to motor control after damage to regions outside of purely motor zones of the cerebral cortex?
apraxia (the inability to carry out complex movements even though paralysis or weakness is not evident and language comprehension and motivation are intact
Mirror Neurons
A neuron that is active both when an individual makes a particular movement and when the individual sees another individual make the same movement
Extrapyramidal Projections
the motor fibers outside the pyramidal tracts
What are two of the most important sources of extrapyramidal fibers?
the basal ganglia and the cerebellum
Basal Ganglia
A group of forebrain nuclei, including the caudate nucleus, globus pallidus, and putamen, found deep within the cerebral hemispheres. They are crucial for skill learning. Helps control the amplitude and direction of movement, and changes in activity in regions of the basal ganglia appear to be important for the initiation of movement
Cerebellum
A structure located at the back of the brain, dorsal to the pons, that is involved in the central regulation of movement and in some forms of learning. Inputs to the cerebellum come both from sensory sources and from other brain motor systems. Both pyramidal and nonpyramidal pathways contribute inputs to the cerebellum and in turn receive outputs
Ataxia
A loss of movement coordination, often caused by disease of the cerebellum
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
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. People with Parkinson’s disease show progressive degeneration of dopamine-containing cells in the substantia nigra
Substantia Nigra
A brainstem structure that innervates the basal ganglia and is a major source of dopaminergic projections to the basal ganglia
Deep Brain Stimulation (DBS)
Mild electrical stimulation through an electrode that is surgically implanted deep in the brain. Can relieve symptoms of Parkinson’s disease
Huntington’s Disease
A genetic disorder, with onset in middle age, in which the destruction of basal ganglia results in a syndrom of abrupt, involuntary writhing movements and changes in mental functioning
