Glossary

 
Adaptation
the decrease in the activity of first order neurons in response to a constant stimulus
Ascending pathway
fiber structure that relays sensory information from the periphery through the spinal cord and brain stem to other structures of the brain
Association area
region of cortex connected to a primary sensory cortical area that further processes the information to generate more complex sensory perceptions
Chemoreceptor
sensory receptor cell that is sensitive to chemical stimuli, such as in taste, smell, or pain
Contralateral
word meaning "on the opposite side," as in axons that cross the midline in a fiber tract
Corticobulbar tract
connection between the cortex and the brain stem responsible for generating movement
Corticospinal tract
connection between the cortex and the spinal cord responsible for generating movement
Crossed flexor
extensor reflex occurs in regards to a painful or destructive stimulus that occurs on a weight bearing body part; in order to retract from the painful stimulus in a flexing motion the other limb must be extended to bear the full body weight
Decussate
to cross the midline, as in fibers that project from one side of the body to the other
Diencephalon
a portion of the brain containing the thalamus and hypothalamus
Dorsal column system
ascending tract of the spinal cord associated with fine touch and proprioceptive sensations
encapsulated ending
configuration of a sensory receptor neuron with dendrites surrounded by specialized structures to aid in transduction of a particular type of sensation, such as the lamellated corpuscles in the deep dermis and subcutaneous tissue
Exteroceptor
sensory receptor that is positioned to interpret stimuli from the external environment, such as photoreceptors in the eye or somatosensory receptors in the skin
First order neuron
neuron that extends from the sensory receptor to the posterior grey horn of the spinal cord; is named as such because it is the first neuron to carry that particular sensory information
Free nerve ending
configuration of a sensory receptor neuron with dendrites in the connective tissue of the organ, such as in the dermis of the skin, that are most often sensitive to chemical, thermal, and mechanical stimuli
General sense
any sensory system that is distributed throughout the body and incorporated into organs of multiple other systems, such as the walls of the digestive organs or the skin
Generator potential
a graded potential produced in a receptor that is part of the sensory neuron in response to a stimulus
Hypothalamus
a portion of the diencephalon that communicates with the limbic system and has both somatic and autonomic functions
Interoceptor
sensory receptor that is positioned to interpret stimuli from internal organs, such as stretch receptors in the wall of blood vessels
Ipsilateral
word meaning on the same side, as in axons that do not cross the midline in a fiber tract
Kehr sign
the presentation of pain in the left shoulder, chest, and neck regions following rupture of the spleen
Lamellated corpuscle
also known as Pacinian corpuscles, are receptors in the skin that respond to deep pressure or vibration
Lower motor neuron
also known as the terminal neuron, extend from the ventral grey horn of the spinal cord to the skeletal muscle effector and stimulate the muscle directly
Mechanoreceptor
receptor cell that transduces mechanical stimuli into an electrochemical signal
Medial lemniscus
fiber tract of the dorsal column system that extends from the nuclei gracilis and cuneatus to the thalamus, and decussates
Merkel's disc (cell)
a specialized receptor cell that detects mechanical stimuli in the epidermis of the skin
Motor homunculus
a topographical representation of a body within the primary motor cortex that demonstrates correspondence between neuronal processing and motor control
Motor unit
one motor neuron and all of the muscle cells/fibers that the neuron innervates, can be large or small depending on the amount of control needed over the resulting movement
Multimodal integration area
region of the cerebral cortex in which information from more than one sensory modality is processed to arrive at higher level cortical functions such as memory, learning, or cognition
Muscle spindle
stretch receptors in skeletal muscles that are stimulated by muscle stretch and act to prevent muscle tearing and over-contraction
Nociceptor
receptor cell that senses pain stimuli
Osmoreceptor
receptor cell that senses differences in the concentrations of bodily fluids on the basis of osmotic pressure
Premotor cortex
cortical area anterior to the primary motor cortex that is responsible for planning movements
Primary motor cortex
region of the cerebral cortex that aids in planning and initiating skeletal muscle movements
Primary sensory cortex
region of the cerebral cortex that initially receives sensory input from an ascending pathway from the thalamus and begins the processing that will result in conscious perception of that modality
Proprioceptor
receptor cell that senses changes in the position and kinesthetic aspects of the body
Receptor potential
a graded potential produced in a standalone receptor cell in response to a stimulus
Referred pain
irregular pattern of projection of conscious perception of visceral sensations
Reflex
response to a stimulus that occurs without conscious thought, the integrating center is the spinal cord instead of the cerebral cortex
Ruffini corpuscles
also known as bulbous corpuscles, are receptors in the skin activated by stretch
Second order neuron
neuron that extends from the posterior grey horn to the thalamus decussating at the medulla or spinal cord; is named as such because it is the second neuron to carry that particular sensory information
Sensation
a perception or feeling that results from a stimulus
Sensory homunculus
topographic representation of the body within the somatosensory cortex demonstrating the correspondence between neurons processing stimuli and sensitivity
Sensory modality
a particular system for interpreting and perceiving environmental stimuli by the nervous system
Sensory receptors
cells or structures that detect sensations
Somatosensation
general sense associated with modalities lumped together as touch
Special sense
any sensory system associated with a specific organ structure, namely smell, taste, sight, hearing, and balance
Spinothalamic tract
ascending tract of the spinal cord associated with pain and temperature sensations
Stretch reflex
response to activation of the muscle spindle stretch receptor that causes contraction of the muscle to maintain a constant length
Supplemental motor area
cortical area anterior to the primary motor cortex that is responsible for planning movements
Tactile corpuscles
also known as Meissner corpuscles, are encapsulated receptors in the skin that respond to light touch
Tendon organ
receptors located in tendons that respond to stretch
Thalamus
a portion of the diencephalon that serves as a relay for communication between the cerebrum and rest of the nervous system
Thermoreceptor
sensory receptor specialized for temperature stimuli
Third order neuron
a neuron that extends from the thalamus to the primary sensory cortex in the parietal lobe; is named as such because it is the third neuron to carry that particular sensory information
Upper motor neuron
neuron that extends from the primary motor cortex of the cerebrum down to the ventral grey horn at the appropriate level of the spinal cord
Withdrawl reflex
retracting the affected pat of the body in response to a painful or destructive stimulus

  

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